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Exploring Multiverse Hypotheses in Physics Courses

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  1. Multiverses by Robert Nemiroff Michigan Tech

  2. Physics X: About This Course • Officially "Extraordinary Concepts in Physics" • Being taught for credit at Michigan Tech • Light on math, heavy on concepts • Anyone anywhere is welcome • No textbook required • Wikipedia, web links, and lectures only • Find all the lectures with Google at: • "Starship Asterisk" then "Physics X"  • http://bb.nightskylive.net/asterisk/viewforum.php?f=39

  3. Multiverse Hypotheses Initial idea from H. Everett.  Expanded by M. Tegmark: • Level 1: Beyond our observable universe • standard general relativistic universe • open universe with infinite volume • universe "started" with infinite volume • expanded by inflation • physical laws and constants are the same • everywhere • at all times • identical volume 10^10^115 meters away

  4. Multiverse Hypotheses • Level 1: Beyond our observable universe: • there are infinitely many exact replicas of you reading an exact replica of this slide, right now. • there are also infinitely many nearly exact replicas of you doing something slightly different, progressing toward a different future

  5. Multiverse Hypotheses • Level II: Universes with different physical constants • Chaotic inflationary epochs (for example) may create universe bubbles were different rules hold. • Some bubbles are "Level 1" bubbles like our own. • Cyclic Universes (Wheeler): Closed universes may "bounce" with different bubbles formed each bounce • Fecund Universes (Smolin): black hole collapse causes new universe to form "inside" • universes that produce black holes proliferate

  6. Multiple Histories Feynman suggested that when a particle moves from A to B, it takes EVERY POSSIBLE PATH.  Each path is assigned an "amplitude", which is related to a probability.  These amplitudes will interfere, however, and only those paths with the greatest constructive interference at the end will result in the most probable endpoints to see in nature.

  7. Multiverse Hypotheses • Level III: Universe Offshoots from Many Worlds Interpretation of QM • every time a quantum measurement is made, every possible outcome of that measurement creates a parallel universe where that measurement occurs  • these universes do not interact • similar to Feynman's multiple histories

  8. Multiverse Hypotheses • Level III differs from Level 1 because • Level 1 twins reside far across 3D space in time and space.   • theoretically a single photon could pass you and your twin. • Level III twins reside in a disconnected physical reality • theoretically, a single photon could NOT pass you and your twin.

  9. Multiverse Hypotheses • Level IV: Ultimate Ensemble • All universes that can be theoretically defined  • all space-time for ... • different constants • different measurements • differences that humans can't imagine • So general that there cannot be a Level V

  10. Multiverse Hypotheses Criticisms: Most multiverse hypotheses are not falsifiable.  There is no present practical test that can indicate clearly which one is correct, if any.  • Multiverse theorists are very sensitive to this criticism and are constantly trying to find falsifiable claims. Multiverse hypthoses are needlessly complex -- hence they violate Occam's Razor. • Entire Multiverse theory might be simpler than any alternative.

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