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Offline thedoc

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What was before the big bang?
« on: 07/08/2015 13:50:01 »
C Bruce Rodgers asked the Naked Scientists:
   
Theologians have an explanation for the pre-bang state of the universe, but is there any scientific speculation on the source of the source?  Even a cosmic yo-yo started from something.

What do you think?
« Last Edit: 07/08/2015 13:50:01 by _system »


 

Offline Mordeth

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Re: What was before the big bang?
« Reply #1 on: 08/08/2015 21:48:41 »
You are asking about a "time before time".  All fundamental physical laws broke down at the Big Bang, and the Universe "started over".  There is no event prior to the Big Bang that is observable, therefore you are free to speculate.
 

Offline PmbPhy

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Re: What was before the big bang?
« Reply #2 on: 09/08/2015 06:24:09 »
Quote from: thedoc
Theologians have an explanation for the pre-bang state of the universe, but is there any scientific speculation on the source of the source?
What is their explanation and what do you mean by "source of the source"?

Regarding the question What was before the big bang?.Depending on what one calls the start of the big bang one could say it was either the inflationary epoch of the Pre-Big Bang epoch. But we don't know with any great certainty.

The Pre-Big Bang Scenario uses string theory so I can't tell you much about it. You can read about it at: The Pre-Big Bang Scenario in String Cosmology by M. Gasperini, G. Veneziano:
http://arxiv.org/abs/hep-th/0207130

The authors are well-known in this field.
 

Offline PmbPhy

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Re: What was before the big bang?
« Reply #3 on: 09/08/2015 06:26:00 »
Quote from: Mordeth
You are asking about a "time before time". 
It's not 100% certain that time started when the big bang did.
 

Offline Mordeth

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Re: What was before the big bang?
« Reply #4 on: 09/08/2015 13:50:06 »
Quote from: Mordeth
You are asking about a "time before time". 
It's not 100% certain that time started when the big bang did.

Hi Pmb

Not many things are 100% certain.  However, at the singularity of the Big Bang, all known laws of physics are understood to have broken down.  Even conservation of matter.  By definition, nothing before the Big Bang is observable, or even knowable.  The Universe effectively reset itself, wiping out all traces of any former incarnation it might have had, including time.  This is because reaching back in time leads us to a singularity. If our past light cone can be focused, then theories of singularities can be used to show that this was the beginning of time, for our universe. There is nothing meaningful one can say regarding events before the Big Bang.  Only idle speculation.
 

Offline Mordeth

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Re: What was before the big bang?
« Reply #5 on: 09/08/2015 13:57:50 »
There was no big bang, the universe has always been here. I could post a pdf of where my theory is now if you are interested, but im having the day off, but your website is restricted to the size of pdf and the file is now 300k.
once you know about the fundamdental force carrier, it falls into place. I think the theory is finished now, im posting worldwide shortly, but it was you that pointed me in the write direction. Quantum mechanics needs i minor tweek not that i understand it that well, general relativity needs a minor tweek.  :)
I am getting paranoid re the lack of response to my posts

Is your theory consistent with the second law of thermodynamics?  An infinite universe would likely be one of uniform temperature.  Do you understand the logical process of tracing backwards the fact of expansion?
 

Offline PmbPhy

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Re: What was before the big bang?
« Reply #6 on: 09/08/2015 18:06:16 »
See also http://www.scientificamerican.com/article/string-theory-predicts-a-time-before-the-big-bang/
Quote
Was the big bang really the beginning of time? or did the universe exist before then? Such a question seemed almost blasphemous only a decade ago. Most cosmologists insisted that it simply made no sense—that to contemplate a time before the big bang was like asking for directions to a place north of the North Pole. But developments in theoretical physics, especially the rise of string theory, have changed their perspective. The pre-bang universe has become the latest frontier of cosmology.

The new willingness to consider what might have happened before the bang is the latest swing of an intellectual pendulum that has rocked back and forth for millennia. In one form or another, the issue of the ultimate beginning has engaged philosophers and theologians in nearly every culture. It is entwined with a grand set of concerns, one famously encapsulated in an 1897 painting by Paul Gauguin: D'ou venons-nous? Que sommes-nous? Ou allons-nous? “Where do we come from? What are we? Where are we going?” The piece depicts the cycle of birth, life and death—origin, identity and destiny for each individual—and these personal concerns connect directly to cosmic ones. We can trace our lineage back through the generations, back through our animal ancestors, to early forms of life and protolife, to the elements synthesized in the primordial universe, to the amorphous energy deposited in space before that. Does our family tree extend forever backward? Or do its roots terminate? Is the cosmos as impermanent as we are?
 

Offline PmbPhy

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Re: What was before the big bang?
« Reply #7 on: 09/08/2015 18:08:19 »
Quote from: Aquarius
There was no big bang, the universe has always been here.
Those are two separate issues, neither of which belong here. They belong in the New Theories section. When people come to this particular forum they're looking to find out what mainstream physicists hold to be true. They're not asking for answers from people who claim that mainstream physics is wrong.
 

