Expanding Universe: Cosmologists Observations & Questions

In summary, Big Bang Theory is poorly constructed and the laws of physics don't allow for the accelerating expansion of the universe. Observations show that the universe is expanding and even accelerating, but this cannot be possible with the laws of physics. The explanation for the acceleration is unknown, but may involve dark energy. There is a mainstream consensus among working professional cosmologists that the gravity law that fits data well allows for the acceleration.
  • #1
ChristianGolfer
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Hey guys,
I've been wondering a lot about this Big Bang Theory, as I think it is terribly constructed. Anyways, I realize that cosmologists have observed that the universe is expanding and even accelerating in it's expansion. However, I don't see how this can be possible with the laws of physics. Since F = (G*m1*m2)/r^2, and every mass exerts a gravitational pull on every other mass, shouldn't galaxies, even if expanding outward, be moving somewhat closer together? Also, what started this expansion, and what is causing the acceleration? Since F = (G*m1*m2)/r^2 and F=MA, shouldn't gravity be slowing down the expansion of the universe? Is it due to dark energy at the border of the universe or the intensity of the initial big bang? What's the Big Crunch, the universe is predicted to eventually come together again? I'm not stupid, I just want to know the common perspective of you guys, as I question both theories.
 
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  • #2
the accerlerated expansion is due to the mysterious force of dark matter...
i personally believe in the big crunch followed by big bang followed by the big crunch...and so on...the big crunch is where the universe comes together to a singularity
 
  • #3
ChristianGolfer said:
Hey guys,
I've been wondering a lot about this Big Bang Theory, as I think it is terribly constructed. Anyways, I realize that cosmologists have observed that the universe is expanding and even accelerating in it's expansion. However, I don't see how this can be possible with the laws of physics...

observation trumps laws
if the laws don't fit, we have to adjust them, don't we?

actually you quoted two laws both of which were shown to be wrong and replaced by corrected versions long BEFORE astronomers observed expansion effects. So for starters, CG, you should probably chuck out those two laws, the F=MA and the Newton gravity law.

F=MA was shown to be wrong in 1905 by Einstein and replaced by a slightly different law involving the change in momentum. No big deal the old one is still approximately right in a lot of cases.

==============

the other law you mention is Newtons gravity law F = GM M'/r^2
and that was shown wrong and replaced by the equation of Gen Rel devised in 1915.
(which had to be tested by observation in 1919 before acceptance)

the 1915 gravity law is our NEW gravity law and is more accurate than the Newton one, it has been tested over and over again with different kinds of observational data and checks out to many decimal places.

it allows for expansion (altho Einstein didnt realize this when he published the law in 1915)

A catholic priest named Lemaitre was one of several people that found out that expansion was allowed by this new gravity law, if you started out with the right conditions.

http://en.wikipedia.org/wiki/Georges_Lemaître

but even though he offered it as one possible solution, in 1927, Lemaitre didn't know that this was really happening.

Expansion is an OBSERVATION thing, so if Einstein's new gravity law had NOT allowed for that possibility then when Hubble SAW evidence of expansion around 1929 there would probably have been a move to throw the 1915 law out and make a corrected version.

(Although people could have argued about different causes of the redshift, but those arguments get old pretty fast because the alternatives are so bad)
==========

So I think you have no problem. The gravity law that we have, that fits observations made on solar system bodies and all the other data extremely well, allows for it.

And it just happens to be observed. So be happy! At least in this department there is no contradiction between the commonsense derived from knowing correct physical law, and the observed facts.
========
BTW you ask about "us guys common perspective"
and I speak for myself only. I don't know that there is a common perspective here at PF Cosmology forum.

You are welcome to believe whatever you want. But there is a kind of mainstream consensus at the moment among working professional cosmologists and if you are going to disagree it is a good idea to understand that professional consensus first so you can differ from it intelligently if you so choose.
Just my 2 cents.
 
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  • #4
Common sense says that the attraction between matter will slow the rate of greater expanse to a lesser degree. Hence the idea of an accelerated expansion of space, should make one somewhat skeptical, rather than make up something like dark energy.
 
  • #5
DE is an entity added to 'save the appearances'; however it may be a necessary 'entity'.

