Re: Mass of Light


"Billy Bob" <billy_bob_felder@xxxxxxxxx> wrote in message
news:1144411527.057084.291580@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I'm reading the theory of relativity, but I've a little problem:
Light travels with the speed of light, so its mass should be zero or
infinite. It couldn't have an endless mass and my teacher says that
light isn't really a wave but a kind of particle, so its mass couldn't
be zero..
What's the mass of light?

Billy Bob

Here's a way to understand it: the "rest mass" of light is zero. When light
isn't traveling somewhere it doesn't exist and therefore has no mass. The
mass you are talking about is due to the energy "contained" in the photon,
which always travels at the speed of light.

When a material object starts moving in a frame of reference, it appears to
gain more mass in that frame of reference, but only if there was mass there
in the first place.



.

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