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Multiverse - Long read. My brain hurts! (1 Viewer)

BrianW

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And somewhere there is another me without a goatee, without a sidearm, who isn't robbing banks.
 

BrianW

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And why on Earth did they refer to our cozy little Level I Multiverse spherical domain (the visible Universe) as a Hubble Volume when the name should obviously have been HUBBLE BUBBLE?

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Whoah, the Theory of Chaotic Eternal Inflation?

Wasn't that during the Carter years?
 

BrianW

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Oh, and I tried to make some kind of joke using the word "brane", but nothing came to mind.
 

Carlo Medina

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Boy what coincidental timing! Scientific American sure is trying to cash in on the upcoming Timeline movie (based on the Crichton novel that deals with a variant of the theory in the article). ;)
 

BrianW

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The prevailing view in physics today is that the dimensionality of spacetime, the qualities of elementary particles and many of the so-called physical constants are not built into physical laws but are the outcome of processes known as symmetry breaking.
Statements like this are like p0rn to a theoretical physicist.

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Richard The Third fell on his knee
But found a solution he could not see.
Though declared insane,
He slipped his brane,
And became Richard the 10^(10^123)
 

BrettB

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You mean somewhere out there, there's another "me" that actually understands this kind of stuff? :b
 

RobertR

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What I don't understand is, if the universe came from the Big Bang, and the subsequent expansion occured at a finite rate, how did space become infinite?
 

DaveGTP

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Good reading, thanks for the link. I think it will need another read or two to really soak it in.

Robert, I think that the level 1 concept was saying that The Universe is infinite, but space (meaning the part of the universe with matter in it) has finite limits based on how far it has expanded?
 

RobertR

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Robert, I think that the level 1 concept was saying that The Universe is infinite, but space (meaning the part of the universe with matter in it) has finite limits based on how far it has expanded?
But I thought that the Universe came from the Big Bang, and that the Universe (including all space-time) is defined by what came after the Big Bang. Otherwise, you'd be saying that the Big Bang happened in an already-existing Universe, in which case the BB wasn't really the beginning of the Universe!
 

Shawn Shultzaberger

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If each universe (Hubble Bubble :D ) in a multiverse is a bubble then what is between each bubble? Nothingness where time and space don't exist?

Also, I thought somewhere in that huge article they mentioned that space was flat? How can that be when they've modeled the known "viewable" universe as a sphere?

It's insane in the mem-brane!

I like to think that my alter ego in the Bizarro universe actually went to college to learn about this stuff. Oh wait, in Bizarro universe I'd be commiting crimes and be eveel. No thanks! ;)
 

BrianW

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Also, I thought somewhere in that huge article they mentioned that space was flat? How can that be when they've modeled the known "viewable" universe as a sphere?
Flatness applies to any dimension. In the first dimension, a straight line is said to be flatter than a crooked line. (Think of a flat or mountainous horizon in a child's drawing.) In the second dimension, a table's surface is more flat than the surface of a bowling ball. And in the third dimension - well, it's hard to visualize.

But this can help: If you were to cut out identical flat squares from a piece of paper, you could use them to completely cover the table top without any gaps or overlap in the paper. Try to cover the bowling ball in the same way, and you'll soon discover that its curved surface will not be covered without some gaps and overlaps in the square pieces of paper.

Well, it's the same if you add a dimension. Try to fill our Universe with a bunch of uniformly-shaped cubes, and you'll find that it's very easy to do across vast distances, which is an indication of its flatness. If our Universe were curved in some fashion, then you'd be unable to fill it with uniformly-shaped cubes without gaps and overlaps eventually appearing somewhere down the road.
 

BrianW

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Shawn, thanks for the link to the article and for starting this discussion. That was a fun read.

