How DOES absolute zero slow down light?

Magnetic · Post by **Magnetic** » 2005-12-05 01:33pm

I saw a post (another site) that said that absolute zero slows down light. How so?

Post by **Darth Wong** » 2005-12-05 01:34pm

They're grossly distorting the fact that light slows down when it passes through materials (that's how diffraction works), and that it really slows down when it passes through certain very very cold exotic materials.

Magnetic · Post by **Magnetic** » 2005-12-05 02:02pm

One guy actually said that "absolute zero slows down the speed of light to a mere 60 mph."

Admiral Valdemar · Post by **Admiral Valdemar** » 2005-12-05 02:23pm

Source? If he doesn't quote a journal like Nature or something from the Royal Society, forget it. We have slowed light via special materials to barely a few metres a second, but that had nothing to do with absolute zero and everything to do with the make-up of the medium being passed through.

Post by **Darth Wong** » 2005-12-05 02:42pm

What do you want to bet that it's a fundie board where this conversation took place? Fundies are notorious for reading bits of headlines about science stories and thinking that they now understand the whole concept.

drachefly · Post by **drachefly** » 2005-12-05 03:00pm

It could be that for the purposes of the experiment, the effective temperature of the apparatus was essentially absolute zero...

much like a million-kelvins-hot white dwarf is effectively absolute zero for purposes of calculating many important quantities.

Magnetic · Post by **Magnetic** » 2005-12-05 03:37pm

Darth Wong wrote:What do you want to bet that it's a fundie board where this conversation took place? Fundies are notorious for reading bits of headlines about science stories and thinking that they now understand the whole concept.

A fundie board? . . . . . . . . . Whatever gave you THAT idea?!?!

Magnetic · Post by **Magnetic** » 2005-12-05 03:39pm

but yes, it is a fundie board, but it is a topic centering around the speed of light. Just another one of those "the speed of light isn't constant, so God could have increased the speed of light, . . . ala. making the universe look older than it is . . . junk".

Admiral Valdemar · Post by **Admiral Valdemar** » 2005-12-05 03:44pm

Sounds like Setterfield (or his bitch of a wife) won't stop posting their bullshit around the web.

Dooey Jo · Post by **Dooey Jo** » 2005-12-05 03:58pm

It's possible to slow down light a lot, if you pass it through a Bose-Einstein condensate and makes creative use of lasers to affect the atoms in the right ways (I think the further details aren't necessary for this thread, but if anyone wants to, feel free to expand).

However, the light still moves at the speed of light (surprise!) between the atoms, it's just that they (the atoms) are taking a really long time re-emitting them once absorbed. Therefore it appears as if the light moves really slow through the condensate, but the actual speed of the individual photons is still constant; 299 792 458 m/s.

There is no way to make an atom emit light to make it move faster, because that would mean re-emitting it before it was absorbed, which would be indeed strange. Your fundies are, as usual, ignorant...

Dooey Jo · Post by **Dooey Jo** » 2005-12-05 04:16pm

I forgot...

Magnetic wrote:One guy actually said that "absolute zero slows down the speed of light to a mere 60 mph."

Ask him if that's a result from an experiment where the made light pass through absolute zero (what at absolute zero, one could ask. Glass? Vacuum?). When he says "yes" laugh at him for being stupid, as it's not possible to achieve absolute zero, and he's obviously talking out of his ass.

And why would absolute zero (again, just absolute zero in general, or what?) slow down light to 60 mph? Why not zero?

Wyrm · Post by **Wyrm** » 2005-12-05 07:44pm

Magnetic wrote:but yes, it is a fundie board, but it is a topic centering around the speed of light. Just another one of those "the speed of light isn't constant, so God could have increased the speed of light, . . . ala. making the universe look older than it is . . . junk".

Observationally wrong. Many millisecond pulsars are in a region where a speedup of old light would be required for us to observe them at all, if the universe is as young as they claim. The thing is that even at its gentlest rate of slowdown, a changing speed of light over 6000 years of the magnitude required would induce noticable slowdown in the pulse rate we recieve from these pulsars, which we just don't see.

Some references on c-decay:

http://www.talkorigins.org/faqs/hovind/howgood-add.html
http://www.talkorigins.org/faqs/c-decay.html

Talk.origins: The anti-fundies!

Plushie · Post by **Plushie** » 2005-12-05 09:23pm

I'm 99% sure they have succeeded in "freezing" light in place. I'll see if I can find the article.

Plushie · Post by **Plushie** » 2005-12-05 09:25pm

Sorry to double post, I didn't think I'd find it this quickly:

http://www.theregister.co.uk/2005/04/12/frozen_light/

Lord Zentei · Post by **Lord Zentei** » 2005-12-06 01:01am

What I fail to get is what fucking difference these morons think any of this will make. When scientists say that the speed of light is a constant, they refer to the speed of light in a vacuum, not under any situation. Are they genuinely this dumb or are they just being sophists?

Post by **NecronLord** » 2005-12-06 03:57am

Lord Zentei wrote:What I fail to get is what fucking difference these morons think any of this will make. When scientists say that the speed of light is a constant, they refer to the speed of light in a vacuum, not under any situation. Are they genuinely this dumb or are they just being sophists?

In space there are G-D particles that speed the light up, making the light go faster, making things billions of parsecs away visible, despite the 6000 year age of the universe. They don't react well to testing by the faithless though, and thus, scientists are only able to measure the slower speed of light through non G-D space. Rest assured, that Faith Scientists of the Christian Science Institutes have measured the faster speed of light...

Pezzoni · Post by **Pezzoni** » 2005-12-08 04:52pm

Wouldn't the fact that it is impossible to reach absolute zero be relevant?

wilfulton · Post by **wilfulton** » 2005-12-08 11:41pm

Pezzoni wrote:Wouldn't the fact that it is impossible to reach absolute zero be relevant?

When arguing with a screaming zealot, relevance is only what they say it is. No matter, theoretically, at absolute zero, all molecular motion ceases, and I was led to believe in my high school science classes that it would cause all atomic motion (the electron orbitals around the atoms themselves) to stop, and that at that point, physical matter simply winks out of existance. I don't know that I believe that, and after a year of chemistry, I found that what passes for science in high school is largely bullshit.