Slowing down light

[nicks90]

An extremely interesting article in the Harvard Gazette

http://news.harvard.edu/gazette/2001/01.24/01-stoplight.html

slowing light down to a stop and then restarting it, very bizaare concept!

[Algieba]

Wow that is really quite interesting and a bizarre concept indeed!

[just_ed]

If the speed of light is not constant as assumed, what does that do to the expanding universe theory ,which comes to that conclusion using the red shift of light?
 

[Superdavo]

If the speed of light is not constant as assumed, what does that do to the expanding universe theory ,which comes to that conclusion using the red shift of light?

I think the speed of light is still constant - but they just slow it down by making it bounce around, which slows down the rate it passes through the material. It's similar to how the drift velocity of an electron through a circuit can be so slow when it moves at near the speed of light - because it is the net result of many bounces of said light. 

David

[Physicist13]

Its only the speed of light in vacuum which is constant and defined. In all other cases it can have any value below this number.

P

[Ronnie67]

Interesting read, that's all I am going to say for the moment, it would be more interesting if she could freeze or actually stop light travelling. One that would be something to talk about

[davkt]

Yep the speed of light in vacuum, but in anything else it is less. In fact your telescopes and binoculars rely on this fact to bring light to a focus at your eye, refraction is caused when light goes from one medium (air) to another where it has a different speed (the glass of the objective or eye peice).

[richyj8]

What about the speed of light, and of everything during the alleged cosmic inflation period. I've read it was greater, much greater by many magnitudes than 186,000 miles per second.

[nicks90]

What about the speed of light, and of everything during the alleged cosmic inflation period. I've read it was greater, much greater by many magnitudes than 186,000 miles per second.

indeed,

however there is still a lot of debate as to what form 'everything' took during this inflationary period - therefore there may not have been any 'light' or matter that we would recognise - and so it may not have broken any of our known laws of particle physics because it was completely different. 

[JulianO]

What about the speed of light, and of everything during the alleged cosmic inflation period. I've read it was greater, much greater by many magnitudes than 186,000 miles per second.

As far as we know, it stayed the same speed, its just space was stretched out "under its feet" very quickly. Inflation is partly brought about as a theory to stop us having to increase the speed of light, and still end up with the universe as it is.

[Alien 13]

The problem i have allways had with the speed of light and the early universe is that "speed" is a function of distance and time  both of which where doing strange things.

Alan

[michaelmorris]

The constant © is the speed of light in a vacuum through space.  By the 'standard model'  the further you get away from us, the faster things are receding from us. This isn't because the objects are moving faster is just that the space is expanding faster.  As (as far as we know) there is no limit to the speed of space, the furthest away bits of the universe are expanding away from us faster than the speed of light and therefore the light from these areas will never reach us. Hence the concept of the 'observable universe'.

This gives a neat explanation of the concept.

http://www.einstein-online.info/elementary/cosmology/expansion

http://www.dnatube.com/video/29042/The-incredible-expanding-universe-explained

Inflation was the expansion of space, not the movement of energy or matter within space and hence would not have been bound by the speed of light

[Vega2]

Who said the speed of light is a constant in a vacuum? Well as a physicist myself - that's what I always thought too. However some clever folks have demonstrated that 'structured' photons travel slower in a vacuum .. http://www.sciencedaily.com/releases/2015/01/150123144158.htm