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Author Topic:   questions about the origin of singularity = nothing
thekid1870
Inactive Member


Message 1 of 38 (218256)
06-20-2005 8:03 PM


How did people come up with the theroy that the singularity was nothing or just a tiny spec? Is there any evidence that supports this theroy?

This message has been edited by thekid1870, 06-20-2005 08:53 PM


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Admin
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Message 2 of 38 (218258)
06-20-2005 8:07 PM


Thread moved here from the Proposed New Topics forum.

    
AdminNosy
Administrator
Posts: 4754
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Joined: 11-11-2003


Message 3 of 38 (218262)
06-20-2005 8:19 PM
Reply to: Message 1 by thekid1870
06-20-2005 8:03 PM


some previous discussion
Here is some previous discussion:
Message 185
Message 194
Message 200
and from 200 on.

also here
Message 70

This doesn't directly answer your quesion I am looking for that.

ABE

This thread might do it: The Big Bang is NOT Scientific

This message has been edited by AdminNosy, 06-20-2005 08:22 PM


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Sylas
Member (Idle past 3549 days)
Posts: 766
From: Newcastle, Australia
Joined: 11-17-2002


Message 4 of 38 (218283)
06-21-2005 12:55 AM
Reply to: Message 1 by thekid1870
06-20-2005 8:03 PM


How did people come up with the theroy that the singularity was nothing or just a tiny spec? Is there any evidence that supports this theroy?

This is a common question, and though it has been discussed previously, I'll give a brief self-contained answer here.

The singularity is not really a "thing", but a condition in which physics breaks down.

The word "singularity" is a mathematical term. It refers to a condition in which a function diverges or becomes undefined. For example, the function f(x) = 1/x has a singularity when x equals 0.

The theory we use for gravity and spacetime is general relativity. When applied to the universe to track the "scale" and "curvature" of spacetime into the past, the functions diverge to infinitesimal scale and infinite or undefined curvature. This is the singularity; and it marks a point at which classical physics breaks down.

As yet, we do not have a physical theory able to describe these conditions. It will require a combination of relativity and quantum mechanics; which is an unsolved problem in physics.

The theories for relativity, spacetime, and the expanding universe are obtained in the same way as all scientific models. Hypothesize and test.

There is copious evidence for relativity, and for the expanding universe. There is no credible basis for doubt that the universe has expanded from conditions of extreme heat and density some 13 or 14 billion years ago.

It is a mathematical theorem that relativistic physics diverges to a singularity of unbounded density and infinitesimal scale as you extrapolate into the past. This marks a point at which we don't know what is going on, because existing physics can't handle those conditions.

I'm choosing words carefully here. "Scale" is a bit like "size". It does not mean that there is any particular object, like a "speck", which developed into the universe. It means that the entire universe was compressed. Everything we see now was once contained within a small region; but this does not mean that this region had any edge.

Imagine we could look into the distant past, when the whole universe was hot plasma a bit like the middle of the Sun, extending in all directions without edge or bound. Now draw an imaginary sphere within that thick hot dense material. That sphere is the "region" which contained all the matter visible today. "Scale" is just an indication of the factors by which things have expanded.

Cheers -- Sylas


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cavediver
Member (Idle past 1933 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 5 of 38 (218329)
06-21-2005 7:09 AM
Reply to: Message 4 by Sylas
06-21-2005 12:55 AM


Just to add a slightly different angle to this:

The thing is... the singularity is not a thing, it's a place: like the North Pole. How big is the North Pole? It has no size whatsoever, but nobody disputes its existance. It is the origin of lines of longitude. The big bang singularity is the origin of lines of time. How can you go north from the North Pole? You can't, you can only go south. But there is no barrier or edge preventing you from going further north; the question just doesn't make sense or apply. In the same way, you can't think of before the big bang, because from the the big bang, all directions lead to "after" the big bang. At time=0, our common understanding of time has disappeared and no longer applies: there is no "before", only "after". Just as our common understanding of north disappears at the north pole: there is no north (or east or west), only south.

