What is the mysterious "gas cloud gatherer/collapser" in Big Bang cosmology?

(Kelly Fitzpatrick) #1

In the big bang model, after hydrogen and helium gas were formed, they were still not dense enough for gravitational collapse to begin. My question has two parts:

  1. “The Great Gatherer”: Why wouldn’t the hydrogen and helium continue to disperse indefinitely in the absolute vacuum of space, as all gases do in a vacuum? What force or condition could cause these gases to defy their natural tendency and begin to collect together rather than disperse, especially in the stages of the big bang cosmology where no stars or galaxies had yet formed to provide possible physical or gravitational loci for such a gathering of gas?

  2. “The Great Collapser”: Conceding the possibility that such gases had formed into clouds rather than dispersed, what forces or conditions might compact such a cloud of gas into a space of sufficient density that gravitational collapse would begin? Such forces or conditions would seem to have to meet two criteria: A) they would have to create a physical “bubble” to physically constrain the gas into a contained space, and the integrity of such a “bubble” would have to be such that it had no points of “leakage” great enough to allow so much gas to escape that density would never reach a critical mass for gravitational collapse, and B) in addition to containing the gas, the “bubble” would have to exert an immense compacting force upon the gas inside it so that the volume of the gas (and, perhaps, the “bubble” itself) would continually decrease, and such a force would have to continually be greater that the ever growing kinetic and thermal forces of the gas itself, which would be fighting continuously against the collapsing “bubble” with increasing pressure for every liter of physical volume that the shrinking “bubble” wants to take away from it.

To me this is the key stage of big bang cosmology, where the chaos created by the “bang” finally started to see the emergence of order and structure. As someone who in the past considered parts of big bang cosmology plausible, I am astonished to find that both secular and Christian sources who believe the universe developed in this way gloss over this problem without providing even a theoretical construct for what could cause primordial gases to behave in the way big bang cosmology needs them to–that is, in direct contradiction to the normal behavior of gases–in order for the structures of our universe to begin forming. All I can find in the many sources I have searched are vague references to “density fluctuations”, which are never defined or described, or to supernova explosions which, even conceding these as a source of forces to contribute to cloud collapse of later stars (there would not have been pre-existing supernovas to aid the formation of the first stars) would certainly further disperse gas rather than compacting it inside a “bubble”.

Thank you!

(Patrick ) #2

Big Bang cosmoslogy has a very precise and accurate answers to your questions. At 379,000 years after the big bang, the universe was just an expanding sphere of protons, electrons, neutrinos. It was very uniform and cooling as the universe expanded. The universe was at an average temperature of 3,000 degrees. There were no stars, or any other type of structures. Once the universe cooled below this temperature electrons attached to protons to form hydrogen atoms. In the process a photon of light was released. This time of last scattering is at a very precise wavelength and energy level. This is the Cosmic background radiation that is still measured today.
The Planck 2015 results have measured the spectrum, temperature of CMBR to an accuracy of 0.1%. The CMBR temperature is uniform to .00001 deg K. But very slight variations are measured. The hot spots are where there is slightly more matter and the cold spots are where there are voids.

So the gas cloud gatherer/collasper is just the magnification of quantum fluctuations of the density of the universe at the time of last scattering. From a tiny quantum fluctuation came galaxies and large cluster of galaxies as well as large voids.

(Brad Kramer) #3

@rkellyfitz welcome, and thanks for the question. Big Bang science is not my specialty. I’ll ask around the BioLogos team and see what I can come up with.

(Robert J. Kurland, Ph.D.) #4

Interesting question, Kelly–I’d first suggest that you might look at some web resources, which give a clear and fairly accurate picture of what we infer about the early history of the universe. Google “the first few minutes after the Big Bang” and you’ll see lots of references.

The Universe started off very dense (small volume for the large number of particles and radiation present); nuclear reactions occurred with protons eventually forming helium. As the universe expanded it was still dense enough that gravitational attraction was sufficient for star formation to occur. Indeed, you can see evidence of star formation occurring even now in gaseous nebula.

