is the velocity of light aconstant ?why??????????

Answer 1

That's a great question. There is an explanation in the following link, but the simple solution is this. Its a theory that helps us explain the physics of the world around us. So far, no one has been able to prove that the speed of light is not constant.

Answer 2

I posed a similar question on Yahoo Answers--Physics about a month ago (What if light is not the absolute constant that we have believed). Several answers stated that this was not possible. Below is a link to an article that states that the velocity of light may have changed at some time in the past.

http://www.newscientist.com/article/dn60...

But I have pondered this question for the better part of ten years. I have come to believe that c can change slightly (minutely) and that it is related to the change in the rate at which the universe is expanding.

Answer 3

It is usually considered a constant, but recent experiments have suggested that it might not be. It doesn't vary by much, but it may have varied slightly over the past 15 billion years. It's still uncertain if this is really what the data means, but at the moment we really don't know if it's a constant or not. Although for practical purposes, it is a constant for now.

Answer 4

Why -- we don't know.
But it follows from experiment.

It is a truly remarkable fact, though.
If you drive toward a car headed in the opposite direction, the other car seems to come with you with the sum of the two speeds.

But if you move toward a lightray, it always seems to have the same speed, no matter how fast you go.

This was such a troublesome fact that a new theory of physics was needed: relativity.

Answer 5

Well from what I know if you put it to an equation, the mass of light becomes Zero. Which means the balance becomes a constant. This also means that it will have the capability to seep through any permeable surface.

Answer 6

yes , as per the theories , velocity of light is constt.in vacuum,i.e.
30,00,00000m/s.