Weight of light, travelling at speed of..... light?

Question

If it is impossible to travel at the speed of light because the mass of matter travelling at this speed would become infinite... how come we don't feel the 'weight of light' when light itself is travelling at this speed?

....OR DO WE?

...OR did i get the theory wrong because is it energy required becomes infinite, yet the mass of matter remains unchanged regardless of whether travelling at speed of light?

If so forget my question. If not....

Does the mass of matter only become infinite when accelerated to the speed of light, or will the mass of matter always be infinite at speed of light regardless if it is accelerated to the speed of light or simply travelling at the speed of light to begin with - assuming that light itself does not accelerate to travel at it's constant?

Hmmm I hope i make sense. I'll edit my question if some people find it a bit weird.

Answer 1

Think of it as the mass of something increasing proportionally to it's rest mass and how close it is to the speed of light.  And going the speed of light, you are infinitely close, so you multiply your mass by infinity.

But, a photon has no mass.  And infinity times zero is still zero.

-- In response to your additional details

Where did you read that? I've never heard that.  Every book I've ever read on it, and the wikipedia article, has said that it's massless.

http://en.wikipedia.org/wiki/Photon

Answer 2

as i have read mass can turn to energy and visa versa.

so in the speed of light mass is in the shape of energy(photons).

but i`m not sure .

Answer 3

Light has mass though very very little. A curio is a 4 wheel paddle suspended in an evacuated tube. Light striking on one edge will cause the paddle to spin.

Answer 4

Light is composed of massless particles called photons. Hence, they travel at the speed of light.

EDIT: No, no, and no to the users suggesting photons have mass. They don't, and that's a matter of fact, not theory. Everything we know in physics would break down if photons had mass.

As for the specific suggestion that the mass is on the order of a nanogram, this isn't even reasonable. The rest mass of an electron (a very light particle) is on the order of a thousandth of a yoctogram, or 10^-27 grams. A nanogram is much larger, at 10^-9 grams. There are a billion billion nanograms in a yoctogram. If photons had mass, they would certainly not weigh a nanogram.

Infinity times any number is infinity, not "a large number." It doesn't make a difference what number you multiply by infinity; infinity is infinitely larger than any number you can name.

As regards phred's comment, the Crookes radiometer does not spin because light is made of massive particles colliding with the vanes. The vanes of the radiometer turn because one side (painted a darker color) absorbs more light than, and is heated more than, the other. This heat differential induces currents in the surrounding air, generating a slight pressure on one side of the vanes. This causes the radiometer to turn.