Fundamental limitations on "warp drive" spacetimes · HackerPapers discussions

Fundamental limitations on "warp drive" spacetimes — mentioned by raattgift

Tue, 14 Aug 2018 07:40:53 GMT

Which of those gives you observables like a very nearly isotropic 2.725 K (and slowly cooling) blackbody spectrum, for example ? The universe gives virtually everything in it some observables it seems silly to ignore: https://en.wikipedia.org/wiki/Scale_factor_(cosmology) just because the vast majority of observers aren't strictly Eulerian and thus there are lots of little details, like a dipole anisotropy in the CMB, or small deviations from a perfect blackbody spectrum. For A and B separated by non-cosmological distances, there are plenty of other local clocks available; around here one…

Paper and discussion history. A mention is not an endorsement.

Fundamental limitations on "warp drive" spacetimes — mentioned by raattgift

Tue, 14 Aug 2018 06:11:12 GMT

> space expansion and the speed faster than c as a result is possible. Without exotic matter, etc. Except that in order to get the observables right, dark energy is required to keep the galaxy clusters running away from each other faster over time. It's a heavy price that no physical cosmologist is really happy about, but the concordance cosmology gets its name from how it is explicitly constructed to match ("concord with") observation (and it is consequently updated from time to time). It is not really surprising that some energy is required to keep the warp bubble from dissipating away from…

Paper and discussion history. A mention is not an endorsement.

Fundamental limitations on "warp drive" spacetimes — mentioned by raattgift

Tue, 14 Aug 2018 04:02:39 GMT

Agreed. The pattern could range practically forever, with "B"s appearing for any "A": A: It's a static solution; the warp bubble is eternal. There is no recipe for turning it on or off. A: It's a vacuum solution; there is no "ship" inside, and no matter outside. It is everywhere exactly flat except for the compact region of spacetime in the bubble wall. The only way to decide whether it is even meaningfully moving in the sort of way intended is to add something else to the spacetime. One could make a more complicated vacuum solution with a qualitatively similar compact region, or "stitch"…

Paper and discussion history. A mention is not an endorsement.