Moderator's Note: Moved from the Audios: Fifth Doctor: Omega thread:

How often has he said time goes faster on the moon? It does, after all

It WHAAAAAAAAAAAAAAAAAAAAT!

Less gravity on the Moon, so time goes faster.

By about a billionth of a second a year.

Give or take.

Less gravity on the Moon, so time goes faster.

EVERY ******* TIME I think I might possibly be getting the hang of SOMETHING science-related, some sadist says something like this.

WHY? Why, for heaven's sake????

By about a billionth of a second a year.

Well, it's QUITE UNDERSTANDABLE if the Doctor doesn't mention THAT. Quite apart from anything else, his time on the Moon must subjectively FEEL like it takes LONGER than it actually does. I mean, either he's in prison (Frontier in Space), he's facing a rather dull and slow Cyberman invasion (The Moonbase) or he's in the company of the somewhat-tedious Martha Jones (Smith and Jones, Blink)...

WHY? Why, for heaven's sake????

Why is true, or why do we say it?

The latter, to stretch your mind a touch, the better to swallow the coming plots. The former, well I can explain, if you like. Are you familiar with tensor calculus, or would you prefer words?

Well, it's QUITE UNDERSTANDABLE if the Doctor doesn't mention THAT.

So we've established that there are some temporal distortions the Doctor wouldn't consider worth mentioning. The rest is just a matter of degree. Why mention something everyone except Rose knows, when there are so many other exciting things going on. Six might have, but not Ten.

Would the time difference explain why Rose's souped-up mobile suddenly refused to phone home?

Yes it would. From the point of view of a distant reciever, the mobile would be transmitting at a much lower frequency than it usually does, making it impossible to establish contact.

Why is true, or why do we say it?

The former. I KNOW why you say it - to make me squeal and tear my hair and gnash my teeth.

The latter, to stretch your mind a touch, the better to swallow the coming plots.

Hey, I have very little problem swallowing plots unless they're of a Wheel in Space standard.

It's these 'FACT' things I can't cope with.

The former, well I can explain, if you like. Are you familiar with tensor calculus, or would you prefer words?

Guess.

So we've established that there are some temporal distortions the Doctor wouldn't consider worth mentioning. The rest is just a matter of degree.

And when it comes to matters of degree, the Doc has an almost human perspective. A billionth of a second a year would be NOTHING to him. The thought of seeing an adorable look of confusion on Rose's face as he claims they're moving at a fifth their normal speed, however...

Why mention something everyone except Rose knows, when there are so many other exciting things going on. Six might have, but not Ten.

Because there AREN'T any other exciting things going on. They seriously think (for some as yet unexplained reason) that they'll be sitting around discussing mortgages and doing the laundry for months to come.

Yes it would. From the point of view of a distant reciever, the mobile would be transmitting at a much lower frequency than it usually does, making it impossible to establish contact.

Thanks! THAT almost makes sense!

It's these 'FACT' things I can't cope with.

You've spent the last 30-odd years trapped between an ocean of molten rock and the pitiless void, surrounded by creatures that want to eat your living flesh, and overshadowing it all, the knowledge of your certain death, as have we all. A few simple facts shouldn't strain you.

Or perhaps you've never thought about the lava seething a few dozen miles beneath your feet, the empty space just miles overhead, the trillions of bacteria constantly trying to feast on you, and the inevitability of death, hopefully on old age, many many decades from now.

Guess.

Another one failed by their maths teacher, I suppose? You should have done as I did, and ransacked the school library. Then you too could work out how to build something bigger on the inside, from first principles. All you need is a little cosmic string, and a convenient star to power it up, preferably one with no inhabited planets. The practical implementation is a mere engineering problem.

A verbal explanation then. Going uphill, against gravity, takes energy. For physical objects, this means they slow down, and eventually stop. For light, which always goes at the same speed, it means the frequency gets lower. Frequency can be used as a clock, so many waves a second, but the lower frequency will mean clock runs slower. having gravity make some types of clock run slow but not others would break Occam's razor, so that means it must make all clocks run slow. (There are certain nuances I've skated over here, but that's the gist of it.)

. The thought of seeing an adorable look of confusion on Rose's face as he claims they're moving at a fifth their normal speed, however..

That's like saying when you walk down a train you're walking at 90mph. Anyone well away from the black hole will see them moving at one-fifth normal speed, and vice versa, but they're both still moving at normal speed.

They seriously think (for some as yet unexplained reason) that they'll be sitting around discussing mortgages and doing the laundry for months to come.

A fascinating new experience for the Doctor, whereas black holes are old hat.

I would like to point out that Occam's razor is NOT a law of physics, and it is in no way, shape or form forbidden to break it.

I would like to point out that Occam's razor is NOT a law of physics, and it is in no way, shape or form forbidden to break it.

Indeed, that being one of the nuances. Broadly though, the principle of equivalence is an example of parsimony, aka Occam's Razor. We look for the simplest most elegant laws of physics that fit the facts, which in this case means all clocks run slow, not just ones based on the frequency of light.

It doesn't have to be this way - it's perfectly possible to devise physical laws which break this principle - but it's proved a pretty good guideline in the past. Stick with the simplest theory that works, rather than any of the infinitely many alternatives, all of them even more complex than General Relativity.

You've spent the last 30-odd years trapped between an ocean of molten rock and the pitiless void, surrounded by creatures that want to eat your living flesh, and overshadowing it all, the knowledge of your certain death, as have we all.

Yeah, but until you pointed that out I HADN'T ACTUALY NOTICED.

Or perhaps you've never thought about the lava seething a few dozen miles beneath your feet

Well, only when I'm watching Inferno.

the empty space just miles overhead

Only when wondering when the HELL an alien spaceship is going to appear in said empty space. Preferably a blue-box-shaped one.

the trillions of bacteria constantly trying to feast on you

Only when watching Invisible Enemy.

and the inevitability of death, hopefully on old age, many many decades from now.

Oh, I think about THAT quite a lot. I have a real moral dilemma - as a devout believer in euthanasia I was resolved to be put down the moment I became old n'useless but THEN it occurred to me how I'd be the most blissfully happy person in the universe if I DID become senile...in front of a looped tape of Season 27. Can you just IMAGINE seeing that over and over again as if for the first time...?

Another one failed by their maths teacher, I suppose?

IF ONLY. I was fantastic at maths up to the age of sixteen, which is why I made the worst mistake of my life and did it for A-Level...

You should have done as I did, and ransacked the school library. Then you too could work out how to build something bigger on the inside, from first principles. All you need is a little cosmic string, and a convenient star to power it up, preferably one with no inhabited planets. The practical implementation is a mere engineering problem.

Well, have you DONE it yet?!

A verbal explanation then. Going uphill, against gravity, takes energy. For physical objects, this means they slow down, and eventually stop. For light, which always goes at the same speed, it means the frequency gets lower. Frequency can be used as a clock, so many waves a second, but the lower frequency will mean clock runs slower. having gravity make some types of clock run slow but not others would break Occam's razor, so that means it must make all clocks run slow.

Um...

Yeah...

Well...

Thanks for TRYING...

The thought of seeing an adorable look of confusion on Rose's face as he claims they're moving at a fifth their normal speed, however..

That's like saying when you walk down a train you're walking at 90mph.

Not to Rose it wouldn't be. She's used to hanging round trains, she's not used to hanging round black holes. And the main reason the Doctor has humans with him is so that he can see the universe afresh through their eyes. (It says so in the Season 5/31 DVD extras, so it must be true. Hell, Christmas on a Rational Planet even implies that the Doctor can psychologically switch between 'human' and 'Time Lord' mode.)

They seriously think (for some as yet unexplained reason) that they'll be sitting around discussing mortgages and doing the laundry for months to come.

A fascinating new experience for the Doctor, whereas black holes are old hat.

You'd think so, wouldn't you? The Doc REALLY doesn't seem happy about it, though. For a story where he comes so close to actually telling Rose he loves her, he meanly freaked out about getting a HOUSE with her.

Yeah, but until you pointed that out I HADN'T ACTUALY NOTICED

Strange. I would have thought watching Doctor Who would have opened your mind to strange perspectives.

IF ONLY. I was fantastic at maths up to the age of sixteen, which is why I made the worst mistake of my life and did it for A-Level...

So they were the ones who failed you.

Well, have you DONE it yet?!

There are some slight technical problems getting hold of the necessary components. For a start, the DIY shop doesn't stock cosmic string, perhaps because the neighbours would complain, in the few seconds before weird gravitational effects killed them all.

Thanks for TRYING...

Which bit wasn't clear? I'm quite happy to explain at great length, if needs be. It'll fill in the empty months until the next new episode airs.

You'd think so, wouldn't you? The Doc REALLY doesn't seem happy about it, though.

Fascinating isn't quite the same as desirable. A dead mouse on your dinner plate, courtesy of your cats, would certainly get your attention, just as the prospect of a mortgage does the Doctor's, and for the same reason. You don't actually want it, but the thought of what it means for you fills your mind anyway.

Like the Doctor, you certainly wouldn't be able to ignore it, continuing with your normal witty banter as if everything were normal.

Strange. I would have thought watching Doctor Who would have opened your mind to strange perspectives.

It certainly has, only when the Doc starts saying that we're clinging to the skin of this tiny little world that's spinning at a thousand miles an hour I start freaking out and wanting to get back to stuff I UNDERSTAND, like the bigger-on-the-inside time machine.

There are some slight technical problems getting hold of the necessary components. For a start, the DIY shop doesn't stock cosmic string, perhaps because the neighbours would complain, in the few seconds before weird gravitational effects killed them all.

Excuses, excuses...

Which bit wasn't clear?

ALL the bits after 'Going uphill, against gravity, takes energy. For physical objects, this means they slow down, and eventually stop.'

I'm quite happy to explain at great length, if needs be. It'll fill in the empty months until the next new episode airs.

It'll take longer than THAT to get me to understand, but if you really want to give it a try, and don't mind me sitting here with a Benton-like look of gormless incomprehension on my face...knock yourself out ;)

Fascinating isn't quite the same as desirable.

True, but how new-and-exciting would getting stuck REALLY be for the Doctor? He spent YEARS being exiled to Earth. At least HERE he's got the option of flying round the galaxy in a normal spaceship (so don't ask why he thinks he's gotta get a mortgage).

Excuses, excuses...

Well, if you don't mind the risks, find me some cosmic string - or are you going to make excuses why you can't?

ALL the bits after 'Going uphill, against gravity, takes energy. For physical objects, this means they slow down, and eventually stop.'

Next step. The energy of light is proportional to its frequency. This is actually per photon, and has been confirmed experimentally. Clear?

If you to know why energy is proportional to frequency, you're out of luck. The best that can be offered are arguments from simplicity and analogy. It's certainly a simple relationship and, as it happens, the equations of classical mechanics are exactly the same shape as the equations that describe the paths of light rays, when that's a sensible concept. Demonstrating this takes a grasp of partial differential equations, so just trust me: if you write the equations for boring old Newtonian mechanics in a special way, then replace energy with frequency and momentum with something else waves have, you get the equations that describe light rays.

True, but how new-and-exciting would getting stuck REALLY be for the Doctor? He spent YEARS being exiled to Earth.

Centuries ago, so he's probably forgotten some of the details, and that time he had Unit to look after him. He didn't need a mortgage, since he lived in their lab, and they'll have provided him with unlimited free meals too, and plenty of tea to drink. Ten wouldn't have been so lucky.

Well, if you don't mind the risks, find me some cosmic string - or are you going to make excuses why you can't?

Yeah. I wouldn't recognise it if it ATE me, for starters.

The energy of light is proportional to its frequency. This is actually per photon, and has been confirmed experimentally. Clear?

Sunshine, it wasn't clear even BEFORE you started throwing words like 'photon' around.

If you to know why energy is proportional to frequency, you're out of luck.

I can categorically assure you that no I don't.

He didn't need a mortgage, since he lived in their lab, and they'll have provided him with unlimited free meals too, and plenty of tea to drink. Ten wouldn't have been so lucky.

Oh, Tennant could have sold his soul to some paramilitary organisation if he'd been THAT desperate for tea. (In fact, I suspect Hand-Ten is happily working for Torchwood as we speak.)

Yeah. I wouldn't recognise it if it ATE me, for starters.

Excuses, excuses.

Sunshine, it wasn't clear even BEFORE you started throwing words like 'photon' around.

You understand energy and frequency, I hope. Say yes, and I'll explain how they apply to light.

Tennant could have sold his soul to some paramilitary organisation if he'd been THAT desperate for tea.

Three didn't much mind if his friends waved guns around. Ten does. Hand-Ten, born in violence, might be different, but the real Ten would only work for Torchwood if they kept all the guns well away.

You understand energy and frequency, I hope. Say yes, and I'll explain how they apply to light.

No.

I mean, I have a vague idea about energy, but now you mention it I only really understand frequency as it applies to the frequency with which Doctor Who is on TV.

Three didn't much mind if his friends waved guns around. Ten does. Hand-Ten, born in violence, might be different, but the real Ten would only work for Torchwood if they kept all the guns well away.

I think you exaggerate Ten's hatred of guns. Sure, like most Doctors (bar Three, who'd merely snarl 'Do you think for once you could arrive BEFORE the nick of time' whenever the Brig splatters someone's brains out) he wasn't overly fond of his Companions gunning people down in front of him - but, as was pointed out in Utopia, he didn't usually have a big problem with non-Companions doing it.

So I strongly suspect his outbursts in Sontaran Stratagem were due to him being in a REALLY bad mood. He was having a thoroughly marvellous time with the thoroughly marvellous Donna when he'd been dragged back to boring old Earth and forced to see boring old Martha (GUILT! GUILT! Hell, even almost-over-the-Time-War Eleven felt guilty over Martha), forced to see UNIT (GUILT! GUILT! He hadn't bothered seeing the Brig in CENTURIES) - all because of UNIT's total failure to so much as invade a factory without him holding their hands.

Let's face it, Helen Raynor just doesn't GET the Doc. Not only was he having hysterics over a MILITARY ORGANISATION having guns, he even went into breast-beating 'Kill me too!' meltdown when a Dalek somewhat predictably killed one of the extras...

I mean, I have a vague idea about energy, but now you mention it I only really understand frequency as it applies to the frequency with which Doctor Who is on TV.

Light is a wave (and a particle, but we can ignore that for these purposes). Its frequency is how many a times a second it waves, give or take a factor of twice pi (there to make the maths neater).