If we live in a "closed" universe, this analogy is even better, because just as the circles of latitude grow from zero size from the north pole, reach a maximum (the equator) and then shrink bank to zero size at the south pole, so too the universe grows from zero size, reaches a maximum then shrinks to zero size again in a "big crunch". The idea is not to look at the lines of latitude, but look at the whole earth: although the lines of latitude begin and end with zero size at the two poles, there is no edge or boundary. Looking at the earth as a whole, we understand that asking what's north of the north pole and south of the south pole makes no sense. In the same way, when we look at the universe not as three-dimensional slices (which is all our eyes and minds can do) but as a four-dimensional whole, we realise that although we can have a beginning of time (big bang) and end of time (bug crunch), asking what happend "before" the big bang and "after" the big crunch simply doesn't make sense... it's not evading the question.

General Relativity (the mathematics which gives us big bang cosmology) only deals in 4 dimensions (3 space + 1 time). So to understand what it is telling us, we have to think in 4 dimensions, which is neither easy nor intuitive when we are so used to a world that appears to be 3-dimensional.


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Dr Jack
Member (Idle past 394 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 6 of 38 (218334)
06-21-2005 7:38 AM
Reply to: Message 5 by cavediver
06-21-2005 7:09 AM


Asking what is before the big bang only doesn't make sense in certain conceptions of the big bang, and using certain physics models. Interestingly, under both String Theory and Quantum Loop Gravity - which are, arguably, the two strongest contenders to replace Quantum Mechanics - the question can be asked, is meaningful, and can probably be answered.

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cavediver
Member (Idle past 1933 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 7 of 38 (218343)
06-21-2005 8:21 AM
Reply to: Message 6 by Dr Jack
06-21-2005 7:38 AM


I was talking Standard Model FRW cosmology with a hint of Hartle-Hawking NB proposal but I'm trying to get across a basic mathematical truth about the geometry of space-time. It doesn't really matter what model you stick in there. Exactly the same priciples will apply, whether your target space is 4, 10, 11, or 26 dimensional. The important point is that time is simply a coordinate... just because it may start somewhere, it does not necessarily introduce an "edge" or "boundary" that would beg the question of "what came before?".

Anyway, the original point was about the singularity being of zero size, and we seem to have drifted off that (my fault!). Again, you need to think in higher dimensions. I've used the north pole analogy... now a slighlty different one: take a box. It has eight vertices. Each vertex is a "point" of zero size, zero volume. Does that mean that we can't fit things in the box? It is the box that contains the things... the vertices are just limits of where those contained things can be. The big bang singularity is simply a vertex to the 4-dimensional universe.

Hmmm, I'm not to happy with this analogy... I'll work on it :-)


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thekid1870
Inactive Member


Message 8 of 38 (218351)
06-21-2005 8:38 AM


First off, I would like to say thanks for responding to my post. But u guys didn't really answer my question. Maybe I should've been more clear. I understand there is evidence to suggest that our universe had a starting point. I also understand that there is evidence to suggest that at the region or place(or whatever u wanna call it)it was really hot and dense. But what I don't get is why people believe it started from ''nothing''. Wouldn't logic dictate that matter can't come from nothing. Doesn't it make more sense if the ''singularity'' was actully a huge object that got to massive and exploded?

This message has been edited by thekid1870, 06-21-2005 08:40 AM

This message has been edited by thekid1870, 06-21-2005 08:42 AM


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Sylas
Member (Idle past 3549 days)
Posts: 766
From: Newcastle, Australia
Joined: 11-17-2002


Message 9 of 38 (218360)
06-21-2005 9:27 AM
Reply to: Message 8 by thekid1870
06-21-2005 8:38 AM


But what I don't get is why people believe it started from ''nothing''. Wouldn't logic dictate that matter can't come from nothing. Doesn't it make more sense if the ''singularity'' was actully a huge object that got to massive and exploded?

Cosmologists don't know how it started, and they don't usually say things like "it comes from nothing".

Part of the problem is that cosmology is very unintuitive and hard to explain, and when trying to explain it without all the mathematics, we have to use simple word pictures that may help with some of the broad concepts, but which fail to capture the details accurately.

