Simple Question on General Relativity

In summary, the direction mass and density sink into space is controlled by the stress-energy tensor. Normal mass and energy always curves space positively, but when dense objects are present the stress-energy tensor can cause a space curve in a different direction.
  • #1
Erus
41
0
Ok, I have studied somewhat General Relativity yet it hasn't fully answered a question that keeps popping up in my head. Though it is probably easy to answer, yet hasn't been comprehended by me. The question is on Space curve caused by dense objects in space. I will ask as simple as possible and hope you all can answer it for me..

What governs the direction mass and density sink into space?

I may be off track completely and not getting general relativity, but this question is bothering me and if I'm not getting it I would like someone to explain the answer so I can understand lol ty
 
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  • #2
the centre of mass does.
 
  • #3
At every point, the stress-energy tensor (which includes mass density) contributes to the curvature of space at that point. Normal mass and energy always curves space positively.

- Warren
 
  • #4
Erus said:
What governs the direction mass and density sink into space?
What does this mean, i.e. what does ..direction of mass and density... I never heard of mass/density having a direction.
chroot said:
At every point, the stress-energy tensor (which includes mass density) contributes to the curvature of space at that point. Normal mass and energy always curves space positively.
Huh? I don't understand what you mean by this. E.g. An open universe is a universe with negative spatial curvature. And that's with normal matter.

Pete
 
  • #5
Apparently the original poster is thinking of the "rubbersheet" analogy in which a marble "sinks into" the rubbersheet, causing a warp that would cause another marble to circle around it.

That is only an analogy. The "sink" would be in a "direction" not defined in the original space.
 
  • #6
To expand on what Halls said, the rubber sheet has a two-dimensional surface, and gets curved in a third direction. Bringing the analogy to reality requires adding one dimension, so the three-dimensionsl surface we call the universe curves in a fourth direction. This is a direction in which we cannot move or look (or point, or even think).
 
  • #7
Erus said:
Ok, I have studied somewhat General Relativity yet it hasn't fully answered a question that keeps popping up in my head. Though it is probably easy to answer, yet hasn't been comprehended by me. The question is on Space curve caused by dense objects in space. I will ask as simple as possible and hope you all can answer it for me..

What governs the direction mass and density sink into space?

I may be off track completely and not getting general relativity, but this question is bothering me and if I'm not getting it I would like someone to explain the answer so I can understand lol ty

I'm guessing that you are imagining normal 3-d space being embedded in a higher dimensional space.

The answer is that the approach used doesn't care about any particular embedding. Geometry is studied entirely from the inside of our 3 dimensional space and 1 dimensional time. SInce any extra dimensions beyond these are not observable, we don't need to theorize anything about them. Mathemeticans call this studying "intrinsic curvature".

The way this is done is by studying distances, and how they add. It's quite similar to the way that people navigate on the ocean using 2 coordinates, turning what would be a three-dimensional problem into a 2-dimensional version of the same problem, an approach that even a hypothetical 2-dimensional being could manage.
 

1. What is general relativity?

General relativity is a theory in physics that describes the force of gravity as a curvature of spacetime caused by the presence of mass and energy. It was developed by Albert Einstein in the early 20th century and has since been confirmed through numerous experiments and observations.

2. How is general relativity different from Newton's theory of gravity?

Newton's theory of gravity, also known as classical mechanics, describes gravity as a force that acts between two objects with mass. General relativity, on the other hand, explains gravity as a distortion of spacetime caused by the presence of mass and energy. It also accounts for phenomena that Newton's theory cannot, such as the bending of light around massive objects.

3. What is the importance of general relativity in modern physics?

General relativity plays a crucial role in modern physics as it provides a framework for understanding the behavior of massive objects and their interactions with spacetime. It has significant implications for astrophysics, cosmology, and our understanding of the origin and evolution of the universe.

4. Can you give an example of how general relativity has been confirmed through experiments?

One of the most famous examples of general relativity being confirmed through experiments is the bending of starlight around the sun during a solar eclipse. This phenomenon was predicted by Einstein's theory and was later observed and confirmed during the 1919 solar eclipse. Other experiments, such as the observation of gravitational waves, have also provided evidence for the validity of general relativity.

5. Is general relativity the final theory of gravity?

While general relativity has been extremely successful in explaining many phenomena, it is not considered the final theory of gravity. This is because it is incompatible with quantum mechanics, which describes the behavior of particles at the subatomic level. Many scientists are currently working on theories that combine general relativity and quantum mechanics, such as string theory and loop quantum gravity, in the search for a unified theory of physics.

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