Garth
 
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  • #6
One might as well placate to God as much as dark energy, as we have not a smidge of proof for either. Perhaps it's Pam Andersons breast? At least we know they exist, and we know they have expanded in an accelerated fashion, this is closer to the truth than dark energy by a long shot.
 
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  • #7
The kind of evidence we have for the existence of dark energy is the same kind of evidence that we have for the existence of every other particle and force in physics. We don't have as much or as convincing evidence for DE as we have for say electrons, but the evidence is of the same nature, i.e. observations of the physical world and the theoretical conclusions that follow from that observation.
 
  • #8
The dark energy bandwagon was launched by the Perlmutter supernova study. Debunking that study would be the place to start. Ideas like that always look pretty cranky out of the chute, and are rightfully treated with a healthy dose of skepticism before they gain traction in the scientific community at large. The evidence for DE, or something that mimics the effect, is difficult to avoid in the face of existing observational evidence. Some alternatives have been proposed, but to date, they are not very attractive. Appending the laws of physics is less extreme than rewriting them. If a rewrite is in order, the evidence usually accumulates rapidly when the tweak is put to the test.
 
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  • #9
Wallace said:
The kind of evidence we have for the existence of dark energy is the same kind of evidence that we have for the existence of every other particle and force in physics. We don't have as much or as convincing evidence for DE as we have for say electrons, but the evidence is of the same nature, i.e. observations of the physical world and the theoretical conclusions that follow from that observation.
If that is true... then like say for the electron you can say we have an instument that detects dark energy? I don't think so. Dark energy is pure speculation. I have no problem with the speculation as long as it doesn't get in the way of other speculations. :smile:

Cripe - we don't even have a firm grasp as to what space is, let alone how it expands, if it actually does at all.

From this perspective - Pam Anderson still looks good and that don't say much for dark energy.
 
  • #10
We don't have instruments that detect electrons either, not in the way you seem to be demanding of DE. What we have are machines that can give us a certain reading, due to some kind of action, that due to our theory of physics that included electrons we are able to interpret as the effects of electrons.

This is the same as what we have for dark energy, in that we have observations of the Universe that indicate the action of something on the material we can see. Our theories tell us that this action cannot be caused by the matter that we know about, and since out theories also tell us that there is much more energy in the Universe that we can see in the matter then it seems that the missing energy could be causing that action as evidenced by our observations. This is why we have DE in our theory.

If dark energy is pure speculation then so is the rest of science. It's a physical theory for this same kind of reasons we have any other physical theory. The evidence is certainly not as strong as the evidence we have for many other theories, but the process is the same.
 
  • #11
I have a question... from my understanding the strong and weak nuclear forces are what holds atoms together. However, these forces only act under small distances. Obviously when the big bang happened, the subatomic particles were racing out of the singularity's gravitational pull at a speed much faster than the speed of light. When the particles exited the gravitational field, they entered a frictionless environment at incredible speeds. Within a second, all of the subatomic particles would have been too far away for the strong and weak nuclear forces to have any affect on the particles. The end result would simply be an incredible amount of subatomic particles speeding away into nothingness. How then, were atoms formed? Also, the forces seem to just hold together protons and electrons. If the protons and electrons magically got together, wouldn't the neutrons have been far off in space by then?
 
  • #12
Obviously when the big bang happened, the subatomic particles were racing out of the singularity's gravitational pull at a speed much faster than the speed of light

You are thinking of the Big Bang as an explosion that occurred at a finite point within some existing space. This is not what the Big Bang theory suggests.

Firstly you cannot speak of the 'singularity' as a place or event. The singularity is the point at which our theories break down and we don't know how to describe the physics. Therefore the Big Bang theory starts not at the singularity but at a short time later. At this point what we can say is that the Universe was incredibly dense and hot. The key point however is that the entire Universe was simultaneous in this state, there wasn't a central ball of stuff flowing outwards into a previously empty universe, the whole Universe was in fact incredibly homogeneous (the same everywhere). The Big Bang didn't happen at a single place, it happened everywhere at once.
 
  • #13
Wow, that made pretty much no sense.

