The largest question that comes to my mind, and really seems to sink the entire theory, is that if pure energy actually had a gravitational component, wouldn't the Big Bang simply have gone "thud," as the gravitation component would have been strong enough to hold in everything, including light (energy)?

But perhaps there's no gravitational component to light. If so, and if there was a massive, universal black hole of matter and it collided with a massive, universal black hold of anti-matter, then when that matter was converted to energy, providing there was at least some assymetry, then the subsequent energy could have produced a massive ball of incredible energy no longer bound by the gravitation pull produced by the matter, and BANG!

The universe begun.

Is there an astrophysicist in the house that could lend some hard science to my meandering thoughts in a way which is contructive and not confusing?

If so, please do!

By the way, this is an offshoot of this thread.

Were that true, the theory would never have survived general relativity. It isn't true, and the theory does. The gravitational component of the energy is not enough to prevent the expansion, that's what general relativity tells you. What you are close to, however, is a second issue that is indeed very puzzling-- why did the energy partition itself between expansion and rest energy (using the terms loosely, GR doesn't use energy like this) in such a way that the expansion neither went "thud", nor occurred too fast for anything interesting to happen in the short times allowed? Both of those possibilities seem vastly more likely in a "blind" universe, so ours seems to be a very carefully selected universe. It is puzzling to find a scientific explanation, though nonscientific explanations abound (the anthropic principle, religion, etc.). This isn't a problem with the theory, it's a mystery of the universe. This is simply the usual misconception that the BBT is an explosion. It isn't, and your picture would fail on many levels, the most notably being that it would give rise to spatial gradients (where did the "collision" first occur?) that are not observed. So the problem has nothing to do with gravity (your picture would certainly overcome any gravitational binding issues, but as I said, they were never an issue anyway), but with fitting observations.

I'll let you be the judge.

I do not believe that pure energy has been defined. The BBT is a theory and as such it does leave many unanswered questions, but it is the best thing going to date as far as nucleosynthesis.

Perhaps if there were a pure energy and it did have gravity it was homogenous with 0 gradiant. Once the energy began to "clump" a gradiant was formed that forces the "pure energy" zero gradiant away from the clumps and generates dark energy. Or perhaps it is a new physics we do not yet understand.

BTW, I am not an astrophysicist, though I love the science...not so much the math.

Well, if you were to convert matter to energy without any residual matter, you'd have nothing but photons.

So, I guess photons are pure energy.

Can the energy be so massive that the photons break down into still smaller constituents, as neutrons break down into quarks which are composed of muons, gluons, and other things I've long since forgotten how they exactly fit together?

Photons aren't supposed to break down any further, but hey, physics has been surprised before! Photons pretty much are pure energy, but that doesn't mean their own gravity can contain them-- it depends on the energy density and the expansion rate.

I think you can start with the GR equations, and explicitly plug in 'only photons' ... it gets a little hairy to also include the Standard Model (of particle physics) in such a way that no matter (or anti-matter) gets created, but as long as the universe remains radiation dominated, I guess you could remove the matter and watch what happens ... (you'd also, probably, have to turn off the weak and strong force; while photon-photon collision cross-sections are small, they are not zero, and so, by the ergodic principle ...)

Mugs,

If the energy density of light (photons) becomes sufficiently great,
heavier particles are formed, not lighter particles. It is thought that
during the first millionth of a second of the Big Bang, the state of
matter/energy was something called "quark soup". Too hot for
protons and neutrons, but too dense for photons alone.

Ken,

Why would "spatial gradients" necessarily be observed if the Big
Bang was an explosion? Are measurments of the Universe's density
at different distances and in different directions precise enough to
reveal such gradients? If I recall correctly, the north and south
Hubble deep field images differed in galaxy density by something
like a factor of two. Maybe with another dozen deep field images
you could really claim that there is no evidence for a gradient.

Also, Inflation was invented to explain the uniform temperature of
the CMBR. It should serve equally well to hide any spatial gradient
from our view.

