I don't understand the no-boundary universe model..

NO-BOUNDARY UNIVERSE

A universe that is finite in size but did not begin with a singularity is the result of one attempt to combine aspects of general relativity and quantum mechanics. The history of this no-boundary universe in imaginary time is like the surface of Earth, with the Big Bang equivalent to Earth’s North Pole and the size of the universe increasing with imaginary time as you head south toward the equator.

A proposal first advanced by Stephen Hawking and Jim Hartle, the no-boundary universe is one in which the universe does not start with a singularity. It uses American physicist Richard Feynman’s proposal to treat quantum mechanics as a “sum over histories,” meaning that a particle does not have one history in space-time but instead follows every possible path to reach its current state. By summing these histories—a difficult process that must be done by treating time as imaginary—you can find the probability that the particle passes through a particular point.

Hawking and Hartle then wedded this idea to general relativity’s view that gravity is just a consequence of curved space-time. Under classical general relativity, the universe either has to be infinitely old or had to have started at a singularity. But Hawking and Hartle’s proposal raises a third possibility—that the universe is finite but had no initial singularity to produce a boundary (thus the name).

The geometry of the no-boundary universe would be similar to the geometry of the surface of a sphere, except it would have four dimensions instead of two. You can travel completely around Earth’s surface, for instance, without ever running into an edge. In this analogy, unfolding in imaginary time, Earth’s North Pole represents the Big Bang, marking the start of the universe. (But just as the North Pole is not a singularity, neither is the Big Bang).

I can only assume they mean it's like we live on the universe instead of in the universe? In the same way we live on the earth so there are no boundaries, where as, if we lived in the earth there would be.

That is just what I am grasping from it.

Think of the surface of an expanding balloon. If you walk in one direction faster than the expansion you will eventually make it to where you started, hence no boundary. This would be an example of a universe with no boundary that is finite, however its only 2D, which makes it possible to imagine for us lowly 3D critters.

Why would it only be 2D? Couldn't we live on the surface just like the idea of a flat universe or like living on the surface of the earth?

Or maybe the 3D part of reality is something our minds are creating or projecting.

Its an example, not the one we would live in, its possible to imagine a 2D universe with our brains. Try for a moment to image a 3D universe with a finite space and no boundary? Can you, if so your the first human ever. Its easy to show mathematically, no so easy to picture.

Steven Hawking pictured it as a sphere: He even has an illustration.

http://www.pbs.org/wnet/hawking/universes/html/bound.html

Its the same example used in college to get across the idea.

This is a great illustration of the concept of a space being finite and not having a boundary. It also illustrates the way that many physicist imagine our universe - as a 3D-space that is curved onto itself, as the 2D surface of a balloon curves back onto itself.

If I understand correctly, then the topic of the OP is even more difficult to grasp than this - it is not simply a proposal that the spacial dimensions are without boundary, but that time itself had no boundary. Imagining our 3d universe folding onto itself is easy for me; trying to imagine that time itself could finite but unbounded... it just seems completely senseless to me. I'm going to quit while I'm ahead.

Yeh, I don't think the model is a correct one.

Whether the model is correct or not is only for Jesus to decide.

But if the evidence to propose such a model is based on a lot of incomprehensible math, then I give up before I even try.

I had heard about this theory when two engineers in my drinking group talked about it five years ago, and I said to myself, quietly, "bullocks". But apparently it's supported by so much math that it must be true.

I just decided to simply not worry about it. Whethe the world is infinite in a three-dimensional space in each direction, and time is a straight-line something, or the world is something that folds into itself, and is still infinite in the possibilities of itself, except what CAN happen MUST happen, is irrelevant to me.

In fact, I totally oppose the very original hypothesis of this theory, which states that what CAN happen MUST happen, in a completely infinite world with no restrictions on replicative combinations. I still object, and I am adamant in saying that what CAN happen DOES NOT NECESSARILY happen. Hence the CAN modal verb, which denotes capacity of doing, or capability, but not actual fact of witness.