There wouldn’t have to be a “physical bubble” at the very high densities in the early universe. Also the expansion of the universe is not equivalent to the expansion of objects–space expands (or more properly space-time), but not objects. Also, we look back in time using radiation to infer what the universe was like. But we are limited to how far back we can look. The universe was a plasma and filled with fundamental particles and therefore opaque to radiation (radiation was scattered), so we can only look back to about a few hundred thousand years after the Big Bang. But as pointed out by Patrick Trischitta, the burning embers of the Big Bang, the CMBR or COBE can be used to infer what things were like before this limit.

(Kelly Fitzpatrick) #5

Patrick, Brad, and Bob, thanks so much for your replies! I really appreciate your taking the time to read my post and offer a reply.

I am genuinely curious and looking for answers to the questions I posted, and look forward to a cordial dialog with you and others about them!

I will be asking some very specific questions below and in future posts, and I want you all to know I’m not being argumentative or just trying to refute what others may say. On the contrary, I’m trying to find some very specific answers about a certain phase of big bang cosmology that I cannot find addressed anywhere–I want to know what people think about this, really! Any and all replies are welcome!

Your replies did not address any of my specific questions, so let me try to clarify below what my questions are:

  1. My question is about the specific phase AFTER the singularity, inflation, etc. where helium and hydrogen gas exist and BEFORE the initial formation of any stars. Patrick and Bob, most of your replies describe the previous phases of the big bang, which I understand quite well through extensive reading in books and many websites, and info about these previous phases does not address my questions.

  2. My questions are ONLY about this phase of the cosmology where, it is claimed, helium and hydrogen gas in the absolute vacuum of the expanding universe did two strange things:

A) the gases collected into “clouds” rather than continuing to disperse, as they would if they were behaving normally according to standard physical laws

B) these “clouds” were then compressed into such an extreme density that gravitational collapse ensued

My questions are: 1) what could possibly cause diffuse, expanding gas in the absolute vacuum of expanding space to ever, for any reason, collect together into “clouds” rather than following the universal tendency of gas to disperse toward a state of lower pressure and density? and:

  1. What forces exist that could compact such a “gas cloud” into a contained space of small enough volume that gravitational collapse would be triggered?

Patrick, your reply says that a “magnification of quantum fluctuations” created everything in the universe, but my question is about the specific behavior of hydrogen gas that was purportedly created after such fluctuations had finished giving birth to the universe.

Given the existence of helium and hydrogen gas in the early universe, and even conceding that these gases were more concentrated in the “hot spots” you mention, what, at that point, would prevent the hydrogen gas from naturally dispersing away from those hot spots in the absolute vacuum of space? At this point in the cosmology there would not be sufficient gravity in the “hot spots” to prevent the gas from obeying the laws of physics and dispersing in a vacuum, as gases always do, or is there something I’m missing here?

As to the “collapser”, what force would cause a gas “cloud” in the absolute vacuum of space to contract in volume to a point of critical mass where gravitational collapse would result? Patrick, you have only offered “quantum fluctuations” as a mechanism in your reply above, but I don’t believe you would claim that this is what happened to these gas clouds, would you? If not quantum fluctuations, then what?

Bob, your reply to this issue is simply to say that “gravitational attraction was sufficient for star formation to occur”, but in the phase of initial gases that I am asking about there was not sufficient gravity to cause the gases to abandon their universal tendency toward dispersal, much less to cause them to come together under conditions of such intense inward pressure as to cause gravitational collapse to begin. It is at just this phase of the cosmology that gravitational attraction was woefully insufficient to cause the gases to abandon their normal behavior and condense radically for star formation to occur.

Bob, your reply says that "There wouldn’t have to be a “physical bubble” of the kind I describe to compact a cloud of gas and overcome its immense pressure to make it dense enough for gravitational collapse to begin–fine, but WHAT, then, DID happen to cause even one gas cloud be compacted in such a way? Gases ALWAYS naturally disperse, they NEVER naturally clump together toward increased density unless some forces are acting on them to compel them toward smaller volume.

