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robross
2009-May-03, 10:02 PM
Hi. I've been lurking for a while but just signed up and I thought I'd start off with a bang, er, a question about the Big Bang.

It is my understanding that about 13.7 billion years ago, all the "stuff" in the universe was located in a singularity with no spacial dimension. At this point, what was the nature of this "stuff"? Was this just pure EM energy (i.e. photons) or something else? Was there just a single photon with an unimaginably large energy, or were there bazillions of photons with slightly less than unimaginably large energies, all superimposed on one another?

I have plenty of follow up questions but I want to start out slowly :)

Thanks!

Rob

Jeff Root
2009-May-03, 10:42 PM
Hello, Rob!

Your guess may be just about as good as anyone's as to how to describe
the Universe at the *very* beginning. We can be very sure what it was
like a few seconds after the beginning, and we have some fairly good
guesses about what might have been like during the first second. But the
beginning of that second is still a total mystery.

We know that a couple of seconds after the time we think must have been
the beginning, the Universe was absurdly hot and absurdly dense. It may
have been filled with particles called "hyperons", which are basically heavy
versions of protons and neutrons. Before that, it may have been a sort
of quark soup. And before that-- Nobody knows.

The earliest moments of the Universe can only be investegated by
extrapolating backward in time from conditions at later times, which are
observed. We currently see all the clusters of galaxies in the Universe
moving away from each other. Extrapolating backward in time, that
implies that everything started out at a single point in time, when all
matter was at a single point in space. That isn't possible, of course.
Something interesting happened at the very beginning, but we don't
know what that something was or how long it took to happen. So we
can't describe conditions then. The singularity is just the mathematical
prediction of the extrapolation backward in time from what we can see.

-- Jeff, in Minneapolis

Cougar
2009-May-04, 01:09 PM
Welcome to the board, Rob.


At this point, what was the nature of this "stuff"?

As Jeff said, this is unknown. It is expected that as one approaches that "point," temperature and density become unimaginably high, and the four known forces of nature unify and become indistinguishable from one another, so it's a very strange state of affairs....

Gandalf223
2009-May-04, 05:37 PM
Welcome to the asylum, Rob!

One of the problems that "nonbelievers" have with the Big Bang, is that the physics we know breaks down as you go backward and near the moment of the BB. In short, the conditions in the "singularity" (probably an inaccurate choice of words, but one that we think we can imagine) cannot be described in terms of anything we know.

There's a point in time (measured from the moment of the BB,) before which we can't even make educated guesses. IIRC, that point is something like 10^-43 seconds after the BB. I have personally named that the "WTF Moment."

robross
2009-May-04, 09:16 PM
Well, if I get to arbitrarily choose my own mythology for t=0, I'm going to have to go with Eru and the Music of the Ainur, since it's the most self-consistent mythology out there right now.

But back to the current universe...

One thing that puzzles me about the matter-creation stage of the Big-Bang is that, especially if there were a slight imbalance of matter over anti-matter creation, why wouldn't that process have continued until all the photons had turned into bits of matter? If a quark/anti-quark pair met and annihilated, that would just create a new photon with the same energy as it had before it split into a quark/anti-quark, right? So why wouldn't that photon have just turned right around and split again back to a quark/antiquark, etc, for a billion and one times until there was just a quark and no anti-quark?

Basically, why were there *any* photons left-over after this energy "froze out" into matter?

Rob

Gandalf223
2009-May-05, 06:44 AM
Supposedly, during the great matter/antimatter mutual annihilation-fest, there was a miniscule bias toward an excess of matter.

Andrei Sakharov proposed conditions which would result in baryonic matter and antibaryonic matter being produced at different rates. Wikipedia article (http://en.wikipedia.org/wiki/Baryogenesis#The_Sakharov_conditions)

cjl
2009-May-05, 07:18 AM
Keep in mind that the period when matter/antimatter was being produced freely from photons was very limited - the freeze out happened an extremely short time after the big bang, and as a result, not all the energy had time to turn into matter through this slight excess. In fact, almost all of it didn't turn to matter, considering the baryon to photon ratio.

Jeff Root
2009-May-05, 08:09 AM
There is a general assumption here that energy was in the form of photons
at or near the very beginning, which then became matter and antimatter.
Generally, that probably is not what happened. More energy is contained
in a volume of hadrons (quark matter) than can be contained in the same
volume of photons. When the Universe was as dense as atomic nuclei,
most of the energy must have been in the form of hadrons at absurdly
high temperature.

-- Jeff, in Minneapolis

robross
2009-May-05, 09:17 PM
There is a general assumption here that energy was in the form of photons
at or near the very beginning, which then became matter and antimatter.
Generally, that probably is not what happened. More energy is contained
in a volume of hadrons (quark matter) than can be contained in the same
volume of photons. When the Universe was as dense as atomic nuclei,
most of the energy must have been in the form of hadrons at absurdly
high temperature.

