Black Hole Universe Model Questions

That's a bump/update...This article is on topic:http://phys.org/...ack-hole-universe-physicist-solution.html

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Our universe may exist inside a black hole. This may sound strange, but it could actually be the best explanation of how the universe began, and what we observe today. It's a theory that has been explored over the past few decades by a small group of physicists including myself.

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I ain't got the time right now to get into this, but want it to be on record for future reference.

Interesting article. Thanks for the bumpdate and course correction.@DrAdequate:What I mean by saying the universe is expanding toward a singularity is basically that the Big Bang and the so-called Big Crunch are the exact same thing. The image I used to describe this in the original blog post was an apple.The skin of the apple represents spacetime. The core of the apple represents a singularity out of which the universe--you, me, all the stars and galaxies--emerged. One can imagine a galaxy, sometime after the Big Bang, moving out and away from this singularity according to Hubble's law, eventually crossing the "equator" of the apple/universe, and finally winding up right where it started.Of course this is just a visual aid and implies nothing about the actual shape or structure of the universe. For a more detailed explanation please see the original blog post here:Refolding the Wayfarer's Clothes: BHUM (bee-hum)Ultimately, the BHUM claims the universe--specifically the multiverse--is one gigantic black-sive-white hole.

In which case when it crossed the equator it would be contracting towards a singularity. You see why I was puzzled?

It's puzzling because 4-dimensional objects are puzzling. But I must insist that this is an expansion, or at least looks like one. From the perspective of an observer anywhere on this apple/universe all the galaxies, everything, will appear to be moving away at an accelerated rate in all directions. And thus the observer is left to conclude the universe is expanding, which it is, toward a singularity.

Not after the "equator" has been passed. Then it'll look like it's contracting. 'Cos it'll be contracting.

If it doesn't stop expanding and start contracting, then it'll look like a horn instead of a sphere or apple:

@Dr AdequateI think we might be veering off into a fruitless semantic argument.@Catholic ScientistI said in the original blog post that the universe is expanding and contracting at the same time. However, from the perspective of an observer at any point the universe will appear to be expanding at an accelerated rate in all directions (according to Hubble’s law).And as for discussing the shape of a hypothetical 4-dimensional object, I think the horn image helps.Wish I could figure out how to paste this image in here but here's a link:http://1.bp.blogspot.com/...w/SkC0D2Q9zKs/s1600/Diagram3.bmpI guess the main pointif we can bracket the shape issue for a momentis the fact that the empirical evidence suggests the universe is expanding toward a singularity. Hubble’s law states that double the distance and the galaxies are moving away twice as fast. This is exactly what one would expect (and can easily observe) of objects falling toward a singularity. The example I used in the blog post was tossing pennies off of a tall building. Drop three pennies in 5 second intervals and the first penny will always be moving faster than the second, and the second than the third, because of the acceleration due to gravity. The observerthe person dropping the penniesmight conclude that space is moving away from him (expanding), or, he might conclude that the pennies (i.e. red-shifted galaxies) are falling toward a gravitational singularity. Which they are, of course: the center of the earth.

It's also exactly what we would expect if the expansion was per FLRW cosmology, which does not include the universe falling towards a singularity.I don't think your idea that the universe is expanding and contracting at the same time matches any observational evidence. Is there any evidence that this notion you have is real?ABE: You believe there is a singularity at the center of the earth? Edited by NoNukes, : No reason given.

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I suppose a black hole could exist within the event horizon of another, but I can't imagin a universe like ours being a really big black whole because, well, to be blunt: because they're really fucking dense...
Isn't our universe less dense than a black hole?