Red light has a low frequency, relatively speaking, and blue light has a high frequency - it waves about twice as fast. Ultraviolet is higher frequency still, then beyond that are x-rays and gamma rays. Microwaves are lower frequency than red light, then come radio waves. (If you've got an old radio, you'll see the frequencies listed on the dial.)

Clear?

So I strongly suspect his outbursts in Sontaran Stratagem were due to him being in a REALLY bad mood.

Plausible enough. However, even if the future Torchwood set him up in luxury, and tried to avoid shooting people where he can see, he'd still be stranded far from his favourite historical period. Quite why he's so fond of the late twentieth/early twenty-first century isn't entirely clear, but he certainly is.

Light is a wave...you'll see the frequencies listed on the dial.

Clear?

Clear-ISH, thanks.

Why did no one explain this stuff before? Like, when I was doing my Physics GCSE?? (No, really - and unlike Jo I actually PASSED.)

However, even if the future Torchwood set him up in luxury, and tried to avoid shooting people where he can see, he'd still be stranded far from his favourite historical period.

True, and I'm not saying he'd be HAPPY, but as he's permanently stranded (or THINKS he is, albeit on the flimsiest of pretexts) I'm just saying the Doc'd almost certainly prefer to be stranded WITH Torchwood rather than without 'em. I mean, he was pretty unhappy during the UNIT years too (or at least he thought he was).

Why did no one explain this stuff before? Like, when I was doing my Physics GCSE??

Because you weren't the only person in the class, and the teacher was dreaming of their next holiday. All I ever learned in the actual lesson was how to look like I'm paying attention while half asleep - my actual education came from library books, read at leisure, and interrogating carefully selected adults.

Now, light is a wave, but since it can go through a vacuum it can't be in anything physical. It's in what's called the electromagnetic field. The details don't matter. The important thing is that light makes electrical charges and magnets vibrate at the same frequency as the light, and vice versa.

Since the frequency of visible light is a few quadrillion Hertz, you won't notice it making things wobble, and you can't move things by hand that fast, but fundamentally, that's what's happening every time something absorbs or emits light. Quantum stuff makes it a bit more complicated, but again that isn't important here.

At much lower frequencies, if you spin a magnet round your head a few times a second, it will produce radio waves. Beam very low frequency radio waves at the magnet, and it will visibly move - they just have to be strong enough to overcome friction. At middling frequencies, microwaves work by making the atoms in the food wobble around a lot, which turns into heat.

Anything you don't understand, just say so.

I'm just saying the Doc'd almost certainly prefer to be stranded WITH Torchwood rather than without 'em.

True, but it's still a depressing enough prospect to account for him not explaining how black holes warp time to Rose.

All I ever learned in the actual lesson was how to look like I'm paying attention while half asleep

Ah. Yes. That sounds familiar.

God, to think some unworthy rug-rats had THE TENTH DOCTOR HIMSELF as their Physics teacher.

Of course, their school blew up shortly afterwards, but that's only to be expected.

my actual education came from library books

Trouble is, I always went for the FICTIONAL library books.

microwaves work by making the atoms in the food wobble around a lot, which turns into heat.

Ooh! That's so clever! I always wondered how they worked.

Just not enough to actually try to find out, obviously.

Anything you don't understand, just say so.

The time-going-faster-on-the-Moon stuff.

True, but it's still a depressing enough prospect to account for him not explaining how black holes warp time to Rose.

Nonsense, talking to his peroxided pet is how the Ninth and Tenth Doctors COPE with depressing thoughts.

Anything you don't understand, just say so.

The time-going-faster-on-the-Moon stuff.

Maybe I can give it a shot?

Trouble is, I always went for the FICTIONAL library books.

They didn't have any of the Target novelisations, or anything else published after 1960, though they did have quite a few boy's adventure annuals full of plucky youngsters expanding the Empire over the bodies of the natives. Presumably, the council had more important things to spend its money on than books, like the shiny new headquarters they built themselves. (It was knocked down recently, for being an hideous eyesore.)

The time-going-faster-on-the-Moon stuff.

I'm getting there, step by easy step.

Next up, energy and frequency. We can tell light carries energy because it makes things hotter. A stone wall out in the sunlight will get nice and warm, just right for a basking cat.

The obvious assumption is that the brighter the light the more energy it carries, and this turns out to be true, but it's not the whole truth. Turn up the power in the microwave, making them brighter, and the food cooks faster, but no matter how much power (energy per second) you put in, your microwave can't split the atom. On the other hand, gamma rays, which are just very high frequency x-rays, can split the atom easily, even if the total power is much less than a microwave.

This puzzled a lot of eminent Victorian scientists, but Einstein came up with the right answer. It turns out that light comes in lumps, called photons, lumps which are always the same, and can't be cut up at all. The energy of an individual lump happens to be proportional to its frequency. Having lots of lumps going in the same direction makes the light brighter.

Thus, with gamma rays, each individual lump has enough energy rip atoms apart, even if there's only a couple of them around, but with microwaves, the lumps are too weak to do more than make the atoms wobble a bit. It'd take millions of them ganging up on a single atom to pull it apart, and that's absurdly improbable,

talking to his peroxided pet is how the Ninth and Tenth Doctors COPE with depressing thoughts.

In this case though, they were so depressing he couldn't talk about anything else, until it got excitingly dangerous.

Maybe I can give it a shot?

EVERYONE please feel free to give it a shot. The one that uses the most words-of-one-syllable wins.

They didn't have any of the Target novelisations

My god I'd've DIED without Targets to keep me going. (Or, of course, turned to factual books. But more likely died.)

though they did have quite a few boy's adventure annuals full of plucky youngsters expanding the Empire over the bodies of the natives.

Ha ha ha!

Funny the Doc has so few British Empire adventures, despite it being a) rather geographically and historically widespread, and b) British.

Next up, energy and frequency.

OK, with you so far, in a hanging-on-by-my-fingernails kinda way.

In this case though, they were so depressing he couldn't talk about anything else

I don't think it works like that for ANY of the Doctors. The more depressed they are about something, the less they talk about it. It took us SIX YEARS before we knew for sure that the Doc had deliberately pressed the big red button (or whatever) to blow up Gallifrey. And Hartnell mentions poor little Susan, what, once or twice since he dumps her? And the amount of time any Doctor spends talking about his late lamented kids, you'd think they'd never EXISTED. (Now you mention it...I DO think they never existed.)

Alright, he's a BIT more open in his Rose-pining, but then it's not HIS fault Donna, Martha and Captain Jack develop a Rose obsession and won't let him shut up about her.

EVERYONE please feel free to give it a shot. The one that uses the most words-of-one-syllable wins.

I'll let Robert finish. No need to confuse things at this point.

Funny the Doc has so few British Empire adventures, despite it being a) rather geographically and historically widespread, and b) British.

There were plans to do an Indian mutiny story with Hartnell, but it fell through. After him, they pretty much abandoned the historicals. I suppose they could do a story where the Doctor helps his good friend Wilberforce, defeating some slave traders who turn out to be disguised aliens, but then people would probably complain about the Doctor not freeing all the slaves with a wave of his sonic screwdriver.

OK, with you so far, in a hanging-on-by-my-fingernails kinda way.

Fortunately for you, this is only general relativity. The equations are complex, but the basic theory is simple enough - space tells matter how to move, matter tells space what shape to to be. Quantum theory is the other way round: the equations are simple enough, for multi-dimensional calculus, but what it all means is far less intuitive than general relativity, a kind of bizarre logic that means everything you're not actually looking at is half dead, in a sense. (And no, I'm not even going to attempt to explain that further. Building my own Tardis would be easier.)

Any, we've near enough established that light has energy and frequency. Now consider what happens when light goes up hill.

The natural assumption is that nothing happens, but if that were the case we could get infinite energy, infinite power, infinite episodes of Doctor Who. The recipe is pretty simple, transport energy uphill as light, move the energy into matter, drop the matter downhill, so it gains energy, turn this extra energy and the energy you stuck in the matter in the first place back into light, and repeat.

Unfortunately, that's too good to be true. Any machine that could give us infinite energy would break the universe, the way the Time Lords did experimenting with black holes, so infinite energy must be impossible, but it turns out that the only way to make it impossible is if light also loses energy when it goes up hill.

There were plans to do an Indian mutiny story with Hartnell, but it fell through.

Ah. I had the vague idea Sarah was originally supposed to die in the Indian Mutiny. Or something.

I suppose they could do a story where the Doctor helps his good friend Wilberforce, defeating some slave traders who turn out to be disguised aliens, but then people would probably complain about the Doctor not freeing all the slaves with a wave of his sonic screwdriver.

•••• right we would!

I realise the whole thing would be fraught with moral difficulties, but is THAT a reason SEXY would accept for not going there? She has a different morality to us, plus she took the Doctor and Donna to ROME and neither of them seemed to have a problem with slavery in the Caecilius/Metella household.

space tells matter how to move, matter tells space what shape to to be

Ooh, that sounds neat! (Incomprehensible, but neat.)

a kind of bizarre logic that means everything you're not actually looking at is half dead, in a sense.

SERIOUSLY?

I should watch more Who, then.

The recipe is pretty simple, transport energy uphill as light, move the energy into matter, drop the matter downhill, so it gains energy, turn this extra energy and the energy you stuck in the matter in the first place back into light, and repeat.

How would you move energy into matter?

Any machine that could give us infinite energy would break the universe, the way the Time Lords did experimenting with black holes

Hey! The Time Lords didn't break the universe! They just...let a few vampires through. Could've happened to anyone.

so infinite energy must be impossible, but it turns out that the only way to make it impossible is if light also loses energy when it goes up hill.

Ah. OK. Any idea WHY it loses energy?

SERIOUSLY? I should watch more Who, then.

Seriously, but a watched pot literally never boils, proven experimentally. If you tried watching it constantly, the screen would freeze. Fortunately, the human eye can only look at things 25 times a second, or so, giving plenty of time in between for things to change. (To get a noticeable freezing effect, you need a camera with a speed of a few dozen quadrillion frames per second, not easy to find.)

That's not the strangest thing you'll find in quantum physics either, and yet, in the discrete case, you can do all the calculates using nothing beyond GSCE maths, plain old matrices are all you need.

How would you move energy into matter?

Very easily. When sunlight makes a brick wall hot, that's energy going from the sunlight into the wall. Put a solar cell on the wall, and the energy from the sunlight can be used to charge a battery instead, which again is a way of putting energy into matter, and so on. It's best to use a method, like the battery, that makes it easy to get the energy out when you want it.

Hey! The Time Lords didn't break the universe! They just...let a few vampires through. Could've happened to anyone.

True. Of course, they weren't after infinite energy, just the equivalent power output of a few 100 billion stars. Infinite energy would be much worse.

Ah. OK. Any idea WHY it loses energy?

If it didn't, you could build the infinite energy producing machine described - but since I already said that, it clearly isn't the kind of answer you're looking for.

Basically, science has axioms of a sort (not quite up to the standards of pure maths) and one of them is pretty much no infinite energy machines.

If you want to know why those axioms are true, consult your nearest sober philosopher. However, we can be fairly sure nothing remotely human could exist in a world where those axioms were false. Since we both seem to be human, that's fairly strong evidence the axioms are true (only fairly strong, since it's conceivable we're just characters in a computer game Amy is playing.)

It may help to know that the axiom in question (called local energy conservation) turns out to be the same as saying the laws of physics don't change when we put the clocks forwards, or back. It takes some pretty complex mathematics to prove this, so I won't try here, but hopefully you'll agree a world where changing the clocks changed the laws of physics doesn't sound like a good idea.

Anyway, since you've accepted light loses energy when it goes uphill (in a vague, it's better than breaking the universe, sort of way), we can move on to the next thought experiment.

For that, I'll put you and all your cats in a secret space station, with plenty of food and a telescope, so you can watch us down on earth, then give you a day or so to settle in.

Robert -- I *LOVE* that description of General Relativity. I'm going to steal it if you don't mind.

"Space tells matter how to move, matter tells space what shape to be."

Robert -- I *LOVE* that description of General Relativity. I'm going to steal it if you don't mind.

Feel free. It's a lightly mangled quote from the physicist John Wheeler, who actually said: "Matter tells space how to curve, and space tells matter how to move."

There are a few other quotes like that around. E.g, the laws of thermodynamics are "You can't win. You can't draw, except at absolute zero. You can't reach absolute zero." And then there's my own original contribution, which can be found floating around online in a few places:

"Matter is fundamentally lazy:- It always takes the path of least effort.
Matter is fundamentally stupid:- It tries every other path first.
That is the heart of physics - The rest is details."

This is literally true, with only two caveats. It should really be 'extremal', not 'least', and the details aren't for the faint-hearted.

a watched pot literally never boils, proven experimentally. If you tried watching it constantly, the screen would freeze.

So if I DON'T watch Who, it's half-dead, and if I DO watch Who, it freezes?

This 'physics' stuff is just PICKING ON ME.

I plain old matrices are all you need.

And I'm sure if I could only remember what 'matrices' are, that would be enormously helpful...

How would you move energy into matter?

Very easily.

Had a feeling it would be, it's just that nothing was springing to mind.

Of course, they weren't after infinite energy, just the equivalent power output of a few 100 billion stars.

Would the Time Lords really need THAT much energy to keep one sparsely-populated planet going, plus power time travel? A couple of Victorian gents created time travel without so much as a BATTERY, if I remember Evil of the Daleks correctly (which I probably don't, what with the BBC EXTERMINATING it, and all).

If you want to know why those axioms are true, consult your nearest sober philosopher.

So scientists haven't worked it out yet? THAT makes me feel better.

It may help to know that the axiom in question (called local energy conservation) turns out to be the same as saying the laws of physics don't change when we put the clocks forwards, or back.

Well, they obviously DO. How else could Faction Paradox have purchased those Eleven Days from King George?

hopefully you'll agree a world where changing the clocks changed the laws of physics doesn't sound like a good idea.

Actually it sounds like a WONDERFULLY EXCITING idea. Why the hell hasn't Who-on-TV experimented with it?

For that, I'll put you and all your cats in a secret space station, with plenty of food and a telescope, so you can watch us down on earth, then give you a day or so to settle in.

OK, what do me n'oochies do now?

And then there's my own original contribution, which can be found floating around online in a few places

Omigawd, you're practically a FAMOUS PHYSICIST!