-- Jeff, in Minneapolis

Ahh, an opportunity to ask about "Temperature". It's been a long time since I took chemistry or physics, but from what I remember, isn't "temperature" a measure of the average kinetic energy of particles in some volume of space? Or are there other subtler meanings which I have forgotten?

I ask because it's not clear to me what "high temperature" means in the context of early universe. Does this just mean that early matter particles had velocities approaching c? (Wouldn't that be the highest temperature matter could attain, just under c?) But, (and I could be wrong here), it's my understanding that the early Big Bang was not an "explosion" which sent matter flying "out" in space, but rather, suddenly a ginormous amount of matter/energy "appeared" and space started expanding, spreading out the matter/energy in newly created space, but not really "moving" with respect to space, until particle collisions transfered momentum, etc.

So when you say that matter in the Big Bang had high initial temperature, what does that mean exactly, and how was it manifested in the early universe?

Thanks,

Rob

Jeff Root
2009-May-05, 10:37 PM
isn't "temperature" a measure of the average kinetic energy of particles
in some volume of space? Or are there other subtler meanings which I
have forgotten?
There are all sorts of definitions of temperature, but average kinetic
energy of particles is the generic description I would use.



I ask because it's not clear to me what "high temperature" means in
the context of early universe. Does this just mean that early matter
particles had velocities approaching c?
That's the biggest part of it. Also, the particles are massive and
packed tightly together. Frequent collisions.



(Wouldn't that be the highest temperature matter could attain, just
under c?)
Apart from a very abstract physics principle that might put an upper
limit on temperature (which I know of but know nothing about), and
assuming that the number of different types of quarks (or other
massive particles) is limited, there really is no limit on temperature.
The more closely the average speed of the particles approaches c,
the higher the kinetic energy. A speed of c is the limit at which
kinetic energy becomes infinite. If there are more than the six known
types of quark, additional energy could go into increasing the mass
of the particles rather than their speed, which would have the effect
of reducing the temperature.



But, (and I could be wrong here), it's my understanding that the early
Big Bang was not an "explosion" which sent matter flying "out" in space,
but rather, suddenly a ginormous amount of matter/energy "appeared"
and space started expanding, spreading out the matter/energy in newly
created space, but not really "moving" with respect to space, until
particle collisions transfered momentum, etc.
Something like that, yeah.

I'm really not an expert, but there are disagreements about whether
the word "explosion" is an accurate or inaccurate description. There
are disagreements about all parts of the description you just gave,
as to whether those descriptions are accurate-- entirely aside from
general agreement on the physics.

I personally question the description of the Big Bang occurring at an
instant of time. I say that that description is just the result of our
mathematical process of extrapolating backward in time, applying
known physical principles, without knowing the relevant physics of
the initial event. Everything else that happened after the Big Bang
takes time to occur. Why should the Big Bang be the exception to
that rule? I suspect that the initial creation event took some time
to happen. (Probably not six days...) In that case, the timeline for
the first second (or possibly longer) is wrong, even if the events in
that timeline are right. I'm saying that, whatever the mechanism of
the creation, it took some time to happen; and that the density and
temperature were both at their maximum during this time and did not
approach infinite values.



So when you say that matter in the Big Bang had high initial
temperature, what does that mean exactly, and how was it
manifested in the early universe?
Just that the matter was hot in the ordinary sense. The particles
had high kinetic energies, they were close together, and there were
frequent collisions. Does that seem adequate?

-- Jeff, in Minneapolis

robross
2009-May-06, 02:44 AM
There are all sorts of definitions of temperature, but average kinetic
energy of particles is the generic description I would use.

<snip>


Just that the matter was hot in the ordinary sense. The particles
had high kinetic energies, they were close together, and there were
frequent collisions. Does that seem adequate?

-- Jeff, in Minneapolis

Yup, that all seems very clear. Thanks.

Cougar
2009-May-06, 01:08 PM
Well, if you really want to get into it, I'd suggest The Mystery of the Missing Antimatter (http://press.princeton.edu/titles/8475.html) authored by Helen Quinn & Yossi Nir in 2008. Unfortunately, we don't yet know the full answer to this mystery, but the story about the quest to find out is fascinating and enlightening.

robross
2009-May-06, 05:54 PM
Well, if you really want to get into it, I'd suggest The Mystery of the Missing Antimatter (http://press.princeton.edu/titles/8475.html) authored by Helen Quinn & Yossi Nir in 2008. Unfortunately, we don't yet know the full answer to this mystery, but the story about the quest to find out is fascinating and enlightening.

