Like most people, my neurons were rebooted a few times between birth and adulthood. So I don’t remember that much about childhood, but I do remember sitting in a schoolyard, perhaps in grade one or two, trying to get my head around the end of the universe.
I’m not at all sure, but I believe at that time, around 1970, I thought of the universe as infinite. Later it became finite, a theoretically countable number of galaxies somewhere between 10-20 billion light years “across” with an estimated age that didn’t quite add up. Then came inflation and the height of a human defined the mid-point between Neutrino and the Universe. That was six or seven years ago.
Those were the good old days. Now we have the Multiverse, and Tegmark’s taxonomy of multiversi …
Level I: Beyond our cosmological horizon[edit]
… A generic prediction of chaotic inflation is an infinite ergodic universe, which, being infinite, must contain Hubble volumes realizing all initial conditions.
Accordingly, an infinite universe will contain an infinite number of Hubble volumes, all having the same physical laws and physical constants….
Level II: Universes with different physical constants…
… In the chaotic inflation theory, a variant of the cosmic inflation theory, the multiverse as a whole is stretching and will continue doing so forever, but some regions of space stop stretching and form distinct bubbles, like gas pockets in a loaf of rising bread….Different bubbles may experience different spontaneous symmetry breaking resulting in different properties such as different physical constants…
Level III: Many-worlds interpretation of quantum mechanics …
Level IV: Ultimate ensemble …
I’m slowly reading Tegmark’s popular book of which some criticism might be made. That review, however, offers little solace to universe nostalgics (emphases mine)…
Level I [is] just lots of unobservable extensions of what we see, with the same physics, an uncontroversial notion. Level III is the “many-worlds” interpretation of quantum mechanics, which again sticks to our known laws of physics. Level II is where conventional notions of science get left behind, with different physics in other unobservable parts of the universe. This is what has become quite popular the past dozen years …
So an infinite number of universes like the one we observe is “uncontroversial” and the idea that our infinite multiverse is only one extreme instance of vastly larger number (mostly unsuitable for particles, much less life) is “quite popular”. There are necessarily an infinite number of John Gordon’s typing versions of this post…
Yes, infinity is like that.
I prefer to think that nothing ever happened, and that we are merely granite dreaming, but I try to creep up on the multiverse by way of metaphor. One person standing on a barren planet is inexplicable; 8 billion people on a planet infested with life is relatively easy to understand.
Perhaps so it is with universes.
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