Definition of singularity: A point in space-time at which gravitational forces cause matter to have infinite density and infinitesimal volume, and space and time to become infinitely distorted.

Definition of a point: A dimensionless geometric object having no properties except location.

Definition of Location: A place or situation occupied

The singularity was a point, or small place, the singularity exploded which means the Big Bang happened at the singularity, a finite point.

Anyway, I often hear the singularity compared to a black hole. Black holes, can't explode because their escape velocity is greater than the speed of light. How then, did the singularity explode, obviously energy magically bursted outward faster than the speed of light. Also, when matter is created by energy in the laboratory, it's antimatter is also created. The energy of the Big Bang would have created equal amounts of antimatter and matter, they would have canceled each other out. "For every action there is any equal but opposite force". Energy turned into matter. Energy converted, and converted is a verb. A verb is an action, so their would have been an opposite created when the matter was created. This is exactly what we find in the lab, whenever energy is converted, so is antimatter. This would have occurred in the Big Bang, and the antimatter would have annihilated the matter, making it the Big Burp.

Also, you say the universe was homogeneous, therefore, I assume you also believe the Big Bang was homogeneous, meaning equal in dispersion. Why then is the universe unevenly distributed? If the explosion was homogeneous, like all explosions (i.e. fireworks) then how could dark matter be so far out there expanding the universe? And, if this dark matter is so strong that it's expanding the entire universe outward, then why are there colliding galaxies?
 
  • #14
hmm, maybe it wasn't the best explanation of Big Bang theory that's ever been written down, but the way you are describing the Big Bang in you last two posts bears no resemblance to current cosmological theory, therefore the apparent problems you are finding with it are simply not relevant.

Perhaps you should try reading a more in depth description of Big Bang theory than I have the time to provide and ability to explain with sufficient clarity. Maybe try "The Big Bang" by Simon Sing (possibile Singh, not sure of the spelling) a very good clear pop science book.
 
  • #15
Conventional theory, math, logic, etc., ceases to be reliable when you enter the quantum realm that was the mother of all quantum realms - the big bang. Was the big bang an impossibly improbable event that occurred under the most improbable of circumstances - without a doubt. That is what quantum theory demands of any universe. Many apply, but few succeed. We reside in a very bizarre universe.
 
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  • #16
Yes you need quantum gravity theory to go to t=0. But what is so often overlooked is that the cosmological Big Bang theory is only concerned with t>0. We can describe the universe right back until t=some very small number. A singularity is a term for when you equations go infinite and your theory breaks down! This is what the t=0 singularity is.

Cosmologist don't care about t=0 only t>0 and this is what the Big Bang theory is all about. It's just poorly named really, leading people to think that the point of Big Bang theory is about what happened at the Bang (t=0) when in fact it is entirely concerned with what happened after that.
 
  • #17
Wallace said:
hmm, maybe it wasn't the best explanation of Big Bang theory that's ever been written down, but the way you are describing the Big Bang in you last two posts bears no resemblance to current cosmological theory, therefore the apparent problems you are finding with it are simply not relevant.

Perhaps you should try reading a more in depth description of Big Bang theory than I have the time to provide and ability to explain with sufficient clarity. Maybe try "The Big Bang" by Simon Sing (possibile Singh, not sure of the spelling) a very good clear pop science book.

Well then, could you please enlighten me (Not sarcastic, it's an honest question, and it's not rhetorical)? Every explanation of the Big bang I've seen has been something like this: Everything in the universe (nothingness) was in a singularity, the singularity was extremely hot (magically), and energy (where'd the energy come from?) exploded outward (magically). Then, the energy magically turned into subatomic particles. The subatomic particles magically started to come together, magically forming gases (hydrogen and helium). Then, the gases magically compressed and somehow magically stopped compressing, forming stars (Gas must be really smart). Then, stars exploded quite frequently, forming heavier elements (magically). Then, after 15 billion years of awesome displays magic, the universe became what it is today. Where'd I go wrong? Honestly...I don't mean to come off as a jerk, it's just that I don't why people believe in this, but not Pinocchio...He was magical...
 