Doesn't this impact your enjoyment of Who AT ALL? I always consoled myself for my scientific illiteracy with the thought that it made being a Fan SO MUCH EASIER.

Robert, my favorite is Pauli's "This isn't right. It isn't even wrong."

So if I DON'T watch Who, it's half-dead, and if I DO watch Who, it freezes?

Yes. The key is to watch intermittently, at the right frequency - slow enough that your TV has time to change while you're not looking, fast enough that your TV doesn't have enough time to change into a heap of mangled wreckage while you're not looking.

Fortunately, this is a pretty easy balance to strike. You can watch the TV every waking hour, and your inability to see more than 25 frames a second will prevent undesirable freezing.

Would the Time Lords really need THAT much energy to keep one sparsely-populated planet going, plus power time travel? A couple of Victorian gents created time travel without so much as a BATTERY, if I remember Evil of the Daleks correctly (which I probably don't, what with the BBC EXTERMINATING it, and all).

Those Victorians only had a time corridor, and it might have been created by Daleks anyway. The Time Lords can travel freely in eternity, and create pocket universes, aka Tardises.

Actually it sounds like a WONDERFULLY EXCITING idea. Why the hell hasn't Who-on-TV experimented with it?

It violates common sense, though admittedly that wouldn't stop them. We change the clocks twice a year; we ought to notice if that changed the laws of physics.

Doesn't this impact your enjoyment of Who AT ALL? I always consoled myself for my scientific illiteracy with the thought that it made being a Fan SO MUCH EASIER.

Not one bit. Being able to imagine half a dozen mutually contradictory things at once is a vital skill if you want to understand quantum physics.

So scientists haven't worked it out yet? THAT makes me feel better.

It's not really a science question. Basically, science is great at telling you what happens, and how it works, but pretty bad at fundamental reasons. It's like asking 'what's 2 and 2' - maths can tell you the answer easily, but if you want to know why it's four, the answer amounts to 'it just is, ok', though mathematicians may disguise this with 300 pages of circular logic.

OK, what do me n'oochies do now?

To start with, you watch me through your telescope, which can see right through roofs - try not to get distracted.

I have a torch shining straight up, so you can see it, with a very fast shutter in front of the torch. It's so fast, it only lets one lump of light through a time. Fortunately, human eyes are good enough you'll still be able to see this - it'll look like a very faint twinkle.

(This may sound like a dull experiment, but it's tradition, and you do get a good view from up there. If you've ever felt like stroking your cats sinisterly, and declaring yourself supreme ruler of the world, now's the time.)

Anyway, you're a long way up hill from me, 24000 miles or so, so the lump of light will lose energy as it climbs against gravity. It won't lose much, the earth's gravity isn't that strong, but it will lose some. So, what does this mean for the lump of light when it reaches you.

It has less energy, but it can't get any smaller - it was already the smallest lump of light possible, thanks to my fast shutter. All lumps the same frequency have the same energy, so since the our lump has lost energy, its frequency has gone down too. (Remember the energy is proportional to frequency.) Frequency going down means the light has got a touch redder.

Lumps of light don't interact with each other at all - you can shine two beams of light through each other and they'll each act as if the other wasn't there. Thus, if I send you lots of lumps of light at once, they'll each act like they were all by themselves. Their frequency will go down, just like when I sent them you one at a time.

However, to send lots of lumps at once, all I need to do is take the shutter off the torch and shine it on full - or just let the light bounce off my hair and up to you. Everything you see through that telescope, you see with light that has lost energy climbing up hill, so everything you see looks a bit redder than it really is.

Conversely, if I look at you in a satellite through a telescope, the lumps of light will have gained energy falling downhill, so they'll look bluer, giving your skin a very faint blue tinge.

In practice, for the light to be noticeably redder to the human eye, we'd have to put you, and your cats, in a spaceship, and dangle me from it just above a black hole or neutron star, but that's a minor detail. The effect is big enough to be noticeable when sending computer signals to satellites.

Near a black hole the effect gets as big as you like. Explode a nuclear bomb near a black hole and, if you're far enough away, the X-rays will have lost so much energy climbing against gravity that they'll have turned into harmless radio waves.

By the way, Emily, the "watched pot never boils" effect is exactly how the Weeping Angels work.

Also, the funkiness in time caused by gravity actually does happen. The GPS system needs to take this into account, or it would be completely inaccurate after once day.

The Time Lords can travel freely in eternity, and create pocket universes, aka Tardises.

They CAN'T travel freely - not in Gallifrey's past or future, and not in the far future (i.e. Frontios, though that's stretching the definition of 'far' quite considerably, unless Plantagenet and co have actually spent a few million years as downloads/sentient gas and forgot to mention it).

And, let's face it, a TARDIS's reputation as a pocket universe has been greatly exaggerated. SEVEN YEARS of the supposedly-infinite (near-infinite. Whatever) machine and we've seen TWO ROOMS. And a corridor.

We change the clocks twice a year; we ought to notice if that changed the laws of physics.

But the laws of physics ARE intertwined with clocks in some manner we haven't fathomed yet. Why else would all the clocks in Caesar Churchill's timeline freeze at 5.02?

Being able to imagine half a dozen mutually contradictory things at once is a vital skill if you want to understand quantum physics.

Ah!

If you've ever felt like stroking your cats sinisterly, and declaring yourself supreme ruler of the world, now's the time.

I couldn't possibly stroke a cat sinisterly. (Declaring myself supreme ruler of the world is a different matter, of course.)

Lumps of light don't interact with each other at all - you can shine two beams of light through each other and they'll each act as if the other wasn't there.

WHY? I mean, if they've got all this energy and frequency and are affected by gravity and stuff?

By the way, Emily, the "watched pot never boils" effect is exactly how the Weeping Angels work.

Well, in the case of the Angels it seems to be more 'a pot which thinks it MIGHT be being watched never boils', these days...

Also, the funkiness in time caused by gravity actually does happen.

Someting insane about getting older faster on high ground?

They CAN'T travel freely - not in Gallifrey's past or future, and not in the far future

Compared to a time corridor, that's still free range. It's like saying you can go anywhere in the UK, as opposed to just Blackpool. You can't actually go on private property, or 50 mile under your house (Which is still British territory) but you can wander over enough of it to reasonably say you can go pretty much where you like.

And, let's face it, a TARDIS's reputation as a pocket universe has been greatly exaggerated. SEVEN YEARS of the supposedly-infinite

Don't forget the previous 26 years - and anyway, even a small pocket universe still requires enormous energy. For one design, it's estimated you'd need considerably more energy than there is in the entire visible universe to build a police box just two or three times larger on the inside than the outside.

Why else would all the clocks in Caesar Churchill's timeline freeze at 5.02?

Because the laws of physics had been badly broken. That's not much of guide to what happens normally.

WHY? I mean, if they've got all this energy and frequency and are affected by gravity and stuff?

Because the photon lives in U(1), a commutative group - a technically accurate answer that probably doesn't tell you anything. If you want to really understand the answer to that question, you need to master quantum field theory, which is rather more complex than normal quantum theory, so it might take a few months, even after you've learned the necessary maths.

However, it might be helpful to think about what it would be like if lumps of light could interact with each other. If they could stick to each other, you could build things out of solid light. If they bounced off each other, you wouldn't be able to see anything - it'd be like filling the air with trillions of microscopic mirrors, one for each lump of light.

Since neither of these options are much like the world we usually see, we can conclude that there's no such interaction.

Anyway, now we've established light gets redder when it goes uphill, we're on the home straight, just one step left to go. Can you stand the excitement?

Compared to a time corridor, that's still free range.

But you can make a time corridor come out ANYWHERE you want! You can pluck the TARDIS itself out of the Vortex with it! It IS free range, albeit no doubt needing a lot of cumbersome reprogramming between trips so not as FAST as the TARDIS. But there's a reason the Daleks developed a TARDIS first and THEN moved on to time-corridor technology. (Alright, I can't actually THINK of said reason, but that's not the point.)

Don't forget the previous 26 years

I'm certainly not fogetting *shudders* the bricks of Invasion of Time. Or the fact everyone had to share a bedroom in Edge of Destruction and Snakedance.

and anyway, even a small pocket universe still requires enormous energy. For one design, it's estimated you'd need considerably more energy than there is in the entire visible universe to build a police box just two or three times larger on the inside than the outside.

Someone's actually worked this OUT? Fantastic!

Why else would all the clocks in Caesar Churchill's timeline freeze at 5.02?

Because the laws of physics had been badly broken. That's not much of guide to what happens normally.

But the inanimate clockwork things SENSED that the laws of physics had been broken. That's REALLY SMART of them.

Because the photon lives in U(1), a commutative group - a technically accurate answer that probably doesn't tell you anything.

The 'probably' is an unnecessary bit of tact ;)

If you want to really understand the answer to that question, you need to master quantum field theory, which is rather more complex than normal quantum theory, so it might take a few months, even after you've learned the necessary maths.

Forget I asked.

Anyway, now we've established light gets redder when it goes uphill, we're on the home straight, just one step left to go. Can you stand the excitement?

Go on, I can take it...

But there's a reason the Daleks developed a TARDIS first and THEN moved on to time-corridor technology.

Are you absolutely sure they did it that way round? Dalek chronology isn't exactly clear.

But the inanimate clockwork things SENSED that the laws of physics had been broken. That's REALLY SMART of them.

No smarter than knowing what the laws of physics are in the first place. Even a stone knows that; put one in mid-air, then let go, and it will fall, just as the laws of physics demand.

The 'probably' is an unnecessary bit of tact ;)

For all I know, you might have accidentally got the theory of Lie groups tattooed on your arms while drunk, giving you plenty of opportunity to learn it despite not doing so well at maths generally. After all, you've said you went to Cambridge, so you had a chance to mingle with people capable of that kind of prank.

Go on, I can take it...

Well, if you're sure not going to start bad poetry about the hidden beauties of gravity while your cats languish unfed - unlikely sounding, I admit, but people have done stranger things, like marrying their dogs.

As you sit in your sumptuous space station, surrounded by flying cats, and peer through your telescope at me far below, you see light that's redder, lower frequency, than when it left earth.

Now watch me spin a magnet round my head, 1000 times a second. Because the magnet is going round in circles, it makes waves in the magnetic field with the same frequency, 1 KiloHertz, and you see those vibrations as radio waves (did I forget to mention your new, improved eyes?)

However, you don't see the waves wobbling 1000 times a second; you see them at a slightly slower frequency. Now, suppose for the moment you see time behaving normally for me. Then what you see is a magnet spinning 1000 times a second producing radio waves at a lower frequency.

That would be a breach of the laws of physics, flatly impossible. You can never see the laws of physics being broken - if you think you have, you've got the laws wrong.

The only way for things to make sense is if you don't see me spinning the magnet 1000 times a second, but a little bit slower, at the same frequency as the radio waves you see.

Since every time anything with electrons in is wobbled around, they give off radio waves like the magnet, and everything has electrons in it, the same applies to everything wobbling. It looks slower to you than it does to me. Since almost all clocks work by counting wobbles - of pendulums, springs or crystals - they'll all appear to run slow.

In other words, you'll see everything on the surface of the earth running more slowly, as if time itself had slowed down. Nor is it just an optical illusion. Suppose we both count the seconds while you're up in your satellite, then you come down to earth slowly (to avoid complications). You'll have seen me count a few seconds less than you while in orbit, so when we meet up again, my count will be less than yours.

Less time passed for me than for you; gravity made my clocks run slower.

The surface of the moon is uphill from the surface of the earth, so time runs slightly faster their. Conversely, if you go and live 3 miles beneath the surface, in some abandoned mine, time will pass slower for you than for us, though not by much.

Near a black hole, this effect is much bigger. Close enough to the event horizon, a billion years in the rest of the universe will seem like a second to you.

This means you can never actually see someone fall into a black hole - you see time slow to a crawl for them, so it takes trillions of years for them to get a millimetre closer - unless, that is, you're falling into the same black hole.

But there's a reason the Daleks developed a TARDIS first and THEN moved on to time-corridor technology.

Are you absolutely sure they did it that way round? Dalek chronology isn't exactly clear.

Alright, I'm not 100% sure. But the Daleks DID only use their own TARDIS once, and OK so the Doctor blew it up but I can't imagine they didn't keep NOTES. And there's no sign of 'em having TARDISes in the Time War - it was flying saucers which attacked Gallifrey (and which they rebuilt during their long game above Earth). Obviously time tunnels were unexpectedly able to hold their own against TARDISes.

But the inanimate clockwork things SENSED that the laws of physics had been broken. That's REALLY SMART of them.

No smarter than knowing what the laws of physics are in the first place. Even a stone knows that; put one in mid-air, then let go, and it will fall, just as the laws of physics demand.

But the seconds WERE ticking by in that wrecked timeline - Churchill, Amy, Rory, River etc acted as if days and nights passed in the same sort of progression we're used to. So automatic clockwork (or whatever clocks RUN on these days) ought to have continued to move the hands on clocks regardless of the technical fact it was always 5.02.

(God, this is (to get things vaguely back on-audio-topic) reminding me of the godawful attempt to exile McGann into what was repeatedly DESCRIBED as a 'timeless universe'. Only everyone was OBVIOUSLY ageing at one second per second, and the seasons were turning, and in the end Big Finish pretty much threw up their hands and said 'Oh, what we MEANT was a universe where no one MEASURED time!' (despite the fact McGann spent most of Scherzo shrieking 'Time! I can't sense time any more!').)

For all I know, you might have accidentally got the theory of Lie groups tattooed on your arms while drunk

I never got drunk in my university days.

I never got drunk AT ALL until I became a writer and Lawrence Miles told me how much EASIER it was to write while drunk.

Yes, like EVERYTHING ELSE IN MY LIFE my near-alcoholism can be directly traced back to Doctor Who...

you've said you went to Cambridge, so you had a chance to mingle with people capable of that kind of prank.

Cambridge had TWO DOCTOR WHO SOCIETIES. I didn't have TIME to mingle with non-Fans, and mercifully Fans were too busy watching Who to even THINK of desecrating our bodies in tribute to Jon Pertwee...

Well, if you're sure not going to start bad poetry about the hidden beauties of gravity while your cats languish unfed

Look, I'm the one who wrote an ode to Adric. I can't make any promises. But I think it highly unlikely.

people have done stranger things, like marrying their dogs.

I've heard of someone who married the Berlin Wall. But SURELY no one would marry a DOG?

(Well, OK, if K9 popped the question I might not INSTANTLY turn him down...)

