Dark matter was actually introduced because galaxies rotate differently to what would be suggested by both GR and Newtons law of gravity. A point mass in a galatic potential follows a Keplerian motion so GR is nothing to do with it specifically (although GR does predict it so does just about...
It depends if the beams were coherent or not. But two beams passing perpendicularly wouldn't be affected either way as the field components would be in the wrong directions
To use gauss's law assume a cylinder that is infinately long with charge density u. E=u/2PIe0r. I though gauss's law was very simple to use as you consider the flux per unit length of the cylinder.
By my reckoning (and that of Gauss's law), the field strength from a infinite line of charge is inversely proportional to the distance from the line of charge. Therefore at infinite distance the field is 0.
If you were to isolate a single photon you would not be able to tell its size. By QM the photon would take up all possible positions for itself in some degree or another. This is QM so its not proper to talk about size or position or motion. You must either consider a range of positions the...
There is inflation theory. This is a possible (and highly theoretical) solution to the cosmological problems. It states that space itself can expand at faster than the speed of light. Any matter within the space isn't actually moving since its the space itself that's moving. If space can really...
The interesting thing about light is it has no mass but has momentum determined by De Broglies(momentum=Planck's constant/wavelength) equation from QM. De Broglie believed that light did have a tiny mass such that it would be slightly slower than what we call the speed of light, however, this...