I really don't know who came up with this hypothesis. It is not true, but I can't prove it false. So I don't even try, but I don't buy it. And hence the curved space, universe, and time, is hogwash, I opine, but that Hawkin guy has not died yet from a disease that ought to have killed him decades ago. This means he has friends in higher places, like in the University Faculty Payroll Office, or in the Dean's Office of Internal Manipulation of Secreteries' Ticklish Parts, and therefore I admit he is infinitely smarter than I, and I bow to his superior opinion.

But I still don't buy it. On the strength of the original hypothesis being wrong in what it claims.

I totally agree.
Not all probabilities become realities. That's a stupid idea.

You know what, you Beeech? With this one sentence you turned my opinion completely around.

I thought of it this way: A probability is never absolute surely to become reality, but it has a chance. The more chances it has, the probability of it happening in a given amount of chances increases, as the total amount of chances to happen increase.

The chance that something with a given probability ALWAYS increases with the more actual situations presenting in which it can happen. The increase may not be large, or proportional, but a chance B2 of something with a probalbilty of X happening, is always larger than B1, when you consider B1 to happen in N1 possible occasions, and B2 in N2 possible occasions, and N2 is larger than N1.

If this is true, and which it is, then if you create an infinite number of chances for B to happen, then B is not only "likely" to happen, but it will happen.

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Another way of looking at it is this: if a chance of something happening increases with the increase in the number of situations in which it has a chance to happen, then P(N(i))[i->infinity] = 1, no matter what. This is to be read, "The probability of N to happen, approaches one (absolute certainty) when the number of occurrances that allow a chance for N to happen approach infinity."

I think the philosophy comes in when one says "let's think of Infinity in a non-strictly math based way, that is, while we agree it is calculus-created, we can still remove it from the confines of its concept by calculus, and say that 'approaches infinity as I approaches infinity' is equivalent to 'infinity when I is infinitely large.'

If you can do that, then it's clear that any event that has any chance of happening, will certainly happen if you give it an infinite number of chances to happen.

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I called you a beeech Jeanniebean, because this realization was big. I first heard about the hypothesis back... ah, around 30 or so years ago, and have been struggling with it. A man who was apparently four times smarter than I, came to this realization right in front of my eyes; and I did not understand it, and it bugged me. I also, ten years after that, had an intellectual debate with a young man, and we were sorta vieing for the graces of the one and same chick, and she was drop-dead gorgeous. The guy and I argued, and I based a point of my argument on what I heard from the genius, that what can happen, must happen; the sparring buck said, no, that's not true at all; and the chick went with him.

I was completely heart-broken. Totally. That chick was awesome.

So now, I called you a beeech because of my awe of your femininity. A woman can be a good witch, and / or a bad witch, but a woman will always wield some awesome power over a man. It is not a direct power; it is some ineffable power, that is mystical and mysterious, and if you ask me, largely inexplicable. The typical Eve in the Garden of Eden exercised this power over Adam. She made her man commit an act, and she did not even have to extend herself to do this, that cast him and her into damnation, by her sheerly asking him to do this or to do that. He had been aware of the consequences; God Himself forbade him to eat the apple; he knew what damnation was, and he knew how cozy and comfy it was to live in the garden of eden; yet he ate the apple ONLY because Eve asked him to. No coercion, nothing. Eat it, she said, and he ate it.

You did this too, now, to me, Jeanniebean, by making me realize a truth that I have been struggling with, like I said, for nearly thirty years.

This... my lady, is not a small feat. This takes a giant, or it takes a woman.

You see, a woman does not have to be a giant to make a man's mind turn, in any direction. She can be a giant, but that's an irrelevant issue. She HAS to be a woman, though; otherwise the chant, the magic, the spell, won't work. Only a woman can put a spell on a man. God certainly can't. (This is the second reason why god is unquestionably male: he can't spellbind men. The first is that he, as the most awesome thing in the universe, must be, or must have, a penis. As per the post in the oscillating universe thread.)

So what do you call a witch of the east, or the witch of the west, or the witch, which is, quiet simply, Eve the Eternal, or woman, or ...

Well. You call her Beeeech, of course. That was easy.

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(F, cold sweat is coming out of every pore of my body as I write this, yet I feel hot and heady.)