Recent content by MeJennifer

True, and that implies there cannot be spacelike hypersurfaces in a Godel solution.

This solution is interesting because it proves that topological features of a spacetime can have physical consequences. It also shows that numerical approaches like using ADM equations can never completely cover all (theoretical) solutions of general relativity.

As far as I understand it a given metric in general relativity could be valid for more than one topology.

In general relativity there are no preferred coordinates so the question would be entirely observer dependent. Seems to me you are asking for a cosmology question as such this topic should be moved to the cosmology section.

If you hover you obviously have to be stationary and thus enable proper acceleration, towards the EH the acceleration would go towards infinity. Even when you are free falling you could determine if you pass the EH by observing the Karlhede’s invariant.

I disagree with your opinion. The difference between an object moving by force and by gravity is that the prior undergoes proper acceleration while the latter does not.

I basically means it has to fit with the Newtonian limit.

In addition GR allows for negative pressure which would create 'repulsive gravity'.

Spacetime certainly has properties!

I find it an interesting question. Does light go from A to B without a medium? We could say yes, but the path in spacetime goes through curvature. So then what is curvature? A medium? No? Then what is it? Just another word for the same thing?

Define what you mean by a gravitational field. The "gravitational field" you describe has zero spacetime curvature.

m is not as straight forward in General Relativity as it is in Newtonian gravity. It seems to me you are looking for generalizations and simplifications that simply do not exist in GR.

Even if you find a way the radiation would kill you unless you make an even more massive spacecraft .

What is your definition of moving? In SR there is no such thing as absolute movement, all movement is relative. What is not relative is proper acceleration.

Ok then, what is the difference between a Born rigid and a non Born rigid congruence of parallel intertial worldlines in Minkowski spacetime? If there is no acceleration it is totally useless to talk about something being Born rigid.