A question obout E=MC2.?

Question

I just finished watching a NOVA program titled E=MC2, the narrator stated that Einstein had discovered that mass and enegy is the same thing, in different forms. If this is entirely accurate, how do you account for gravity, energy has no gravity, to my knowledge, if it did, the incredible gravity of the singularity would have prevented its expasion. He also stated that the sun loses four million tons of mass each and every second, I know that this is incorrect, that may be the amount of mass that is used to convert hydogen into helium, every second, but only a small portion of this mass is lost in the process of fusion and converted into radiation. Is there something missing in the first statement?

Answer 1

Hello John and Eileen -

I think E=mc^2 is pretty well established at this point - not to claim that we understand it perfectly, but the equivalence of mass and energy has been demonstrated repeatedly since Einstein figured it out 100 years ago or so.

Energy probably creates no gravity worth mentioning. Mass creates what we think of as gravity by warping spacetime. It takes A LOT of mass to create a little gravity. As an example, the magnetic force needed to overcome the gravitational force of the entire earth can be created by moving a toy magnet over a small metal object. On the other hand, it takes only a very small amount of mass to create A LOT of energy, as seen in a fusion reaction. So if energy had gravity, we would not be able to see it very well. If the gravity of a mountain is insignificantly small, then the gravity of a photon must be sort of tough to even discuss.

Energy is certainly affected by gravity, just like mass is affected. The light from distant galaxies is bent and warped as it passes other galaxies on its way to earth.

I would not be surprised at the 4 million tons / second lost - considering that 4 hundred million tons / second is the amount of hydrogen converted to helium (ref. Carl Sagan - Cosmos p. 225).

I don't think much is missing - but I'm sure that there's more to learn. Hope this helps a little.