  • #18
ChristianGolfer said:
Well then, could you please enlighten me (Not sarcastic, it's an honest question, and it's not rhetorical)? Every explanation of the Big bang I've seen has been something like this: Everything in the universe (nothingness) was in a singularity, the singularity was extremely hot (magically), and energy (where'd the energy come from?) exploded outward (magically)...

You have been looking at unscientific accounts, evidently.
I've seen websites where they seem to be INTENTIONALLY misrepresenting mainstream cosmology so as to make it ridiculous or needlessly incredible.

Please understand that Nature is not assumed to have "singularities". A singularity is technically a failure mode in some particular theoretical model.
A singularity is not assumed to consist of a single point (although the name sounds like that).

In the normal course of things in the history of science various theories have had singularities and they were "cured" by improving the model so that it would no longer break down in that particular circumstance.

This is in the process of happening today with General Relativity (which breaks down at the start of expansion)

If you have a book or a website that tries to persuade you that the cosmological singularity is something real and tries to describe it as having certain properties like temperature----I can only advise to chuck the book or avoid the website.
 
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  • #19
I see this is a test of you, Christian, to see if at heart you really want to understand modern cosmology (classical and quantum) or if you want the satisfaction of thinking you can dismiss it.

if you cover your ears and repeat loudly that it doesn't make sense and you can't understand we will know what to think of you. the natural universe is a Book that some refuse to read.

let me explain my difference with Wallace (we differ, but can understand each other much of the time nevertheless)

the human mind instinctively desires CLOSURE, it connects the dots, it wants to see the pattern and finish the picture (like of a tiger in the grass).

Part of a scientist's training is to avoid over-interpreting the data, and to restrain himself from jumping to an unfounded closure.

a scientist like Wallace, working only with CLASSICAL Gen Rel vintage 1915 must practice a kind of ascetic self-denial. As the philosopher said:
Whereof one cannot speak, thereof one must remain silent
Because the classical 1915 model only goes back to smaller and smaller t > 0----it never actually gets to t=0.
It breaks down at t=0, gives meaningless results, and does not achieve closure.

As a scientist he realizes the model's limitation, and he refuses to speak about where it does not apply.

A child or untrained person may ask the obvious question what is it supposed to be like at t = 0. And authors of mass-market books have striven to satisfy the demand for an answer to that question by verbal analogies, mythologizing, or whatnot. But the question cannot be honestly answered within the context of classic (pre-quantum vintage 1915) Gen Rel gravity and attempts to do so can lead to commercially motivated doubletalk.
=======================

However other mathematical models have arisen since 2001 which DUPLICATE the Gen Rel model as closely as we can determine for all times a few instants after t = 0 and which nevertheless do NOT break down.

Typically they keep on cranking back into the past, probing a prior contracting phase on the other side of t=0.

So far we cannot say the new models are RIGHT. We only know that vintage 1915 Gen Rel must be wrong (or have "limited applicability" as they say) because it suffers a singularity and goes off the rails---it stops modeling nature at a certain point.

The new models must be tested, just as Gen Rel has been tested for the past 89 years. maybe they will be killed by the first test, maybe some of them will survive.

Again, we have to use a kind of mental asceticism or self-restraint. We must not believe, but instead must look forward to observational tests of the new models.

And note that this is in the specialty called "quantum cosmology" and ordinary day to day working cosmologists still only do "classical" by and large.
 
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  • #20
marcus said:
You have been looking at unscientific accounts, evidently.
I've seen websites where they seem to be INTENTIONALLY misrepresenting mainstream cosmology so as to make it ridiculous or needlessly incredible.

Please understand that Nature is not assumed to have "singularities". A singularity is technically a failure mode in some particular theoretical.
A singularity is not assumed to consist of a single point (although the name sounds like that).

In the normal course of things in the history of science various theories have had singularities and they were "cured" by improving the model so that it would no longer break down in that particular circumstance.

This is in the process of happening today with General Relativity (which breaks down at the start of expansion)

If you have a book or a website that tries to persuade you that the cosmological singularity is something real and tries to describe it as having certain properties like temperature----I can only advise to chuck the book or avoid the website.
Please then, give me a brief description of the real Big Bang...Wow, that was sort of paradoxical, real and Big Bang back to back Just joking, please give me your description...
 