Do you have any other reasons for believing that the Big Bang was
not an explosion?

-- Jeff, in Minneapolis

__________________
http://www.FreeMars.org/jeff/

"I find astronomy very interesting, but I wouldn't if I thought we
were just going to sit here and look." -- "Van Rijn"

"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves

Indeed, there is an extended early phase of the Big Bang that is radiation dominated (and note that all relativistic particles behave the same way as light), so this is not a hypothetical question. The GR equations are actually the easiest in this situation, and you get a decelerating expansion but nothing that is "gravitationally bound" in the way mugaliens seems to be imagining. Indeed, were it not so, we would not be here now.

Because you would need them to explain the redshifts in that case-- were it an explosion, the redshifts would have to be caused by said pressure gradients.
It would be apparent in the CMB, not thee galaxy density, because the CMB is exquisitely smooth and dates back to the time when the universe was in thermodynamic equilibrium. During that phase, any kinetic energy gradients that gave rise to the CMB redshift in an explosion scenario would have to be generated by pressure gradients that would be clearly visible. Pressure is a scalar, so in order for it to have a gradient, it has to be bigger in one direction than the other-- unless one really believes that the Earth is at the center of the pressure peak. Yes, I agree inflation could do something to mimic this effect, but if you have inflation, it's already not an explosion! The issue was can you get the Big Bang model from an explosion scenario, and inflation, as an explosion, would violate special relativity.

Yes-- it's called general relativity. It's a good theory, and it would have to be totally wrong for the Big Bang to be an explosion, in addition to the observational problems with the explosion interpretation.

mugaliens, would you mind clarifying your OP please?

That photons, as pure energy, "actually [have] a gravitational component" is already built in to GR, and (as Ken G points out), the early universe (in the concordance model) did comprise 'pure energy'.

What do you mean by "gravitation component would have been strong enough to hold in everything, including light (energy)"? The universe is everything, and the "gravitation component" of its (mass-)energy content is what determines its history.

Cool.

It's probably a perceptual/conception thing on my part, but my brain finds it difficult to perceive how black holes, which weigh much less than the entire universe, can exist, while when you put all the mass of the universe in a space the size of a marble, it someone fails to collapse into a black hole, and instead, this quark soup expands.

Ah well, would you be interested in seeing how GR, when applied to the universe, produces a Big Bang?

There are quite a few websites where this is explained, at varying levels of detail (and math!) - Sean Carroll's Cosmology Primer may be a good place to start, or this resources page of his.

mugaliens. Neutrons break down into protons by a quark transmutation...down to an up with emission of a W^-, which is transitory, breaking immediately into an electron and an electron-type antineutrino. The neutron is a baryon (heavy particle) as is the proton, and baryon number is conserved here.No neutron has ever been seen converting to muons or gluons.
Quarks are pointlike, with no known substructure, like the electron, not composed of muons or gluons. Muons are capable of decaying into electrons and a muon type neutrino, so think of them as a heavy lepton (as the Tau is also). Gluons exchange color charge between quarks the way virtual photons exchange the electromagnetic force between electrons and protons in an atom, except colored gluons operate in nuclei. That's how they fit together. Pete

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A third rate theory forbids.
A second rate theory explains after the fact.
A first rate theory predicts.
A. Lomonosov

Here it is stated that the universe began as "pure energy" yet when I try to nail down an elemental entity from which all of matter is derived posters like Celestial Mechanic adamantly state that matter can not be derived from photons (due to considerations of spin, charge, etc.).


Here the mention of "photon-photon" collisions are invoked to explain the creation of matter from photons but then no explanation of how the momentum changed from expanding purely radial photons (no collision possible) to a momentum state that allows such photon-photon collisions to occur. (remember my Big Bang Momentum thread?)

It would be nice if these things were tied together cohesively to allow one to understand all these seemingly contradictory conditions.

