Freezing Light creates paradoxes?

[browndn]

i read an article on bbc where they said scientists froze a photon for about 10-20 microseconds. Doesn't this contradict einstein's theory that photon has no mas because if you are able to stop a photon, then it should have some type of rest mass and if it has rest mass, then it can't possibly achieve the "speed of light". Please correct me if i am wrong. And also, if light can be slowed down to a speed of bullet, then how can you call light a constant and how can we rely on light to tell us distances in space since it can slowed down drastically.Sorry if it's a bit long.

 

 

Article: http://news.bbc.co.uk/2/hi/science/nature/3308109.stm

http://www.livescience.com/php/video/player.php?video_id=itm1005_freezinglight

[thedarkshade]

You can't bring a photon at rest!

 

And yes you are correct. Photons have no rest mass, because sending an object with rest mass at the speed of light requires infinite energy (you can work that out very simply), and infinity is something beyond practice I believe!

[Riogho]

It is the distance between A and B that they slowed light, the actual photon is always traveling at C.

 

You can shoot a photon through a big gunk of Einstein-Bose Condensate and it will get absorbed, and re-emitted multiple times, making it take longer to get through, but between those absorbtions and re-emissions it is always traveling at C.

[swansont]

You'll note that the scientists never say that the light was stopped — they say it was stored. It's the journalists who say that light was stopped. The trick here is that the information contained in the photon was reproduced; the coherence of the pulse of light was preserved.

[Riogho]

Could you explain that more, I'd really like to know what you mean by coherence of light being conserved.

[Klaynos]

Could you explain that more, I'd really like to know what you mean by coherence of light being conserved.

 

The photon before and the photon afterwards are indistinguishable from each other.

[Riogho]

Ah, big lingo for a known concept. Got ya.

[thedarkshade]

The photon before and the photon afterwards are indistinguishable from each other.

Strangely, this reminds me something like:

"What happens if you follow a photon at the speed of light?"

"Well, the photons runs away at the speed of light!"

 

It is indeed as you say Klay:D!

[swansont]

It's a little more subtle, though — AFAIK if you send in a pulse of coherent light (e.g. from a laser) you will get a coherent pulse out. So you've preserved the relative phase of the light. That's a little different than some other storage mechanisms that also rely on photon absorption. Atomic absorption and emission doesn't normally do this.

[Riogho]

Hmm... I'll read up on it then.