These, then, are my specific questions: 1) What would cause gases in the vacuum of space to collect into “clouds” rather than obeying the natural tendency of all gases to disperse?

  1. What scenario can be described in which a cloud of gas has immense forces working on it which compact and crush the gas into such a small volume of incredibly high pressure and density so that a critical mass is reached for gravitational collapse to begin?

I ask these questions because I can find no book or website of the many, many sources I’ve research that address this key phase of big bang cosmology.

I appreciate your previous replies, but if you are able to reply again, please reply to the specific questions I mention about rather than giving me a basic “primer” about the whole process of the big bang. I am already familiar with the model as a whole and have done much reading on it, which had led me focus on the two specific questions I mention above.

Thanks Patrick, Brad, and Bob for any replies and help you may be able to pass on to me! I look forward to our dialog continuing!

(Patrick ) #7

What I was describing to you was what was happening 380,000 years AFTER the big bang.

At that time, the universe was a gas in equilibrium so the laws of statistical thermodynamics apply.
This was your gas of mostly of hydrogen, helium and a little lithium. Once it cooled (by expansion), hydrogen atoms formed releasing the CMBR.

Regarding quantum fluctuations, have you studied Quantum mechanics yet? If not see if you can pick up a little on quantum physics and the Heisenberg uncertainty principle. And of course, gravity. Do you understand Newtonian gravity? Gm1m2/r^2

So do a little homework and then come back. I will help you with the details as I am pretty current on the subject.

(Kelly Fitzpatrick) #8


Thanks so much for your quick reply, I appreciate it!

We seem to be talking past each other–the replies you are so nice to offer unfortunately aren’t addressing my specific questions. Let me try again to clarify what my questions are:

I am not asking about anything related to what happened before the formation of hydrogen and helium gas–for this discussion right now I’d like to skip right past the singularity, inflation, cooling, etc., past the whole first 380,000 years, and simply assume that these gases have formed and exist in a universe that does not yet contain any other structures like stars, galaxies, or planets.

My question is about the specific behavior of this hydrogen and helium gas that found itself emerging in the the absolute vacuum of space at that time.

My questions are as follows:

  1. Why would this hydrogen and helium gas gather closer together over time, as would be necessary for star formation to begin, rather than disperse over time, as gases normally do? Gases in a vacuum always tend toward dispersal, why wouldn’t they have behaved the same way at that time in the early universe?

  2. In what kind of specific scenario, and under what specific forces, would such a “gathering” of gas become compacted into such a small volume that it would reach a critical mass for spontaneous gravitational collapse leading to star formation?

That’s it, just these two questions. Any replies you can offer or resources to point me to that talk specifically about these things would be greatly appreciated, thanks!

(Patrick ) #10

Your questions are easily answered using simulations of gas in equilibrium. Note that the temperature of this gas is about 3000 degrees K. Note that temperature is a measure of the random motion of particles, in this case, hydrogen and helium. This is quite hot, so the particles are banging into each other quite often. The force that is really important is electromagnetic force as molecules and ions are formed, broken apart, reformed. Even though the gas is uniform it has slightly different densities in the expanding (cooling sphere). These causes clumps, mainly by electromagnetic forces. This creates dust. As these dust clumps get bigger, the force of gravity becomes important. Eventually, I am talking hundred of millions of years, the clumps are big enough that gravitation pressure ignites nuclear fusion, i.e. a star is born.
A simulation of this is very easy to do just using electromagnetic and gravity. No matter what your starting conditions, you get clumps, first dust, then eventually stars. Nothing else needed besides quantum electrodynamics, thermodynamic and Newtonian gravity.

(Kelly Fitzpatrick) #11


Thanks again for the speedy reply!

I’m very confused by the mention of dust in your answer. As far as I can understand in scouring everything online from NASA to Herschel to Wikipedia, there would have been no dust present in the early universe before the formation of the the first stars–all these websites said that cosmic dust is a product of nuclear reactions in stars, and therefore would not have been present in the early universe before the first stars had formed.

