Origin of our universe

[Aught3]

I don't know much about this topic and would like to see some discussion of the current ideas surrounding the origin of the universe.

Some questions to reveal the extent of my ignorance:
Was there actually a singularity? (I have heard some disagreement on this point), and what the hell is a singularity?
Did something exist 'before' our universe? Is it necessary that something did exist for our current theories to work? And, if so, what the hell existed 'before' our universe?

Let the educating commence

 

[Lichtbringer]

Okay, let's start with the basics.
When we trace the expansion of space back in time, we can extrapolate the size of the universe at the beginning of time (t = 0). At t = 0 all the space and all the energy of the universe should be combined in a single point with an extension of 0 - a so called singularity.
This seems reasonable because of simple extrapolation. But scientificly speaking it is only a hypothesis since we can't test it. For reasons of quantum mechanics the first time in the history of the universe we can observe is t = 5,39124 * 10^-44 s.

When it comes to the time before the Big Bang we hit the borders of science. Science can only work on observable phenomena and we can't observe what was before the Big Bang. But our the Big Bang Theory can still give us quite a good hind.
Stephen Hawking once said, the question 'What came before the Big Bang?' was like asking: 'What lies north top the north pole?'
Nothing lies north to the north pole, not because there is vacuum but because the point 'north to the north pole' doesn't exist. Similar the point in time 'before the Big Bang' doesn't exist. Time began with the beginning of the universe.
Sience still can't say what caused the universe, but if you wan't to claim some cause, you have to invoce a entire different form of time for it. Ever heard of occam's razor?
In addition there is no reason whatsoever to assume the universe had a cause. The human intellect exspects a cause for every effect, but that is because this universe has causality build in. There isn't the slitest reason to assume that the universe itself had to have a causal reason for beginning.
Also, if you claim a cause for the universe, the next question would be, what the cause for that cause was. You can't say: 'It doesn't need a cause', since one could also claim that for the universe itself and that destroys your own argument.

 

[Aught3]

Thanks for the response.

When we trace the expansion of space back in time, we can extrapolate the size of the universe at the beginning of time (t = 0). At t = 0 all the space and all the energy of the universe should be combined in a single point with an extension of 0 - a so called singularity.

What does an extension of zero mean? Also, this seems like a lot of mass/energy to compress into a singularity, or is it that the sum of all the energy in the universe is very close to zero?

Stephen Hawking once said, the question 'What came before the Big Bang?' was like asking: 'What lies north top the north pole?'
Nothing lies north to the north pole, not because there is vacuum but because the point 'north to the north pole' doesn't exist. Similar the point in time 'before the Big Bang' doesn't exist. Time began with the beginning of the universe.

Yes, I understand this point. It is meaningless to talk about our experience of time before the big bang and the origin of our universe.

Sience still can't say what caused the universe

Ah, so we don't know. I guess I was after more of a discussion of different hypotheses then. Surely some of them must rely on something existing 'before' the big bang. The only one that doesn't, as far as I can see, is the idea that our universe always existed - but then what caused the rapid expansion in the early universe?

 

[Lichtbringer]

In a black hole a singularity means that all the mass (= energy) is compressed into a single point with infinite density. When it comes to the Big Bang, it's complicated. Scientist originally believed the sigularity at the beginnig of the universe to be similar to that of a black hole.
Newer theories in cosmology now propose that with the gravitational energy being negative and the vacuum energy being positive the total amount of energy in the universe could be 0.
I kinda like the idea, because it would mean that the old question 'Why is there something rather than nothing?' is false. There really is nothing, it's just elegantly distributed.
(Of course, that I like the idea doesn't make it true in anyway.)

Modern physics speculate that a great number of universes is caused by fluctuations of multidimensional membranes. But that's really out of my league.
Maybe someone else hear can answer it...

 

[irmerk]

Just in case any of this helps, if you have not seen it yet:
Link here.
Link here.

 

[Ozymandyus]

I wonder sometimes about this idea if time being completely non-existent 'before' the big bang. We are pretty certain that black holes of every size emit radiation at various rates - There is probably such radiation outside of our 'universe' if universe is defined as only what was inside the singularity at the time of the big bang. That radiation has its own time scale implications that could be used to establish a timeframe before the big bang.

We certainly could never observe this radiation, but it still breaks the idea of a 'beginning' of time for me. I may just misunderstand though - I am by no means an expert.

 

[Josan]

I wonder sometimes about this idea if time being completely non-existent 'before' the big bang. We are pretty certain that black holes of every size emit radiation at various rates - There is probably such radiation outside of our 'universe' if universe is defined as only what was inside the singularity at the time of the big bang. That radiation has its own time scale implications that could be used to establish a timeframe before the big bang.

We certainly could never observe this radiation, but it still breaks the idea of a 'beginning' of time for me. I may just misunderstand though - I am by no means an expert.

