Ever since I read about false vacuum decay a few years ago, I've always been having thoughts about whether or not it would be detectable (the end is near!). As the vacuum bubble propagates at the speed of light, no one would be able to know if it happened - they either would get destroyed by the bubble and couldn't tell (because they no longer exist now), or they will never see it because the universe's expansion outruns the vacuum.

So would it ever be possible to observe the creation and expansion of a true/lower-energy vacuum?

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    $\begingroup$ FWIW, Greg Egan sidesteps this problem in the story Schild’s Ladder by having the novo-vacuum expand at half the speed of light. $\endgroup$
    – PM 2Ring
    Mar 14, 2022 at 13:52
  • $\begingroup$ It depends on the nature of the "true vacuum". If the true vacuum is identical to this universe except for a slightly different cosmological constant, it might be be practically undetectable for a different reason. The change could be too slight to measure, and have no effect on the local or short term structure of the universe. $\endgroup$
    – James K
    Mar 14, 2022 at 18:05


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