Definite statements that it started from nothing should not appear in any credible exposition of the scientific models. We don't even know that the notion of time is meaningful as you approach the singularity.

However, this is not because of any logical rule about matter not being able to come from nothing. In fact, matter can come from nothing in quantum mechanics; depending on how you think about it. Space is full of virtual particles popping in and out of existence, all the time, from nothing.

The reason we don't say "it comes from nothing" is because we really just don't know about the very earliest beginnings.

Logic is not how to approach this. Logic is a way of carefully figuring out the consequences of your starting assumptions; but logic is useless unless you've got those assumptions right to begin with. In cosmology, that means having to learn a lot of advanced physics. Without that, using "logic" is generally very misleading.

In cosmology, you have to get rid of simple intuitions. You can apply mathematical logic to derive the consequences of a mathematical model, but sweeping intuitive notions are invariably just wrong.

The singuarity is not an object. It is a condition, or state, in which physics breaks down. The notion of something exploding is not a good way to think about the Big Bang, or the singularity.

Intuitive ideas about exploding objects are wrong.

Cheers -- Sylas


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Dr Jack
Member (Idle past 394 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 10 of 38 (218361)
06-21-2005 9:32 AM
Reply to: Message 8 by thekid1870
06-21-2005 8:38 AM


Wouldn't logic dictate that matter can't come from nothing.

No, it doesn't. That would be fallacy of composition (that a group will have the same properties as it components) - in other words just because everything in the universe has a cause and cannot create/destroy energy1 would not imply that the universe itself has a cause or cannot have come from nothing (and vice-verse, doesn't imply it did either).

1 In fact neither of these things appear to be true, in QM things don't have causes and energy can be created and destroyed.


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cavediver
Member (Idle past 1933 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 11 of 38 (218363)
06-21-2005 9:34 AM
Reply to: Message 8 by thekid1870
06-21-2005 8:38 AM


This idea of creation out of nothing is a complete misunderstanding. Also, it's playing into this misunderstanding to say that the big bang was a "starting" point. It's just "a" point. Our simple notions of time, before and after, only apply in this very quiet region of the universe where we live.

Caveat for the technical: the following is related to a closed FRW universe...

The universe didn't appear out of nothing. It just "is". There is, at one point in the universe, a thing called the initial "big bang" singularity, and at another point a thing called the final "big crunch" singularity. These are just two points, not beginnings or endings. There are some very strange inhabitants of this universe, called humans. They cannot see the four dimensional nature of this universe, and are restricted to a three dimensional view. They "age" along lines joining the two singularities, and invent terms such as "before", meaning points in the universe closer to the initial singularity than their "now" and "after" meaning points in the universe closer to the final singularity than their "now". To the universe, this is all very mysterious, especially as these terms have no meaning close to either singularity. But that's ok, because none of the humans' "now" points are anywhere near either singularity: the humans only live in the middle bit of the universe, well away from either singularity. The universe is still confused though, because these humans keep asking what happened "before" the big bang. But if you are at the big bang, how can you get any closer to it? Do these humans really know what they're asking? "how did the big bang come out of nothing?" What do they mean, nothing??? If they stood at the big bang they would see the entire universe stretching out around them. There is no nothing. The universe concludes that it must be very sad to be a human, restricted to this narrow 3-dimensional view, suffering from all these worries just because they can't see clearly... oh well.

Sorry, got carried away there :-)


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cavediver
Member (Idle past 1933 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 12 of 38 (218365)
06-21-2005 9:46 AM
Reply to: Message 9 by Sylas
06-21-2005 9:27 AM


However, this is not because of any logical rule about matter not being able to come from nothing. In fact, matter can come from nothing in quantum mechanics; depending on how you think about it. Space is full of virtual particles popping in and out of existence, all the time, from nothing.

