Re: does gravity attract energy?

Hi,

You've covered a lot of ground here, so I think my answer will make more sense if I mix it in with the different parts of your question.

You said "I believe the reason we say mass does not increase with velocity is because, although its inertial mass increases, its gravitational attraction does not.":

So far as we know (and there have been some fairly serious attempts to measure this), gravitational and inertial mass are always exactly the same. Mass *does* increase with velocity. There's something called the "rest mass", which refers to the mass an object would have if it were not moving. Rest mass doesn't change with velocity because we've defined it that way, but gravitational mass and inertial mass both increase with velocity, and in exactly the same way.

You said "But, also, isn't there a paralell of magnetism in gravitation for moving objects due to a length (density) contration? Is this phenomena the same as saying its gravitational mass has increased, or are inertial mass and gravitational mass only proportional by G at low velocities?":

It's not exactly a parallel of magnetism, but it's certainly true that for moving objects the mass increases. In order to increase the speed of an object, you have to put energy into it. This energy is called the kinetic energy. The mass of an object is proportional to its total energy, including the kinetic energy. Mass and energy are related by the famous formula E=mc^2, where c is the speed of light, E is the energy, and m is the mass. If you put any kind of energy into an object (by heating it up, or making it move faster, or charging up a battery, etc.), the mass increases. We don't ordinarily notice this, because c is such a big number that a little mass goes a very long way in the energy department. G is a constant used when calculating gravitational force between two masses.

You said "but my real question is this: If the attration between two bodies does increase with velocity due to gravi-magnetism, this attraction is parallel to an increase in kenetic energy. And since E=mc2, all mass is potentially electromagnetic energy even at rest. I have not heard this connection explored and wondered if there is a greater body of thought out there which connects gravitation and energy (electromagnetic and otherwise). It seems that somebody must be exploring this to try to connect relativity and the electromagnetic force but i can't find anything about it.":

When you increase the velocity, the mass increases, so the gravitational attraction increases. I guess it's true that all mass is potentially electromagnetic energy, in the sense that mass represents energy and one could in principle convert that energy into electromagnetic form. You could also convert it into some other form of energy, like heat or kinetic energy. I don't see how this connects relativity with the electromagnetic force, but it's certainly true that there is a connection between relativity and electromagnetism. In almost any textbook on electromagnetism, you can find a description of the close relationship between electromagnetic theory and the theory of special relativity. The math can get heavy, but for an online example take a look at http://farside.ph.utexas.edu/teaching/jk1/lectures/node6.html .

If you want to read more about relativity and gravity, here are some interesting places to start:
http://www.astronomycafe.net/gravity/gravity.html
http://www.physlink.com/Education/AskExperts/ae161.cfm
http://scienceworld.wolfram.com/physics/SpecialRelativity.html
http://www.captaincosmos.clara.co.uk/relativity.html
http://www.upscale.utoronto.ca/GeneralInterest/Harrison/GenRel/GenRel.html

There's also an excellent book called "Spacetime Physics", by Taylor and Wheeler, published by W.H. Freeman and Co. , which you might find helpful.