Mass and Energy

[ZenitYerkes]

I was wondering...

What's the difference between matter and energy? I know they are convertible thanks to Einstein's equation, but is the only difference between them a coefficient, an addition?

What makes matter different from energy?

Sorry if it's a stupid question; but I just realized that... how if they were made out of the same thing? Specially on a subatomic level.

[txen]

At one level you can think of matter as condensed energy. However there is one big difference. At the quantum mechanics level you have two major categories that go by the name of fermions and bosons. Fermions are what we call matter and have a quantized spin that is 1/2 in "natural units." These are the electrons, protons and neutrons that make up everything. The Bosons have interger spins and are force carriers. The one we all know are photons that make up light, radiated heat, radio, X-rays, etc.

If you go back to just a split second after the big bang everything was in thermodynamic equilbrium. Matter and energy were more or less the same. Particles were created from energy and energy from particles. This back and forth only lasted for as long as the universe was hot enough. After about a second of expansion the temperature was cool enough that existing matter froze out and that is the matter we are left with today. The energy was no longer concentrated enough to make the particles.

From a philosophical perspective I have to go with the anthropomorphic principle. The universe is the way it is because we are here to observe it. If it were much different we wouldn't be here.