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

Beyond The Shadow of A…?

“Alright, Vinnie, what’s the rest of it?”

“The rest of what, Sy?”

“You wouldn’t have hauled that kid’s toy into Al’s shop here just to play spitballs with it. You’re building up to something and what is it?”

“My black hole hobby, Sy. The things’re just a few miles wide but pack more mass than the Sun. A couple of my magazines say they give off jets top and bottom because of how they spin. That just don’t fit. The stuff ought to come straight out to the sides like the paper wads did.”

“Well, umm… Ah. You know the planet Saturn.”


“Are its rings part of the planet?”

“No, of course not, they go around it. I even seen an article about how the rings probably came from a couple of collided moons and how water from the Enceladus moon may be part of the outside ring. Only thing Saturn does for the rings is supply gravity to keep ’em there.”

“But our eyes see planet and rings together as a single dot of light in the sky. As far as the rest of the Solar System cares, Saturn consists of that big cloudy ball of hydrogen and the rings and all 82 of its moons, so far. Once you get a few light-seconds away, the whole collection acts as a simple point-source of gravitational attraction.”

“I see where you’re going. You’re gonna say a black hole’s more than just its event horizon and whatever it’s hiding inside there.”

“Yup. That ‘few miles wide’ — I could make a case that you’re off by trillions. A black hole’s a complicated beast when we look at it close up.”

“How can you look at a thing like that close up?”

“Math, mostly, but the observations are getting better. Have you seen the Event Horizon Telescope’s orange ring picture?”

“You mean the one that Al messed with and posted for Hallowe’en? It’s over there behind his cash register. What’s it about, anyway?”

“It’s an image of M87*, the super-massive black hole at the center of the M87 galaxy. Not the event horizon itself, of course, that’s black. The orange portion actually represents millimeter-radio waves that escape from the accretion disk circling the event horizon. The innermost part of the disk is rotating around the hole at near-lightspeed. The arc at the bottom is brighter because that’s the part coming toward us. The photons get a little extra boost from Special Relativity.”

Frames again?”

“With black holes it’s always frames. You’ll love this. From the shell’s perspective, it spits out the same number of photons per second in every direction. From our perspective, time is stretched on the side rotating away from us so there’s fewer photons per one of our seconds and it’s dimmer. In the same amount of our time the side coming toward us emits more photons so it’s brighter. Neat demonstration, eh?”

“Cute. So the inner black part’s the hole ’cause it can’t give off light, right?”

“Not quite. That’s a shadow. Not a shadow of the event horizon itself, mind you, but of the photon sphere. That’s a shell about 1½ times the width of the event horizon. Any photon that passes exactly tangent to the sphere is doomed to orbit there forever. If the photon’s path is the slightest bit inward from that, the poor particle heads inward towards whatever’s in the center. The remaining photons travel paths that look bent to a distant observer, but the point is that they keep going and eventually someone like us could see them.”

“The shadow and the accretion disk, that’s what the EHT saw?”

“Not exactly.”

“There’s more?”

“Yeah. M87* is a spinning black hole, which is more complicated than one that’s sitting still. Wrapped around the photon sphere there’s an ergosphere, as much as three times wider than the event horizon except it’s pumpkin-shaped. The ergosphere’s widest at the rotational equator, but it closes in to meet the event horizon at the two poles. Anything bigger than a photon that crosses its boundary is condemned to join the spin parade, forever rotating in sync with the object’s spin.”

“When are you gonna get to the jets, Sy?”

~~ Rich Olcott