My specific interest is in the formation of the first stars in the early universe, which, as far as I can understand from the various sources on big bang cosmology, would have formed at a time when only gas existed.

So, my question is specifically how gas in the early universe could behave in such a way as to give rise to the first stars, not how later stars could have formed from cosmic dust.

In the early universe, when only hydrogen and helium gas existed, what would cause this gas to gather rather than disperse, as gases normally do in a vacuum? I ask this because the continued dispersal of these gases would prevent the formation of stars, wouldn’t it?

And, secondly, what forces could cause these gases–in the absence of any other elements, dust, or solid matter in the early stages of the universe–to become so densely compacted as to trigger their own gravitational collapse?

In the many sources I have searched, I cannot find one that addresses this critical juncture of big bang cosmology.

Thanks for any insight you might give!

(Patrick ) #12

I don’t think that the period you are looking at was a “critical juncture of big bang cosmology.” I think you are looking in the wrong places, as what you are describing were conditions 150 million to one billion years AFTER the big bang. It took hundreds of millions of years for the universe to expand enough such that the temperature of the universe cooled enough so that only hydrogen and helium gas (plus the CMBR) existed in the universe. Given these conditions, the universe at that time can described as a gas in thermal equilibrium. The universe at this time behaves according to statistical thermodynamic. Look up Brownian motion as this is how the universe works at this time. Hydrogen molecules (H2) and He2 would be present in a uniform density but not perfectly uniform. There was slightly different densities at every point in space. Photons would brake hydrogen bonds and quantum electrodynamics would result in clumps of molecules. After hundreds of millions of years these clumps will just get bigger and bigger under the influence of gravity. Population III stars started forming and reionized the hydrogen gas again.

Look up what is called The Epoch of Reionization
Read this about reionization period. It is the time period you are interested in https://en.wikipedia.org/wiki/Reionization

(Kelly Fitzpatrick) #13


Thanks so much for the great info, I looked up Brownian motion and the link about the epoch of reionization, as well as a lot of other related websites.

You have already been so gracious to spend so much time reading and replying to my messages, and I really appreciate it.

I do have further questions and if you might have time to keep replying it would certainly be appreciated.

As I’ve said, I’m most interested in the conditions that led to the formation of the first stars. Any info you can share or websites you could direct me to to help me get more details would be helpful (of course I don’t expect you to type out long replies yourself, I’m very willing to go and do the work of reading on any websites you could refer me to).

  1. In your reply you said “Photons would brake hydrogen bonds and quantum electrodynamics would result in clumps of molecules”–I have never heard about this proposal before, and did not find it referred to or described in any of the sources I searched. Could you give more details about the specific process of how H2 and He2 could clump together under the influence of these forces?

  2. After these molecules clumped together, would they not still be in a gaseous state, and be subject to normal laws describing the behavior of gases?

  3. Any other sources you could point me to that would go into greater detail about the different proposals for how gases in the early universe could lead to the formation of the first stars? There are no shortage of sources that state that this happened, but I cannot find any that describe the process in step-by-step detail.


(Patrick ) #14

This was a very “boring” period in the existence of the universe that extended from about 379,000 years after the Big Bang to 500 million years after the Big Bang. No stars, nor galaxies, just hydrogen and helium molecules but still a lot of very energetic photons - the CBMR. This gas is anisotropic meaning that it is not completely uniform and it is expanding. Parts of this gas is actually swirling (rotating). The 21-cm line in hydrogen is a means of studying this period. The 21-cm line occurs in neutral hydrogen, due to differences in energy between the spin triplet and spin singlet states of the electron and proton. The transition is also highly temperature dependent, meaning that as objects form in the “dark ages” and emit Lyman-alpha photons that are absorbed and re-emitted by surrounding neutral hydrogen, it will produce a 21-cm line signal in that hydrogen. By studying 21-cm line emission, it will be possible to learn more about the early structures that formed. So you have microscopic density variations in the gas as well as motion - outward due to expansion and swirling due to density variations. Photon energy is driving the process as the universe is still hot (but cooling slowly) from 3000 degrees K to 3 degrees K . Photons hit hydrogen molecules breaking it apart into two hydrogen ions. Electromagnetics (charge differences) bring ions together to form molecules. Molecules clump together and swirl together. More clumping until your have swirling gas regions within the gas (whirlpools, vortexes). Once the universe is cool enough and since densities are anisotropic, gravity begins to hold particles together. Once photons spread out, gravity is dominant force and swirling clumps grow and compress in the center until the first stars ignite.