Now watch me spin a magnet round my head, 1000 times a second.

You ROCK at magnet-spinning.

The only way for things to make sense is if you don't see me spinning the magnet 1000 times a second, but a little bit slower, at the same frequency as the radio waves you see.

THIS is your definition of SENSE??

Since every time anything with electrons in is wobbled around, they give off radio waves like the magnet

Ooh, that reminds me! Reversing the polarity of the neutron flow - impossible, right? Neutrons don't flow - that's the only thing I remember from five years of physics.

Conversely, if you go and live 3 miles beneath the surface, in some abandoned mine, time will pass slower for you than for us, though not by much.

HOW much? I note that ex-boyfriend of Jack's didn't bother with THAT particular life-extending measure in Miracle Day...

And there's no sign of 'em having TARDISes in the Time War - it was flying saucers which attacked Gallifrey

But a Tardis can be any shape on the outside, so those saucers could have been tardises.

But the seconds WERE ticking by in that wrecked timeline - Churchill, Amy, Rory, River etc acted as if days and nights passed in the same sort of progression we're used to.

When the laws of time are shattered wreckage, there's no particular reason why mechanical clocks should play by the same rules as biological clocks.

I've heard of someone who married the Berlin Wall. But SURELY no one would marry a DOG?

They would, to another dog. People with more sentiment than sense stage weddings for their dogs, as if they were capable of being faithful.

THIS is your definition of SENSE??

It's logically coherent, and less insane than the alternatives - like a universe where going up and down in a lift usually result in time travel. That's not much, I know, but it's the best we can do.

Reversing the polarity of the neutron flow - impossible, right? Neutrons don't flow - that's the only thing I remember from five years of physics.

A beam of neutrons can be loosely said to flow, and they also have polarity - every neutron is a minuscule magnet, with north and south poles - so reversing the polarity of the neutron flow is possible, though mere human science hasn't worked out why it'd be useful.

HOW much? I note that ex-boyfriend of Jack's didn't bother with THAT particular life-extending measure in Miracle Day...

Under a microsecond a year. You'd have to be really desperate to avoid death to go to those lengths. For useful life extension, you need to park yourself just above the surface of a black hole or neutron star, which enough shielding to make sure you don't accidentally fall in.

Moderator's Note: Moved from the end-of-the-universe discussion in Novels: Bernice Summerfield: Ghost Devices:

But surely stars would still BE there, just more...spread out?

Sadly, stars don't live forever. The Big Bang produced a lot of hydrogen, which is the fuel that powers stars, but it didn't produce an unlimited supply of it. Eventually it will be depleted, no new stars will form and the existing ones will go out. The dead stars WILL still be there, but only as cold dark corpses.

So there were PREVIOUS universes that Banged and Crunched, but OURS will just go on and on FOREVER?

It is not specified how the previous universe died. It could have crunched or it could have expanded, and still be expanding, into cold oblivion. Either way, the Beast and the Legions of Light could have escaped death by moving to our fresh young universe.

As for what professor Yana said, well, they are at least a hundred trillion years in the future. A lot can happen during that time.

Sadly, stars don't live forever.

Yeah, I knew THAT, I just thought that new ones would...pop up. Or something.

The Big Bang produced a lot of hydrogen, which is the fuel that powers stars, but it didn't produce an unlimited supply of it. Eventually it will be depleted, no new stars will form and the existing ones will go out. The dead stars WILL still be there, but only as cold dark corpses.

Oh.

So what you're saying is, all this 'universe will last forever' stuff is a complete disaster. EVERYTHING will die out and DEADNESS will expand forever, with NO WAY any new universe will ever take its place...

Now I'm REALLY depressed. (Not as depressed as at the thought of NO NEW WHO AT EASTER but depressed nonetheless. Which disproves ANOTHER claim of Ghost Devices AND Oblivion, that humans just don't give a •••• about what'll happen in a few billion years' time. Though admittedly they made said claim before Who had ever bothered to go billions of years into the future, which certainly alters one's perspective.)

It is not specified how the previous universe died. It could have crunched or it could have expanded, and still be expanding, into cold oblivion.

Hang on, how did OUR universe come about if the old one is still around?? And what does science, as opposed to Who, say about universes existing before ours?

Either way, the Beast and the Legions of Light could have escaped death by moving to our fresh young universe.

Well, I don't see any Legions of Light. Maybe they went down with their own universe, having considerately ensured that the Beast got to survive, and indeed contaminate every corner of OUR reality. Morons.

Hang on, how did OUR universe come about if the old one is still around?? And what does science, as opposed to Who, say about universes existing before ours?

There are theories that would permit that. Our universe could be infinite in extent, but still fit inside a minuscule bubble floating inside an earlier universe, or we could be living on a 3-brane.

However, we don't know if those theories are right yet, and may not for some time. The maths is so complex even the experts don't fully understand what it means, and the necessary experiments would require pieces of equipment a few hundred thousand light years long, and take several hundred thousand years to do, not exactly practical.

Well, I don't see any Legions of Light.

There's always the Doctor. It wouldn't be that surprising if he turned out to be a reincarnation of the commander of those legions.

So what you're saying is, all this 'universe will last forever' stuff is a complete disaster. EVERYTHING will die out and DEADNESS will expand forever,

Kinda bleak and depressing, isn't it?

with NO WAY any new universe will ever take its place...

Actually, good news, there are ways.

Hang on, how did OUR universe come about if the old one is still around?? And what does science, as opposed to Who, say about universes existing before ours?

Essentially, our universe is a bubble of normal space in an exponentially expanding volume of what physicists call "false vacuum". The scenario goes like this. The process starts with a bit of mass-energy that is as dense and as hot as the laws of quantum physics allow. Believe me, that's DENSE and HOT. At that enormous density, every distinctions between mass, energy, gravity, electric charge, space, and everything else is non existent. That bit of mass-energy is as dense, uniform and featureless as is possible.

It immediately starts expanding. As it does so, its density and temperature decrease. At certain critical temperatures, the various physical laws acquire their distinct characteristics. Physicist call those events "phase changes". It's very similar to water vapor (a gaz) turning into water (a liquid) then into ice (a solid) at specific temperatures when you cool it. Water has different properties according to temperature, and the laws of physics also have different manifestations according to temperature.

Now, here's the trick. Normally, water freezes at 0 degrees celcius. But, if you use very pure water and cool it carefully enough, you can get its temperature several degrees below zero and have it remain liquid. That's called "supercooling". It is an unstable state, and simply tapping on the side of a container filled with supercooled water will make it freeze instantly. The expanding bit of mass-energy can also get into a supercooled state. The most interesting point at which this can happen is at the final phase change, the one that results in the laws of physics that govern the universe we live in. The expanding mass-energy overshoots the point at which that last phase change should occur and becomes supercooled.

The supercooled mass-energy becomes the "false vacumm". It has interesting properties. It appears perfectly empty. It expands exponentially, doubling in size in the merest fraction of a second, over and over and over again. Despite appearing empty, that exponential expansion fills it with a mind boggling ammount of potential energy. Its density does NOT decrease at it expands. And finally, like all supercooled states, it is unstable. Sooner or later, it makes the final transition and the laws of physics we are familiar with come into existence.

The potential energy contained in the false vacumm making the transition now gets dumped into the newly formed normal vacumm. That's a LOT of energy. This is where everything our universe contains comes from, protons, neutrons, electrons, neutrinos, etc,. That big energy dump is what we observe as the Big Bang. At that point, a universe is born. It starts expanding normally, it grows bigger, cools down, forms stars, galaxies, planets, life, and everything.

However, and that's the other neat trick, not ALL of the false vacumm makes the transition at the same time. One bit does, what remains continues its exponential expansion, then another bit makes the transition, and another, and another, without end. The result is a vast number of normal space bubbles we call universes forming in the eternally expanding false vacumm. Once started, the process never ends. Interestingly, the false vacuum closely resembles the void the Doctor describes in Army of Ghosts, empty, featureless, timeless. It is what exists between the universes and separates them, and none of the laws of physics we are familiar with apply within it.

And so, in this scenario, countless universes preceded our own, and countless others will succeed it. Even though each universe eventually expands into a cold, dark, and ever expanding dead place, there will always be fresh new ones that sufficiently advanced civilizations can migrate to. I think the Timelords qualify, and so too, apparently, did the Legions of light.

Our universe could be infinite in extent, but still fit inside a minuscule bubble floating inside an earlier universe

This is getting ridiculous. Are you quite sure you're not getting this 'physics' stuff confused with Hitchhikers Guide to the Galaxy or something?

or we could be living on a 3-brane.

A what??

the necessary experiments would require pieces of equipment a few hundred thousand light years long, and take several hundred thousand years to do

Excuses, excuses...

There's always the Doctor. It wouldn't be that surprising if he turned out to be a reincarnation of the commander of those legions.

Ugg, no, I've decided that I don't like the Doctor being a reincarnation of ANYONE - the Other, Legion Commander, whatever. He's just...the Doctor.

the laws of physics also have different manifestations according to temperature.

Grrrrr!

Now, here's the trick. Normally, water freezes at 0 degrees celcius. But, if you use very pure water and cool it carefully enough, you can get its temperature several degrees below zero and have it remain liquid.

Ooh! Like icecanos on Spiridon!

The potential energy contained in the false vacumm making the transition now gets dumped into the newly formed normal vacumm. That's a LOT of energy. This is where everything our universe contains comes from, protons, neutrons, electrons, neutrinos, etc,.

For the first time in my life I'm seeing the appeal of the 'God waved a magic wand and created everything in six days' stuff.

Interestingly, the false vacuum closely resembles the void the Doctor describes in Army of Ghosts, empty, featureless, timeless.

And also full of weird background radiation, not to mention Daleks and Cybermen sqabbling over their holiday snaps of the Doctor...

Even though each universe eventually expands into a cold, dark, and ever expanding dead place, there will always be fresh new ones that sufficiently advanced civilizations can migrate to. I think the Timelords qualify

They certainly gave it a go in the Fifth Doctor audio Singularity. Unfortunately they're now all DEAD. Cos the losers never thought to emigrate to other universes just for the fun of it BEFORE the Time War.

This is getting ridiculous. Are you quite sure you're not getting this 'physics' stuff confused with Hitchhikers Guide to the Galaxy or something?

Hitchhiker's Guide isn't even one-tenth as bizarre as the real thing - gluons, winos, extra dimensions. There's all that weird gravity stuff we were just discussing, and the even weirder quantum stuff.

3-branes - just as there are elementary particles, 0-dimensional, and strings, there are also elementary building blocks with 2-11 dimensions, called m-branes, a pun on membrane. The three dimensional ones, naturally, are called 3-branes.

Think of it as like a soap bubble, only with an extra dimension, and flopping around eleven dimensional space rather than the 3-dimensional one you're used to. Now stick a bunch of strings to it. As long as they stay stuck, they can't tell there's anything outside the 3-brane, so they act as if they're in a 3-d universe. We're made of such strings.

For the first time in my life I'm seeing the appeal of the 'God waved a magic wand and created everything in six days' stuff.

Of course, that just sweeps the complexity under the carpet, and multiplies it drastically. An handful of mathematical equations are much simpler than any god.

Cos the losers never thought to emigrate to other universes just for the fun of it BEFORE the Time War.

Maybe. If some of the renegades had gone universe-hopping, how would we know?

All of that 3-brane, strings, eleven dimensions stuff is mathematically elegant, even consistent, but there are NO experimental results for or against it at all. Even the false vacumm scenario I outlined is bareley within reach of the experiments physicists can perform today. The totally surprising discovery of Dark Energy proves how little we actually know about how things work. Somebody will have to build those hundreds of thousands light years long instruments, or their equivalent, or we'll never be able to say anything significant about any of this.

Btw, a small suggestion, if I may. It could be interesting to create a new thread called "Science and the Whoniverse" or something similar, where posts of this kind would find a more appropriate home.

A SMALL suggestion? Have you ANY IDEA how HAPPY I was that the audios and the Benny books were FINALLY getting a bit of action?! I was Bwahaha-ing so hard I half-expected the Doctor to turn up and thwart me under the misapprehension I was one of those planning-on-conquering-the-universe megalomanics...

Then I must thank you from the bottom of my heart for accepting my suggestion at the cost of your own happiness.

Physicist call those events "phase changes".

I thought it was called breaking symmetry.

But a Tardis can be any shape on the outside, so those saucers could have been tardises.

Oh. Yeah, that's a point...

By the way, the Dalek TARDIS-creation MUST have been early in their timeline cos they only knew about Hartnell - and indeed, thought that Vicki must be Susan...

It's logically coherent, and less insane than the alternatives - like a universe where going up and down in a lift usually result in time travel.

That's not insane! I WANT THAT UNIVERSE!

A beam of neutrons can be loosely said to flow, and they also have polarity

••••.

3-branes - just as there are elementary particles, 0-dimensional, and strings, there are also elementary building blocks with 2-11 dimensions, called m-branes, a pun on membrane. The three dimensional ones, naturally, are called 3-branes.

Sorry I asked.

Think of it as like a soap bubble, only with an extra dimension, and flopping around eleven dimensional space rather than the 3-dimensional one you're used to.

Ah no, I'm not falling into THAT trap. We all know what happened when the Doctor said 'Imagine a great big soap bubble with one of those tiny little bubbles on the outside.' Rory said 'OK' and the Doc said 'Well it's nothing like that.'

Now stick a bunch of strings to it. As long as they stay stuck, they can't tell there's anything outside the 3-brane, so they act as if they're in a 3-d universe. We're made of such strings.

I've heard the phrase 'string theory' (super-string theory? Oh, something to do with string anyway). I just didn't realise I was supposed to be the bloody string.

For the first time in my life I'm seeing the appeal of the 'God waved a magic wand and created everything in six days' stuff.

Of course, that just sweeps the complexity under the carpet, and multiplies it drastically.

Yeah, but the great thing is, you can just threaten to burn alive anyone who points this out!

If some of the renegades had gone universe-hopping, how would we know?

Well, I ASSUMED that the Time Lords would vaguely keep tabs on which of their Potentially Universe-Detroying Renegades were actually IN THIS UNIVERSE (they did, after all, EVENTUALLY work out that Romana was in E-Space) but I was forgetting that hundreds of Time Lords had got eaten by an extra-universal asteroid without anyone noticing their absence.

Somebody will have to build those hundreds of thousands light years long instruments, or their equivalent, or we'll never be able to say anything significant about any of this.