  • #21
ChristianGolfer said:
...I don't mean to come off as a jerk, it's just that I don't why people believe in this, but not Pinocchio...He was magical...

In your post you used the word "magic" or "magical" a total of eight times. Yet you insist that you are not being sarcastic and don't mean to appear to be a jerk.
 
  • #22
ChristianGolfer said:
Please then, give me a brief description of the real Big Bang...Wow, that was sort of paradoxical, real and Big Bang back to back Just joking, please give me your description...

You sound a bit over-excited, possibly hostile to scientific explanation and description in general.

To understand you will have to have a strong desire to learn, and not be put off by math. Mathematical models don't translate completely into English, you always lose something.

If you want to learn (I assume using an absolute minimum of math) then you should probably go to the videos of the most recent major international workshop of people who are working on removing the singularity.

Go here
http://online.kitp.ucsb.edu/online/singular_m07/

and at a minimum, listen to the talks by Ashtekar and Bojowald

In the past two years, mostly in 2006 thru present, they have both made significant advances which might almost be called breakthrough. The underlying reason for this 2007 international workshop was actually their work----so that others in the same line could get together with them and discuss it. It was a 3-week affair. The other people had little that was new to report but it is still good to get together and talk each-other's shop.

To a rough approximation, this is what the leading edge looks like, if you want to know. Here are their two talks:
http://online.kitp.ucsb.edu/online/singular_m07/ashtekar/
http://online.kitp.ucsb.edu/online/singular_m07/bojowald/

If you click there you will see SLIDES as well as audio and video of the talk.

Of course they are not talking about the "Big Bang" because that is a misnomer giving a mistaken impression. They are talking about the smooth evolution that replaces the classical singularity.
Both have a half-dozen collaborators. Ashtekar's team has been running computer simulations of the universe before and after the time which used to be called the "Big Bang"
 
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  • #23
Well, I don't see how else gas that was expanding suddenly started to condense. Gas naturally expands unless there is a substantial mass somewhere to pull it together. Fick's law of Diffusion. Then, once the gas started to somehow condense, it somehow convinced itself to stop condensing. Either the Big Bang should have produced an expanding cloud of gas, or it would have produced an expanding cloud of gas that magically condensed, and kept condensing until there was another singularity. This would kind defeat the purpose of a big bang.

Also, I simply cannot come up with another reasoning other than magic that tells us how subatomic particles were going supersonic speeds and expanding in every direction, but somehow came together. In a fraction of a second, the particles would have been too far away from each other for the strong and weak nuclear forces to do their job.

Given the benefit of every doubt, the best thing a big bang could form is an expanding cloud of gas

That's useful...

Please explain your model, because all of the Big Bang models I've heard are suck. I'll be open minded...
 
  • #24
ChristianGolfer said:
... Either the Big Bang should have produced an expanding cloud of gas, or it would have produced an expanding cloud of gas that magically condensed, and kept condensing until there was another singularity...

You are not listening. You have a STRAW MAN version of what you call "Big Bang" which has nothing to do with the model cosmologists use---even the classical model!

In your fake BigBang model, there is a pre-existing space and some gas explodes in it with particles whizzing outwards into the void.

That never was the idea, even back in 1927 when Father Lemaitre presented an expanding cosmology solution of Einstein's equation.

There are plenty of people here who can talk about the conventional BigBang with you and show you that your Straw Man version is not the real thing.
The real thing is not magical in any respect and makes sense, back up to but not including t=0.

However the classical BigBang does not interest me. I am interested in the emergence these days of models which go back smoothly to time prior and do not suffer the classical singularity.

If you want to talk with me, you need to stop focusing on your pre-conceived BigBang notion.
I don't use the words BigBang, I think we need to stop using those words.

"Bounce" would be more appropriate, since in these quantum models gravity turns out to be repulsive when very high density is reached. And the thing one wants to understand is the transition between the contracting-space and the expanding-space phases.

But I really think you should have a look and listen to those two workshop videos.
 