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My invisible elf ??? Why he is made of dark matter and lives off of dark energy !!!
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The formatting of your post is a little messed up, Squashed, could you perhaps have a go at editing, to make it easier to read?

The apparent contradictions are just that - apparent.

It is certainly worth going through this, slowly, to nail down the pieces. However, in a nutshell, the contradictions come about because the posts are too terse - the detailed context of each phrase, or sentence, needs to be spelled (that would be a good start).

In this post: Matter From EM Radiation; is the beginning of a trail of posts that explore what I refer to.

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My invisible elf ??? Why he is made of dark matter and lives off of dark energy !!!
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Same here. If the gravitation of all the matter in the Universe
is capable of slowing down the expansion, why isn't it capable
of preventing the expansion in the first place? The gravitation
of a far smaller amount of matter causes stars to collapse.

-- Jeff, in Minneapolis

__________________
http://www.FreeMars.org/jeff/

"I find astronomy very interesting, but I wouldn't if I thought we
were just going to sit here and look." -- "Van Rijn"

"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves

Why? This is the first time I've seen an assertion to that
effect, and there is no obvious reason the pressure gradient
would have to be involved. Either way, explosion or not,
pressure gradient or none, the redshift appears to be a
combination of Doppler shift and gravitational redshift.

Why would they have to be clearly visible?

Maybe there was a large sphere of essentially uniform high
density expanding into a surrounding region of lesser density,
and all we can see is a portion of the high density region.
The pressure could also be essentially uniform within that
region. It would still expand into the lower pressure region
surrounding it.

If you have a spherical rubber balloon filled with air, and
compress it into a small volume, then release it, will there be
a pressure gradient within the balloon as it expands, or will
all the air be at essentially uniform pressure at any instant?
I think it will be at essentially uniform pressure.

I certainly don't believe that we are at the center of such a
pressure peak, but I'm not aware of any evidence that we can't
be close to the center-- say, in the central 20%, 10%, or 5%.

Yeah, it does seem to be a self-defeating argument. But if
you are going to posit an original expansion which has no
cause or explanation and Inflation a miniscule fraction of an
attosecond later which also has no cause or explanation, but
serves to make the original expansion plausible, then I will
put some pressure on you!

As it is, expansion does not violate special relativity simply
because the theory of expansion asserts that "space expands",
meaning that when stuff moves apart, you expand the coordinate
system to follow the stuff, instead of leaving the coordinate
system alone and letting the stuff move through it. You could
do the same thing with an explosion: Let the coordinate system
follow the stuff which is moving apart. Voila! No violation
of special relativity!

Why?

Are you referring to something other than what you referred to
above? I asked for "other reasons". "Observational problems"
is extrordinarily vague. It isn't even clear whether or not
it is responsive to my request.

-- Jeff, in Minneapolis

__________________
http://www.FreeMars.org/jeff/

"I find astronomy very interesting, but I wouldn't if I thought we
were just going to sit here and look." -- "Van Rijn"

"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves

The whole point of saying that the Big Bang is an explosion is to generate the redshifts with pressure gradients, right? And those pressure gradients would be encoded into the CMB right up until recombination, right? So you'd see the signal of the pressure gradient in the CMB. The point is, you can't get redshifts from a pressure gradient without seeing the pressure gradient in the CMB, unless you are really at the center of the "explosion" (which does have to have a center to be an explosion).Yes, and the breakdown between them is merely a reflection of your own chosen coordinatization, it isn't "physical".

