Relatavistic gravity

[ApeApeMan]

Newtonian gravity...instantaneous action...curved spacetime...gravitons...?????

I very much need a coherent answers:

It is easy to accept gravity as a force...yet, Relativity describes gravity as merely curved spacetime. In terms of planetary orbits, curved spacetime around the Sun offers the only path(s). Envisioning a flat rubber sheet with a mass depression to simulate curved spacetime does convey the effect upon orbiting bodies. Great!!

The difficulty I have is in understanding gravity and its effect upon me...ie...I feel gravity and observe its effects on everything around me. Newtonian gravity conceived as a force pulling me down to the surface of the Earth works well conceptually. If, however, gravity is merely a distortion of spacetime...why do I "feel" like a force is attacting me to the Earth? How does one explain gravity in relativistic terms as it affects me and my body? If not a "force" then what? How is the illusion of force created when mere spacetime distortion makes the apple fall at 32 feet per second per second. Explain to me why I feel a "force" when apparently I am reacting to varying densities of spacetime. And just what in the hell are gravitons? Sheesh.

Now, if I could just ask coherent questions. Or is it Gravitrons? Whatever

AAM

 

[epepke]

Actually, you don't feel gravity. You feel the Earth pushing you up against it. That's the force in GR, if you are standing on the Earth. If you were orbiting around the planet, you would feel nothing. For an approximation of this experience at an affordable price, I recommend the Tower of Terror.

It's much like centrifugal versus centripetal force. If you are in a car that is turning, you might think that there is a force pushing your upper body outward. In a proper frame of reference, though, it's the force of the seat and the seatbelt pushing you inward.

As far as gravitons go, the quantization of gravity does not necessarily mean that GR is wrong. And, of course, nobody has observed a graviton. But there should be something like that if the quantum field equations apply to gravity as well.

 

[Paulhoff]

It's much like centrifugal versus centripetal force. If you are in a car that is turning, you might think that there is a force pushing your upper body outward. In a proper frame of reference, though, it's the force of the seat and the seatbelt pushing you inward.

Daaaaaaaaaaaaaaa

Paul

 

[mhaze]

Newtonian gravity...instantaneous action...curved spacetime...gravitons...?????

I very much need a coherent answers:

It is easy to accept gravity as a force...yet, Relativity describes gravity as merely curved spacetime. In terms of planetary orbits, curved spacetime around the Sun offers the only path(s). Envisioning a flat rubber sheet with a mass depression to simulate curved spacetime does convey the effect upon orbiting bodies. Great!!

The difficulty I have is in understanding gravity and its effect upon me...ie...I feel gravity and observe its effects on everything around me. Newtonian gravity conceived as a force pulling me down to the surface of the Earth works well conceptually. If, however, gravity is merely a distortion of spacetime...why do I "feel" like a force is attacting me to the Earth? How does one explain gravity in relativistic terms as it affects me and my body? If not a "force" then what? How is the illusion of force created when mere spacetime distortion makes the apple fall at 32 feet per second per second.

AAM

Replace "mere" with "very - formidable" and you have the answer.

 

[Cuddles]

Think of a rubber sheet with a weight on it. On a flat part of the sheet you can roll a ball and it will just travel in a straight line. Roll a ball near the weight and the curvature of the sheet will cause it to bend, and depending on the exact conditions could just orbit around the weight or fall into it. There is no force between the weight and the ball, only the distortion of the spacetimerubber. Gravity is exactly the same but with more dimensions and less rubber.

 

[Schneibster]

The difficulty I have is in understanding gravity and its effect upon me...ie...I feel gravity and observe its effects on everything around me. Newtonian gravity conceived as a force pulling me down to the surface of the Earth works well conceptually. If, however, gravity is merely a distortion of spacetime...why do I "feel" like a force is attacting me to the Earth?

Because the curvature of spacetime is such that it looks to you like you're accelerating upward.

Explain to me why I feel a "force" when apparently I am reacting to varying densities of spacetime.

Not densities; curvatures.

And just what in the hell are gravitons?

They are the so-far hypothetical exchange particles of the gravitic interaction.

Part of what's hanging you up (and you're not alone) is that you haven't understood that the explanation of forces as exchanges of virtual particles, and the explanation of forces as curvatures of space, are not mutually exclusive. How precisely these two explanations fit together is something physicists are working on now; the two most popular descriptions of gravity as a force are loop quantum gravity and string theory.