Gravity and the 4th dimension

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Froth
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Gravity and the 4th dimension

Postby Froth » Tue Aug 04, 2009 1:09 am

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wigginboy
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Postby wigginboy » Tue Aug 04, 2009 9:39 am

Now, I am no physicist by any means at all, and this is just what I know mixed with what I think. I know from physics that the fourth dimension is generally regarded to be time. I myself would see gravity not so much as a dimension, but as a part of a framework for the third dimension. Like I said, i am not a physicist or even a scientist so this is just an opinion, but it seems this would be the most logical. I don't see how gravity itself could be its own dimension, but I can see how it facilitates the third dimension by giving us a means of direction within that dimension. Please, someone with a grounding in this field, shed some light, this has got me interested.

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Postby Froth » Tue Aug 04, 2009 12:16 pm

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Last edited by Froth on Wed Jul 09, 2014 11:40 am, edited 1 time in total.
*Insert hilariously accurate quote about the way the world works and a tad sexist about woman, that 99.9% of the forum wont laugh at, but Ill rofl for hours at*

such is me and my humor.

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Postby jotabe » Mon Nov 09, 2009 4:12 pm

The image of a massive body curving a patch of elastic "space-time" is just a useful image. We use the word "curving" for spacetime because that's what gravity geometrically does. And it's a very visual idea, it helps a lot to understand how gravity works.

But it really doesn't "curve" space-time "around" anything. What gravity does is tell the regions of space-time how to connect with each other. Imagine a flat spacetime. You draw a cubic lattice of points. From any point of this lattice, if you go following the x,y,z axes, you will find any of the nearest 6 points. But now you place a body with mass close by. This body will start emitting gravitons, and what gravitons do is tell every point in the lattice that their closest points aren't anymore arranged along the neat x,y,z axes. There is a change of a number of degrees in the direction they have to follow to go to their nearest lattice points. So, you are changing the directions on how points of the spacetime connect to each other, not really curving them in a 4th geometrical dimension.

Of course, a flatlander would say the same thing, if he lived on the surface of the sphere. He could say there is an arrangement of masses changing the geometry of his 2D reality, so the way points of his flat universe connect with each other is as if he lived in a 3D spherical surface, without needing to think that he actually lives on a 3D sphere.

So, we might live in a universe with 4 or more geometrical dimensions. But it isn't necessary to understand how it works.
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