Be careful here, because we're in danger of confusing "nothing". This is certainly not nothing. You've got mathematics, also physics, and a bunch of quantum fields, and a background space-time for it all to live in. This is hardly nothing. This is the universe. The universe cannot comes from this, as it already includes this! "Nothing" in my book is an absence of: definitely space-time, definitely quantum fields, possibly physics... hmmm, mathematics... well God sometimes appears to be a mathematician, so I'll allow mathematics :-)


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Modulous
Member (Idle past 393 days)
Posts: 7789
From: Manchester, UK
Joined: 05-01-2005


Message 13 of 38 (218369)
06-21-2005 9:52 AM
Reply to: Message 8 by thekid1870
06-21-2005 8:38 AM


The question
First off, I would like to say thanks for responding to my post. But u guys didn't really answer my question.

You asked how the conclusion that a singularity "was nothing or just a tiny spec?" You were informed that the singularity is neither
defined as nothing nor is it defined as a tiny speck. So the answer to your question is "Nobody came up with that theory, that isn't the theory"

Wouldn't logic dictate that matter can't come from nothing

Logic might break down unfortunately. If you define an event as something which has a cause, then logic implies an infinite series has led to where we are now - which is logically impossible. However, since time itself came into existence at the Big Bang, then there might be no 'cause' that preceded it. There might be no 'where' that existed before it. Unfortunately high level physics at these extremes frequently defies what seems logical to us. Indeed, when discussing big bang even high level physics is inadequate.

What does logic dictate happened before time began?

But what I don't get is why people believe it started from ''nothing''.

People believe that due to a simplification of extremely difficult relativistic mathematics. In the end, where it 'came from' remains unknown. There is a point it time before which we simply do not, as of the moment, know what went on. As such we can't say where it all 'came from', if anywhere.

Doesn't it make more sense if the ''singularity'' was actully a huge object that got to massive and exploded?

No - the universe is expanding, so it must have been smaller in the past. Extrapolating that back to a singularity, and then using the maths to take it forwards again, we can predict certain things which must be true. Such predictions have since been confirmed.

Its all rather complicated of course, and the maths is beyond my comprehension - us mere mortals just have to follow the steps, and accept the maths is accurate :)

This message has been edited by Modulous, Tue, 21-June-2005 02:56 PM


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cavediver
Member (Idle past 1933 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 14 of 38 (218370)
06-21-2005 9:53 AM
Reply to: Message 12 by cavediver
06-21-2005 9:46 AM


Just to add to what I've just said, when a lay-person asks about creation from "nothing", they are almost certainly implying some form of naive absolute nothing. So when physicists all-to-often reply with the pair-creation argument, they are not addressing the real concern. You cannot pair-create without a universe in which to pair-create. And if you want to pair-create universes, you still need some form of super-arena for your physics. Is this nothing?

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Sylas
Member (Idle past 3549 days)
Posts: 766
From: Newcastle, Australia
Joined: 11-17-2002


Message 15 of 38 (218378)
06-21-2005 10:41 AM
Reply to: Message 14 by cavediver
06-21-2005 9:53 AM


Just to add to what I've just said, when a lay-person asks about creation from "nothing", they are almost certainly implying some form of naive absolute nothing. So when physicists all-to-often reply with the pair-creation argument, they are not addressing the real concern.

Good point: I agree. Thanks for the caution.

The point of pair creation, in my opinion, is simply to shake up the intuitions people bring to the subject; it's not a model for the origin of the universe.

Although it could be close... some folks (Stanford cosmologist Andrei Linde and chaotic inflation?) speculate about a "universe" popping into existence as a quantum fluctuation; though of course as you point out this presumes a quantum foam and a multiverse in which many such events may occur, and so just pushes the "ultimate origin" question to a new domain.

Or it could be totally different... the universe may fit the nice smooth zero-boundary Stephen Hawking notion with no larger meta-universe in which you can speak of our universe as a thing coming into existence at all.

Bottom line (IMO). For a beginner, be ready to drop every intuition or logical assumption you might expect; and stretch your mind as far as it will go. It won't be far enough. For someone who has a good grasp of the subject matter, get ready to revise your understanding. Although much has been discovered about expansion and the history of the universe, there are still enormous gaps in our knowledge.

Cheers -- Sylas


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