Stephen Hawking’s book talks about large objects (stars, quasars, galaxies) that move (rotate?) causing the emission of gravitational waves that “carry energy away from the objects that emit them.” If your system is the object and the surrounding space, where does this energy come from, and what type of energy is it (gravitational seems wrong, because it is not gravity acting on the object)? The book says that they travel at the speed of light, so are they waves as well, or are they similar to, as Hawking puts it, the “particles that carry the gravitational force of the sun?” What type of energy is gravity (i.e., how does it affect objects. For example, friction is the interaction of two objects, elastic energy is the force of the coiled spring acting on the object, so how does gravity act on an object) and why does Hawking describe the sun’s gravity as being “carried” by particles?

Originally posted by ishbo
Stephen Hawking’s book talks about large objects (stars, quasars, galaxies) that move (rotate?) causing the emission of gravitational waves that “carry energy away from the objects that emit them.” If your system is the object and the surrounding space, where does this energy come from, and what type of energy is it (gravitational seems wrong, because it is not gravity acting on the object)?It sounds like we're talking about rotating/revloving bodies, that is, at least one chunck of mass rotating around another. A force is required to cause a mass to take a curved path. They are contantly accelerating (since moving in a curved path requires an acceleration). This acceleration causes an emmition of gravitons, I think.




Originally posted by ishbo
... are they waves as well, or are they similar to, as Hawking puts it, the “particles that carry the gravitational force of the sun?”There is particle-wave duality, which, as far as I know, applies to every fundamental thing, gravitons included.




Originally posted by ishbo
What type of energy is gravity (i.e., how does it affect objects. For example, friction is the interaction of two objects, elastic energy is the force of the coiled spring acting on the object, so how does gravity act on an object) ...It is the energy associated with the distortion in space-time itself. The more distorted, the more gravitational energy, as I understand it.




Originally posted by ishbo
... why does Hawking describe the sun’s gravity as being “carried” by particles? He is probably talking about gravitons.

Originally posted by errandir
A force is required to cause a mass to take a curved path.

Not really, according to Einstein, gravity is really a fictional force but is actually du to space-time being warped around massive objects. A stellite orbiting the earth is still travelling in a straight line through space-time. This is another example of how modern physics looks at Newtons laws in a different way.

>>Stephen Hawking’s book talks about large objects (stars, quasars, galaxies) that move (rotate?) causing the emission of gravitational waves that “carry energy away from the objects that emit them.” If your system is the object and the surrounding space, where does this energy come from, and what type of energy is it (gravitational seems wrong, because it is not gravity acting on the object)? <<

Gravity waves are said to be caused by time dependant quadrupole moment in mass. Cosmic events such as mass accretion into Black Holes, binary pulsars etc are expected to be sources for observation of these waves.
They interact with other mass, causing the mass to display the same quadrupole moment as the source. That is, the mass should distort in height and width, but the expected distortion of mass should be so small that detecting them will be a real problem.
The energy for these waves come from the momentum of the mass that generates them. They are distortions in spacetime curvature that are expected to propagate at light speed.

>>so how does gravity act on an object) and why does Hawking describe the sun’s gravity as being “carried” by particles?<<

He's probably referring to 'gravitons'.
Gravity, in general relativity, is the curvature of spacetime, caused by mass or energy density.

Originally posted by John Connellan
A stellite orbiting the earth is still travelling in a straight line through space-time.Uh, yeah. Maybe I should go edit my post to say a "curved path" instead of a "straight path." Oh, wait, I did say "curved path." Actually, in hind sight I think it would have been much better to just say a "deviation from a geodesic." That would have saved any confusion.

Could light emmissions be just a form of gravitational wave.

Not unlike a wave at sea.

The ocean being the gravatational field and the wave being the light wave or frequency?

I do know this analogy has been used many times and yet there seems to be an emphasis on light some how being distinct to gravity as in particle or Em arguements.

Could this emmission of gravity waves act as a repellor thus mitigating the atrraction of primary gravity, thus keeping the stars apart? The waves having an energy due to their direction ( kinetic??)

It is often suggested that when a star dies it ceases to emit light.
The star becoming stronger as an attractive source. The light ceases to shine therefore it could be postulated that the gravity mitigater (light) has gone thus creating a "blackhole" so to speak.

there is an adendum to special relativity that refers to frame dragging.