Offline Mordeth

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Re: What was before the big bang?
« Reply #8 on: 09/08/2015 20:22:04 »
See also http://www.scientificamerican.com/article/string-theory-predicts-a-time-before-the-big-bang/ [nofollow]
Quote
Was the big bang really the beginning of time? or did the universe exist before then? Such a question seemed almost blasphemous only a decade ago. Most cosmologists insisted that it simply made no sense—that to contemplate a time before the big bang was like asking for directions to a place north of the North Pole. But developments in theoretical physics, especially the rise of string theory, have changed their perspective. The pre-bang universe has become the latest frontier of cosmology.

The new willingness to consider what might have happened before the bang is the latest swing of an intellectual pendulum that has rocked back and forth for millennia. In one form or another, the issue of the ultimate beginning has engaged philosophers and theologians in nearly every culture. It is entwined with a grand set of concerns, one famously encapsulated in an 1897 painting by Paul Gauguin: D'ou venons-nous? Que sommes-nous? Ou allons-nous? “Where do we come from? What are we? Where are we going?” The piece depicts the cycle of birth, life and death—origin, identity and destiny for each individual—and these personal concerns connect directly to cosmic ones. We can trace our lineage back through the generations, back through our animal ancestors, to early forms of life and protolife, to the elements synthesized in the primordial universe, to the amorphous energy deposited in space before that. Does our family tree extend forever backward? Or do its roots terminate? Is the cosmos as impermanent as we are?

Hi Pmb,

Thanks for the link.  As you know, any "theory" that attempts to describe the conditions that existed prior to the Big bang is untestable and not falsifiable.  Therefore, it is pure speculation, and does not nor cannot follow the scientific method.  The Big Bang, by definition, was a singularity.  There is no event prior to The Big Bang that is observable, nor can there ever be if the theory is accurate (which I believe it is).  We can go even further with this and state that anything that may have happened prior to The Big Bang is not even relevant.  The state of the Universe today was the result of the conditions OF the Big Bang, not before.  Period. That is to say that due to the singularity of the Big Bang, if there was anything prior it was FOREVER essentially erased and the Universe literally started over, whereby all physical laws were broken down.   Everything we observe today is a consequence of the Big Bang.  Not before (assuming before even has meaning in this context). Any and all attempts to avoid this conclusion are not scientifically valid, if The Big Bang is correct.  Time had a beginning, and it is called The Big Bang.

Humans intrinsically want to know what caused what and what came from where.  Our origin, and the origin of everything is as deep a subject as one can contemplate.  All that we can do today is say that the Big Bang accurately predicts and describes the Universe as we see it now.  It has not been falsified and it is possible to do so.  If you agree that the Big Bang theory is accurate, then you are forced to also agree that no scientific discussion can occur that produces testable conclusions or predictions regarding what happened before.  Therefore, your guess is as good as mine.  Better that we say: "We do not know, and likely CANNOT know".

« Last Edit: 09/08/2015 20:25:10 by Mordeth »
 

Offline Bill S

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Re: What was before the big bang?
« Reply #9 on: 10/08/2015 18:35:34 »
Mordeth, your last post contains a number of dogmatic statements, the upshot of which seems little better than saying something like "God created it, so there's nothing to talk about".

My own feeling is that if there is something in nature we don't understand it is worth looking at to see if there is any insight to be had. You say:

Quote
The Big Bang, by definition, was a singularity.

That might be a good place to start, but you would need to say what you understand by a singularity.
 

Offline PmbPhy

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Re: What was before the big bang?
« Reply #10 on: 10/08/2015 23:02:06 »
Quote from: Mordeth
As you know, any "theory" that attempts to describe the conditions that existed prior to the Big bang is untestable and not falsifiable.
Where did you get that idea from? You're thinking that there is only one model of the Big Bang and that's not true.  One cannot rule out cyclic cosmological models, in which there is no Big Bang. Everything that you've said in this thread has assumed that there was a singularity and we don't know that there was such a thing.

In any case just because something is not falsifiable doesn't mean that it doesn't belong in science. The falsifiability criteria was proposed by Karl Popper but not all physicists/philosophers think that it should be adhered to. See:
https://en.wikipedia.org/wiki/Falsifiability#Criticisms

Please note that people have the wrong idea about the Big Bang. As Peebles explains in his text on physical cosmology
Quote
If there were an instant, at a "big bang," when the universe started expanding, it is not in cosmology as now accepted, because nobody has thought of a way to adduce objective physical evidence that such an event really happened.

Quote from: Mordeth
  Therefore, it is pure speculation, and does not nor cannot follow the scientific method.
That's quite wrong. Falsification is not part of the scientific method. See the article What is science? by American Physical Society, Am. J. Phys. 67 (8), August 1999
I placed this online at http://home.comcast.net/~peter.m.brown/ref/what_is_science.pdf
Quote
Science is the systematic enterprise of gathering knowledge about the world and organizing and condensing that knowledge into testable laws and theories. The success and credibility of science is anchored in the willingness of scientists to:

(1) expose their ideas and results to independent testing and replication by other scientists; this
requires the complete and open exchange of data, procedures and materials;

(2) abandon or modify accepted conclusions when confronted with more complete or reliable experimental evidence.

Adherence to these principles provides a mechanism for self-correction that is the foundation of the credibility of science
Nowhere in that does it speak of falsification.