Are you sure you're not being pessimistic? After all, scientific knowledge has obviously moved on enormously just since Ghost Devices...

Physicist call those events "phase changes".

I thought it was called breaking symmetry.

It is, but breaking symetry is a type of phase change and I didn't want to introduce any more new concepts than was absolutely necessary.

Are you sure you're not being pessimistic? After all, scientific knowledge has obviously moved on enormously just since Ghost Devices...

Probably. Reminds me of this philosopher name Auguste Comte. He said, among other things, that we could never study the chemical composition of the stars, that this knowledge would forever remain out of our reach. Three decades later, a scientist named Gustav Kirchhoff (who obviously hadn't read that memo) discovered that chemicals absorb and emit specific wavelengths of light, allowing them to be idendified and studied from any distance. And there were those late 19th century physicists who declared that all of physics was known, and all future scientists could do would be to refine measurements to the next decimal. They said that just in time for General Relativity and Quantum Mechanic to totally overturn what they thought they knew and shatter their comfortable vision of reality. Many similar shifts in the way we do science have occured, and no doubt many more await us in the future.

That's not insane! I WANT THAT UNIVERSE!

It would make your brain hurt. In such a universe, if you, Ace, and Donna walk into a shop together, then split up, visiting different combinations of floors in a different order, before returning to the ground floor, all three of you could see the other two arrive five minutes later. That is, you see Amy and Donna step out of the lifts after you've been waiting for five minutes, but Donna sees you and Ace step out of the lifts simultaneously, five minutes after she got there.

Admittedly, to get a five minute time difference, either the lifts were moving at near light speed, or the shop had a black hole in the cellars, but the principle remains. Such a world would be even more bizarre than our reality.

I just didn't realise I was supposed to be the bloody string.

You aren't. The electrons and quarks are the strings. You're made of a few trillion strings, a bit like a ball of elastic bands.

Somebody will have to build those hundreds of thousands light years long instruments, or their equivalent, or we'll never be able to say anything significant about any of this.

Well, if certain speculations are true, and the compact dimensions are a few cm across, we might be able to prove it within a few decades. Alternately, someone might invent a more efficient particle accelerator: there have been major improvements before, and the total amount of energy we need to pump into each particle is really pretty small.

Incidentally, these compact dimensions form the Calabi-Yau manifold that Quantum Archangel and others kept going on about,

I didn't want to introduce any more new concepts than was absolutely necessary.

*Nods approvingly*

there were those late 19th century physicists who declared that all of physics was known, and all future scientists could do would be to refine measurements to the next decimal. They said that just in time for General Relativity and Quantum Mechanic to totally overturn what they thought they knew and shatter their comfortable vision of reality.

Bless!

Hang on, how could they POSSIBLY have thought that all physics was known?? How the **** did they think the universe came into being?

Many similar shifts in the way we do science have occured, and no doubt many more await us in the future.

*Perks up* maybe I should stop trying to grasp all this 'science' nonsense, or at least give it a few more decades in case you're, y'know, TOTALLY WRONG about it all.

I WANT THAT UNIVERSE!

It would make your brain hurt.

Yeah, like THANKS TO YOU this universe doesn't make my brain hurt.

In such a universe, if you, Ace, and Donna walk into a shop together

If we WHAT!

I do not shop.

I most specifically do not shop when in the company of The Perivale Dalek-Killer and The Most Important Woman In The Universe.

Well, maybe if the shop was overrun by Autons...

all three of you could see the other two arrive five minutes later. That is, you see Amy and Donna

AMY and Donna? What is this, Dimensions in Time?!

I just didn't realise I was supposed to be the bloody string.

You aren't.

Excellent!

You're made of a few trillion strings

You just promised me I WASN'T made of string!

Incidentally, these compact dimensions form the Calabi-Yau manifold that Quantum Archangel and others kept going on about

You actually REMEMBER stuff from The Quantum Archangel? I don't even remember whether it had a Quantum Archangel in it...

Hang on, how could they POSSIBLY have thought that all physics was known??

Because they were arrogant gits who sincerely believed they were the best the universe would ever come up with.

How the **** did they think the universe came into being?

Either they believed God took care of that, or they brushed aside the question as unanswerable.

*Perks up* maybe I should stop trying to grasp all this 'science' nonsense, or at least give it a few more decades in case you're, y'know, TOTALLY WRONG about it all.

A very sensible strategy.

I most specifically do not shop when in the company of The Perivale Dalek-Killer and The Most Important Woman In The Universe.

If they suggest you need new shoes, all the better to run away from Daleks in, would you dare say no?

AMY and Donna? What is this, Dimensions in Time?!

No, just a universe so bizarre Amy and Ace could be the same person consecutively living their alternate histories.

You just promised me I WASN'T made of string!

I said you weren't the string, singular, not quite the same.

You actually REMEMBER stuff from The Quantum Archangel? I don't even remember whether it had a Quantum Archangel in it...

How could you forget the Doctor ascending to godlike power? It's not as if it happens every week.

Anyway, it claimed the chronovores and eternals lived in the Calubi-Yau manifold. Since it's a just a high dimension knotted doughnut, less than an inch across, and probably well under an a billionth of a yoctometre, this was rather implausible - even more so than the mad black hole supercomputer.

If they suggest you need new shoes, all the better to run away from Daleks in, would you dare say no?

I only EVER wear sensible shoes. You wouldn't catch ME climbing a mountain in high heels...

How could you forget the Doctor ascending to godlike power? It's not as if it happens every week.

The Doctor is ALREADY the Lonely God, how could anything POSSIBLY make him more godlike...

...Oh. It IS Colin Baker we're talking about, isn't it.

Anyway, it claimed the chronovores and eternals lived in the Calubi-Yau manifold. Since it's a just a high dimension knotted doughnut, less than an inch across

Ha ha ha!

and probably well under an a billionth of a yoctometre

A WHAT?

this was rather implausible - even more so than the mad black hole supercomputer.

There was a - oh, never mind.

A yoctometre is a small fraction of a metre, much smaller than a atom. It's like measuring things in millimetres, but more so.

To be precise, there are 1000 millimetres in a metre, 1000 micrometres in a millimeter, 1000 nanometres in a micrometer, 1000 picometres in a nanometre, 1000 femtometres in a millimetre, 1000 attometres in a femtometre, 1000 zeptometres in an attometre, and 1000 yoctometres in a zeptometre - and then they ran out of sensible names. The same applies going in the opposite direction: kilometre, megametre, gigametre all the way up to yottametres

The Doctor is ALREADY the Lonely God, how could anything POSSIBLY make him more godlike...

Throwing planets around might help, but even Six found that a little too flamboyant.

Yoctometre is a sensible name?

Physicists have been known to measure area in barns, time in jiffies, and mass in slugs, so yes yoctometre is relatively sensible.

Physicists have been known to measure area in barns, time in jiffies, and mass in slugs, so yes yoctometre is relatively sensible.

PROFESSOR KETTLEWELL is starting to look relatively sensible...

how could anything POSSIBLY make him more godlike...

Throwing planets around might help, but even Six found that a little too flamboyant.

Whereas Tennant did it BEAUTIFULLY.

The Doctor may not have CREATED the universe, but he did RE-create it, and that should make him a god in anybody's book.

PROFESSOR KETTLEWELL is starting to look relatively sensible...

Exactly. Half those who mock Dr Who science have no idea how bizarre real science can sound. However, that doesn't mean everything that sounds bizarre is right. Dr Who has its scientific implausibilities, they're just not what you might think.

The premise behind Silver Nemesis was that the Doctor *did* create the universe, although as this would make him God, JNT stopped short of having this said onscreen.

Moderator's Note: Moved from the Original Series: Season Fifteen: The Invisible Enemy section:

EMILY: 'They're developing a resistance to radiation' - those blasters shoot people with RADIATION?

AMANDA: Are they lasers? That's radiation.

EMILY: Seriously?

Well, technically yes. Lasers are electromagnetic radiation, but so is light. In fact, a laser is simply a beam of coherent light, meaning it shines with a single frequency and all of its waves are synchonized and move in parallel. What makes them useful as weapons is that they can be made very intense and will stay focussed over long distances. Someone developping resistance to a laser would be like an ant developping resistance to being burned with a magnifying glass. So those blaster weapons are probably not lasers.

*Look of blank incomprehension* What the hell ARE those blaster weapons then?!

What the hell ARE those blaster weapons then?!

The visible ray in all these devices is clearly just for aiming, since light can't have that kind of effect, but the actual damage must be done by something unknown to modern science. However, the obvious guess is exotic particles with a resonant interaction with some common biochemical.

the obvious guess is exotic particles with a resonant interaction with some common biochemical.

THAT'S your definition of an obvious guess??

And if it's NOT radiation why the hell did the Doctor say whatshisface survived several blasts of it cos he's built up an immunity to radiation?

THAT'S your definition of an obvious guess??

Obvious to anyone with A' Level grade knowledge of maths, and particle physics, noting beyond the grasp of a moderately bright 10 year old. Of course, not quite everyone is so well read - too many people waste their time watching football and soaps. In your case, I can only assume that rather than study you chose to spend your childhood reading target novelisations non-stop while simultaneously cuddling any cat that happened by, a natural enough temptation.

if it's NOT radiation why the hell did the Doctor say whatshisface survived several blasts of it cos he's built up an immunity to radiation

It's not light that does the damage, but that doesn't mean it's not radiation. Anything with negligible mass, in a technical sense, can be called radiation - that is, anything for which E=pc is approximately or exactly true. Strictly speaking, the equation ought to be exact, meaning the radiation has zero rest mass, but as long the mass is negligible, the particles behave like radiation rather than matter.

The other explanation is that the weapon beam produces radiation when it hits matter. Suppose, for instance, that when the exotic particles in the beam hit a carbon-12 nucleus in DNA, they turn one of the protons into a positron, antimatter, which promptly annihilates, producing boron-11 and gamma rays. The result would be DNA riddled with holes, and a burst of radiation, even though the dangerous component of the beam wasn't any kind of radiation.

However, for it only to affect carbon in one particular molecule, rather than disintegrating everything organic, the beam would have to be fine tuned with ridiculous precision (the resonant interaction).

In your case, I can only assume that rather than study you chose to spend your childhood reading target novelisations non-stop while simultaneously cuddling any cat that happened by, a natural enough temptation.

HELL yeah.

The slightly worrying thing is, thirty years on, nothing has changed...

Anything with negligible mass, in a technical sense, can be called radiation

What, my SHADOW is radiation?

Since when!

I always thought radiation was, well, y'know, RADIATION. The stuff that kills Third and Tenth Doctors even if there are more benevolent kinds of radiation that he can expel into his shoe.

that is, anything for which E=pc is approximately or exactly true.

Um....Energy equals...particles...something?

Strictly speaking, the equation ought to be exact, meaning the radiation has zero rest mass, but as long the mass is negligible, the particles behave like radiation rather than matter.

That's QUITE alright, I'm not gonna insist that the particles of the negligible mass start behaving like matter.

The other explanation is that the weapon beam produces radiation when it hits matter. Suppose, for instance, that when the exotic particles in the beam hit a carbon-12 nucleus in DNA, they turn one of the protons into a positron, antimatter, which promptly annihilates, producing boron-11 and gamma rays.

Oh for god's sake why can't these guys just use guns that blow holes in their opponents like sensible, CIVILISED people, instead of messing around with ANTIMATTER? We KNOW that NEVER ends well. (Except that ships in the twenty-sixth-or-whatever-it-is century run on antimatter just fine, but never mind THAT just now.)

EMILY in Original Series: Season Sixteen: The Pirate Planet section:

Quartz is only found on Earth?

Nope. Quartz is simple silicon dioxide. It will be abundant on any Earth like planet, and even on most asteroids.

I KNEW IT!!!!

(And, to be fair, KAM knew it about eleven years before I did...)

Even THE DOCTOR knew it in this very story, as he was going on about rubies and diamonds being valuable EVERYWHERE (NB: is this true? Why wouldn't some planets form an abundance of such gems?)...but he didn't exactly fall on bits of quartz with similar enthusiasm.

NB: is this true? Why wouldn't some planets form an abundance of such gems?

Because forming gemstones require special conditions of temperature, pressure and chemical environment. For instance, rubies are basically aluminium oxide, and diamonds are just pure carbon. To become a ruby instead of ordinary abrasive powder, aluminium oxide has to form in the presence of just the right ammount of chromium and without too much other impurities. And, of course, carbon will only form diamonds under extreme conditions of heat and pressure, otherwise you only get plain old graphite. It's difficult enough to make gemstones in the lab, where all conditions can be precisely controlled, so you can imagine how hard it is for them to form "in the wild", and why they would be so rare.

But what if you've got a planet with loads of heat and pressure...?

Earth has loads of heat and pressure, in its deep interior. That's where the diamonds we mine come from, after they are brought close to the surface by volcanoes.

There could be a very interesting kind of planet out there, called a carbon planet. It's something only recently imagined, nobody knew planets like these could exist when the Key to Time season was filmed. Their formation depends on how oxygen rich the gaz cloud from which they form is. If the gaz contains more oxygen than carbon, then you get planets like Earth, with silicon based minerals. If however the gaz contains more carbon than oxygen, then the planets will instead form out of carbon based minerals, called carbides.

Such minerals are harder and more heat resistant than silicon based ones (carbide tools will cut through steel like butter), and planets made out of them would be very different from Earth. And, there would be layers of pure carbon in their deep interiors, a shell of diamond hundreds of kilometers thick. If someone found a way to mine that diamond, I suppose the expression "diamond cheap" would soon become part of everyday language.

What the hell is gaz?

And what about that Midnight planet? I assume they weren't REAL diamonds or people would have done a lot more than stick a stupid resort on the planet and run bus trips...

What, my SHADOW is radiation?

Your shadow isn't a thing, in the relevant sense, merely an absence. Basically, your shadow has no substance: it's not made from stuff, it's just a place where light isn't.

Radiation, on the other hand, is made from stuff, it's just stuff that happens to have no mass, or near enough.

Um....Energy equals...particles...something?

Energy equals momentum time the speed of light. By ancient tradition, p stands for momentum and c for the speed of light. For anything that's not moving, energy = mass times c squared, but for radiation, and anything moving at near enough light speed, E=pc. In between, it's more complicated.

Oh for god's sake why can't these guys just use guns that blow holes in their opponents like sensible, CIVILISED people

Since they were on a space station, they might have been worried about accidentally blowing holes in the walls, and letting the air leak out.

