So Many Lunches

<shudder> “I don’t like Everett’s Many Worlds multiverse, Sy. When I think of all those A‑B entanglements throughout space I just see history as this enormous cable with an exponentially growing number of strands and it keeps getting thicker and more massive. Besides, that’s all about observations at the micro level and I don’t see how it can build up to make two me’s enjoying our different lunches.”

“Most physicists agree with you, Susan, although there have been entire conferences devoted to arguments for, against and about it. His proposal does solve several known problems associated with other interpretations of quantum mechanics but it raises some of its own. To my mind, it just tastes bad. How about another multiverse idea?”

“Is it as cumbersome as that one?”

“Well, it still involves infinity, but probably a smaller one. I think the best way to describe it is to start with black holes. Each one has a region at its geometric center where spacetime is under such stress that we don’t have the physics to understand what’s going on in there. You with me?”

“So far. I’ve read some of your posts about them.”

“Cool. Anyway, one conjecture that’s been floating around is that maybe, especially for the supermassive black holes, the energy stress is so high that Nature relieves it by generating a new blister of spacetime. The blister would be inside the Event Horizon so it’s completely isolated from our Universe. Visualize one of those balloon artists who twists a patch on the surface of a blown-up balloon and suddenly it grows a new bubble there.”

“Like yeast budding new yeastlets?”

“That’s the idea, except these spacetime buds would be rooted inside our Universe like a yeast cell’s internal vesicles rather than budding from the cell’s surface. Because it’s isolated, each bud acts as an independent Universe.”

“But Hubble has shown us a trillion galaxies. If there’s a supermassive black hole at the center of nearly every galaxy…”

“Yup, lots of Universes. But it gets better—”

“I see where you’re going. Each baby Universe can have its own collection of black holes so you can have a cascade of Universes inside Universes like a matryoshka doll. Except the people in each one think theirs is the size of a whole Universe. If there are people there.”

“All of that’s possibly true, assuming there are baby Universes and they have the same physical laws and constants that we do. The speed of light could be different or something. Anyway, I was going to a less exotic scheme. The Observable Universe is the space that contains all the light that’s been directed towards us since the Big Bang 13.7 billion years ago. Thanks to the expansion of the Universe, it’s now a sphere 93 billion lightyears in diameter. Think of it as a big bubble, okay?”

“Mm-hm. You’re thinking about what’s outside that bubble?”

“Mm-hm. Of course light and information from outside haven’t had time to get to us so we have no chance of observing what’s out there and vice‑versa. Do you agree it’s reasonable to assume it’s all just more of the same?”


“Well then, it must also be reasonable to assume that our observability bubble is surrounded by other observability bubbles and they’re surrounded by more bubbles and so on. The question is, does that go on infinitely far or is there an outermost shell?”

“By definition there’s no way to know for sure.”

“True, but it makes a difference when we’re thinking about the multiverse. If there’s only a finite number of bubbles, even if it’s a big number, then there’s a vanishingly small chance that any of them duplicates ours. No copies of you trying to decide between noodles for lunch or a sandwich. If the number is infinite, though, some cosmologists insist that our bubble in general and you in particular must be duplicated not just once but an infinite number of times. Some of you go for noodles, some for sandwiches, some maybe opt for pizza. All in the same consistent Universe but disconnected from each other by distance and by light’s universal speed limit. Does that count as a multiverse?”

~~ Rich Olcott