My dad was saying something the other day about the relationship between the speed of light and absolute zero. I am confident he didn’t have his facts right, but IIRC, there is some way in which they are related. Can the usual suspects enlighten me?
It should be noted that any kind of matter slows down light. Cherenkov radiation (when charged particles move faster through matter than photons) is a neat example of this.
I saw on www.livescience.com last year that scientists have actually made light go in reverse. I didnt understand the physics of it at all, hopefully someone can find this article, because i have not been able to find anything.
Nothing too fancy there. Once you get the trick of slowing light down to 38 mph or 15 mph or whatever, you just put the whole apparatus on a truck driving in the other direction at a faster speed.
c is the speed of light in a vacuum and is the maximum rate that light, or anything else, can have. Electro magnetic waves such as light travel slower in a medium such as glass or air or water.
I understand that, but it’s the relativistic aspects I don’t get - if we have light travelling at, say, 0.75c in water and I am travelling at 0.75c in the opposite direction towards it (ignoring for a moment that such velocity would be rather difficult for a physical object in water), do I observe the light as incoming at a greater velocity than c?
No. Light moving at .75c relative to water behaves the same way as anything else moving at .75c relative to water, and in no case will your velocity ever be greater than c relative to anything.
I often hear them compared because neither can be reached, only approached. You can’t ever accelerate to lightspeed, nor can you chill something to absolute zero.