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Considering the amount of energy necessary to accelerate a particle to the speed of light (ie; half the energy in the entire universe) how could we have so many things already going the speed of light?

Maybe there should be only two or three things (objects or particles etc.) in the universe already going that fast. Just a few photons for example, in the whole universe.

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half the energy in the entire universe No, it's MUCH bigger, infinite in fact. – jinawee Jan 16 '14 at 16:55

1 Answer 1

The amount of energy needed to accelerate any particle with non-zero rest mass is indeed infinite. But that does not stop mass-less particles (like photon for light) to travel ALWAYS at the speed of light. Also many non-zero mass particles (neutrinos) can be accelerated to ALMOST (say 99.9999%) speed of light without infinite energy. The energy requirement is exponential so its not the same energy required for a change of say 30% of C to 31% of C and 98% of C to 99% of C.

For the galaxies moving apart from each other in almost or even greater than the speed of light is not a problem as Galaxies are not actually moving but the universe (the space) is expanding. And relativity laws does not prevent this expansion rate to be greater than the speed of light.

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Good answer, but note that this is an incorrect use of the term 'exponential', which is technical and reserved for quantities whose growth is proportional to the quantity itself. – Emilio Pisanty Jan 16 '14 at 16:53

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