And what about that Midnight planet? I assume they weren't REAL diamonds or people would have done a lot more than stick a stupid resort on the planet and run bus trips...

Not if real diamonds cost the equivalent of 2p a tonne to make. People would still find them pretty to look at, but they wouldn't be remotely valuable.

It's like aluminium. Once, the metal was so rare Napoleon had cutlery made out of it, to show off, and the Americans melted down rubies to get the aluminium out. Then chemists found a better way of making it. Now, it's so cheap, we can keep a roll in our kitchens, and throw it away after one use.

The price of diamond could collapse just as dramatically.

What, my SHADOW is radiation?

Your shadow isn't a thing, in the relevant sense, merely an absence. Basically, your shadow has no substance: it's not made from stuff, it's just a place where light isn't.

*Pouts* OK, fair enough.

*Perks up* But supposing I have TWO shadows? Are the Vashta Nerada radiation?

By ancient tradition, p stands for momentum and c for the speed of light.

Ancient tradition is BLOODY STUPID.

(Of course, I've always known that, I grew up under a monarchy. Plus the sight of Tom in the traditional Gallifreyan white nightdress sticking the Matrix-accessing crown on his head has always haunted me.)

For anything that's not moving, energy = mass times c squared

I knew that! (Obviously don't exactly grasp what it MEANS, but that's beside the point.)

Oh, and don't forget that in the Vortex, E = MC CUBED.

Since they were on a space station, they might have been worried about accidentally blowing holes in the walls, and letting the air leak out.

Oh yeah, good point. Pity Solos's Marshal never thought of THAT.

Alright, why are they using those killing-with-a-blob-of-light guns in Pirate Planet?

Not if real diamonds cost the equivalent of 2p a tonne to make. People would still find them pretty to look at, but they wouldn't be remotely valuable.

But the Fourth Doctor has categorically stated that THAT'S never gonna happen.

It's like aluminium. Once, the metal was so rare Napoleon had cutlery made out of it, to show off, and the Americans melted down rubies to get the aluminium out.

Tee hee!

Then chemists found a better way of making it. Now, it's so cheap, we can keep a roll in our kitchens, and throw it away after one use.

But I know someone whose husband made her diamond engagement ring, so scientists CAN already do that sort of thing. But still 'real' diamonds are worth a fortune, despite being African-war-causing boring bits of GLASS as far as I'm concerned. And isn't a distinction drawn between 'real' pearls and 'cultured' ones where they, hell, I dunno, I just assumed they SHOVED a bit of grit in an osyter's shell instead of EATING it, or something...

What the hell is gaz?

Oops, sorry. Gaz is the french word for gas. Some words in the two languages are so similar that I get them confused with each other sometimes.

But I know someone whose husband made her diamond engagement ring, so scientists CAN already do that sort of thing.

Yes they can. In fact, they can make almost any sort of gemstone you can think of. But people apparently still put a lot a value in gemstones that formed in the wild, without human intervention. That can be a problem, because there is, in principle, no way of distinguishing natural gems from manufactured ones.

*Perks up* But supposing I have TWO shadows? Are the Vashta Nerada radiation?

Having two shadows is easy. You just need two lights nearby, but they'd still be absences, places where the light wasn't. The Vashta Nerada, on the other hand, have substance, but aren't actually shadows. That's just what they look like. In actually, they're clouds of microscopic killers, made of matter.

Alright, why are they using those killing-with-a-blob-of-light guns in Pirate Planet?

Style? Some people would want their guns to look good, even if it made them less effective.


But I know someone whose husband made her diamond engagement ring, so scientists CAN already do that sort of thing

in principle, no way of distinguishing natural gems from manufactured ones.

In principle, but not in practice. Artificial diamonds can be distinguished from the natural kind, because they carry traces of how they were made. It requires elaborate equipment to tell the difference, but that's enough to keep the natural ones more expensive.

Making artificial diamonds completely indistinguishable from the natural product is theoretically possible, but you'd have to duplicate the flaws in the crystal structure the natural ones have, and the exact mix of impurities, and isotopes. For all practical purposes, it can't be done, yet.

Oops, sorry. Gaz is the french word for gas. Some words in the two languages are so similar that I get them confused with each other sometimes.

That's a relief, I was wondering if it was some weird chemical I was supposed to know about but (of course) don't.

It's also reassuring to know your bilingualism isn't perfect - I was getting a serious inferiority complex, as I'm even worse at languages than science.

But people apparently still put a lot a value in gemstones that formed in the wild, without human intervention.

Any diamonds that formed on Midnight would certainly fall into that category. I suppose humans are a speciest bunch who might put diamonds forming naturally on other planets on the same inferior level as artificial ones? Though if they're willing to have sex with any aliens they come across, they ought to be willing to nick their diamonds too.

Having two shadows is easy. You just need two lights nearby

Oh.

Yeah.

SOME people might be embarrassed to realise they'd completely forgotten that rather basic fact, and assumed that some alien piranhas-of-the-air were the only possible explanation for having two shadows but...not me.

Alright, why are they using those killing-with-a-blob-of-light guns in Pirate Planet?

Style? Some people would want their guns to look good, even if it made them less effective.

Fair enough, those guards were so mind-bogglingly useless ANYWAY that the quality of their guns wouldn't have made much difference.

Making artificial diamonds completely indistinguishable from the natural product is theoretically possible, but you'd have to duplicate the flaws in the crystal structure the natural ones have, and the exact mix of impurities, and isotopes. For all practical purposes, it can't be done, yet.

You'd think people who've learnt how to dematerialise planets would manage, however...

Taking of Planet 5:

'Before our universe, there was another. It expanded almost for ever, until its space-time was locally flat and devoid of matter or gravity. Eventually, pure randomness within the deep-foam structure of its underlying superstrings produced a number of acausal point formations in which parity was invalidated and gross amounts of either matter or antimatter could come into "real" existence. These events, separated by billions of light years of black, flat, emptiness, expanded out, forming bubbles of their own...our universe is one of these second-generation events'...Oh-kay, BEFORE we get to the creatures-lurking-in-the-old-universe-coming-to-eat-us stuff...is ANY of this REMOTELY plausible?

Oh-kay, BEFORE we get to the creatures-lurking-in-the-old-universe-coming-to-eat-us stuff...is ANY of this REMOTELY plausible?

Well, as I explained before, new universes could be bubbling out of an ever expanding sea of "false vacuum" all the time. This appears to be something different. In quantum mechanics, the uncertainty principle states that certain associated values cannot be defined with arbitrary accuracy. For instance, the more precisely you know the location of an object, the less precisely you know its velocity, and vice versa. Another such pair of values is energy and duration. The more precisely the energy of a system is defined, the less defined is its duration.

Because of this, "virtual" particles appear and disappear all the time throughout space. They "borrow" their energy from their uncertain duration, then pay it back almost immediately and vanish. There is no limit, in principle, to the amount of energy such virtual particles can borrow, or how long they can exist, provided both values are balanced against each other according to the uncertainty principle.

Here's the neat thing. The net energy content of our universe is ZERO. If you add up all the positive mass-energy and all the negative potential energy it contains, you come up with ZERO, nothing, nada. And because the universe contains no net energy, it never has to pay back that energy and can exist forever. So, given enough time, fresh new universes could pop out of the cold space of an old dead one, but the probability of such events is so low that these second generation universes would be separated by a LOT more than mere billions of light years.

The net energy content of our universe is ZERO. If you add up all the positive mass-energy and all the negative potential energy it contains, you come up with ZERO, nothing, nada

How do you KNOW? It sounds like a pretty big sum to do, maybe you misplaced a decimal point somewhere along the line while adding up all this suspiciously-imaginary-sounding potential negative energy stuff.

How do you KNOW?

Well, I'm just reporting what physicists and astronomers are saying, I don't ACTUALLY know this. But you asked if ANY of this was REMOTELY possible, and that's the answer the laws of physics as we currently understand them would give you.

Potential energy is very real. It's what gets converted to electricity in hydro electric dams, or where the exploding force of meteorites hitting the ground comes from. Any time you have objects acting on each other through gravity, or electric charges, or magnetism, or any other force, you have potential energy, which is always counted as negative. If I lift a rock a certain height, I put potential energy into it. Then if I let it go and fall to the ground, the damage it does when it lands comes from that potential energy being converted to mechanical energy. The universe contains enormous amounts of matter, dark matter, dark energy, all of it attracted to itself by gravity over colossal distances. That creates a LOT of negative potential energy, enough to cancel out the positive energy of all the mass-energy stuff in the universe.

Another way I have seen it explained is this. Suppose you have a vast, flat plain, and you need to build a hill of some sort on it. Well, you take a shovel, dig up some dirt and pile it up to make the hill. But each shovelful of dirt you use leaves a same size hole in the plain. The hill (positive mass-energy) and the hole (negative potential energy) grow at the same rate, one going up and the other going down. In the end, hill and hole would always add up to a perfectly flat plain if you were to put them back together.

How do you KNOW? It sounds like a pretty big sum to do,

You measure the shape of the universe. In the simplest case, if the universe has zero net energy, it is asymptotically flat, and vice versa - asymptotically flat meaning we can ignore the bumps caused by little things like galaxies and super clusters, and look at the big picture.

Cosmological constants and dark energy complicate things, but the basic principle is the same. By looking at the shape of the universe, and the stuff it's made of, we can deduce the total energy content.

We do need to assume our corner of the universe is typical, in a technical sense, but that's a necessary precondition for science in general.

One other thing, in general relativity, there's no such thing as the total energy of the universe. There is something that behaves as if it were the total energy of the universe, as long as said universe is sufficiently well behaved, which ours seems to be, which is what Francois is talking about, but you have to be careful, or you end up in bizarre places.

As for the earlier question, it's plausible enough. There are theories that match that description tolerably well, though this is this wild frontier of physics - a myriad theories, and no known way to test most of them, short of building a particle accelerator the size of a galaxy, which is just a little beyond current human capabilities.

the exploding force of meteorites hitting the ground comes from.

WHAT exploding force! Many's the meteorite/Nestene energy unit that's landed peacefully...

Well, you take a shovel, dig up some dirt and pile it up to make the hill. But each shovelful of dirt you use leaves a same size hole in the plain. The hill (positive mass-energy) and the hole (negative potential energy) grow at the same rate, one going up and the other going down.

Ooh! I TOTALLY understand the total energy of the universe!

there's no such thing as the total energy of the universe

...oh.

Here's a video that explains how universes can spring out of nothing, complete with nice visuals.

'Some kind of space-time quantum-foam sort-of-something existed before our universe began' - well, I suppose that doesn't contradict Who. But what was it DOING there in the first place?

'One one-hundred-thousandth of a gram...interestingly, the uncertainty principle allows this much stuff to be created out of nothing' - which came first, the theory that one one-hundred-thousandth of a gram could be created out of nothing, or the realisation that one-hundred-thousandth of something was inexplicably hanging around?

That American accent was pretty distracting. I was wondering whether 'adams' were some weird physics thing I'd never heard of before the penny dropped that they were 'atoms'.

Thanks, by the way, you guys. I can really feel my mind steeetching. Not enough to understand what the **** is going on, mind you. DID this explain how galaxies were moving faster than the speed of light...?

'Some kind of space-time quantum-foam sort-of-something existed before our universe began' - well, I suppose that doesn't contradict Who. But what was it DOING there in the first place?

That can simply be ordinary 'empty' space, which is not really empty but is filled with virtual particles always popping in and out of existence because of the uncertainty principle.

DID this explain how galaxies were moving faster than the speed of light...?

Did you see the link to a 'Chapter 2' that appears at the end on the video. Chapter 2 explains how that works.

No I bloody didn't! I was too relieved at getting to the end of Chapter 1 (well, I didn't NOTICE it was Chapter 1!) without my head exploding!

I suppose that doesn't contradict Who. But what was it DOING there in the first place?

Good question. There's a Noble prize waiting for a really good answer. The scientists have got a few ideas, but we've got no chance of testing them experimentally, and the maths needed to link the theory to experiments we can actually do is formidably difficult, even by mathematical standards.

The thing is, we are just pushing things back, not solving the problem. The video doesn't really say that the universe was created out of nothing, it says that it was created out of a quantum fluctuation in some kind of space-time quantum-foam sort-of-something. Where did that come from? Empty space form a dead previous universe? Ok, where did THAT come from?

What about the laws of physics? Why is the speed of light 299,792,458 meters per second? Why not 299,792,459? Or 10?. Where does gravity come from? Why is there such a thing as the Heisenberg Uncertainty Principle? And so on, and so on. Some people will say that God did it, and be all happy and smug that they have "solved" the problem. Well no, all that does is push the problem back one more notch. Where would God have come from?

It reminds me of that story about a man who visited a great sage in India to learn about the nature of the world. The sage told him that the world is a large disk of rock riding on the backs of four giant elephants. Fine the man said, what do the elephants stand on? The back of a giant turtle answered the sage. And what does the turtle stand on? The back of a still larger turtle. And as the man was about to ask what that turtle stood on, the sage said "Don't bother, it's turtles all the way down."

That's the kind of answer physics has to offer at this time, turtles all the way down. It's messy, clumsy, and it really answers nothing. We need something much better. Who will be the Newton or the Einstein that will figure it out?

it was created out of a quantum fluctuation in some kind of space-time quantum-foam sort-of-something.

Wow! That actually sounds like the sort of 'timey-wimey' explanation the Doctor would give!

Moderator's Note: Moved from the Ask the Matrix: Top/Bottom Ten Lists thread:

EMILY: Whereas THE TENTH DOCTOR solemnly assuring me (well, Rose and Mickey) that every single gesture we make creates a new universe renders my life, and more to the point, Doctor Who, rather meaningless. Why should I CARE if the Doctor falls on the fields of Trenzalore, or if the entire universe gets blown up, when all I have to do is scratch my nose to replace them?

Well, it all may just be mathematical hand waving that sweeps unwelcome paradoxes under the carpet, so to speak. Physicists have been known to do that, while they wait for something better that explains the paradoxes. Quantum mechanics shows many indications that it is not the end of the road. The best one is that physicists are incapable to reconcile it with general relativity, which forces them into the uncomfortable position of accepting two distinct models to describe the universe, one for the very large stuff (relativity) and one for the very small (quantum mechanics). Someone will eventually discover a way to bring the two models together (string theory being a good but not really successful attempt at this) and all these troublesome parallel universes may just vanish into a puff of mathematical methaphysics, making everything make sense again.

