Animated Gravity : Einstein vs. Newton

In summary: Thanks AT!In summary, people are confused about the basic idea of Gravitation in General Relativity. They understandably don't understand how the very common balls-on-rubber-sheet-analogy explains anything. I usually post those two links to help them:- http://www.physics.ucla.edu/demoweb/demomanual/modern_physics/principal_of_equivalence_and_general_relativity/curved_spacetime.html- http://www.relativitet.se/spacetime1.htmlNow I made an animation based on those illustrations (watch in HD):
  • #1
A.T.
Science Advisor
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There are many threads about this on this forum: People are confused about the basic idea of Gravitation in General Relativity. They understandably don't understand how the very common balls-on-rubber-sheet-analogy explains anything. I usually post those two links to help them:
http://www.physics.ucla.edu/demoweb..._and_general_relativity/curved_spacetime.html
http://www.relativitet.se/spacetime1.html

Now I made an animation based on those illustrations (watch in HD):

https://www.youtube.com/watch?v=izKLw1V7YJ8
 
Last edited:
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  • #2
Thanks AT! This will definitely come in handy when trying to correct the misconceptions of people who were mislead by the "rubber sheet" analogy.
 
  • #3
Very Nice Animation! :smile:
 
  • #4
Great animation! Congratulations!
 
  • #5
Thanks for the positive feedback. I polished it a bit. The latest version is here (watch in HD):

https://www.youtube.com/watch?v=DdC0QN6f3G4
 
  • #6
Thanks A.T. Well done. Your animation has help me better understand GR.
 
  • #7
A.T. said:
Thanks for the positive feedback. I polished it a bit. The latest version is here (watch in HD):

A.T. I read on Wiki that gravity is "curved space". Looking at your animation it appears though the time axis is curved.
 
  • #8
nitsuj said:
A.T. I read on Wiki that gravity is "curved space". Looking at your animation it appears though the time axis is curved.
Gravity is distorted space-time. For apples falling on Earth the time part is crucial. Spatial curvature is relevant on a more global level and at higher speeds (orbit precession, light bending).

The term "curvature" is confusing and ambiguous:

What you probably mean is the "extrinsic curvature" of the time axis in the diagram, which is irrelevant physically. What matters are the distances within the diagram (metric). As long you preserve that metric you can roll the the diagram as you wish for better visualization:
- the unrolled state seen initially shows the geodesic property of the falling worldline better
- the cone-like rolled state has better correspondence to the apple as we see it falling radially

What wiki means is the "intrinsic curvature" of the space-time manifold, which is implied globally by the distortion, but not really relevant locally. The diagram in the animation doesn't have intrinsic curvature.
 
  • #9
Nice video!

How did you do the graphics? and the animation?
 
  • #10
A.T. said:
Gravity is distorted space-time. For apples falling on Earth the time part is crucial. Spatial curvature is relevant on a more global level and at higher speeds (orbit precession, light bending).

With curved space,

If i had a "straight" ruler 13,000km long and I made it in absence of gravity. Then brought the ruler next to Earth, would the "straight" ruler appear curved? Having the same curvature as a "light bending" (all else equal).
 
  • #11
nitsuj said:
With curved space, If i had a "straight" ruler 13,000km long and I made it in absence of gravity. Then brought the ruler next to Earth, would the "straight" ruler appear curved?
Locally the ruler would be still straight, but the ends would point into directions that are not 180° apart. So yes, globally it would appear bent.
nitsuj said:
Having the same curvature as a "light bending" (all else equal).
I think the light ray bends more than the ruler, because it also affected by the time-distortion (like the apple). Gravitational time dilation means that the lower part of a wave front advances slower than the upper one. This adds to the effect from spatial distortion.
 
  • #12
jedishrfu said:
Nice video!

How did you do the graphics? and the animation?

Thanks. It's done with a free software called "blender", mostly via the integrated scripting API (python).
 
  • #13
A.T. said:
Locally the ruler would be still straight, but the ends would point into directions that are not 180° apart. So yes, globally it would appear bent.

I think the light ray bends more than the ruler, because it also affected by the time-distortion (like the apple). Gravitational time dilation means that the lower part of a wave front advances slower than the upper one. This adds to the effect from spatial distortion.

Thanks so much A.T.!
 
  • #14
A.T. said:
Thanks. It's done with a free software called "blender", mostly via the integrated scripting API (python).

Great I'll check that out.

You should check out processing.org too. Its sw designed for graphic artists that want to paint in code (java). There's also a webish version called processing.js There are some vimeo videos where the art is done with processing search "processing video" on vimeo
 

1. How does Einstein's theory of relativity differ from Newton's theory of gravity?

Einstein's theory of relativity states that gravity is not a force, but rather a curvature of spacetime caused by the presence of mass. Newton's theory, on the other hand, states that gravity is a force that acts between two objects with mass.

2. Why is Einstein's theory of gravity considered to be more accurate than Newton's?

Einstein's theory of relativity has been tested and proven to be accurate in a wide range of scenarios, including the bending of light around massive objects and the precise measurements of the orbit of Mercury. Newton's theory, while still useful in many situations, has been shown to have limitations and does not fully explain certain phenomena.

3. Can Einstein's theory of gravity be applied to objects with small masses, like a basketball?

Yes, Einstein's theory of relativity can be applied to objects of any mass, including a basketball. However, the effects of gravity on smaller objects are so minuscule that they are negligible and can be accurately described by Newton's theory.

4. How does the concept of time dilation play a role in Einstein's theory of gravity?

Einstein's theory of relativity states that time is relative and can be affected by gravity and the speed at which an object is moving. This means that time can appear to pass slower or faster depending on an object's proximity to a massive object, such as a planet or star.

5. Does Einstein's theory of gravity have any practical applications?

Yes, Einstein's theory of relativity has many practical applications, including GPS technology. The precise measurements and calculations required for GPS to accurately pinpoint locations on Earth would not be possible without taking into account the effects of gravity and time dilation as predicted by Einstein's theory.

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