Quote from: Mordeth
  The Big Bang, by definition, was a singularity.
You're wrong. It certainly isn't how the Big Bang was/is defined and there's no supporting evidence that there was a singularity

Quote from: Mordeth
There is no event prior to The Big Bang that is observable, ...
Yet. Physical cosmology isn't that old. While cosmology as a science dates back about 100 years our real understanding of the universe is in its infancy. We've only just begun to start applying modern methodology to the study of it.  Those answers might not be forth coming for hundreds of years as far as we know.

Quote from: Mordeth
We can go even further with this and state that anything that may have happened prior to The Big Bang is not even relevant.  The state of the Universe today was the result of the conditions OF the Big Bang, not before.  Period.
Please keep in mind that just because you're not interested in something it doesn't mean that the rest of the world isn't. Some scientists mind be very interested in Pre-Big Bang Scenarios as possible theories and couple that with the notion that there might be other universes out there in parallel to ours. And if we can build an Einstein-Rosen Bridge (aka wormhole) we can have access to those universes.

You're simply ruling out a lot of ideas just because you haven't thought of them. Suppose it's possible to create wormholes. The it'd be possible to go back in time. If we could do that and the universe didn't start out at a singularity then it might be possible to tunnel into the universe prior to the Big Bang with a micro wormhole and use it as a probe for information. Is that possible? I don't know either way. But that doesn't mean that we should not consider such things.

Anyway, all of your claims are based on one false assumption, i.e. that there was a singularity. But that's merely an extrapolation. According to the way you've been reasoning about there's no way to prove such a thing.
 

Offline Mordeth

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Re: What was before the big bang?
« Reply #11 on: 14/08/2015 21:51:24 »
Quote from: Mordeth
As you know, any "theory" that attempts to describe the conditions that existed prior to the Big bang is untestable and not falsifiable.
Where did you get that idea from? You're thinking that there is only one model of the Big Bang and that's not true.  One cannot rule out cyclic cosmological models, in which there is no Big Bang. Everything that you've said in this thread has assumed that there was a singularity and we don't know that there was such a thing.
Hi Pmb,

I am aware that there are many models of the Big Bang theory.  I think there are something like 70+ models of "Inflation" alone.   As you know, The Big Bang model itself was built on General Relativity.  And the results suggest a singularity of infinite density at the so called "beginning".  Now I realize that this supposed singularity is different than the singularity proposed to exist inside a black hole.  For the Big Bang, it would probably be more accurate to say that the math and modern physics simply break down and everything results in infinities.  Even more accurate to say all that we know is that it was "hot and dense".  The term singularity here is simply another way to say WE DON'T KNOW and that the physics break down.  Which has been my entire point.  If we could focus our past light cone, it would be possible to prove the singularity.

Do you understand the significance of time = 0 when referring to how the equations of Relativity lead to a singularity at the Big Bang?   Time did not exist prior to the Big Bang, at least not the way we measure or understand it. 

Quote from: PmbPhy
In any case just because something is not falsifiable doesn't mean that it doesn't belong in science. The falsifiability criteria was proposed by Karl Popper but not all physicists/philosophers think that it should be adhered to. See:
https://en.wikipedia.org/wiki/Falsifiability#Criticisms [nofollow]
This is ludicrous.   Falsifiability simply implies testability.  I am aware that there are string theorists and other scientists who challeng Popper, mainly because they believe falsifiability is too blunt an instrument (and they enjoy whatever funding they are receiving for pursuing an untestable theory).  Fact is, testability is the hallmark of good science and the scientific method.  This is not the pseudoscience board.    Also, there are others who defend falsifiability, and do not think that simple "elegance" is enough.

See:
http://www.nature.com/news/scientific-method-defend-the-integrity-of-physics-1.16535 [nofollow]

How could you ever change or modify or discard a theory if you don't feel that testability and falsification principles are important? 

https://en.wikipedia.org/wiki/Scientific_method [nofollow]

"Properties of scientific inquiry
Scientific knowledge is closely tied to empirical findings, and can remain subject to falsification if new experimental observation incompatible with it is found. That is, no theory can ever be considered final, since new problematic evidence might be discovered. If such evidence is found, a new theory may be proposed, or (more commonly) it is found that modifications to the previous theory are sufficient to explain the new evidence. The strength of a theory can be argued to be related to how long it has persisted without major alteration to its core principles."





Quote from: Mordeth
  The Big Bang, by definition, was a singularity.
Quote from: Pmb
You're wrong. It certainly isn't how the Big Bang was/is defined and there's no supporting evidence that there was a singularity

Well, you should update Wikipedia, and just about every other source on planet Earth that refers to the Big Bang "beginning" as having a singularity (which simply means WE DON'T KNOW):

https://en.wikipedia.org/wiki/Big_Bang [nofollow]

"The Big Bang theory is the prevailing cosmological model for the universe from the earliest known periods through its subsequent large-scale evolution.[1][2][3] It states that the universe expanded from a very high density state,[4][5] and offers a comprehensive explanation for a broad range of observed phenomena, including the abundance of light elements, the cosmic microwave background, large scale structure, and Hubble's Law.[6] If the known laws of physics are extrapolated beyond where they are valid, there is a singularity."  (emphasis mine)

Quote from: Mordeth
There is no event prior to The Big Bang that is observable, ...
Quote from: PmbPhy
Yet. Physical cosmology isn't that old. While cosmology as a science dates back about 100 years our real understanding of the universe is in its infancy. We've only just begun to start applying modern methodology to the study of it.  Those answers might not be forth coming for hundreds of years as far as we know.

