Warped Space time Problem

[Darkpassenger]

Having a Problem with warped space time Please tell me if i am wrong, in

 

Books, mags, and on TV and videos i have seen the same diagram over and

 

over again. they show a planet of large object that is warping the space

 

time fabric like how a lead ball would warp the fabric of a trampoline.

 

The Object warps the space time fabric in one Direction and that's it. My

 

problem with this diagram is that in space there is no direction, you cant

 

say this is up this is down and so fourth. Direction in space can only be

 

relative, meaning you cant have direction until you make something your

source of reference for direction. so i come to this conclusion since there

is

no direction is space, that when an object warps space time it must warp

 

the space time fabric in all directions. The only diagram that i have ever

 

seen that depicts what i am talking about is in the book the fabric of the

 

cosmoses by Brian Greene. unfortunately he dose not talk about the Space

 

time fabric being warped in all directions. so if i am correct then the

 

poor/incomplete diagrams are the reason that i cant sleep at night thinking

 

about minute details of diagrams would probably not bother anyone else.

so i ask can you please tell me if i wrong or on the right track here,Thanks.

[Tom Vose]

Yes, seems fine to me

[ajb]

The pictures of heavy objects warping a sheet are just analogies. You should not try to extract too much out of them.

 

What you should take out is the notion that matter tells space-time what shape it should be and space-time tells matter how to move (i.e. gravity). In essence, that is all that general relativity says.

 

In order to go much further than this you will need to know some differential geometry.

[swansont]

In addition to what ajb said, consider that the representation is attempting to convey a 2-D representation — all of the warping is happening to a plane, or what would be a plane away from any gravitational perturbations. But you can't show this non-Euclidean effect in a Euclidean 2-D space; you have to "borrow" the third dimension to depict it.

[Darkpassenger]

Thanks for you feed back, yes it must Be that 2-D plane with the 3-D object that keeps throwing me off. wish that the would just show it all in a 3-D format so that you can get the full visual effect of what is happening.

[swansont]

Thanks for you feed back, yes it must Be that 2-D plane with the 3-D object that keeps throwing me off. wish that the would just show it all in a 3-D format so that you can get the full visual effect of what is happening.

 

You can't, though, because you'd need 4 spatial dimensions to depict it.

[alextwo]

I agree with Darkpassenger. I think that the whole idea of spacetime being curved and proven to curve during solar eclipses is hokum. It proves that light is bent by gravity and nothing more. It is a convoluted explanation for something that is quite simple. Einstein was the only one that I can think of that could get away with mind experiments. Didn't we get away from that during the Rennaisance? String theory is another example of trying to force something to make sense instead of shutting up and just admitting we just don't know at this time what the heck is going on at that level. I've been looking at these things for over 40 years and the logic goes right out the window. Sorry to be so blunt.

[mooeypoo]

The discussion of north's notion about the bendiness of light was moved to another thread, so this one can continue on topic. Fasten your seatbelts and enjoy your stay.

Edited December 22, 2008 by swansont
added link

[Darkpassenger]

I agree with Darkpassenger. I think that the whole

idea of spacetime being curved and proven to curve during solar eclipses

is hokum. It proves that light is bent by gravity and nothing more. It

is a convoluted explanation for something that is quite simple. Einstein

was the only one that I can think of that could get away with mind experiments. Didn't we get away from that during the Rennaisance? String theory is another example of trying to force something to make sense instead of shutting up and just admitting we just don't know at this time what the heck is going on at that level. I've been looking at these things for over 40 years and the logic goes right out the window. Sorry to be so blunt.

 

Yes, i agree with the post above i not sure what topic you are on, it dose

not relate to my original post in anyway. My post is about trying to understand why most diagrams show the space-cure in one direction on a d-2 plane, and not a 3-d ish observation on a plane at can give a better observation of just how much an object can warp space time. Also i have to disagree with your statement abut Einstein being the only scientist to use his mind to think through experiments without being testable and the use of theses theory's until they were testable. In fact some of our greatest minds have used this same thought and experimenting process , Newton, Maxwell, Hawking and may others all have used this way of experimenting. I also have to use this same experimentation because i don't have a strong enough grasp on the mathematics nor the tools to test my theory. This doesn't mean that that our theory are wrong it just means that until they can be testable that are just theory's and that is in my opinion better then to not have given them any attention at all especially when something seems so all encompassing like String theory it is just to hard to ignore.

