# How to imagine distorted space

1. May 13, 2005

### Neitrino

Gents,

I'am trying to imagine/visualize how does the distorted Space look like.

But geometry of Schwarzschild solution reminds us the Geometry on the sphere. So if in Schwarzschild geometry I want to look at a triangle lying in an equatorial plane, I just look at it on the sphere. so That's why in textbooks distortion of space-time is represented as a plastic surface pushed by finger.
If to put a BH on a flat plane, I was thinking that distorted space time will look like in images shown bellow, but geometry on such "plane" is not the same as Schwarzschild's one .(so was I wrong?) So it seems it is mandatory to think about distortion in higher dimensional space when thinking about gravity and it's not possible to imagine how does gravity distort two dimensional plane without deforming in 3rd dimension?

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2. May 13, 2005

### DaveC426913

No, it bends the other way around. See attached pics.

Think about what happens when space is distorted by gravity i.e. gravitational lensing. An object directly behind a massive object would normally not be seen - the light rays emanating from it would be blocked by the object in front. (Top pic in diagram.)

But the distorting effect of the massive object in front causes light rays to bend around it, so that a light ray that was behing it is now actually pointing right at us. (bottom pic in diagram)

So, the net effect of distorted 3-D is that it "grows" what's at the centre, as in the brick wall image.

Last edited: Nov 28, 2006
3. May 13, 2005

### JesseM

What's the exact connection between the distortion of space in the Schwarzschild solution and the path taken by light rays? In general relativity, objects don't take the shortest path through curved space, they take the path through curved spacetime with the greatest proper time (which should be zero in the case of a path between events with a lightlike separation). But in flat spacetime, the longest path through spacetime is also the shortest path through space...is the same true for other static solutions to the GR equations, like the Schwarzschild solution? Or would it be wrong to explain gravitational lensing in terms of light rays taking the shortest path through the curved space around a black hole?

4. May 13, 2005

### Mortimer

Since in the Schwarzschild geometry the radial distance is $$dR=\frac{dr}{\sqrt{1-2m/r}}$$, an observer at infinity would see a large $$dR$$ being cramped into a small $$dr$$. The tangential distance however is equal to that of a normal Euclidean sphere. So an object near $$2m$$ would seem crushed in the radial direction only.

5. May 13, 2005

### pervect

Staff Emeritus
I'd suggest taking a look at

and more specifically the description of the embedding diagram

6. May 15, 2005

### Neitrino

Gents,
To imagine the gravity in two dimensional space (plane), one pushes it (this palstic plane) and deforms it into 3rd dimension (like trivial examples in any textbook on GR).

Is it possible/how to imagine gravity working in plane... and not to deform it in 3rd dimension?

7. May 16, 2005

### Zanket

Sure. The use of the 3rd dimension in the "examples in any textbook on GR" is just a way to impart the information (the degree to which gravity is working) about each coordinate in the plane. That info could be alternatively imparted by the use of different colors, like how temperature is imparted on a thermal map. Or by the use of numbers, like how elevation is imparted on a road map. Or...you get the idea.

8. May 16, 2005

### kleinwolf

Yes...moreover you cannot anyhow create a space-time with negative metric coefficients by curving a higher dimensional space (with euclidean metric)....

But there is a nice way how to imagine a distorded space (R^3) (not space-time).....

A distorded space is a 3-dimensional manifold embedded in 4 dimensional space....however I cannot imagine 4-dimensional space....

But a kind of "inverse" of a distorded space can be seen as a time-dependent transformation (distortion) of usual space....(hence an animation of space transformation if you want).

9. May 16, 2005

### Neitrino

So if a can imagine gravity working in plane... and not to deform it in 3rd dimension (just to apply may be some streching/compressing of my grid elements) can i say that my PICTURE IS OK? (attached bellow)

In this picture I tried to represent space as a grid beeing distorted (this distortion is obtained when gravitational centre attracts=distorts inward that grid )gravitational force.

Gents,

Thks

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10. May 16, 2005

### Zanket

Can't speak for accuracy, but in general that looks fine to me. Looks like a top-down view of the 3D "examples in any textbook on GR". The degree of distortion of the grid at any given point represents the 3rd dimension value of the 3D example at that point.

If you want to improve it, I suggest using polar coordinates and a color or grayscale gradient that changes radially (e.g. darkens toward the center). The 3D example is probably still better but is misleading unless it's carefully explained.

Last edited: May 16, 2005
11. Jan 7, 2006

### Boffin

How about viewing a distorted space continuum as a solid object with variable densities? So the density around large objects such as the suns and planets would be greater, and inbetween lesser?

Or what about thinking of the space continuum as white and the closer one's gets to large objects the darker grey the space continuum becomes?

These are all just imperfect representations of the real thing. Anyone have any other ideas? Neitrino asked the original question awhile ago but I'd be interested in more ideas.