  • #25
Absolutely right there Marcus, Christian as I've stated your description of the Big Bang model is nothing like the model we have in science and hence all of your objects are meaningless. Please take the time to look at some of the resources Marcus and I have pointed you towards. Your attitude really displays a desire to refute the science a priori without making any attempt to understand what you are refuting in the first place.

I'll make one more attempt to explain your misconceptions.

Fundamentally, as both Marcus and I have explained, you are thinking of the Big Bang as an explosion of material from a point in existing space that sent that material 'outwards' this is a common misconception about the Big Bang that bears no resemblance to the scientific model of the same name.

The Big Bang occurred everywhere at once, there is no empty space that the universe is expanding into, the whole universe looks roughly the same everywhere. This means that you don't have any issues about the gas running away from the rest of the gas since the entire early Universe consists of the same density of material, rather than a high density region diffusing into a low density one. As the Universe expands, which means that the distance between things increases, not that there is a finite ball of stuff getting bigger, it cools until it is at a temperature at which the material can condense into atoms and molecules.
 
  • #26
ChristianGolfer said:
Well, I don't see how else gas that was expanding suddenly started to condense. Gas naturally expands unless there is a substantial mass somewhere to pull it together. Fick's law of Diffusion. Then, once the gas started to somehow condense, it somehow convinced itself to stop condensing. Either the Big Bang should have produced an expanding cloud of gas, or it would have produced an expanding cloud of gas that magically condensed, and kept condensing until there was another singularity. This would kind defeat the purpose of a big bang.

Also, I simply cannot come up with another reasoning other than magic that tells us how subatomic particles were going supersonic speeds and expanding in every direction, but somehow came together. In a fraction of a second, the particles would have been too far away from each other for the strong and weak nuclear forces to do their job.

Given the benefit of every doubt, the best thing a big bang could form is an expanding cloud of gas

That's useful...

Please explain your model, because all of the Big Bang models I've heard are suck. I'll be open minded...

1. Could you please give a citation on where you read this BB model that "suck"? You will understand that it is not our responsibility to correct the wrong idea that you got out of reading some crackpot website. The responsibility of making sure your source is valid lies entirely on you. Based on what you have described as your understanding of the BB, I seriously doubt that you were reading what cosmologists have the BB to be.

2. Since WHEN does the Fick's Law of Diffusion is deemed to be valid at that stage of the universe? Have you understood the conditions surrounding such a time period? We are not simply talking about an "explosion" here. We are talking about the creation of spacetime at the same time that both energy and early indication of matter being created. It is highly dubious that you would apply a simplified diffusion model and expect it to work under SUCH a condition. After all, figure out what has been simplified out of such a model (hint: there's no gravitational interaction included).

3. Why do you read a paper on BB Nucleosynthesis and correct several of your wrong perception of what the BB process really is? There are several out there:

http://arxiv.org/abs/astro-ph/0502588
http://arxiv.org/abs/astro-ph/0208186
http://xxx.lanl.gov/abs/astro-ph/9903309

Zz.
 
  • #27
C.G., I can see your frustration, I really can. I'm a layman myself (and I BEG those with more expertise to correct the many mistakes I'm probably going to make trying to explain this layman to layman).

First C.G., the thing is, what these guys are trying to get across is that the very bottom line fundamental basis of your questions seem to be grounded within a conceptual framework that's got nuthin to do with how "the big bang" is thought to have worked.

For instance - you keep talking about gasses, and how gasses behave. But early in the b.b. THERE WEREN'T ANY GASSES YET.

To have a gas you have to have atoms. A few instants after the b.b. started, pressures were SO high, and energy levels were SO dense, that structures like atoms weren't possible. Even "subatomic particles" like electrons, protons, neutrons, etc. hadn't formed yet.

Photons (light) couldn't even exist under conditions like that.

What you had, at first, was a kind of homogeneous energy "soup".

That "soup" had to expand and cool a bit before structures like photons could essentially precipitate out, and it had to expand and cool a bit more before things like electrons, protons, neutrons etc. could precipitate out, and expand and cool even more before subatomic particles could begin to condense into atoms.

QUESTION FOR THE ADVISORS:
Have I got that right - i.e. no atoms or photons at first, if so...
How far into the b.b. did photons start to form?
How much later before atoms and gasses, of any kind, were able to form?

