# The Naked Scientists Forum

### Author Topic: What does E=mc^2 actually mean?  (Read 1183 times)

#### thedoc

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##### What does E=mc^2 actually mean?
« on: 17/07/2012 16:30:01 »

I have a question that might be to difficult to answer easily.

I have just begun to understand the theory of relativity and  I would like to see if I have it right.  ENERGY EQUALS MASS TIMES THE SPEED OF LIGHT SQUARED.  As a formula, energy, mass, and the speed of light values depend on each other, right?  If I understand it right we can never go as fast as the speed of light because the speed is a constant, that leaves energy and mass, these are variables.

As you use energy you can't supply more mass to make the formula work.  So isn't light energy, which means for it to maintain its constant speed it must need to replace mass.  I am either way off base or just misunderstanding the principals involved.  I just have a curiosity to try to understand this, if you think you can help me please do, my curiosity is peaked.

Thank you.

Darryl

What do you think?
« Last Edit: 17/07/2012 16:30:01 by _system »

#### yor_on

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##### Re: What does E=mc^2 actually mean?
« Reply #1 on: 18/07/2012 00:53:07 »
Are you thinking that a 'photon' burns energy to maintain its motion, and as it does it need to replenish it?
I'm not sure what you mean there?

A photon is 'mass less' meaning it's not matter, it's radiation. The energy it has is equivalent to a mass but it is still radiation. Then you have the idea of 'timelessness' meaning that photons does not decay, only annihilate in interactions with matter.

#### yor_on

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##### Re: What does E=mc^2 actually mean?
« Reply #2 on: 18/07/2012 01:01:03 »
A photon always takes the 'shortest path' or least energy expedient if one like. It never argues instead choosing the path following the 'warping/distortions' gravity impose on 'space', just as matter does. Both matter, as planets suns etc, and radiation use 'uniform motion' to 'move' which is a mode expending no energy. A photon does not accelerate, either it is 'there' interacting or, it will be unmeasurable to us.

#### simplified

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##### Re: What does E=mc^2 actually mean?
« Reply #3 on: 18/07/2012 09:29:27 »
That is problem for me.Lost mass is kinetic energy.But fastly escaping traveler(concerning radiator) does not  see such energy.He(she) feels a loss of gravitation,but can't recieve this quantity of energy.
« Last Edit: 18/07/2012 16:36:33 by simplified »

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##### Re: What does E=mc^2 actually mean?
« Reply #3 on: 18/07/2012 09:29:27 »