THE TENTH DOCTOR solemnly assuring me (well, Rose and Mickey) that every single gesture we make creates a new universe renders my life, and more to the point, Doctor Who, rather meaningless. Why should I CARE if the Doctor falls on the fields of Trenzalore

Creating a new universe is a gross simplification. All the myriad alternate histories are actually different facets of the same universe. You, Emily, simultaneously weigh 25 stone and 6 stone 10, have no children and 17, are a multi-billionaire and flat broke.

However, thanks to decoherence, all these different facets act as if they were the only one.

This doesn't make your decisions meaningless though, because not all those facets are equally likely, and some are vanishingly improbable. There is zero chance you will celebrate Guy Fawkes day this year by burning Tom Baker alive on a pile of Fourth Doctor videos while clutching a poodle to your chest - you're just not that kind of person, as far as I can tell.

Anyway, some people have suggested a way to use this quantum stuff to our advantage. Suppose that tonight you rig up a machine which will painlessly kill you in your sleep unless Eccleston announces overnight he wants to star in 26 new Doctor Who episodes next year. When you wake up, he will have made that announcement, because you will only exist in the worlds where he does. The idea is called Quantum Suicide, quite popular in certain circles, though I don't think anyone's put it into practice just yet.

Let me see if I got this right. If I rig such a machine to kill me in my sleep unless the lottery ticket I bought is a winner, then I will wake up a millionnaire the next day?

If I rig such a machine to kill me in my sleep unless the lottery ticket I bought is a winner, then I will wake up a millionnaire the next day?

As far as you're concerned, yes. If you don't win the lottery overnight you won't wake up at all, so you will only experience worlds where you do win. If you don't want the rest of us to see you losing the lottery, you have to go a step further, and arrange to destroy the world if you don't win. See http://en.wikipedia.org/wiki/Quantum_suicide_and_immortality

I don't often encounter new and interesting concepts anymore, but this one surely qualifies.

all these troublesome parallel universes may just vanish into a puff of mathematical methaphysics

Excellent! Let me know when this Happy Day arrives.

Creating a new universe is a gross simplification. All the myriad alternate histories are actually different facets of the same universe.

Not in the Whoniverse they aren't.

You, Emily, simultaneously weigh 25 stone and 6 stone 10, have no children and 17, are a multi-billionaire and flat broke.

There is NO UNIVERSE in which I have 17 kids or, indeed, ANY.

There is zero chance you will celebrate Guy Fawkes day this year by burning Tom Baker alive on a pile of Fourth Doctor videos while clutching a poodle to your chest - you're just not that kind of person, as far as I can tell.

Actually THAT'S vaguely possible. I lived for several years near Lewes, a town renowned for burning people alive on Bonfire Night (admittedly mainly in effigy), I don't need my videos any more now I have DVDs, if Tom refused to star in The Eleven Doctors (or whatever our fiftieth anniversary story will be called) I will be SEVERELY DISPLEASED with him, and OBVIOUSLY if I WAS frying my beloved Tom I'd feel the need to punish myself for my sins, and what better way than to clutch a disgusting dawg?

Anyway, some people have suggested a way to use this quantum stuff to our advantage. Suppose that tonight you rig up a machine which will painlessly kill you in your sleep unless Eccleston announces overnight he wants to star in 26 new Doctor Who episodes next year. When you wake up, he will have made that announcement, because you will only exist in the worlds where he does. The idea is called Quantum Suicide, quite popular in certain circles, though I don't think anyone's put it into practice just yet.

*Jumps up and down* I'm vounteering! I'm volunteering!

Though not till AFTER Season 7/33a, obviously. Just in case.

If I rig such a machine to kill me in my sleep unless the lottery ticket I bought is a winner, then I will wake up a millionnaire the next day?

Pretty stupid risk to take just for MONEY. Money won't buy you any more Who, y'know.

Pretty stupid risk to take just for MONEY. Money won't buy you any more Who, y'know.

Don't worry. I like gambling, but not for stakes THAT high.

And enough money COULD allow me to buy the rights to the franchise, in which case you could be sure that we'd have more than a measly 13 episodes per year to sink our teeth into.

Well, since you put it like THAT...

GO for it!

There could be a very interesting kind of planet out there, called a carbon planet. It's something only recently imagined...there would be layers of pure carbon in their deep interiors, a shell of diamond hundreds of kilometers thick. If someone found a way to mine that diamond, I suppose the expression "diamond cheap" would soon become part of everyday language.

And now they've gone and FOUND one:

http://www.independent.co.uk/news/science/newly-discovered-superearth-is-made-of-diamonds-say-scientists-8207414.html?origin=internalSearch

It's SO STUPID of The Pirate Planet not to see this coming.

It was imagined at least as far back as 1982. That was a plot point in the novel 2010.

'A physicist friend assures me that, while asphyxiation and cold would finish you off almost instantly, the "dragged out into space" scenario is nonsense: depending on the ratio of cabin air to aperture size, the escaping oxygen would create no more than a mild waft' - DWM. Blimey. Lucky Satan didn't know that...

From Emily in Audios: Eighth Doctor: Dark Eyes 3

But my problem with 'We all rewrite history...every decision we make' was with the Web of Time being shattered so EASILY (isn't it supposed to require a being of Sutekh's power?), not with us HAVING FREE WILL. (And how this fits in with New Who's 'every decision we make we CREATE A NEW UNIVERSE' I have no idea...)

It's complicated, but I'll give it my best shot.

In classical mechanics and relativity, there is no choice possible. Every single event everywhere and everywhen was completely determined at the exact moment of the Big Bang. There is only one reality, one history, and no changes of any kind can be made to it. Even time travel or Sutekh's power will not break you out of this situation because anything you could try to change the past is actually already part of the past, always was and always will be. Plainly, this is not the kind of universe in which Doctor Who takes place.

Things are different once you add quantum mechanics to the mix. The problem is that nobody is exactly sure how. In quantum mechanics nothing real exists except something called the wave function. This is an entity that gives you the probability of a given system finding itself in a given state. For instance, the wave function of a uranium atom will give you the probability of that atom decaying at any given time. It will not however tell you the ACTUAL moment the decay will occur. This appears to be determined at random. The atom "picks" a time of decay from all the possible times in a process that seems completely undetermined.

There are three main proposed interpretations of quantum mechanics that try to deal with that random process. The first is the hidden parameters interpretation. This states that there is no wave function at all. All parameters of a system are completely determined, but some of them are "hidden" because we do not have intruments sophisticated enough to measure them. Once we do, all of that quantum nonsense will evaporate and reality will once again be completely and rigidely determined. Einstein was a proponent of that interpretation. Unfortunately for him, clever experiments have pretty much eliminated it from the running.

The second is the Copenhagen interpretation, proposed by Niels Bohr and Werner Heisenberg. In it, the wave function of a system is all that exists, until a "measurement" of it is made. In this case, a measurement is nothing more than a quantum interraction with another system, like a photon colliding with an electron, or an atom responding to a magnetic field, that sort of thing. Once such a measurement occurs, one of the possible states of the system is selected at random and all other vanish. This is called collapsing the wave function. This is where the statement that nothing really exists until someone observes it comes from, something that is not actually true.

The third is the Many Worlds interpretation first proposed by Hugh Everett and further developped by Bryce Seligman DeWitt. It says that when a quantum system is measured, the wave function does not collapse to give one definite result. Instead, ALL possible outcomes of that measurement occur, each in its own separate universe. Reality is continuously branching off at every quantum fork in the road, every possible events occur, all histories are realized somewhere. This, btw, is how 'every decision we make we CREATE A NEW UNIVERSE' would work.

Doctor Who appears to lean toward one or the other of those last two interpretations depending on what the story requires. A universe with an immutable history would be the result of the Copenhagen interpretation, in which travel to the past would have to "restore" the already collapsed wave function at that particular point so it could be altered, something that may require the vast powers of a being like Sutekh. Unraveling the timeline would be the result of the Many Worlds interpretation, where travel to the past would cause the many different timelines issued from that point to collapse back into each other. Depending on how far reaching the effect is, you could get a mild and soon corrected deviation from the history you remember, all the way to the complete dissolution of the universe into total chaos.

This is it, in a nutshell. I hope I have not strayed too far from scientific accuracy. The thing is, we know that quantum mechanics is not the best theory, nor is relativity. Both theories have deficiencies indicating the need for a better theory. The simple fact that the two theories cannot be reconciled, even though both work very well in its own domain, is proof of that. I guess the Timelords have figure out that better theory, and all that time travel mumbo jumbo that causes us so many headaches makes perfect sense to them.

There is only one reality, one history, and no changes of any kind can be made to it. Even time travel or Sutekh's power will not break you out of this situation because anything you could try to change the past is actually already part of the past, always was and always will be. Plainly, this is not the kind of universe in which Doctor Who takes place.

Though, interestingly enough, it seems to be the kind of universe HARTNELL thinks he's in, at least up until The Time Meddler.

Einstein was a proponent of that interpretation. Unfortunately for him, clever experiments have pretty much eliminated it from the running.

Odd that, of all the genii in the universe, the Rani chose one from such a primitive time-period who also happens to be WRONG.

It says that when a quantum system is measured, the wave function does not collapse to give one definite result. Instead, ALL possible outcomes of that measurement occur, each in its own separate universe. Reality is continuously branching off at every quantum fork in the road, every possible events occur, all histories are realized somewhere. This, btw, is how 'every decision we make we CREATE A NEW UNIVERSE' would work.

But surely the Time Lords would have NOTICED this BEFORE the Doctor discovered alternative universes in Inferno?

And I can't bear it, I just CAN'T, to think that IT DOESN'T MATTER what happens in any episode of Who cos it creates a billion alternatives in which there are other outcomes...

Even if that WOULD mean there are a LOT more Eccys out there...somewhere...

(OK, I'm not over the moon at the thought of zillions more Emilys out there either. But obviously the Who considerations are the most important.)

Odd that, of all the genii in the universe, the Rani chose one from such a primitive time-period who also happens to be WRONG.

Well, your average punter in the audience thinks Einstein is the definition of genius.

Even if that WOULD mean there are a LOT more Eccys out there...somewhere...

(OK, I'm not over the moon at the thought of zillions more Emilys out there either.

Try to wrap your mind around this one. Under the Many Worlds interpretation, there are universes in which you and Eccleston are living in marital bliss

Like how Fisher on Home and Away ended up with a wife young enough to be his daughter?

Well, your average punter in the audience thinks Einstein is the definition of genius.

I suppose he ALMOST makes sense...at least compared to Hypatia. SHE didn't even have the sense to duck when a bunch of god-botherers turned up with flaming torches...*

Try to wrap your mind around this one. Under the Many Worlds interpretation, there are universes in which you and Eccleston are living in marital bliss

*Ponders this carefully*

*Starts constructing universe-ripping-apart dimensional cannon*

Like how Fisher on Home and Away ended up with a wife young enough to be his daughter?

Oi! I'm young enough to be Eccy's great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-granddaughter, thank you very much!

*Well, actually, according to the Library of Alexandria Companion Chronicle...oh, never mind.

But surely the Time Lords would have NOTICED this BEFORE the Doctor discovered alternative universes in Inferno?

They surely knew about the Many Worlds interpretation, but that interpretation also says that all these universes cannot communicate with each other, even in principle, so visiting them is forever out of the question.

It is not, however, the only way parallel universes can exist. One way would be if our own universe was actually infinite. Any finite part of such a universe will be repeated an infinite number of times within it. Of course, the larger the part of the universe you consider, the farther away its copies will be. You would already have to travel many quintillions of light years to have a reasonable chance of finding an EXACT copy, molecule for molecule, of a grain of sand. The distances you'd have to travel to find a copy of the Earth are positively mind boggling, which makes visiting such parallel worlds problematic, even for a TARDIS.

Another way is the continuous creation of new universes from an eternally inflating false vacuum. Such a vast (and I do mean VAST) number of universes could contain a few that are reasonable facsimiles of our own. The parallel universes in Rise of the Cybermen and Inferno are probably of this kind. Travelling between such universes is possible, but it would be quite difficult, possibly far more difficult than time travel, which might be why the Time Lords had never achieved it before Inferno.

They surely knew about the Many Worlds interpretation, but that interpretation also says that all these universes cannot communicate with each other, even in principle, so visiting them is forever out of the question.

So why didn't they at least MENTION it during (presumably) a century's-worth of lessons at the Academy? Or was the Doctor off daisy-spotting with a hermit that day, the way he obviously was when OTHER RACES IN THE UNIVERSE LIKE THE DALEKS were (hopefully) mentioned...

Also, when did everything CHANGE? To make flitting between universes easy and frequent (as mentioned in Rise of the Cybermen if never actually seen on-screen)?

You would already have to travel many quintillions of light years to have a reasonable chance of finding an EXACT copy, molecule for molecule, of a grain of sand. The distances you'd have to travel to find a copy of the Earth are positively mind boggling, which makes visiting such parallel worlds problematic, even for a TARDIS.

Distance SHOULDN'T be problematic for a TARDIS, though, once she's in the Vortex - though if it WAS that would certainly help explain why everyone hangs round one particular galaxy all the time...

Another way is the continuous creation of new universes from an eternally inflating false vacuum. Such a vast (and I do mean VAST) number of universes could contain a few that are reasonable facsimiles of our own. The parallel universes in Rise of the Cybermen and Inferno are probably of this kind.

Any mention of a Void in this theory?

Any mention of a Void in this theory?

The false vacuum would be the Void, their stated physical features are quite similar. I go into more details on the subject of universe formation in the Thursday, March 08, 2012 - 7:51 pm post on this board, if you feel like reading it again, and the next to last paragraph is the one containing the comments about the Void, if you don't.

Thanks, I kinda went for the next-to-last-paragraph only...

Any way the Void could have 'Void Stuff' if it's so •••• EMPTY?

Any way the Void could have 'Void Stuff' if it's so •••• EMPTY?

Of course. There's a lot of exotic "stuff" in there, it only LOOKS empty because most of it is in the form of unstable potential energy. It's very difficult to know exactly what exists in such an alien environment anyway because the laws of physics as we know them have not yet asserted themselves.

OK, so OBVIOUSLY this Big Rip thing is nonsense - only 22 billion years till the end of the universe?!

Come to think of it, shouldn't OUR universe have perished already, what with its distinct lack of Logopolitans and CVEs?

