Crazy Physics Question

[Yoga Face]

Scientists can slow the speed of light

Light passing through super-cooled rubidium has been observed to travel as slow as 60 KPH !

So what happens to the light behind the slowed down light ?

It seems to me it has no where to go because the slowed down light is blocking its' path yet the light behind the slowed light has not slowed down so where does it go ?




As well, light in nuclear reactors goes faster than the "speed of light"


Source is The Lexicon - York University student paper vol 37 issue 4 Science and Related Quirks column

yorku.ca/lexicon

 

[blackrock13]

My guess is 42.

 

[Perry Mason]

And I say 4:20!

Perry

 

[fuji]

If light slows down in that material, then the photons "behind" will slow down at the same rate as the photons "ahead" in the material. Think of it as a traffic jam where everybody slows down at the same rate as they pass through it.

 

[basketcase]

Nothing happens to it. Light travels at different speeds in different mediums. As soon as the light behind enters the new substance, it also changes it's speed. Essentially the light waves/photons just travel closer together.

 

[opieshuffle]

Best Analogy: Imagine a line of people running at full speed on asphalt at the same speed. Then you hit waist high water. You're running at the same intensity (energy), but the medium is slowing you down...you all slow. You exit the water back to asphalt and are running full speed again.

 

[GPIDEAL]

Scientists can slow the speed of light !

Light passing through super-cooled rubidium has been observed to travel as slow as 60 KPH !

So what happens to the light behind the slowed down light ?

It seems to me it has no where to go because the slowed down light is blocking its' path yet the light behind the slowed light has not slowed down so where does it go ?




As well, light in nuclear reactors goes faster than the "speed of light"


Source is The Lexicon - York University student paper vol 37 issue 4 Science and Related Quirks column

yorku.ca/lexicon

Well IMHO, when light hits a wall or solid object, it lights up the spot on the wall. It requires a steady stream of photons to keep that spot lit. It literally stops at the wall and dissipates in energy, only to be replenished by the continual stream of photons.

In the case of light slowing down thru super-cooled rubidium (I've never heard of that element), I would imagine that part of the photonic energy dissipates or is expended at the interface between the faster medium (say air) and the slower medium (rubidium).

 

[fuji]

And I say 4:20!

Perry

*Cough*

 

[AdmiralG]

Fuji and Basketcase both have the correct analogy for what's going on with the light for the first (and second) of your questions.

As for the third question, the effect produces Cherenkov radiation, often associated with the blue glow you see accociated with nuclear fuel in storage pools.
More info here: http://en.wikipedia.org/wiki/Cherenkov_radiation

 

[GPIDEAL]

Best Analogy: Imagine a line of people running at full speed on asphalt at the same speed. Then you hit waist high water. You're running at the same intensity (energy), but the medium is slowing you down...you all slow. You exit the water back to asphalt and are running full speed again.

Yes, but if you had a marathon of people running at full speed before they hit water, won't the people running behind crash into the slower runners at the water-contact point?

In my lay explanation, I mentioned that part of the light must dissipate or reflect or get 'used up' at the interface between the faster and slower mediums.

 

[GPIDEAL]

Fuji and Basketcase both have the correct analogy for what's going on with the light for the first (and second) of your questions.

As for the third question, the effect produces Cherenkov radiation, often associated with the blue glow you see accociated with nuclear fuel in storage pools.
More info here: http://en.wikipedia.org/wiki/Cherenkov_radiation

Ahh okay, compression! But isn't that blue glow a dissipation of energy or loss of energy from the faster photons being forced to slow down as I've sort of alluded to?

 

[basketcase]

Yes, but if you had a marathon of people running at full speed before they hit water, won't the people running behind crash into the slower runners at the water-contact point?
...

Except with people there is a finite space that each person takes up. For light that isn't the case (at least at any practical distance). All that happens is the wavelength gets shorter. It would be equivalent for that marathon of people starting out a couple km from each other and in the when they get to the slow section they end up 100m from each other. In no way would they effect each other and would return to their original spacing when they come out the other side.

(It's the exact same thing when light enters water, just on a more extreme scale)

 

[GPIDEAL]

Except with people there is a finite space that each person takes up. For light that isn't the case (at least at any practical distance). All that happens is the wavelength gets shorter. It would be equivalent for that marathon of people starting out a couple km from each other and in the when they get to the slow section they end up 100m from each other. In no way would they effect each other and would return to their original spacing when they come out the other side.

(It's the exact same thing when light enters water, just on a more extreme scale)

I got the compression analogy but thanks again!

Terb is educational too!

 

[Yoga Face]

Nothing happens to it. Light travels at different speeds in different mediums. As soon as the light behind enters the new substance, it also changes it's speed. Essentially the light waves/photons just travel closer together.

Interesting conjecture - or do you consider your statement to be scientifically accurate ?

It seems to me that there is a limit to how packed the light waves can become as the source of the light can last billions of years


But then again light can behave like a particle or a wave or both at the same time

Trying to imagine what light is is beyond our ability to grasp I suspect

 

[Yoga Face]

If light slows down in that material, then the photons "behind" will slow down at the same rate as the photons "ahead" in the material. Think of it as a traffic jam where everybody slows down at the same rate as they pass through it.

So the light slows down all the way to the source !

This could be a sun billions of light years away

This does not seem right

 

[basketcase]

Interesting conjecture - or do you consider your statement to be scientifically accurate ?

I think It's not my conjecture. If I recall correctly, it was a part of grade 12 physics class a couple decades ago and I have not heard any breakthroughs to counter it so I would consider it widely accepted as scientifically accurate.

It seems to me that there is a limit to how packed the light waves can become as the source of the light can last billions of years

There may be a feasible limit but we based on what we know, there doesn't seem to be. We do know the wavelength of gamma rays is in the range of 1,000,00 times smaller than visible light (a million times 'closer together'). With visible light at 60 kph, it would put the wavelength of the slowed light not too far off that of gamma rays.

The length of time the source lasts is irrelevant because each photon is just passing through the medium in question, not building up.

 

[basketcase]

So the light slows down all the way to the source !

This could be a sun billions of light years away

This does not seem right

It's not. The light travels a constant speed until it enters a new medium. The source has nothing to do with it from the moment the photon is generated.

 

[Ceiling Cat]

All right, you Einsteins, get back to work and pluck those chickens! What the fuck do you guys thing this is? This is not the Los Alamos National Laboratory for atomic research, and your not a bunch rocket scientist.

 

[blackrock13]

All right, you Einsteins, get back to work and pluck those chickens! What the fuck do you guys thing this is? This is not the Los Alamos National Laboratory for atomic research, and your not a bunch rocket scientist.

Yes Sir Mr Boss Man!

 

[Yoga Face]

The length of time the source lasts is irrelevant because each photon is just passing through the medium in question.

Thx Basketcase but it seems to me the time length of the source is highly relevant

If as the light is slowed down it becomes compacted then the longer the light shines the more compacted it becomes as more and more light enters than escapes


In the case of light entering the ocean for example the light diminishes as it transforms into heat

But in my example the light does not diminish for it exits the material in the same form it entered I would think