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The universe is no less dense than a universe-sized black hole would be. It uses the Schwarzchild equation here. "Common Sense" from small blackholes - that they are massively dense, doesn't hold for black holes of truly massive size."The Schwarzschild radius is proportional to the mass " (see e.g. wikipedia or any other site about the equation). You can infer all you need to from that one mathematical observation.Doubling the mass, doubles the radius of the event horizon. When the radius of a sphere doubles, the volume is 8 times as great. This means each time you double the mass of a black hole, density drops by 3/4.There is an inter-relationship between mass, radius and density. Given any one of these you can calculate the other 2 black hole values.you can plug the observed density of the known universe in, and get an estimate of the size of event horizon which is not far off the observed distance to the earliest galaxies.Oh, and btw, a "closed" space would wrap-around, so there's no "point" for the singularity to be, just as we do not observe a "middle" from which the universe expands. A totally curved space doesn't need a "middle".Edited by jasonlang, : No reason given.Edited by jasonlang, : No reason given.

If you're going to use the word "expanding" to mean "contracting", then I'm very much afraid that that's what we shall do.You could avert this by using "expanding" to mean "expanding" and "contracting" to mean "contracting".

@Dr AdequateI think I’ve made it pretty clear that to any observeraccording to the BHUMthe universe will appear to be expanding.You said:Not after the equator has been passed. Then it’ll look like it’s contracting.So I must ask you: Where would an observer need to be positioned for the universe to look like it’s contracting?Unless you’ve mastered some sort of magical gorilla geometry to match your smugness, I’m afraid it’s mathematically impossible.Maybe this example will be simpler to understandPicture a piece of plain old flat computer paper. The paper is the universe in this analogy! An observer (if it helps pretend you’re the observer) is positioned at the center of said piece of paper. Everything the observer can seei.e. red shifted galaxiesappears to be moving away from him/her according to Hubble’s Law. From this empirical observation the observer concludes the universe is expanding. Yes, expanding. Hubble’s Law is the reason scientists believe the universe is expanding.Now picture the edges of said piece of paper. The edges represent the singularity in this analogy. (Wait I though a singularity was a point not a square blah blah blah). You may need to take a piece of computer paper from your printer to see how it can be folded back to resemble a sphere. Yup, space can bend. Fancy that.I should probably mention again, though I’ve stated this point before in multiple posts, is that we are talking about a hypothetical 4-dimensional object. You can’t picture a 4-dimensional object. Neither can I nor anyone! They don’t make sense. The closest we can get is a Mobius strip or a Klein bottle.If you had actually read the original blog post this would not have been such a distracting issue.When I said we were veering off into a fruitless semantic argument I didn’t mean to be an ass. I just meant that we were veering off into a fruitless semantic argument. You could avert this by having less of an ego, and understanding that when I use the word expanding I mean just that: expanding.So I must ask you again, because this is the question you’ll dodge to save face: Where would an observer need to be positioned for the universe to look like it’s contracting?I’ll tell you the answer: The observer’s head needs to be positioned somewhere near Uranus.@jasonlangGreat information. I wonder if more evidence than this needs to be presented to at least get people to admit there is a possibility that the universe is one gigantic black hole?

* sighs *In order for there to be a Big Crunch, in order for the universe to end up "finally winding up right where it started", it has to contract. Then we will not observe it expanding. We'll observe it contracting. The stars will appear blue-shifted to an observer. They will be getting closer together.This is why we know that this isn't happening now. Anywhere inside it, during the phase in which it is in fact contracting.Edited by Dr Adequate, : No reason given.

You can't be inside it. The surface is spacetime.

@NoNukesA gravitational singularity, yes, at the center of earth. This is gravity 101.From Einstein’s Universe, Nigel Calder elaborates:In Einstein’s theory the main features of gravity around the Earth are exactly the same as they would be if our planet were hollow, with a faked-up papier-mch surface of mountains and seas, but having a black hole at the centre with the same mass as Earth. [...] The German theorist Karl Schwarzschild offered this very useful interpretation almost immediately after Einstein published his theory. (74).Edited by Echetos, : To add @NoNukes

I can, in fact, be in the universe. I am habitually in the universe. It's getting out of it that would be tricky.