User:178.30.6.228

Welcome to wikipedia

Look, nobody has time to go into this with you. Read the article carefully first. The stress-energy tensor only talks about energy-momentum flow through a point, and if you want energy in a volume you need to integrate around the volume of the thing. That's why some energies can't be expressed as dE/dV quantities-- you have to define your volume, integrate around it, and then step away and look at it from flat space. The energy that volume contains is then its invariant mass and the thing that generates that volume's gravitational field. There's your energy.

Gravitational waves are like shock waves (especially shear waves in a solid) but they carry away energy just as shock wave does. They do work (force x distance) on the emitter, and on the receiver. They exert forces on the emitter and the receiver. Example: read the article on the Hulse-Taylor binary system, which is a system of two neutron stars, one of which is a pulsar. This system orbits with a period of only 7.75 hours, coming as close to each other as twice the distance from Earth to moon. The power of the gravitation radiation from this is calculatable in general relativity and is 7.35 trillion trillion watts (10^24 watts). That's almost 2% of the energy that our Sun puts out as light, only this is coming out as gravitational waves. It exerts a force on the system and causes the stars to in-spiral as they lose energy and angular momentum-- they might as well be swimming in some viscous fluid. That's real work, a real force, and a real effect, which has been measured because the rotating pulsar is so great as a clock. Because it's polarized gravitational wave radiation, it carries away the angular momentum from the system, like a polarized light beam would do, but not like any nonpolarized EM radiation from any star (like ours) would do. It only has one possible explanation, and it fits Einstein's prediction over 30 years to within 0.2%. It won a Nobel Prize in 1993 for the guys who discovered and analyzed it (your Swedish contrymen did that).

So-- the book raised to the table only increases the potential of the system, but its mass wouldn't change if the force and distance to put it there didn't come from somewhere else in the system (like my muscles, or you could do it with a coiled spring). The mass and gravity field of the whole Earth wouldn't change if you just moved energy from here to there like that, but if you believe energy left the coiled spring, you must believe it went into the system of book+Earth. Just WHERE, you can't say, but from far away, it's still there, even though not in the spring. So where else would it be? In the gravitational potential.

Finally, remember where those atoms heavier than iron and nickel come from. It takes energy to make them and fusion to larger atoms is losing propositon that saps and stores energy, not creates it. So where does this energy come from. It turns out that it's mostly gravitational energy from the collapse of a supernova, so that's stored gravtiational potential also-- except this time in heavy atoms. On a larger scale you can see that a planet like Jupiter still radiates more energy than it gets from the Sun. It's obviously still slowly colapsing, and that potential energy is converted to infrared.

and would you please sign your posts with four tildes: ~~~~. Or pick a username like Yoron? SBHarris 07:56, 12 March 2011 (UTC)