Can the effects of gravity be derived from SR? (split)

[geordief]

Can I go a little off topic? I have heard (if I recall correctly) that the effects of "gravity" can be derived simply using Special Relativity.

 

If that is so , can Minkowski Space-time diagrams be roped in to illustrate how objects move in the vicinity of mass and energy?

[ajb]

Can I go a little off topic? I have heard (if I recall correctly) that the effects of "gravity" can be derived simply using Special Relativity.

Do you remember where you heard this?

 

People have tried to develop gravity theories that are based on flat space-time. For example it is possible to think about an addition spin-2 field on Minkowski space-time and construct the corresponding theory. I am not sure if this fully works, but the claim is that theories like that can be equivalent to general relativity.

[geordief]

Do you remember where you heard this?

 

 

I remember who it was but it is a little difficult to track down the post as it was in the nature of an "aside" and search terms are not immediately apparent to me.

 

Actually I have pm'd the poster now and perhaps he will be able to tell me if I have interpreted his post correctly or even remember it (it goes back a good few months if not more like a year)

 

Perhaps I should wait for an answer from him so as not to "put any words in his mouth".

[swansont]

If it's based on a post, you could quote it and put it in this thread, so we can all see it, and discuss it.

[geordief]

I will as soon a I can find it. The poster may remember it better than myself (maybe not as it was an "aside" I think) but it may save me time trying to track it down myself if he is able to jog my memory.

 

That said I will have a go now and give myself a space to try and find it (it is sometimes easier once you actually make an effort)

 

It was not this forum by the way.

[geordief]

I remember who it was but it is a little difficult to track down the post as it was in the nature of an "aside" and search terms are not immediately apparent to me.

 

Actually I have pm'd the poster now and perhaps he will be able to tell me if I have interpreted his post correctly or even remember it (it goes back a good few months if not more like a year)

 

Perhaps I should wait for an answer from him so as not to "put any words in his mouth".

I have got a reply from the "poster" now.

He cannot recall the post and is very confident that he either did not say anything like that or that ,if he did it would not have been right.

Possibly (he guesses) he may have said that it was possible to derive GR using SR as a starting point .

But of course ,that would be if the post actually existed .

I am still confident that the post exists and maybe I will track it down but that is just curiosity value for me (and the poster) now.

I apologize for my poor recall and understanding in this case.

[ajb]

Possibly (he guesses) he may have said that it was possible to derive GR using SR as a starting point .

That makes sense. Part of Einstein's (and others) motivation for developing general relativity was to include gravity, which for them was Newtonian gravity, into a set-up that is consistent with special relativity. This was not so easy, but lead to the idea that the geometry of space-time is not just Minkowski. From there Einstein worked out this field equations, his first attempt was flawed, but he got here in the end.

Edited February 18, 2016 by ajb

[geordief]

So is it possible to show the effects of massive bodies using the Minkowski spacetime diagram?

 

If the x- and the t -axes extend to a sufficient distance is it possible to place massive bodies at a particular (region of ) spacetime points and would that cause the (x(prime)=0:t(prime) =0) axes of anything in that region to be curved around them as seen from the perspective of an observer at another point on the map(esp. the origin)?

 

I am not suggesting that any straightforward geometrical or mathematical (except by using a computer) calculations could be performed but can it be illustrative?

 

What I am trying to describe with these axes is that ,instead of turning into the normal scissor shape with a centre on the x=ct line (as speed increases wrt the observer) that these new axes should be curved when in the vicinity of mass etc -whilst still keeping some of the basic "scissor shape" around the x=ct line.

Edited February 18, 2016 by geordief