Here's how an explosion works. You have a pressure difference, which is a difference in kinetic energy flux. That means you have a volume that has a net kinetic energy fluxing into it, and this shows up as motion of that volume. The total amount of bulk kinetic energy that appears in the volume is entirely given to you by that pressure difference, so you simply can't have one without the other. During the time when the CMB was coupled to the gas, radiation pressure played a key role, so a large fraction of the energy in the universe was still in the form of pressure, not bulk motion. Since the CMB clearly encodes what was happening during that epoch, you would clearly see the pressure gradient responsible for the expansion. Later on, the pressure is a very weak player and mostly all you have is what you might call bulk kinetic energy, so by then the pressure gradient would no longer be very apparent, but that's not the case during the radiation dominated epoch. The formation of the CMB happens after about a 40-fold drop in pressure, but that implies the pressure difference across the visible universe would still be on the scale of a few percent-- easily detectable by WMAP by orders of magnitude.
No chance, such a model only accelerates at the edges, not in the center part you're claiming we are seeing. As I said, you can't get the bulk motion without the local pressure gradient, the two are one and the same-- if you want that center part to expand too, the pressure gradient has to eat its way into that region, again becoming clearly visible.
You are asking the right question, but coming up with the wrong answer.

Being close to the center might reduce how well we could see the pressure gradient, but we have so many orders of magnitude to play with that we'd have to be really really close not to see the gradient with WMAP. Even if we were at the center, I would imagine that more careful physical investigations could rule out the explosion idea, but you'd have to look at very careful fits to the expansion and the CMB formation. I would certainly imagine that has been done, but if not, it should be.

Actually, I'd say just start the whole thing after inflation. My argument shows that what happens next was not an explosion, even though there was plenty of pressure around to cause further expansion if that was indeed its cause. What was lacking was pressure gradient, and that's what you actually need to be able to explain motion as being induced by an explosion. Then you just say that inflation couldn't have been an explosion either, because of the relativistic physics needed.

As for before inflation, I'd say that all bets are off-- we really have no idea what was going on before then, even if we assume inflation did happen. So you can imagine you had an explosion before that, but what's the point? You still have 3 phases of Big Bang, and the only one you can imagine as an explosion is the one with zero observational constraints. You still need explanations for the other two, and it's really only the last one that you actually observe. The sole explanation for that one comes from general relativity, not explosion physics, this is my point. That's why "Big Bang" is an unfortunate misnomer.

No, it would violate special relativity, because to use special relativity you have to have a global inertial reference frame, and in such a frame, most of the universe is separating from you faster than the speed of light (given our interpretation of current observational data). That's the violation that requires general relativity to resolve, because in general relativity, the universe does not possess a global inertial reference frame, so it isn't a problem. You are now talking about the Milne universe, but that doesn't fit WMAP and supernova data.

I hope I've clarified that now.
It's responsive. Reason 1 was the absence of CMB gradients, and the "other reason" is that no special relativity model, explosion or otherwise, could fit the WMAP and supernova data. You need general relativity, and it isn't an explosion. The explosion stuff is just a picture to satisfy people with very little physics education, but personally I don't like using wrong models to give people a false sense of understanding. It's not that hard to say it basically right, and still make it understandable to people with little physics background.

There are many ways this cohesive tying together could be done; here's one suggestion:

Start with GR - establish common understanding of the bare basics, sufficient to handle what is needed later.

Apply GR to the universe - see how that results in an expanding universe; do this with the absolute minimum of math.

Discuss what these GR solutions have to say about the nature of mass-energy which the universe (in such solutions) comprises.

Relate the (general) nature of the (GR) mass-energy to what we commonly understand to be mass and energy (this is a transition stage).

Review the Standard Model, in terms of the mass-energy entities it contains.

Close the discussion, by tying the mass-energy in GR to the mass-entities in the Standard Model.

The advantage of this approach is that it starts with mugaliens' question, and with the primary (physics) theory relevant to cosmology (GR).

The disadvantage is that the minimum math to get to stage three may take us several months ...

Thoughts?

Yes, I remember that thread, and your question was answered there. But once again, the radial expansion of the universe does not in any way imply that photon trajectories are radial. The expansion obeys the cosmological principle, which means that no directions are any different from any other directions, and the photon distribution at every point is isotropic (that means the photons are streaming in all directions at all points, and so collide quite willy nilly if their energies are high enough to make particles). Just look at the CMB that we observe today-- does that look like it's "radially streaming"? (No.) Could that make particles in our living rooms if the energies were high enough? (Yes.) It seems your error stems from the common misconception that the "Big Bang" happened at one particular point, from with all the photons would emanate, when in fact it happened in every direction you look (ergo the CMB), and at every point you can imagine.

