On Friday, January 10, 2020 at 11:31:03 AM UTC-6, John Clark wrote:
>
> On Wed, Jan 8, 2020 at 5:56 AM Lawrence Crowell <[email protected]
> <javascript:>> 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
>
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
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