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Re: The Graviton

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Posted by Zephram Cochrane/">Zephram Cochrane on December 20, 1999 23:40:45 UTC

: Is it safe to say that since the photon interacts with the gravitational field, it emits gravitons? If this is so, then the photon will kinda fizzle out into pure gravity; actualy....... everything in the known universe that has energy will be turned into pure gravity.

It soulnds like your trying to force macroscopic sense onto the quantum world in a way which doesn't quite work. Gravitons don't need to carry away energy unless the energy carrying object is accelerated. If the object contains electromagnetic fields then the energy of those fields does contribute to the amount of force required to accelerate it. It is the force doing the work in the acceleration from which the gravitational radiation ultimately gets its energy. Yes it can be electromagnetic forces doing the work, but I wouldn't think of it as individual real photons boiling away.

:Also...... can two gravitons interact, or (since they are simply the quantized piece of a gravity wave) can they have constructive/destructive interference? Are they subject to a Doppler shift?

The Doppler shift and interference is best understood in terms of waves comprised of many quanta. Yes such effects can occur although the Doppler effect will only behave as expected from linear waves when velocity transformations remain small enough to keep use of the linear approximation for gravity waves.

: P.S. Referring to the web sight above.......just to make sure I'm getting a correct basis in understanding physics equations, does the terms "dy^2" and "dz^2" stand for special axis in for dimensional space-time?

Yes. x,y and z are the axis of a Cartesian coordinate system and t is the time.

:Does "d" stand for distance in this case?

To describe the location of an event in this universe requires three spacial dimensions and one time. It happens somewhere at some time. To describe the distance between two events you might use the Pythagorean theorem in three special dimensions

DI2 = Dx2 + Dy2 + Dz2

D means "a finite change in"

So for instance Dx means the displacement along the x axis.

However the events may also occur at different times in which case this should be a part of the 4 dimensional displacement between the events. Introducing the time is done in the following equation

DI2 = -Dct2 + Dx2 + Dy2 + Dz2

I use a sign convention for personal preference which switches all of them

Ds2 = Dct2 - Dx2 - Dy2 - Dz2

When going from finite displacement to infinitesimal displacement you replace the D with d. So d means "an infinitesimal change in". So for instance dx is the displacement between two infinitesimally close events along the x axis.

Then the net displacement becomes

ds2 = dct2 - dx2 - dy2 - dz2

This is called the invariant interval of special relativity. General relativity allows this space-time to have some nonCartesian geometry which changes the form of this equation and manipulating that geometry is what makes warp drive possible.


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