Is General Relativity Really About Physics on Curved Spacetimes?

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In summary, Carlo Rovelli mentioned that there is no background in quantum field theory, and this is the challenge for the 21st century.
  • #36
atyy said:
Yes, that's true, but not what I meant. I meant that there may be spin 2 fields that produce "gravity" that is different from that of GR, even below the Planck scale.

http://arxiv.org/abs/1007.0435

I actually read the paper above. It's talking about higher spin (more than 2) that produce "gravity" that is different from that of GR. It's not talking about spin 2.. so maybe you are mistaken above?

Also your analogy "A chair can be made of wood, but not everything made of wood is a chair." is not related to the above paper but as an answer to my other question, isn't it?
 
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  • #37
atyy said:
Yes, that's true, but not what I meant. I meant that there may be spin 2 fields that produce "gravity" that is different from that of GR, even below the Planck scale.

http://arxiv.org/abs/1007.0435

I think what you meant was that since spin-3 or spin-4 describe GR. Then spin-2 describe "gravity" that is not 100% GR. This is very important to distinguish because it means spin-2 over flat spacetime is not equivalent to GR even those describe by harmonic coodinates.

The meaning of equivalent is "=". So when something is not matched 100%. They are not equal. So when you said before it is equivalent and later said spin-2 is not sufficient to produce GR. Then your statements conflict. Try to be consistent in descriptions especially when dealing with such complicated subject. Thanks.
 
<h2>1. What is General Relativity?</h2><p>General Relativity is a theory of gravity developed by Albert Einstein in 1915. It describes how massive objects interact with each other and how they affect the curvature of spacetime.</p><h2>2. How does General Relativity differ from Newton's theory of gravity?</h2><p>While Newton's theory of gravity describes gravity as a force acting between two objects, General Relativity explains gravity as the curvature of spacetime caused by the presence of mass and energy.</p><h2>3. What is meant by "curved spacetime" in General Relativity?</h2><p>In General Relativity, spacetime is a four-dimensional fabric that is curved by the presence of mass and energy. This curvature affects the motion of objects and is responsible for the force of gravity.</p><h2>4. How does General Relativity explain phenomena such as black holes and gravitational waves?</h2><p>General Relativity predicts the existence of black holes, which are regions of spacetime where the curvature is so strong that nothing, including light, can escape. It also explains the existence of gravitational waves, which are ripples in the fabric of spacetime caused by the acceleration of massive objects.</p><h2>5. Is General Relativity still considered a valid theory in modern physics?</h2><p>Yes, General Relativity is still considered a valid theory and is widely used in modern physics. It has been extensively tested and has accurately predicted various phenomena, such as the bending of light by massive objects and the precession of Mercury's orbit.</p>

1. What is General Relativity?

General Relativity is a theory of gravity developed by Albert Einstein in 1915. It describes how massive objects interact with each other and how they affect the curvature of spacetime.

2. How does General Relativity differ from Newton's theory of gravity?

While Newton's theory of gravity describes gravity as a force acting between two objects, General Relativity explains gravity as the curvature of spacetime caused by the presence of mass and energy.

3. What is meant by "curved spacetime" in General Relativity?

In General Relativity, spacetime is a four-dimensional fabric that is curved by the presence of mass and energy. This curvature affects the motion of objects and is responsible for the force of gravity.

4. How does General Relativity explain phenomena such as black holes and gravitational waves?

General Relativity predicts the existence of black holes, which are regions of spacetime where the curvature is so strong that nothing, including light, can escape. It also explains the existence of gravitational waves, which are ripples in the fabric of spacetime caused by the acceleration of massive objects.

5. Is General Relativity still considered a valid theory in modern physics?

Yes, General Relativity is still considered a valid theory and is widely used in modern physics. It has been extensively tested and has accurately predicted various phenomena, such as the bending of light by massive objects and the precession of Mercury's orbit.

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