On 10/9/2014 7:04 PM, rickman wrote:
On 10/9/2014 5:14 PM, Jerry Stuckle wrote:
On 10/9/2014 1:04 PM, rickman wrote:

The only mass a photon has is that which is equivalent to its energy, E
= mc^2.


I understand it has no rest math. But where does the mass come from?
There has to be mass to exert pressure. Does the mass just appear from
nowhere? I doubt it...

When a proton is accelerated and the mass quadruples, where does that
extra mass come from?


It comes from the energy used in the acceleration of the proton, based
on Einstein's equations. Mass and energy are just different
manifestations of the same thing.

But by definition, anything moving at the speed of light must be
massless, because it takes an infinite amount of energy to accelerate
even an electron to that speed. Which means a photon cannot have mass.

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