The Big Rip scenario would occur if dark energy became stronger with time. The best measurements to date indicate that it is constant, an intrinsic property of space itself that does not change, just like the speed of light or the gravitational constant.

Come to think of it, shouldn't OUR universe have perished already, what with its distinct lack of Logopolitans and CVEs?

We have not explored enough of OUR universe to make meaningful statements about the existence or non-existence of such features.

Come to think of it, shouldn't OUR universe have perished already, what with its distinct lack of Logopolitans and CVEs?

Christopher Bidmead makes Sarah Palin look intelligent.

Posted by Kate Halprin (Kitten) on the 'Lines you will never hear on Doctor Who' board

Surely it would be, "Oh don't be ridiculous. Pluto isn't a planet any more."

I consider Pluto to be a full fledged planet. There is only one possible physically meaningful definition of a planet. It is a body massive enough for its gravity to shape into a sphere, but not massive enough to ignite themonuclear reactions in its core. Objects less massive are asteroids, objects more massive are brown dwarfs if they can only manage to fuse deuterium, and stars if they are hefty enough to fuse hydrogen.

The objects falling under that definition can then be subdivided in three main categories. First, the classical planets, bodies orbiting one or more stars. Second, moons, objects orbiting something other than a star. Third, nomads, objects moving freely in interstellar or intergalactic space. Only after that can you get into the finer subcategories, such as gas giants, rocky planet, carbon planet, dwarf planet, etc.

Under that scheme, objects not normally considered planets are recognized as such. The Moon is a planet, so are Io, Europa, Ganymede, Calisto, Titan, Tethys, Dione, Rhea, Iapetus, Ariel, Umbriel, Titania, Oberon, Triton and Charon. Granted, these 16 objects are normally considered mere moons. However, some of them are larger than Mercury and many would be called planets if they orbited the Sun directly. Furthermore, the type of celestial body an object orbits has little to do with its intrinsic structure and composition, which is the only thing that should be considered when drafting a definition. I mean, the definitions of an insect, a mammal or a star make no appeal to the specific environments such entities exist in, or their influence over those environments, so why should the definition of a planet be any different?

Posted by Robert Shaw (Robert_shaw) on the 'Original Series: Season Two: The Web Planet' board

There are sound scientific reasons why we don't get giant insects here, which should also apply on alien worlds.

And Emily's response

WHAT!

There are two main reasons.

First, insects have a rigid exoskeleton, which means they have to molt in order to grow. In and of itself that would not be an obstacle to becoming big, but right after a molt, the new exoskeleton is soft and pliable, which would make it difficult for a large creature to support itself in a way that would avoid said skeleton from hardening in a permanently bent and distorded shape. Crustaceans have the same problem, but living in water helps them cope with it and many species can grow to considerable sizes for that reason.

A second and more significant reason is the way insects breathe. They do not have lungs, instead they have a network of tubes connected to the outside through a serie of openings along their abdomens and branching out into even smaller tubes carrying air directly to every part of their bodies. However, fluid mechanics impose an intrinsic limit to how far air can be made to travel through such a system, so an insect's body cannot become so big that its innermost parts are beyond the range of that process. There were times in the prehistoric past when the atmosphere had more oxygen than it does today, which would make that method of breathing more efficient. Indeed, there are fossils of giant insects, such as dragonflies with a 60 cm wingspan, or a 45 cm long cockroach, from those times.

Of course, insect like creatures evolved on other planets would not necessarily breathe in this manner, and size limits would not be as stringent for them as the are for our earthly ones.

This is not really Who related, although it DOES involve everybody's favorite egg . There is a total eclipse of the Moon occuring tonight. If anyone is interested in having a look, the link will tell you if the eclipse is visible where you live and when it occurs if it is.

http://www.timeanddate.com/eclipse/lunar/2015-september-28

Pah.

MY favourite egg is the Young Blon one.

My favorite egg is hard boiled.

Mmm... space chicken.

Can see which way YOU'D'VE voted, Kate.

And after the lovely chicken laid us a new moon and everything...

Life on Earth began 300m years earlier than we thought

Does this affect City of Death?

An extra 300 million years won't make much of a difference at this point.

But *hastily checks Reference Guide* if they only went back 400m years to the origins of life, then -

- ah. 4.1 billion years, eh. OK, when you're BILLIONS of years out, I suppose the odd 300m doesn't make much odds.

Another fine example of a science advisor needing replacement. When that episode was made it was already known that life had appeared on Earth MUCH earlier than 400 millions years ago.

Why this curious belief that Doctor Who has a science advisor? It's been fifty years since they bothered with one and he came up with the plot of 'The Wheel in Space'.

It's the BBC, who has a long tradition of very well done documentaries. It's a show with a lot of science into it. I just assumed they must have some way of checking scientific facts at some level. Although, now that you mention it, it WOULD explain a great many things.

We're talking about a show where a guy flies around time and space in an old British Police Box.

I think the ship has long since sailed on actual science here folks.

---
I just assumed they must have some way of checking scientific facts at some level.
---
Beyond a quick look on Wikipedia, probably not much...

I think the ship has long since sailed on actual science here folks.

And yet somehow we STILL manage to be outraged by the likes of Kill the Moon...

Beyond a quick look on Wikipedia, probably not much...

Yeah, they probably couldn't have done THAT in '79...

Yeah, they probably couldn't have done THAT in '79...

No, but I am told there was something called 'Encyclopedia Britannica' back then.

It is apparently the case that the old series production office was an on-again off-again subscriber to 'New Scientist', but I can't imagine any of the new series team stretching much further than 'Grazia'.

From 'Tomb of the Cybermen', Emily: That makes sense, except that isn't our galaxy orbited by lots of other galaxies, how do we know the dim stars don't come from one of THEM instead of Andromeda?

Most of them are in completely the wrong direction. For the ones that are in the right direction, there are various ways of measuring their distance and velocity. If they're not roughly 2.5 million light years away, and moving at the same speed as the rest of the stars in Andromeda, a radial velocity of roughly 300 km/s, in the same direction, they're not in that galaxy.

Also, while we can see the Andromeda galaxy with the naked eye, we can't see individual normal stars: they're too close together. It just looks like a roughly circular patch of white mist.

Ah, thanks.

Of course MY chances of spotting ANYTHING more than a few feet away with the naked eye are somewhat limited, I'm pretty short-sighted.

Dinosaurs were in decline for 50 million years pre-asteroid

That's one HELL of a slow decline.

Still, it might help explain why Whitaker's dinosaurs just generally stood around looking quite pathetic and...plasticine-y.

And this partially lets dear old Adders off the hook vis-a-vis his accidental act of dinosaur-genocide. Not that he's in a position to appreciate this.

Comet has life's building blocks

Which bit of 'The amniotic fluid from which ALL!!!! life on Earth will spring, where the amino acids fuse to form minute cells. Cells which eventually evolve into vegetable and animal life. You, Duggan' does this stupid Rosetta Comet JUST NOT GET?

Well, those amino acids had to come from somewhere.

Ah! Well, that's OK then.

The Doc gave me the impression they were home-grown but I certainly don't want to imply that a SINGLE SACRED LINE of City of Death should be interfered with to clarify the comet situation.

Anyone else embarrassed to read a headline like Asteroid wiped out nearly all mammals as well as dinosaurs and find themselves automatically thinking 'Typical ••••••• Adric'?

Actually no, it wasn't his fault and he did his best to stop it from happening.

It totally WAS his fault! If he hadn't done his best to stop it from happening, the freighter would have crashed into twenty-fifth-or-whatever-it-was-century Earth - thus sparing several galaxies from being conquered by Great and Bountiful Empires - and the poor old dinosaurs (AND MAMMALS) would have been JUST FINE.

Naked mole rats survive without oxygen

Any chance THIS was the sort of thing the Doc was using to survive oxygen-deprivation on numerous occasions? And hypnotised Sarah into doing too, in Terror of the Zygons?

That's possible in the case of Timelords, who obviously have several adaptations we lack, but it would take more than mere hypnosis to trigger such a drastic metabolic change in a human.

Huh. So scientists think time-travel is possible...IF they ever manage to discover magical exotic matter that can bend space-time in impossible ways. I wouldn't have bothered to comment on this piece of inanity if the scientists hadn't named their paper after the TARDIS.

If a message from aliens could destroy us, why haven't the millions of aliens who've invaded Earth tried that particular method...?

I suppose the closest they've ever come is the Blathereen handing Sarah Jane a pot plant...

No fun that way, I guess.

But how many aliens find invading us FUN anyway (I mean, BEFORE that meddling Doctor turns up). The Master, obviously, and the Slitheen, and the Sontarans once they stopped being so po-faced about it and started jumping around chanting 'Sontar-HA!' but the REST of 'em...?

The point of invasion is not JUST to destroy us, it's to then occupy the planet, establish military bases, loot our resources, enslave the survivors, etc., etc. Invading in person is a much better strategy than sending a killer message.

I don't know why Hollywood in the sixties thought alien women would look like Raquel Welsh-type sex bombs eager to learn this human thing you call love...

NASA names constellation after the TARDIS - bless!

You cannot take the science out of science-fiction

Doctor Who, a program about spaceships and laser guns, robots and domed cities in the far future, is the very definition of a science-fiction television show. But science-fiction television has a long history of being very bad at science -- stand up and take a bow, Star Trek genetics. Here is the first look in a series at (Very) Bad Science in Doctor Who.

Exhibit A: DNA Bombs

"Micro-implants which code to your DNA. On detonation, they disrupt the foundation of your genetic code, melting your DNA. Fast and nasty, and outlawed in every civilised galaxy." -- The Doctor, The Woman Who Fell to Earth

Except they're not -- fast, that is.

The main role of DNA is long-term storage of information. The key term there is "long-term". Our DNA is vital to us when we're growing; as everyone knows, the DNA is the blueprint that describes what we're going to be like, whether we'll be blonde or ginger, whether we'll have sideburns or Jon Pertwee's nose. When you stop growing, your DNA's job is done. You already have your full complement of legs, you don't need instructions on how to grow a new one.

Of course, DNA is still needed. Our bodies are constantly growing new cells to replace old ones -- approximately every seven years, every cell in your body is replaced by a new copy. (So the version of you that is watching series 11 is entirely different from the you that watched David Tennant's first story.) DNA is also used to code for proteins, some of which are used in metabolism. When you eat, sleep, breathe, your proteins are working merrily away generating energy and capturing oxygen. Your proteins produce antibodies that keep your immune system running. You get the picture: proteins are important, and you always need new proteins.

So assuming a DNA bomb goes off in your collarbone and carries some kind of payload through your bloodstream. Suddenly you can't create new proteins: but the old proteins are still there. You wouldn't notice any difference straight away. It's only as time went on that your body would start to break down. Nasty indeed. But hardly too fast when you have a Doctor on hand!

And where did you plunder this from, Natalie?

Once again, cite your source please.

Have to admit, Judi, I’m a bit suspicious myself, may have to just delete anything like this in future rather than give it the benefit of the doubt.

it's a piece for a local fanzine. I belong to a local fan group. It's not on google cause it's a dead tree fanzine. I spent ages typing it out and trying to make clear it was an article not me.

Just put the name of the original author, Natalie, and you'll be fine.

When it comes to both Missy and Thirteen, the show has been unwilling to address the problems of gender dysphoria.

For example in the real world, If a girl-to-boy trans person DOESN'T have gender affirming reconstructive surgery, there is a high chance of happening to them what happened to Brandon Teena when some good ole' boy hicka found out Brandon still had v-ulva, v-agina etc - they raped and murdered him.

If they DO have reconstructive surgery, they may still not being able to feel a "real" man and may even take their own life, as David Reimer did. (he was forcibly surgically re-assigned into "Brenda" as a baby in a monstrous "is it nature or is it nurture?" gender experiment).

When it comes to both Missy and Thirteen, the show has been unwilling to address the problems of gender dysphoria.

That's because they didn't HAVE any problems.

Why should they have any problems?

They both got a gender-upgrade and neither needed surgery. In fact, it sounds as if Missy was even spared any regeneration-trauma ('I just woke up one day even more fascinating than usual' - Diary of River Song Season Five).

This was done by regeneration. No surgery was needed in either case.

Of course, one could ask why we never saw this happen on Classic Who. I'm gonna stick with my default idea, that the Time War changed something.

Of course, one could ask why we never saw this happen on Classic Who.

We had Eldrad ask the Doctor WTF was his PROBLEM, that will do for me.

I'm gonna stick with my default idea, that the Time War changed something.

The Corsair was gender-swapping long before the Time War.

We had Eldrad ask the Doctor WTF was his PROBLEM, that will do for me.

We should have got a woman as the fifth Doctor!

(some might say, we did...)

I s'pose he had that combination of weakness and irritability that some may associate with PMS-prone females, but I certainly wouldn't.

The Corsair was gender-swapping long before the Time War.

Huh??

DOCTOR in The Doctor's Wife: The mark of the Corsair. Fantastic bloke. He had that snake as a tattoo in every regeneration. Didn't feel like himself unless he had the tattoo. Or herself, a couple of times. Oooh, she was a bad girl.

As the Doctor believed the Corsair had died in the Time War, s/he must have gender-upgraded a few times pre-New Who.

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quote:

I'd like to see which Who story inspired someone to believe ethics get in the way of science... "Aren't you forgetting, Professor, that in both science and morality the end doesn't justify the means"seems a fairly stable constant from Who's inception to the present.

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Here is a fun discussion of the various types of parallel universes that could exist.

This should have said "various types of multiverses", but whatever.

potate-o, potat-o

OK, turns out SJA: Vault of Secrets and the Dreamland cartoon and suchlike's we've-got-crashed-alien-spaceships stuff was actually...true...

Wasn't the lunar rover put together on the moon? Proof! Proof of a vehicle not made on Earth.

*rolls eyes*

Tim Pool did a nice, if long, analysis of this.

Wasn't the lunar rover put together on the moon?

Nope, it was folded up in it's storage compartment and all they did was take it out and let it unfold itself.

Ah, okay.

We could get to the Moon in 1969, but not in 2020.

According to Power Of The Daleks, in the Whoniverse, Earth has a colony in another solar system by 2020.

Unlike the Whoniverse, we've really dropped the ball here.

Of course, we don't have the Silence aliens whispering in our ears to get our lazy butts off this rock and into space.

Of course, we don't have the Silence aliens whispering in our ears to get our lazy butts off this rock and into space.

And exactly how could you be sure of that?