Yes, they will be in gaseous state until temperature of universe drops from 3000 deg K until the freezing point of hydrogen occurs at a few degrees about absolute zero.

Going from a swirling cloud of gas to a star is all gravity. You can do simulations, or you can just do a thought experiment. Take a sphere of anisotropic gas, somewhere in the sphere, gravity will pull together enough mass in a region to ignite a star. It would be happening all over the sphere. Before the expansion of the universe was discovered, General relativity had a problem in that every possible universe would collaspe under the influence of gravity. Without the outward expansion and thus cooling of the universe, it could never produce stars. It would just collaspe back into the initial singularity.

(Kelly Fitzpatrick) #15

Thanks Patrick for the reply, I didn’t have time to do my “homework” today so it may be a day or two before my next questions, I appreciate you sharing with me what you know

(Patrick ) #16

No rush. I have been interested in cosmology my entire life. Amazing progress in understanding of the universe in the last 50 years. Take your time, read, think about it, read some more, think some more.

(Kelly Fitzpatrick) #17

Hi Patrick, thanks again for the info, I did some reading and also looked at the link you sent on Baryonic Acoustic Oscillations.

A couple questions:

  1. You said “Going from a swirling cloud of gas to a star is all gravity” , that is, if I catch your meaning, gravity acting on differences in density. It seems as though you’re suggesting that, at the most basic level, differences in density in gases + gravity are sufficient conditions to initiate the process of star formation.

To me I still can’t see how these conditions would be sufficient, primarily because of the natural behavior of gases in our common observation. Despite the inherent dangers of imperfect analogies, let me share an example to try to show what I mean:

Say I am boiling a pot of water in my kitchen, which happens to be on the surface of the moon (let’s put aside questions of the feasibility of boiling water in a moon kitchen for now). This produces H2O gas. The H2O disperses throughout my kitchen, out the windows, and straight out into space. It does this despite the inherent gravity of the H2O molecules themselves, the differing initial densities of the H2O in different regions of the kitchen, and the presence of additional gravitational forces from every other solid object in the room. Even the relatively massive gravity field of the moon, on which my kitchen sits, does not keep the gas from dispersing toward the maximum entropy it could achieve in my kitchen, and then throughout space as it goes out the kitchen window.

Now (please bear with my analogy) say my kitchen was suddenly moved to the surface of the earth. Although the increased gravity of the earth would keep the H2O from escaping into space, the gas still would not gather together, as a result of any gravitational force, anywhere in my kitchen, nor anywhere within the earth’s atmosphere–it would again disperse and seek maximum entropy.

Now, finally, say my kitchen was moved to the surface of Jupiter. Jupiter’s gravity is massive enough to overcome the expansive pressure of the H2O gas in my kitchen. In the same way Jupiter has no atmosphere, neither would my kitchen, as all the gas would be sucked by Jupiter’s gravity straight to the floor. Finally, we have a force great enough to “gather” the gas while still in gaseous form.

In all these scenarios, anisotropic density + the gravity of the gas itself are not sufficient to overcome the expansive pressure of the gas. An additional outside gravitational field–and a staggeringly massive one at that–was the only thing that stopped the expansion of the gas.

What was it in the early universe that might act in a similar way to overcome the natural expansive pressure of gas?

Do cosmologists have to invoke vast clumps of dark matter to gather and hold gases together? I’m genuinely at a loss–what am I missing?

  1. Would Baryonic Acoustic Oscillations affect the natural tendency of gas to disperse? Here I’m not talking about how the waves might lead to differing densities of matter in the first place, I’m referring to what the effect would be on gases that had already formed, and whether it would prevent gases from dispersing as time went on.