One thing that puzzles me though, is that how can we be certain there are no anti-matter galactic super clusters out there? From what I understand, by just observation an anti-matter galaxy would look and behave exactly like a matter galaxy by any of our instruments. We would only be able to tell it was anti-matter by observing the radiation from collisions of matter particles with the anti-matter, which assumes there's a lot of both in that local vicinity. But if we allow for an entire galaxy super cluster to be made of anti-matter, such that it is gravitationally bound to a system comprised only of anti-matter, then we would not expect any more anti-matter/matter collisions to occur than occur in our own local group/local super cluster.

So how do we know every other galactic super cluster is not made of anti-matter?

Rob

rommel543
2009-May-06, 09:06 PM
Welcome to BAUT Rob.

I've read about quite a few theories regarding the Big Bang and what happened at the t=0 moment.

On of the questions people point to in regards to the big bang is the idea of a singularity expanding. I theory a singularity is dimensionless, therefore if expansion happened from a singularity then it should have happened evenly. But looking at the CMB and the distribution of matter in space we can tell that it defiantly did not expand smoothly or evenly. In fact some point out that if it had expanded evenly we would not be here to have this conversation. If the BB occurred as theorized the all matter and anti-matter was created in that instant. Because the expansion occurred unevenly there was slightly more matter than anti-matter and thus our universe was born.

There are numerous theories regarding the actual cause of the Big Bang, from Lee Simon's fecund universes theory where Universes are created from the collapse of matter into a black hole, to the Big Bounce theory where using loop quantum cosmology they can show that our Universe occurred from the collapse of a different universe (kind of like the theory of the big crunch only bouncing back out afterward).

I personally have issues around the entire big bang theory. One of the big proofs of the big bang is the CMB. The problem is they have found inconsistencies with it. Galactic clusters should cause shadows in the CMB, kind of like someone standing between you an a bright light. The problem is some galactic clusters cause shadows and some don't. A lack of a shadow would indicate that the CMB is coming from a source between us and the distance cluster. Much of my other issues come from the fact that we are collecting data from a single location in the Universe and until we can start collecting data from other locations we can't be 100% sure of the information that we are getting isn't caused by something local.

Amber Robot
2009-May-06, 09:27 PM
I personally have issues around the entire big bang theory. One of the big proofs of the big bang is the CMB. The problem is they have found inconsistencies with it. Galactic clusters should cause shadows in the CMB, kind of like someone standing between you an a bright light. The problem is some galactic clusters cause shadows and some don't. A lack of a shadow would indicate that the CMB is coming from a source between us and the distance cluster. Much of my other issues come from the fact that we are collecting data from a single location in the Universe and until we can start collecting data from other locations we can't be 100% sure of the information that we are getting isn't caused by something local.

Well, if you are willing to admit that some galaxy clusters cause shadows then it can't be local, right? And I wouldn't hold my breath for a time when we can collect information from another location that is significantly far away from where we are now.

rommel543
2009-May-07, 02:03 PM
Well, if you are willing to admit that some galaxy clusters cause shadows then it can't be local, right? And I wouldn't hold my breath for a time when we can collect information from another location that is significantly far away from where we are now.

Ok, 'local' isn't the best word, but it seems like the CMB is not all pervasive though as they thought.

I'm not holding my breath either, but until that time comes I will still have issues with some of the theories making absolute statements based on observations from this single point in the universe.

Spaceman Spiff
2009-May-09, 05:05 PM
This topic of galaxy cluster shadows in the cosmic background radiation signal was also discussed here (http://www.bautforum.com/space-astronomy-questions-answers/87844-updates-2006-article-titled-bb-afterglow-fails-intergalactic-shadow-test.html#post1481843). And it's not that no shadows were found, but that they weren't as "deep" as we expected from the models.

cosmocrazy
2009-May-13, 03:23 PM
Hi. I've been lurking for a while but just signed up and I thought I'd start off with a bang, er, a question about the Big Bang.

It is my understanding that about 13.7 billion years ago, all the "stuff" in the universe was located in a singularity with no spacial dimension. At this point, what was the nature of this "stuff"? Was this just pure EM energy (i.e. photons) or something else? Was there just a single photon with an unimaginably large energy, or were there bazillions of photons with slightly less than unimaginably large energies, all superimposed on one another?

I have plenty of follow up questions but I want to start out slowly :)

Thanks!

Rob

Hi Rob and welcome!

Just a thought,
if we consider the math and physics behind the BB to be correct then at some point in time, as you have said, all the known "stuff" in the universe came from a "singularity" known as the primordial atom. But since a "singularity" by definition has no physical properties and only exists as a mathematical construct then the only answer i can offer you is that the initial physical state of the universe as we could know it is 0, zero, zilch, nothing. This seems so contradictory to our physical sense of reality that either - A. the theory is wrong, or B. the theory/math is flawed or in complete, or C. there is another state of reality that we are unaware of (with possibly more/different physical laws).