I am not sure what the point of this statement is Pmb.   It is common sense that many things are not known "yet".   The OP did not ask about what is "yet" to be known.  What we know is that we know absolutely NOTHING relating to anything that could or might have happened prior to 10^-43 seconds (Planck time).  This is the earlier period of time that our equations are at all useful to describe anything.  Nothing is known from t=0 to Planck time.  And anything prior to t=0 is BY DEFINITION not observable. Now take the velocity of light and multiply by Planck time and you get Planck length (10^-35meter).  No distance less than this can be defined.  It is thought of as a singularity in SPACE and in TIME.  Physicists have made many efforts to avoid this "singularity" at the "beginning", and quite frankly I don't blame them.  The fact is though, we simply do not know what happened prior to t=0 or even t=10^-43 seconds and it is unlikely we ever will.  The calculations that result from General Relativity being applied to the so called "origin" of the universe create a finite beginning of both time and space.  I don't even know how you can argue against this.

Quote from: Mordeth
We can go even further with this and state that anything that may have happened prior to The Big Bang is not even relevant.  The state of the Universe today was the result of the conditions OF the Big Bang, not before.  Period.
Quote from: PmbPhy

Please keep in mind that just because you're not interested in something it doesn't mean that the rest of the world isn't. Some scientists mind be very interested in Pre-Big Bang Scenarios as possible theories and couple that with the notion that there might be other universes out there in parallel to ours. And if we can build an Einstein-Rosen Bridge (aka wormhole) we can have access to those universes.

Other universes?  What other universes?   Which forum are we in again?


Quote from: PmbPhy


You're simply ruling out a lot of ideas just because you haven't thought of them. Suppose it's possible to create wormholes. The it'd be possible to go back in time. If we could do that and the universe didn't start out at a singularity then it might be possible to tunnel into the universe prior to the Big Bang with a micro wormhole and use it as a probe for information. Is that possible? I don't know either way. But that doesn't mean that we should not consider such things.

I have certainly thought of them.  Please do not tell me what I have thought of or not thought of.  But conjecturing over tunnelling to other universes when there is not even evidence of other universes is speculation of the highest order, and belongs in the new theory section, not here.
 

Offline Mordeth

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Re: What was before the big bang?
« Reply #12 on: 14/08/2015 22:03:57 »
Mordeth, your last post contains a number of dogmatic statements, the upshot of which seems little better than saying something like "God created it, so there's nothing to talk about".

My own feeling is that if there is something in nature we don't understand it is worth looking at to see if there is any insight to be had. You say:

Quote
The Big Bang, by definition, was a singularity.

That might be a good place to start, but you would need to say what you understand by a singularity.

Hi Bill,

In the context of the Big Bang theory, a singularity is the point where density and temperature become infinite (or at least beyond the scope of our equations) and general relativity breaks down.  We can no longer explain what happened.  "Hot and dense" is a another way to describe it, but I feel is a gross understatement of how we understand it . Time literally "began" at this point, at least how we define it.  This is, the "Big Bang".   

See here:
https://en.wikipedia.org/wiki/Lambda-CDM_model [nofollow]

"The model includes a single originating event, the "Big Bang" or initial singularity, which was not an explosion but the abrupt appearance of expanding space-time containing radiation at temperatures of around 1015 K."
 

Offline PmbPhy

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Re: What was before the big bang?
« Reply #13 on: 15/08/2015 02:23:58 »
Quote from: Wikipedia
As you know, The Big Bang model itself was built on General Relativity.  And the results suggest a singularity of infinite density at the so called "beginning".
That's not true at all. While there could be a solution where there's a singularity there need not be one. As I've always held since a professor pointed this out to me in the late 80s, the singularity is merely an extrapolation. See: https://en.wikipedia.org/wiki/Big_Bang
Quote
If the known laws of physics are extrapolated beyond where they are valid, there is a singularity.
...
Extrapolation of the expansion of the universe backwards in time using general relativity yields an infinite density and temperature at a finite time in the past. This singularity signals the breakdown of general relativity and thus, all the laws of physics. How closely we can extrapolate towards the singularity is debated[/u]—certainly no closer than the end of the Planck epoch. This singularity is sometimes called "the Big Bang", but the term can also refer to the early hot, dense phase itself,[22][notes 1] which can be considered the "birth" of our universe.
First of all we don't really know if there was a big bang at all. There no big-bang cosmological models that are consistent with current observations. I.e. they don't extrapolate back to a singularity but rebound. One such no big-bang is referred to as the bounce model. See: https://en.wikipedia.org/wiki/Big_Bounce

Quote from: Mordeth
The term singularity here is simply another way to say WE DON'T KNOW and that the physics break down.  Which has been my entire point.  If we could focus our past light cone, it would be possible to prove the singularity.
That's not what the term singularity means. The proper definition is found here:
https://en.wikipedia.org/wiki/Initial_singularity
Quote
The initial singularity was the gravitational singularity of infinite density thought to have contained all of the mass and spacetime of the Universe before quantum fluctuations caused it to rapidly expand in the Big Bang and subsequent inflation, creating the present-day Universe.

