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 December 17th, 2016, 03:46 PM #1 Senior Member   Joined: Jul 2016 From: USA Posts: 108 Thanks: 13 Are Gravity Visualizations Accurate? I am trying to understand how curvature in spacetime as depicted in many diagrams can cause a force that behaves like gravity. The curvature lines depicted in in this diagram to not follow the path the object would take under the influence of gravity. Just with your eyes, follow one of the curvature lines... An object would not follow that path under the force of gravity. And the text books always just say that objects only follow the curvature path.. nothing more.. But like I said, if you follow those curvature lines, it does not behave like a force. I could use some help understanding why these curvature lines would cause an object to follow the path that mimics an object under the influence of gravity. OR are these diagrams accurately portraying how warped space would look from 3 dimensions???
 December 18th, 2016, 09:06 PM #2 Member     Joined: Oct 2016 From: labenon Posts: 33 Thanks: 4 To understand the idea, you need to understand the main concepts of how general relativity deals with gravity: matter/energy cause spacetime to become curved, and particles in free-fall (no non-gravitational forces acting on them) follow geodesic paths in curved spacetime, which for slower-than-light particles means paths that maximize the proper time relative to other nearby paths. If you haven't come across these ideas before, I recommend reading a good non-mathematical introduction to the concepts of general relativity written for a layman audience, like General Relativity from A to B.
 December 20th, 2016, 04:13 PM #3 Senior Member   Joined: Dec 2015 From: Earth Posts: 224 Thanks: 26 Complexity of dimension is not known Influence of gravity is not uniquely defined , maybe gravity is a side-effect
 March 5th, 2017, 10:18 AM #4 Newbie   Joined: Mar 2017 From: netherlands Posts: 1 Thanks: 0 Gravity visualizations are not easy to understand. curvature in spacetime is also difficult to understand. There is a theory about curvature in space time and also an visualization of space time explained in a website called universeforever.com under the tab relativity you perhaps can find the answers you seek. Keep in mind, this is also an theory which can be wrong.
 March 5th, 2017, 11:14 AM #5 Math Team     Joined: May 2013 From: The Astral plane Posts: 1,797 Thanks: 715 Math Focus: Wibbly wobbly timey-wimey stuff. I admit I didn't look at the whole thing but IMHO it looks like pseudo-science to me. I do want to say, though, that the disclaimer is a nice touch, so I'll stick to the interpretation of the author not knowing enough about what is being talked about. -Dan
March 6th, 2017, 07:45 AM   #6
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Quote:
 Originally Posted by VisionaryLen ...The curvature lines depicted in in this diagram to not follow the path the object would take under the influence of gravity. Just with your eyes, follow one of the curvature lines... An object would not follow that path under the force of gravity.
Consider a bog-standard, flat, uniform space which has 3D grid lines forming cubes, where each line is at a right-angle to any other line. Now add the gravitational mass...

In your image, the lines don't represent trajectories objects would take in that space or gravitational field lines, they represent the lines of the uniform cubic grid that have been distorted by the presence of the gravitational mass. Basically, as you get closer to the mass, the space appears "stretched" so that the space an object would travel in is not uniform.

In relativity, the idea is that objects in warped space just follow the shortest distance, so if you:

1. pick any arbitrary point out in space to place a mass;
2. draw a straight line from that point to the centre of the Earth (the shortest distance); and then
3. translate the warped space back into the uniform space, along with the line...

... you'd see that the line has become curved. This curved line would be the trajectory a mass would take. The curved trajectory is equivalent to the case where space is flat but the object undergoes a gravitational force.

I don't know whether the image is super accurate or not, but if the purpose was to demonstrate how the space is distorted by the mass, I don't see anything too onerous about the plot.

Quote:
 And the text books always just say that objects only follow the curvature path.. nothing more.. But like I said, if you follow those curvature lines, it does not behave like a force. I could use some help understanding why these curvature lines would cause an object to follow the path that mimics an object under the influence of gravity. OR are these diagrams accurately portraying how warped space would look from 3 dimensions???
There's loads of images of gravitational field lines because they're really standard (a lot like the electric field lines of a uniform charge sphere). There's probably quite a lot if images of trajectories if you look up any orbits. You might find Halley's comet interesting!

Last edited by Benit13; March 6th, 2017 at 07:48 AM.

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