Question regarding Einstein's E=mc2 formula and light

am_karn | 08:51 Thu 22nd Dec 2005 | Science

6 Answers

Dear answerbank,
I would like to know if it is possible for 1 ray of light in air to catch up against another ray of light in vacuum that was released 1 second before the first ray of light and also, whether as according to to Einstein's formula E=mc2, does it show that 1 gram of Uranium have the same amount of energy as 1 gram of water.
Thankyou very much for your time.

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The second part of your question is a little bit of a trick one. Just like the ton of feathers vs the ton of lead, the key is that the mass of both is 1 gram. Since c^2 is a constant, the energy must be the same.

fo3nix

first part of question: probably not, as air can be approximated to a vacuum as it won't make that much of a difference to the speed of light.

gen2

Light travels slightly slower in air than in a vacuum so it could never catch up.

Been thinking about the first part. In 1 second the light rays are going to be 300,000km apart. Your unlikely to be able to create an experiment where the two rays have enough time and distance to catch up to each other.

I've done some quick calculations and I make it about half an hour. Fair amount of guess work and assumptions in there mind. In this time light can travel about four times the distance from the Earth to the Sun. (~4AU).

Gef

CT did you miss gen2's answer?

Oops, got that the wrong way round there.

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