  2. A somewhat unrelated question regarding further star formation after the first stars had already formed: in scenarios I read about describing what could trigger gravitational collapse of a gas cloud, the most common force posited is a supernova explosion. This is extremely puzzling to me–let me try to use another analogy to explain why.

Say an astronaut out on a space walk has a high-tech mechanism by which he can smoke a cigarette in his helmet but then blow the smoke outside of it into space (I realize that cigarette smoke is largely particulate matter and not really gas, but let’s just use this as an analogy for now). He blows out a giant puff of smoke and goes back into the space station. A second astronaut comes out on a space walk, pulls the pin out of a grenade, floats it toward the puff of smoke, and it detonates right next to the puff.

It would be inconceivable that anything other than a sudden and massive dispersion of the puff of smoke would occur.

How could a shock wave from a supernova have any other effect on a cloud of gas than a similarly sudden and massive dispersion of the cloud?



In all of your thought experiments you are assuming that gases always act like the small quantity of gas you are using. A small quantity of gas does not generate a gravational field strong enough to hold the gas together at the temperatures you are using. A very large cloud of gas can result in enough gravity to hold itself together and even collapse into itself. The very low temperature of the gas also helps as that reduces the kenetic energy of the gas molocules.

(Kelly Fitzpatrick) #19

Bill, thanks for the reply!

I see what you’re saying about how the quantity of gas–and resultant total gravity–would affect possible dispersal, but wouldn’t volume and relative density also be influencing factors?

If a small quantity of gas would disperse because it is has sufficiently high volume and/or sufficiently low density to overcome it’s own inherent gravitational force, would not a large quantity of gas do the same?

I can see how total quantity is an influencing factor–as is temperature, as you note–but not a sufficient one to prevent dispersal unless something at the same time causes volume to become small enough for the gravity to win out over the expansive pressure of gas.

(Kelly Fitzpatrick) #20

I guess what I’m saying, Bill, is that it seems to me that gas cloud formation is not simple, and does not naturally follow because of the existence of gravity alone. Instead, would it not require a “perfect storm” of different factors existing and constraints being met before gas molecules in open space would start clumping together due to their own gravity to form clouds–at the very least some minimum mass within some maximum volume of space, no?

As for the inherent gravity of gas molecules being sufficient to bring about gravitational collapse, which your response seems to imply when it says that it could cause a cloud to “even collapse into itself”, does not the invocation of supernova explosions in most descriptions of later stellar formation imply that gravity itself should never be expected to be able to do such a thing? If it could, why the appeal to such additional forces to “trigger” a collapse?

Thanks for the dialogue!


You need to read up on the ideal gas law. The pressure of a gas is the result of the kenetic energy of the gas which varies with temperature and volumn. There is no “expansive pressure of gas”. If you take a sealed tank of gas at a given pressure and temperature and start to lower the temperature the pressure will also lower. Gas doesn’t expand because it is surrounded by a vacuum. It expands because of it’s kenetic energy. Once the density of a gas exceeds a given value the gravational attraction will overcome the kenetic energy and the gas will start to contract. As the gas is compressed it will become hotter. This is what starts the fusion that generates the heat of a star. So yes it is gravity that can lead to a supernova if the sun was big enough.

(Patrick ) #22

Only gravity and the electromagnetic force of molecular bonds. That is all you need to compress gas into stars.
Regarding dark matter. Galaxies today are spinning too fast for the mass that it has so dark matter was postulated to add mass to galaxies. If dark matter wasn’t added, galaxies should have spun apart billions of years ago and we wouldn’t be here.

The BAO is the shock wave from the big bang. It makes matter clump into spheres that today are 400 million lightyears in diameter. In those clumps stars, galaxies form

NASA banded smoking while in space suit given oxygen rich environment.

A supernova sends heavy elements into space. The shock wave also “clears the area of dust” So after a supernova, another area of space has heavy elements to aggregate into rocky planets in orbit around a newlly formed second generation star. Supernova’s gives birth to new solar systems like our own.