SO, how many Planck singularities were there in...

1. Our current 13 billion light year sphere? When? T=0, T=10^-43, T=10^-35 T= 3 minute, etc. In what volumes?
2. In all of 'space'?

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RussT
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Everything is, as it should be, otherwise, it wouldn't be!

Essentially zero, at this point, as the energy required to probe that scale simply doesn't appear anywhere in our universe.

Okay, so what does every point you can imagine really mean?

What does everywhere at once really mean?

What does shrinking the universe down to a point really mean?

What does the universe getting smaller and smaller the further we go back in time really mean?

Siince Einstein knew NOTHING about the Voids (or SMBH's, Non-baryonic DM, Inflation), when he "Made his Biggest Blunder", he was most certainly postulating the Cosmological Constant as holding back the universe from collapsing to "A SINGLE POINT"!!!

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RussT
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Everything is, as it should be, otherwise, it wouldn't be!

None of those things have any scientific meaning.That means that the scales of interest get smaller and smaller as you go back in time.Well, collapse into something that it isn't, anyway.

Or expanding to infinite volume. At the time, the universe was thought to be static. Einstein's cosmological constant was a "fudge factor" to keep it that way. No more, no less.

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This is how one university shows it.

http://abyss.uoregon.edu/~js/lectures/early_univ.html

How many mainstreamers agree with this, and if not, what changes would you make?

Just main points is fine to start.

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RussT
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Everything is, as it should be, otherwise, it wouldn't be!

The article makes some common mistakes. Here are two:
First of all, there was never "zero" radius-- such a thing would be impossible to describe with science. Secondly, the "moment" of Creation was not the "Big Bang", the Big Bang model is a model of the evolution of the universe after its creation. There is no theory for the creation of the universe, as there is no "theory of initial conditions" in science. Initial conditions are a device used throughout science, no more and no less.

Then it goes downhill from there. It misspells "Olbers' paradox", and it goes on to make the remarkably inaccurate statement: The age is now thought to be 13.7 billion years, not 15, and worse, the common model is to assume the universe has infinite size simply because there is no evidence of a finite size. That doesn't mean we know it's infinite, it means we don't know it's finite, and have no reason (other than philosophical, for some) to think that it is finite. That is has a "creation point" is another misnomer-- all its points are the creation point, and none of this requires a finite size. I didn't bother to read any more.

If this universe is just 13.7 billion years old which is an incredibly short period in an infinite time possibility isn't a binary finishing universe say one charge positive and one negative also a valid start.

The two would not collide as such but be rapidly rotating as the event horizons came together.
It is possible the mass contained within each super singularity would be at a great distance from the Schwartzchild radius.

When these horizons meet or form an equilibrium, gravity is cancelled and instantly a potential Planck time interval. Nett effect nil gravity and releases both charged new universes, pure conservation.

The release would have the effect of flipping their charge and starting a cyclical set of thermodynamically conserved paired universes equal but opposite in charge and perfectly balanced in electron to proton ratio.

Cheers

If the photons are streaming in every direction at all points (isotropic) then that suggests an absolute reference frame since the sum total of all the vectors would equal zero?

The CMBR is not "flowing" in any one direction, like air or water have currents, which means that any spherically enclosed region will have a zero net affect from the CMBR - the CMBR will not "push" the region any one way.

My "error" stems from the description of the big bang as originating from a singularity-like point. It seems to me that the current descriptions of the big bang are of a static universe because the entire structure was "predetermined" by the "momentum state" of its creation - the only thing that has changed since that moment of creation is the apparent size.

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My invisible elf ??? Why he is made of dark matter and lives off of dark energy !!!
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