Particles (The Universe) Popping Up Into Existence

RobinSky

I recently watched another program with Stephen Hawking called "Did God Create The Universe?" However this topic isn't religion related but my questions popped up due to this.

I am having problem understanding how the universe could pop up from nothing when time did not exist. They said this was possible due to (quantum mechanics if I remember right?) particles (they said particles like protons) popping up into existence and also disappearing shortly after that.

However, how can a particle pop up into existence, when time did not exist? They also proudly mentioned "Since time did not exist, there was no time to cause to happen, and since no cause could happen, god could not be the creator of the universe" something like that.

I hope you understand my question, I find it always a challenge to ask these deep cosmology questions as well as understanding the answers to them!

Regards, Robin Andersson.

Simon Bridge

It is not a trivial question.

And it is really difficult to talk about because we don't have commonly understood words to deal with the concept of "before" when there is no time to have a "before" in. We do have a language to describe these concepts in but they are mathematical - you have to learn them. Until you do you are stuck with having these clumsy analogies like you saw on the show... or we just have to wave our hands and chant "quantum" at you.

I take it from the phrasing that you don't have a problem with space appearing in time even though there is no pre-existing space to appear in?

So why can time not appear without a "pre-existing" time? Time is just another dimension of space after all. It can do it the same way the rest of space did.

The various models have space-time show up out of not-even-nothing as a set of undifferentiated dimensions ... at the appearance of the universe, time has not separated out as a special dimension.

To give you a taste:
http://ws5.com/spacetime/quantum%20cosmology.pdf
... this is a preprint chapter of a book on quantum cosmology - it focusses on the concepts rather than the math (but math is unavoidable).

RobinSky

Quote by Simon Bridge

It is not a trivial question.

I take it from the phrasing that you don't have a problem with space appearing in time even though there is no pre-existing space to appear in?

Ahh, that was a good one. I understand it's hard and very common to see questions like these because it's always (or mostly) some kind of error in the thinking, it's out of common sense. But what you stated above was in fact a very good statement, I understand the concept of my question better - the "fault" of my thinking.

Quote by Simon Bridge

To give you a taste:
http://ws5.com/spacetime/quantum%20cosmology.pdf
... this is a preprint chapter of a book on quantum cosmology - it focusses on the concepts rather than the math (but math is unavoidable).

And regarding that PDF, I'll return to it in 3,5 years. Then I have finished my two courses in Engineering Physics regarding quantum thingies, Quantum Physics & Applied Quantum Physics. I hope I will understand this better then ;).

But at the same these things are so interesting it's hard to avoid trying to understand them, at least when you are young and curious about the universe.

By the way Simon, you said: "as a set of undifferentiated dimensions"
What does that mean?

Simon Bridge

If you skim through that pdf down to the "no boundary proposal" where the Hartle-Hawking instanton ... basically, time started "after" the universe did. To talk like this we have to imagine a meta-time for these things to happen in while remembering there's no such thing.

"Before" this, the universe had 4 space-like dimensions (sort of).

From Hawking (lecture 94):

The problem of what happens at the beginning of time is a bit like the question of what happened at the edge of the world, when people thought the world was flat. Is the world a flat plate with the sea pouring over the edge? ... As we all know, the problem of what happens at the edge of the world was solved when people realized that the world was not a flat plate, but a curved surface. Time however, seemed to be different. It appeared to be separate from space, and to be like a model railway track. If it had a beginning, there would have to be someone to set the trains going. Einstein's General Theory of Relativity unified time and space as spacetime, but time was still different from space and was like a corridor, which either had a beginning and end, or went on forever. However, when one combines General Relativity with Quantum Theory, Jim Hartle and I realized that time can behave like another direction in space under extreme conditions. This means one can get rid of the problem of time having a beginning, in a similar way in which we got rid of the edge of the world. Suppose the beginning of the universe was like the South Pole of the earth, with degrees of latitude playing the role of time. The universe would start as a point at the South Pole. As one moves north, the circles of constant latitude, representing the size of the universe, would expand. To ask what happened before the beginning of the universe would become a meaningless question, because there is nothing south of the South Pole.

RobinSky

Quote by Simon Bridge

/.../because there is nothing south of the South Pole.

I must admit I love these analogies. Just like the show I saw earlier they showed an analogy of negative energy with a man digging a hole, the hole in the ground represented negative energy, and the big pile with sand and rock represented the positive energy.

However, as I have understood this now. Asking how the universe did come out of existence when time did not exist, when no "cause & affect" could happen, is the same thing as asking what's south of the South Pole? Or am I talking completely nonsense now (bear in mind I'm not a mathematician or physicist, yet - which can be the result of very dumb questions

!)?

Best Regards, Robin Andersson.

Simon Bridge

That's pretty much it.

Hawking is describing his own efforts of course. There are other models - eg. see the tunnelling model in the pdf - but they all seek to remove the "beginning of time" singularity from the historical Big Bang Theory.

"How does time start?" becomes a meaningless question in these schemes.
It's highly speculative though - so far it is mostly a kind of reverse-engineering by inspired guesswork. There's no guarantee that any of them are actually true.

RobinSky

Thanks Simon!

Simon Bridge

No worries.

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