Quote from: Mordeth
Time did not exist prior to the Big Bang, at least not the way we measure or understand it. 
I've already explained why that's not necessarily correct. Even if the pre-big bang scenario can't be falsified it doesn't mean that it didn't occur. And as my GR prof at MIT told me - the universe might be infinitely old.[/i[

Quote from: Mordeth
In any case just because something is not falsifiable doesn't mean that it doesn't belong in science. The falsifiability criteria was proposed by Karl Popper but not all physicists/philosophers think that it should be adhered to. See:
https://en.wikipedia.org/wiki/Falsifiability#Criticisms
This is ludicrous.
[/quote]
Up to this point you appeared to me to be just another member with a few misconceptions about the big bang theory and the philosophy of science. However when you start using terms like "ludicrous" then you're violating forum rules. In particular: http://www.thenakedscientists.com/forum/index.php?topic=8535.0
Quote
Keep it friendly 
 
Do not use insulting, aggressive, or provocative language.

If you feel another forum user is using insulting language, seek to calm things down, or if that fails, report the matter to the moderators.  Under no circumstances should you seek to trade insults, or make accusatory remarks to that, or any other, forum user.

Show respect to other forum users.  In particular, there are times when forum users might post about delicate personal issues.  Please refrain from trivialising or making inappropriate remarks, or remarks that might embarrass the poster.

The term ludicrous is a pejorative. See:
http://www.merriam-webster.com/dictionary/ludicrous
Quote
1:  amusing or laughable through obvious absurdity, incongruity, exaggeration, or eccentricity

2:  meriting derisive laughter or scorn as absurdly inept, false, or foolish
all of which mean that the term is pejorative.

Physics does use concepts which aren't falsifiable such as the many worlds interpretation of quantum mechanics and the cosmological principle which is one of the fundamental postulates of the big bang.

If a theory is not falsifiable all it means is that we can't construct a test which will prove that it's wrong. However the theory may become more and more acceptable and that's how some postulates which are not falsifiable remain important, the cosmological principle being one of the most obvious ones that I can think of off hand.

But this thread is not about that subject and there's plenty of literature on the internet if you wish to learn more about it. For example; there's a talk about this on pbs at: http://www.pbs.org/wgbh/nova/blogs/physics/2015/02/falsifiability/

In any case I don't know string theory and as such I don't know whether it is or isn't falsifiable. There's an article on this subject that I haven't read at http://arxiv.org/abs/gr-qc/9911104

What you haven't noticed yet is that the Big Bang theory itself isn't falsifiable because one of the postulates that it's based on, i.e. the cosmological principle isn't falsifiable. That postulate states that the distribution of matter in the universe is both uniform and isotropic. However this can't be falsified because we'll never be able to determine whether it's valid or not. We can only observer matter out to the particle horizon.

In any case if you've assumed that I don't think that falsifiability should be part of science then you've assumed incorrectly.

Quote
https://en.wikipedia.org/wiki/Scientific_method
There's never a need to explain the scientific method to a professional physicist with 30 years experience. You need to learn a lot more about the role of falsifiability and why philosophers of science criticize its usage in science.

Quote from: Mordeth
Please do not tell me what I have thought of or not thought of. 
Alright. That's enough. You've proven to be too rude for me to want to converse with again. You're far too rude for my taste.
« Last Edit: 15/08/2015 12:13:14 by PmbPhy »
 

Offline Bill S

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Re: What was before the big bang?
« Reply #14 on: 15/08/2015 23:20:06 »
Quote from: Mordeth
In the context of the Big Bang theory, a singularity is the point where density and temperature become infinite (or at least beyond the scope of our equations) and general relativity breaks down.

There is a vast difference between “become infinite” and “beyond the scope of our equations”.

Something can become beyond the scope of our equations; but something “finite” cannot become “infinite”. 

Quote
Time literally "began" at this point, at least how we define it.

Here again you are, perhaps, talking about two different things.  Are “time”, and “time as we define it” necessarily the same thing?

One thing we do know about time is that it is what we use to measure change.  If there was no time before the BB, how could the universe change from not being to being.

I’m not saying that there was time before the BB, just looking at/for ideas.
 

Offline evan_au

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Re: What was before the big bang?
« Reply #15 on: 17/08/2015 00:07:24 »
Quote from: Bill S
Something can become beyond the scope of our equations; but something “finite” cannot become “infinite”.

In quantum physics, infinities pop up in a number of inconvenient places, including some where the answers are known to be finite. One example is in the Casimir Effect:
Quote from: Wikipedia
Summing over all possible oscillators at all points in space gives an infinite quantity. Since only differences in energy are physically measurable... this infinity may be considered a feature of the mathematics rather than of the physics. This argument is the underpinning of the theory of renormalization.

In the vicinity of a gravitational field, physicists have not (yet) discovered the right mathematical incantations that will make the infinities go away, producing the familiar finite answer that we experience in the laboratory.
 

