[RoughDobermann]

I have a question. Is it not true that E=MC2 states that as an object with mass approaches the speed of light, its mass will increase to the point that it cannot accelerate further and never achieve "light speed"? If so, then how does light travel at the speed of light? Light has mass, doesn't it? If not, why is it effected by gravity?

Please forgive the question, but I have zero background in such matters. It just seems like a logical question...

[boris]

"I have a question. Is it not true that E=MC2 states that as an object with mass approaches the speed of light, its mass will increase to the point that it cannot accelerate further and never achieve "light speed"? If so, then how does light travel at the speed of light? Light has mass, doesn't it? If not, why is it effected by gravity?"

Photons have no "rest mass". They are essentially zero-mass. In fact, objects with zero mass must travel at light speed.

E=MC2 does not say you can't reach lightspeed.

The Lorentz equations are the operable ones. They predict that the mass of a body increases without limit as "C" is approached. In essence, the energy you are putting in to "push" the object to go faster just gets soaked up in its increasing mass, not in velocity.

Photons have no mass, but the do carry momentum.

The reasons that light is affected by gravity is that light always follows "space-time geodesics". Ordinarily, such geodesics are "straight lines". Near a large mass (like the Sun or a black hole) the geodesics of space-time are not "straight" but bent by the gravitation of the body. Therefore light departs from a "straight line" and travels in a curve. This is because--in effect--the warping caused by the mass causes a curved path to be the "shortest distance" for the light to travel.

--Boris

[TopQuark]

Is it not true that E=MC2 states that as an object with mass approaches the speed of light, its mass will increase to the point that it cannot accelerate further and never achieve "light speed"? If the mass of an object is not zero when it is at rest, then it increases and becomes infinite as the object's speed approaches c (this does not follow from the E=mc^2, incidentally).

If so, then how does light travel at the speed of light? The condition above does not hold: light has zero rest mass.

why is it effected by gravity? It is not affected by gravity directly: the space trough which it travels "changes" in the presence of gravity.