# Could this be true?

In an article which I had read last year about a couple of scientists slowing the speed of light to almost 38mph by reaching almost Absloute zero.

since the speed of light in a vacume is the maximum universal speed limit, would this mean that 38mph is the minimal universal speed limit?

if this Idea is wrong can someone please give reasons why it is wrong so I can understand and hopefuly learn from my mistakes

Oh incase anyone wants to read the article here is a link

http://www.news.harvard.edu/gazette/1999/02.18/light.html

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Well its wrong because I know about a million things that go slower than 38 mph, as to why its wrong I'm sure you will get better answers from someone else. But it's not just the super cold temperature that makes the light slow down by itself for starters.

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ZapperZ
Staff Emeritus
bayan said:
In an article which I had read last year about a couple of scientists slowing the speed of light to almost 38mph by reaching almost Absloute zero.

since the speed of light in a vacume is the maximum universal speed limit, would this mean that 38mph is the minimal universal speed limit?

if this Idea is wrong can someone please give reasons why it is wrong so I can understand and hopefuly learn from my mistakes

Oh incase anyone wants to read the article here is a link

http://www.news.harvard.edu/gazette/1999/02.18/light.html
You are several years too late. The same group headed by Lena Hau has managed to "halt" light completely, i.e. 0 m/s.[1] So there is no "minimal unversal speed limit", at least not from this.

Zz

[1] C. Liu et al., Nature v.409, p.490 (2001).

Would 38mph have been the 'maximum universal speed limit' in the ~0K conditions? For those of us who don't have access to journals, can you summarize the experiment?

ZapperZ
Staff Emeritus
whozum said:
Would 38mph have been the 'maximum universal speed limit' in the ~0K conditions? For those of us who don't have access to journals, can you summarize the experiment?

http://physicsweb.org/articles/world/14/9/8/1

Zz.

What happens when the light pulse slows down is that it is compressed by a factor of some ten million, leaving an almost negligible amount of energy in the pulse. (In free space the pulse contains 25 000 photons and, once compressed, it contains only 1/400 of a free-space photon.) When we turn the coupling laser off abruptly, the light pulse comes to a grinding halt, and the atoms within the localized pulse region are left in their superposition "dark states". In these states, the relative proportions of states 1 and 2 is a measure of the electric-field ratio between the light pulse and the coupling laser before turn off. In effect, we imprint a phase grating in the atom cloud as if we were recording a hologram.
I thought the photon was fundamental? How can there be 1/400th of a photon?

ZapperZ
Staff Emeritus
whozum said:
I thought the photon was fundamental? How can there be 1/400th of a photon?
It's 1/400th of 25,000 free-space photons!

Zz.

Am I misunderstanding or did they make a critical grammatical error?

seems like I am several years back :) hah. had not read about them being able to stop it.