Offline PmbPhy

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Re: What was before the big bang?
« Reply #16 on: 17/08/2015 00:23:57 »
Quote from: Bill S
Something can become beyond the scope of our equations; but something “finite” cannot become “infinite”.
I disagree. Before the Big Bang there was no matter in the universe since there was no universe. If the universe has a flat geometry it means that space is flat and therefore infinite. If that's the case, and assuming that cosmological principle is true (universe is homogeneous and isotropic) then there's an infinite number of atoms.
 

Offline Mordeth

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Re: What was before the big bang?
« Reply #17 on: 17/08/2015 15:24:27 »
Quote from: Mordeth
In the context of the Big Bang theory, a singularity is the point where density and temperature become infinite (or at least beyond the scope of our equations) and general relativity breaks down.

Quote from: Bill S
There is a vast difference between “become infinite” and “beyond the scope of our equations”.

Something can become beyond the scope of our equations; but something “finite” cannot become “infinite”.


Hi Bill.  The math describing these events is very complex.  General Relativity predicts singularities, and these can be defined different ways depending on a number of factors.  In simple terms, a singularity is considered "geodesic incompleteness".  This is a fancy way to say infinite curvature.  At a singularity, the path of light cannot be extended any further in proper time and spacetime simply comes to an end.  Even a change in coordinates produces the same result.  A "hole" in spacetime.   Normally, a free falling particle follows a geodesic, which is simply a straight line through spacetime. At a singularity, the geodesic stops and the particle, for lack of a better term, vanishes.  This is where General Relativity breaks down, which essentially and unfortunately for us makes it an incomplete theory.  It cannot describe or predict what happens at the singularity.

By the way, a simple way to make something infinite from something finite is as such:  Take a 1 meter length of rope.  It is finite in length. Now connect the ends of the rope.  You have just created an infinite loop.

Quote from: Mordeth
Time literally "began" at this point, at least how we define it.

Quote from: Bill S
Here again you are, perhaps, talking about two different things.  Are “time”, and “time as we define it” necessarily the same thing?

One thing we do know about time is that it is what we use to measure change.  If there was no time before the BB, how could the universe change from not being to being.

I’m not saying that there was time before the BB, just looking at/for ideas.

The age of the universe is presently measured to be 13.798 billion years, plus or minus 37 million years.    This is the beginning of time Bill, as_we_define it. According to the International Astonomical Union, the age is defined as the duration of the Lambda-CDM expansion.  Put another way, it is the elapsed time since the Big Bang.   This is the beginning of time by our own definition.  I don't know how else to explain it. 

From Planck time (10^-43 seconds) until now, we feel we have a OK understanding of how things came to be.  Research the Epochs.  If we could directly observe the cosmic neutrino backround, we could know more of the events from Planck time to the "dark ages". 

However, from t=0 to Planck time, we know nothing.  This is the "singularity".   It simply means we don't know and likely can't know IN THIS CONTEXT.  If we could focus our past light cone we could maybe prove an actual singularity. 

Before t=0, we know less than nothing.  We can't even properly speculate, as no event from before t=0 is observable or even can be observable.    Quantum fluctuations of "space foam"?  Cyclic Big Bang universes?  Loop quantum gravity? How about from nothing at all?  Your guess is as good as mine.   The problem is that anytime you answer the question of what came before, you will also face the same dilemna:   Well Bill, what came before that?    It will always be TURTLES Bill, Turtles! All the way down.  And "from nothing" models don't define where the energy came from.  So it is the same two answers every time. 

The Big Bang model does not attempt to describe events prior to 10^-43 seconds.  It does not know what happened from t=0 to t=10^-43 seconds (singularity, hot and dense, etc), and anything before t=0 is pure conjecture.  As I have said here better to simply say we DO NOT KNOW.  This does not imply we should not still ask the question.
 

Offline PmbPhy

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Re: What was before the big bang?
« Reply #18 on: 17/08/2015 15:53:30 »
Quote from: Mordeth
General Relativity predicts singularities, ...
Bill - I've already explained to him, that's an extrapolation of the use of GR back to the Big Bang. I.e. only if the known laws of physics are extrapolated beyond where they are valid is there a singularity. See: https://en.wikipedia.org/wiki/Big_Bang

As Ohanian and Rufini explain in Gravitation and Spacetime - Second Edition (2013) page 466
Quote
The absence of a singularity at the first moment of the Big Bang would seem to be in contradiction with singularity theorems that have been proved for the solutions of Einstein's equations. But these theorems deal only with the classical regime; that can be circumvented in the very early universe, where matter is in the forum of quantum fields and where geometry is quantized. Furthermore, the presence of a positive cosmological constant can lead to a violation of the energy condition for the Hawking-Penrose theorem even in the classical regime. As we will see, in the inflationary epoch of the early universe, the cosmological constant was large and positive, and singularity theorems were inapplicable. .... Thus, the question of whether there is an actual singularity at the first moment of the Big Bang still remains open.
An analogy has been made with biology. See Did The Universe Really Begin With a Singularity?
http://profmattstrassler.com/2014/03/21/did-the-universe-begin-with-a-singularity/
Quote
Did The Universe Really Begin With a Singularity?

