Time Machines

[John Clark]

On Wed, Jan 8, 2020 at 5:56 AM Lawrence Crowell <goldenfield...@gmail.com> wrote:

 

> Gödel's cosmology violates the Hawking-Penrose condition T^{00} >= 0. This corresponds to the closed timelike curves in the spacetimes. The whole cosmology has a net angular momentum that frame drags geodesics into closed timelike curves.

So you could make a Time Machine if Gödel's solution to Einstein's field equations was relevant for our universe, but it's not because the universe we live in doesn't spin.

 John K Clark

[spudb...@aol.com]

I know you're correct regarding the Hubble Volume, however, as the total universe is not the hubble bubble, and we may never get info beyond what we can detect, via the limitation of lightspeed, I still ponder if we might devise some manner of detection? Do go on other topics, because thumbs up or down on Godel, this'll take a while....

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[Lawrence Crowell]

The Gödel universe is a sort of time machine. The anti-de Sitter spacetime also has closed timelike curves. We do not live in these spacetimes. It is curious that Einstein's field equations predict them, and they are eliminated because they do not obey the weak energy condition T^{00} >= 0. They may play some sort of vacuum role in quantum gravity,

LC