How Does Water Slow Down Light Without Violating Special Relativity?

[Jake]

Basic SR question here. But Einstein said that the Speed of light is an absolute constant. Why then do we hear of experiments of laser light and some kind of substance used to SLOW light down to some ridiculously slow speeds? And how water slows down light too. Isn't that "violating" SR? If the Speed of Light is constant, then how can SR mean anything when something as simple as water can slow down light?

I'm sure there's a perfect explanation, I just don't know it :)

 

[Jake]

Why do I always find the answer to my question AFTER I make a topic?



Found here

http://www.physlink.com/Education/AskExperts/ae509.cfm

 

[R0man]

Great question! The key to understanding this apparent contradiction is to remember that while the speed of light is an absolute constant in a vacuum, it can be affected by the medium through which it is traveling. In other words, the speed of light is not constant in all materials. This is known as the refractive index of a material, and it is a fundamental property of light.

In the case of laser light, the experiments you mentioned are typically done using substances such as glass or water, which have a higher refractive index than air. This means that light traveling through these materials will be slowed down, as it interacts with the atoms and molecules in the substance. This is not a violation of special relativity, as the speed of light in a vacuum is still the same and remains a constant in all reference frames.

As for water, it is a well-known fact that light travels slower in water than in air. This is due to the higher refractive index of water, as well as its density and other properties. Again, this does not contradict special relativity as the speed of light in a vacuum is still the same and remains the ultimate limit for the speed of anything in the universe.

In fact, the concept of the refractive index is actually incorporated into special relativity, as it is necessary for understanding the behavior of light in different materials and reference frames. So while it may seem counterintuitive that something as simple as water can slow down light, it is actually a fundamental aspect of how light behaves in our world.

I hope this helps clear up any confusion and shows that special relativity is still a valid and accurate theory, even in the face of seemingly contradictory observations.