Posted on March 21, 2014 | 307 Comments
 
Did the universe begin with a singularity?  A point in space and/or a moment in time where everything in the universe was crushed together, infinitely hot and infinitely densely packed?

Doesn’t the Big Bang Theory say so?

Well, let me ask you a question. Did you begin with a singularity?

Let’s see. Some decades ago, you were smaller. And then before that, you were even smaller. At some point you could fit inside your mother’s body, and if we follow time backwards, you were even much smaller than that.

If we follow your growth curve back, it would be very natural — if we didn’t know anything about biology, cells, and human reproduction — to assume that initially you were infinitesimally small… that you were created from a single point!

But that would be wrong. The mistake is obvious — it doesn’t make sense to assume that the period of rapid growth that you went through as a tiny embryo was the simple continuation of a process that extends on and on into the past, back until you were infinitely small.  Instead, there was a point where something changed… the growth began not from a point but from a single object of definite size: a fertilized egg.

The notion that the Universe started with a Big Bang, and that this Big Bang started from a singularity — a point in space and/or a moment in time where the universe was infinitely hot and dense — is not that different, really, from assuming humans begin their lives as infinitely small eggs. It’s about over-extrapolating into the past.
« Last Edit: 17/08/2015 16:22:02 by PmbPhy »
 

Offline Bill S

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Re: What was before the big bang?
« Reply #19 on: 17/08/2015 18:41:17 »
Quote from: Pete
I disagree. Before the Big Bang there was no matter in the universe since there was no universe.


Pete, this is a rhetorical tautology.  Of course it must be true that if there is no universe, there is no matter in it.  However this is different from saying if there is no universe, there is no matter; because that assumes that we know what conditions were before the BB, which we don’t. 

 
Quote from: Pete
If the universe has a flat geometry it means that space is flat and therefore infinite.
 

We have been here before; and, unless you are Lewis Carroll’s Bellman, repetition does not guarantee veracity.  :)

I accept that this is true, but only within the mathematical usage of “infinite” which does not even take account of Cantor’s “Absolute infinity”; which, you will recall, even he thought might be equated with “God”.

How much sense does it make to say: There is no overarching infinity, but infinities are infinite, so there must be an “Absolute infinity” which doesn’t exist, anyway?   

Quote from: Pete
If that's the case, and assuming that cosmological principle is true (universe is homogeneous and isotropic) then there's an infinite number of atoms.

Even if we assume that the multiplicity of assumptions involved here is acceptable; and I think we have to if we are to make any progress in cosmology; then you have still missed the point of the nature of infinity. 

If the number of atoms is infinite, it has always been infinite.  If you are arguing that this quantity of atoms is infinite, then it must always have been infinite.  The alternative is that it started as a finite quantity, in which case it is still increasing. To reach infinity would require infinite time which, if there were such a thing, has certainly not passed since the BB. 

BTW, Mordeth, I'm not ignoring you; just out of time.
 

Offline Bill S

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Re: What was before the big bang?
« Reply #20 on: 17/08/2015 21:22:54 »
Quote from: Mordeth
The age of the universe is presently measured to be 13.798 billion years, plus or minus 37 million years.    This is the beginning of time Bill, as_we_define it. According to the International Astonomical Union, the age is defined as the duration of the Lambda-CDM expansion.  Put another way, it is the elapsed time since the Big Bang.   This is the beginning of time by our own definition.  I don't know how else to explain it.

Mordeth, I don't know what your scientific background is, but you certainly possess one quality common to many scientists and mathematicians: the ability to answer a question with a perfectly valid (and often detailed) answer to a different question.  :)

Your answer doesn't touch on the question as to how nothing could even begin change into something without time in which to initiate change.
 

Offline Mordeth

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Re: What was before the big bang?
« Reply #21 on: 18/08/2015 01:03:14 »
Quote from: Mordeth
The age of the universe is presently measured to be 13.798 billion years, plus or minus 37 million years.    This is the beginning of time Bill, as_we_define it. According to the International Astonomical Union, the age is defined as the duration of the Lambda-CDM expansion.  Put another way, it is the elapsed time since the Big Bang.   This is the beginning of time by our own definition.  I don't know how else to explain it.

Mordeth, I don't know what your scientific background is, but you certainly possess one quality common to many scientists and mathematicians: the ability to answer a question with a perfectly valid (and often detailed) answer to a different question.  :)

Your answer doesn't touch on the question as to how nothing could even begin change into something without time in which to initiate change.

Hi Bill,

I don't know.  Nor does science. I hope that answers your question directly.  What I say below is only an extension of the words: "I don't know".

In Big Bang cosmology, t=0 is not properly defined or understood.  All we understand are causes and events from Planck time forward (t>10^-43 seconds).  The models derived from General Relativity do not even describe the Big Bang as an event, so by definition it needs no cause.  An event in GR can only occur in space-time at t>0.  In fact, space-time itself only exists for t>0.  Understand the significance of this? There is no explanation, and likely won't ever be for causes at t<0 that impact events at t>0, because we cannot define t=0 in this scenario (The Big Bang). GR breaks down, and unfortunately it is all we have.   t<0 is a boundary for modern science and t=0 is not understood. A quantum theory of gravity might help describe what happened before Planck time though, when all the forces were likely united, but before that we likely will never know.  And the answer today is we simply don't know.  So for us, time began at the Big Bang.