About the Level I Hubble Bubbles: I think the article may have left you with the impression that Level I Hubble Bubbles are colossal structures that a pan-dimensional superbeing can step back, see, and identify the boundaries of. But the locations and sizes of Hubble Bubbles in spacetime are completely arbitrary and don’t make even the slightest ripple in the structure of spacetime. We, by definition, are at the very center of our own Hubble Bubble, its radius and location determined solely by our self-centered (literally) perception of the Universe. But somewhere within our own Hubble Bubble may be another sentient observer pondering the same questions. His Hubble Bubble’s location and size are determined by his location and how far he can see. His Hubble Bubble overlaps with ours, since we can both see much of the same stuff as we look around the cosmos. (Indeed, if he is inside our Hubble Bubble, then we can see him, and he can see us.) The further away he is, the less his Hubble Bubble overlaps with ours.

But, amazingly, you don't have to go to a distant galaxy to find another sentient being to compare Hubble Bubbles with. There are many sentient beings you can compare Hubble Bubbles with via email, or even over the phone! You see, technically speaking, your Hubble Bubble is slightly different from my Hubble Bubble since their centers, determined by our respective locations, are separated by several hundred miles. Though they overlap by a considerable margin, there are some things you can see that I can’t, and vice versa.

Just pick any spot (at any time), determine how far you can see from that spot (and time), and you’ve got a Hubble Bubble. So these bubbles are not really distinct structures, like bubbles in a foam or sponge. That analogy was used simply because only non-overlapping (thus qualifying as Level I) Hubble Bubbles were considered in the discussion. Rather, they’re more like templates, or masks, that you use to overlay the broader spacetime continuum to isolate an arbitrary area of interest.
 

Jordan_E

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I tried to read through the whole thing, but my brain had a Big Bang of it's own and I had to go off and eat ice cream just to recover!:D
 

BrianW

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What I don't understand is, if the universe came from the Big Bang, and the subsequent expansion occured at a finite rate, how did space become infinite?
Robert, that’s a good question. I haven’t read many articles seriously presuming that our Universe is infinite. Even with hyper-inflation theory making our Universe mind-bogglingly, incomprehensibly, gobsmackedupsidetheheadedly more huge than what we will ever be able to observe, the Universe, I have always believed, cannot be infinite. Even with Chaotic Eternal Inflation Theory proposing that at the unreachable edges of the unknowable Universe, unfreakably countless microscopic pockets of spacetime are undergoing spontaneous hyper inflation, billions of time each second, each billionth of a second for each microscopic pocket adding to our Universe enough space, matter, and energy to fill any respectably, unfathomably large universe, and with its hyper-expanded edges undergoing subsequent, but similar, hyper inflation, and so on, at a gut-roasting exponential rate…

Well, it’s big, I’ll grant you that. It may even be large enough to handle the god-only-knows-how-large numbers the author used in the article. (10^(10^118)? Jeepers! How can… I mean… JEEPERS!!!) But since it’s been going on for only a finite amount of time, my belief is that it can’t truly be infinite.

But it could well be that, by now, it may as well be infinite.


And that’s just Level I. :)
 
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In the last couple of years the only thing I've read regarding modern cosmology is Guth's book about inflation, so my insight here is pretty limited:

I've always thought that the jump from the inflation theory to the inflationary multiverse theory implied that the Big Bang that we see in the cosmic background radiation is a kind of local phenomenon, but neither Guth's book nor this article seem to explicitly say that, though if I recall, Guth's book entertained Linde's idea that an inflationary universe may have always existed, which would imply that the Big Bang we are aware of was the formation of our little Hubble Bubble of normal space-time out of the foam of inflationary space. The question of whether there was ever a "bigger" bang becomes the chicken and egg problem all over again.

The author is clearly implying that the Hubble Bubble is infinite, but he only seems to reference arguments that maybe it isn't instead of arguments that it must be, so ? Guth's book seems to only imply that the universe seems flat because it is tremendously huger than we thought, not that it was infinite.

And in the vein of seeing everything as a nail if you've got a hammer, I've wondered for a while if this mysterious new force that is causing the universe to expand faster couldn't be some kind of friction with the "external" inflationary multiverse. That is, the inflation going on outside of our bubble is pulling it outward somehow, like a balloon in an airlock that the air is being sucked out of. Why it wouldn't have been happening all along is not explained by my rigorously worked out theory, but I'll let real theorists work out the messy details of the soon-to-be-famous "balloon in an airlock" theory.

-Robert
 

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