[D H]

The rubber sheet analogy is just that: An analogy. It is important to keep in mind that *all* analogies fail in some sense. The visual explanation from the rubber sheet is imperfect. (Can you see four dimensions?) Compounding this imperfect explanation, you are looking at the analogy incorrectly. The analogy isn't describing up and down. The crux of your misunderstanding is in this statement: "The Object warps the space time fabric in one Direction and that's it." The rubber sheet analogy warps portrays warping of the space time fabric in two dimensions -- the two dimensions on (not normal to) the rubber sheet.

 

Where the rubber sheet analogy goes wrong is that it gives the impression that there is some other dimension involved. You have carried this misrepresentation even further, taking that out of plane stretching to be the only warping of space time that is occurring on the rubber sheet. The think to look at is the grid lines on the rubber sheet, not how far the sheet is been stretched from the flat plane.

[ajb]

If Darkpassenger or indeed anyone else is interested, you an see the slides on a talk I gave a little while back on an introduction to general relativity. It may be of some use.

[Darkpassenger]

I Just read you Power point you gave on a Introduction to general relativity It was some what helpful. also made me remember that i should have payed more attention in Math class. I thank you for posting that for me, any bit of info i can get to help me understand GR is alway greatly appreciated.

 

The rubber sheet analogy is just that: An analogy. It is important to keep in mind that *all* analogies fail in some sense. The visual explanation from the rubber sheet is imperfect. (Can you see four dimensions?) Compounding this imperfect explanation, you are looking at the analogy incorrectly. The analogy isn't describing up and down. The crux of your misunderstanding is in this statement: "The Object warps the space time fabric in one Direction and that's it." The rubber sheet analogy warps portrays warping of the space time fabric in two dimensions -- the two dimensions on (not normal to) the rubber sheet.

 

Where the rubber sheet analogy goes wrong is that it gives the impression that there is some other dimension involved. You have carried this misrepresentation even further, taking that out of plane stretching to be the only warping of space time that is occurring on the rubber sheet. The think to look at is the grid lines on the rubber sheet, not how far the sheet is been stretched from the flat plane.

 

 

Yes I did miss state what i was trying to explaining you are correct i should have said in 2 directions or more as in reference to the rubber sheet analogy even though this analogy dose not fully explain what it is that i am trying to describe maybe i will find some better way to describe what it is that troubled with.

[ajb]

I Just read you Power point you gave on a Introduction to general relativity It was some what helpful. also made me remember that i should have payed more attention in Math class. I thank you for posting that for me, any bit of info i can get to help me understand GR is alway greatly appreciated.

 

I am glad it was of help. Please be aware that I said a lot more during the presentation than is written on the slides.

[pioneer]

There is a conceptual problem with space-time. It is easier to see by looking at SR first. If we were traveling in a rocket near C, space-time contracts in that reference, but the objects within the ship don't compress since only the reference changes. In the ship all appears the same as before.

 

With gravity and GR, not only is space-time contracting, but the physical separation between objects is also changing. If I took two Deuterium atoms on the SR ship, one meter apart, velocity would not cause fusion within the rocket's new space-time, since in that reference the two units will still remain at one meter. But with GR, we also get a space-time well that will get them to physically get closer, so the short range nuclear forces will act, like in stars. Are three two types of space-time? Or does the GR version of space-time have something extra to physical move things closer so the short range nuclear forces become close enough to become active. SR space-time does not do this.

[swansont]

No, I don't think that is the case.

 

If you have two deuterium atoms at some separation and you move by them at high speed, the will be closer together as measured in your frame. But the separation they need to have, in order to fuse, will be different in that frame. I suspect that concept also applies in the GR case as well. When comparing the local frame to a distant observer, you will get different results of length and time measurements. But under no circumstance can the nuclei fuse in one frame and remain apart in another.

[Norman Albers]

Recently solidspin wrote to me: consider a planar graph of <ct, x>. We can consider the light-cone, etc. Now "just expand in your mind" the x to the three spatial dimensions. When you have spent enough time in 4-space, these things make sense.