I don't know how something can change without time in which to initiate the change (we could talk about quantum entanglement if you prefer. or the Casimir effect, or Hawking radiation), nor can I (or anyone) explain why or how our observable universe was initially created.  If I did properly, I might win myself a Nobel prize.  All we can do here in this context is explain when.  And that was 13.798 billion years ago, give or take a few 10s of million of years.  And we can explain what happened and how and why since "then".  So by our own definitions, this is when time began for our space-time.

Is your question a philosophical or metaphysical one?  I guess I am confused as to your intent.   Are you trying to convince me of something or are you honestly trying to understand something?

Best regards.
 

Offline Mordeth

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Re: What was before the big bang?
« Reply #22 on: 18/08/2015 01:17:39 »
Hi Pmb,

I sincerely apologize for my puerile use of the word ludicrous in response to an earlier post of yours. I should not have used this word and I retract it.  You are a committed member of this forum and clearly devoted to science.  I was out of line.
 

Offline PmbPhy

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Re: What was before the big bang?
« Reply #23 on: 18/08/2015 03:41:32 »
Hi Pmb,

I sincerely apologize for my puerile use of the word ludicrous in response to an earlier post of yours. I should not have used this word and I retract it.  You are a committed member of this forum and clearly devoted to science.  I was out of line.
Apology accepted. :)  And thank you for that clearly sincere apology. I admire people who are able to correct themselves when they recognize that they've made a mistake as you did here. My compliments.

By the way. A good friend of mine is an authority in general relativity. I've discussed the existence of an initial singularity with him and he noted that there is no simple answer to the question on singularities in the solution to Einstein's field equations. In cosmology, everything depends on the class of models one adopts. He mentioned that he questioned the usual assumption that one should start by assuming that the sources are homogeneous and isotropic and wrote to Penrose about it. I guess they know each other. He noted that if this assumption is dropped and we insert some hierarchical source into the field equations, we don't have any idea what GR would predict.

He told me that others have questioned the assumption that the torsion can be set = 0. If we drop that assumption and include torsion, there are non-singular solutions to the field equations. These are only two examples, but I hope they are enough to show that answers to such questions depend on the class of models one accepts.
« Last Edit: 18/08/2015 06:54:24 by PmbPhy »
 

Offline PmbPhy

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Re: What was before the big bang?
« Reply #24 on: 18/08/2015 04:05:36 »
Quote from: Bill S
Pete, this is a rhetorical tautology.  Of course it must be true that if there is no universe, there is no matter in it.  However this is different from saying if there is no universe, there is no matter; because that assumes that we know what conditions were before the BB, which we don’t. 
I agree. However it is quite conceivable. And in that case it provides a example of something infinite coming from something finite. A good example is the existence of, say, electrons. The early universe was too hot to have particles such as electrons or atoms. Eventually it cooled off enough for it to happen. If the universe has zero spatial curvature, which is quite possible and is actually looking that way, then, as will all models, its size started off with zero and in an instant grew to infinite. Then when it cooled off enough an infinite number of electrons, atoms, protons etc were created.

Quote from: Bill S
We have been here before; and, unless you are Lewis Carroll’s Bellman, repetition does not guarantee veracity.  :)
Come on, Bill. I can hardly be expected to recall what I've said to you in the past or what you remember. And you're not the only one reading this. Its for those reasons I state it, especially since I have to in order to make clear what it is that I'm explaining.

Quote from: Bill S
I accept that this is true, but only within the mathematical usage of “infinite” which does not even take account of Cantor’s “Absolute infinity”; which, you will recall, even he thought might be equated with “God”.
Who's Cantor and what does God have to do with any of this?

Quote from: Bill S
Even if we assume that the multiplicity of assumptions involved here is acceptable; and I think we have to if we are to make any progress in cosmology; then you have still missed the point of the nature of infinity. 
I hardly ever miss a point being made or that has been made.

Quote from: Bill S
If the number of atoms is infinite, it has always been infinite.
Cosmology and particle theory is inconsistent with your assertion. What is your justification for this speculation of yours?

Quote from: Bill S
If you are arguing that this quantity of atoms is infinite, then it must always have been infinite.  The alternative is that it started as a finite quantity, in which case it is still increasing. To reach infinity would require infinite time which, if there were such a thing, has certainly not passed since the BB. 
From what you just said here it's clear to me that you don't understand the physics of the early universe. The first atoms, i.e. hydrogen, didn't form until the universe had cooled down enough which was 377,000 years after the Big Bang. This epoch of the early universe is called recombination.

If I were you I'd get a book and read about it. You an download one at http://bookos-z1.org/  An Introduction to Modern Cosmology - 2nd Ed. by Andrew Liddle would be a good text for you. In fact I myself am studying it. While I know all the matter in it I haven't memorized it nor have I worked with the equations all that much. That's why I'm using it. Ohanian and Rufini is good too but more mathy.

First start with these:
https://en.wikipedia.org/wiki/Chronology_of_the_universe
http://www.physicsoftheuniverse.com/topics_bigbang_timeline.html
 

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Re: What was before the big bang?
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