I might be a little slow, but I don't understand why there should be any radiation "outside our universe". You compare it to hawking radiation, but I don't really see what they have in common? From my understanding of hawking radiation it is related and caused by quantum fluctuations.

If you could elaborate a bit, I would be grateful.

 

[Ozymandyus]

I might be a little slow, but I don't understand why there should be any radiation "outside our universe". You compare it to hawking radiation, but I don't really see what they have in common? From my understanding of hawking radiation it is related and caused by quantum fluctuations.

If you could elaborate a bit, I would be grateful.

I am saying that hawking radiation implies time/space outside of the singularity at the time of the big bang. This concept that nothing 'pre-dates' a black hole singularity does not hold, as such a singularity may be, at least from a theoretical external standpoint, lodged in a time frame - emitting radiation at some rate. If we are talking about the 'internal' time frame of the black hole then there is no time, space-time (as we know it) is a singularity.

The reason I say the radiation is 'outside' our knowable universe is that we have defined this universe as 'beginning to expand' 16 billion(ish) years ago. There was radiation BEFORE that expansion, when you consider an external timeframe that includes that radiation - from the internal timeframe of the singularity there was no 'time' before the big bang, but in a time frame inclusive of such radiation there clearly is.

Sorry if its still not clear. In short: In a universe defined as 'beginning' at the moment of the big bang does not include that radiation.

 

[diagoras54]

Everything came from nothing.
As always, it just comes down to quantum mechanics.

 

[Aught3]

That is one cool vid, it actually sparked my posting of this topic.

Everything came from nothing.

Nothing? Even the video says there was some 'quantum mechanical foam-sort-of-something'. Is it necessary for these hypotheses that something like that exist 'before' the universe.

 

[diagoras54]

Nothing in terms of what we recognize as "something", meaning no space, time, matter, or energy. There was "something", but not that which is contained within our universe. The point of the video is that a quantum fluctuation in a scalar field, whether that's in spacetime or some other "structure", can produce a universe out of no energy or matter.

 

[Aught3]

In a scalar field? I thought the fluctuation created a scalar field - and if it was the right sort we get a universe.

Nothing in terms of what we recognize as "something", meaning no space, time, matter, or energy.

Amusingly, this reminds me of a cosmological argument for the existence of god. Whatever created the universe had to be spaceless, timeless, and so on. Now I can nod along with this part instead of wondering how they managed to figure it out.

 

[diagoras54]

You're right, I apologize; I wasn't paying attention to the terminology I was using. The fluctuation creates energy in the form of a scalar field. The important issue is that the universe could have been created out of nothing, despite what creationists insist.
Anything which can exist exclusive of the universe could have contributed to creating it. Since time, space, matter, and energy as we know them can only exist within the universe, these must have had nothing to do with the Big Bang. That's not to say, however, that there isn't some underlying structure such as the "quantum foam" in which space is held; particle behaviour at the scale of quantum mechanics indicates that this structure is unlike anything with which we're familiar, and we have no reason to assume it didn't exist before the Big Bang.

 

[GoodKat]

Maybe there is nothing, maybe the metaverse taken as a whole is 0. Maybe we are 1, and somewhere there is a -1, perhaps there is also a 2 and -2, maybe the infinite number of different universes that theoretical physicists speak of are actually all existent numbers and their negatives.

This is the simplest answer I can think of that doesn't beg the question. We are here because -1+1=0

 

[Pulsar]

At the moment, it's all more speculation than science.
But if you want to know what the M-theory guys have to say about it, then these videos are a good place to start:





(The first part of the documentary is http://www.youtube.com/watch?v=2_vpEyE6rug).

 

[scikidus]

There's also the idea that our universe broke off from an earlier universe.

http://www.newscientist.com/article/mg19125591.500-create-your-own-universe.html?full=true

 

[Salv]

The one thing I've always disliked is how space-time is usually illustrated in two dimentional way.
Would it be possible for gravity to rip and tear space-time? So in illustration the mass at the center is separated from the current universe to create a separate baby universe. So the warped space-time goes back to "normal"?

 

[ahdkaw]

I've always liked the idea of a continually expanding and then contracting universe.

Singularity -> Expansion -> Contraction -> Singularity (aka Rinse & Repeat)

I have no links for this, and it's probably wrong, but it was mentioned somewhere or other at some point in time.

 

[Nelson]

I've always liked the idea of a continually expanding and then contracting universe.

Singularity -> Expansion -> Contraction -> Singularity (aka Rinse & Repeat)

This depends on the critical density of the universe, the basics of which are discussed here: Big Crunch and
here: Big Rip. Most of the evidence seems to show that the universe is in fact accelerating which would mean, unfortunately, no Big Crunch. See: Accelerating Universe.