"Gas naturally expands unless there is a substantial mass somewhere to pull it together. Fick's law of Diffusion. Then, once the gas started to somehow condense, it somehow convinced itself to stop condensing. Either the Big Bang should have produced an expanding cloud of gas, or it would have produced an expanding cloud of gas that magically condensed, and kept condensing until there was another singularity. This would kind defeat the purpose of a big bang. Also, I simply cannot come up with another reasoning other than magic that tells us how subatomic particles were going supersonic speeds and expanding in every direction, but somehow came together. In a fraction of a second, the particles would have been too far away from each other for the strong and weak nuclear forces to do their job."

Man. No 'fense C.G., but you've got all this SO tangled up that I literally don't know where to start. I really don't. I'm not trying to put you down, or embarrass you, heck it's not like I "get" much of this either but, sheeesh. Where to start?

Maybe piece by piece?

"Gas naturally expands unless there is a substantial mass somewhere to pull it together."

What you're missing here is that there IS "a substantial mass somewhere to pull it together". And that would be the mass of the cloud of gas itself.

Picture a cloud of hydrogen in deep space. Picture a single hydrogen atom at its edge that flies away from the cloud. That atom isn't going to just go on forever right? I mean, it's got a finite amount of momentum to keep it going, but the gravitational attraction of ALL the atoms in the cloud of hydrogen gas it left behind are going to be trying to pull that stray atom back - no matter how far away it gets.

The farther it gets from the cloud, the less the gravitational attraction of all the atoms in that cloud are going to be pulling on it, but that gravitational attraction is never - ever - going to become zero.

The mass of the gas cloud forms essentially a kind of gravitational bowl where, the walls of the bowl start out quite steep, and get less steep the farther you get from the center of the bowl, but the bowl NEVER gets to a point where it's flat, the stray atom is ALWAYS essentially going "up hill", with the hill always getting less and less steep, BUT NEVER FLAT.

Eventually, since the stay atom started out with a very finite amount of momentum, it's going to run out of steam, stall, and start to fall back toward the center of mass of the gas cloud it came from - unless...

There's another gas cloud out there someplace, in which case the stray atom could get caught in the gravity well of THAT cloud of hydrogen gas, in which case the stray atom would wind up getting sucked into that second cloud. Got it so far?

"Fick's law of Diffusion." Has nothing at all to do with any of this. Seriously. Fick's laws cover how, and how quickly, things mix by diffusion.

"Then, once the gas started to somehow condense, it somehow convinced itself to stop condensing."

No! No it wouldn't. In fact this is exactly how stars form.

With a little gas, you wind up with a nebula. A gas cloud. That acts like a bowl full of marbles bouncing off each other. And just like the example above, any atom at the edge that flies off into space, will only go as far as its momentum will carry it from the center of mass of the gas cloud, until it runs out of steam, stalls, and falls back into the gas cloud.

With enough gas, a lot of gas, the condensing doesn't stop.

The more atoms that get drawn to the center of the gas cloud, the steeper the gravity well gets.

The steeper the gravity well gets, the more atoms get drawn in, and the more the pressure goes up as they start piling up on each other.

The more the pressure goes up, the more the temperature of the gas goes up.

If this keeps up, eventually the pressures and temperatures get SO high that nuclear fusion begins, and you get - A STAR - a gas cloud of hydrogen maintained in a fine balance between fusion trying to drive it apart, and gravity trying to crush it together.

And this is exactly what the big bang produced.

Once it had cooled enough for things like atoms to exist, what you wound up with is a HUGE cloud of mostly hydrogen gas with enough momentum to keep expanding - for a while.

But that cloud wasn't absolutely perfectly homogenous. There were imperfections in the mass distribution. Areas of very slightly higher and lower density.

So it started clumping up as it continued to expand.

It started forming into clumps of hydrogen gas with each clump competing for and stealing hydrogen atoms from each other as in the first scenario I described.

(an atom only gets so far from the gas cloud - unless... it gets grabbed by another gas cloud)

The clumps condensed into galaxies. Clumps within the galaxies formed nebulae. Many of the nebulae collapsed into stars, etc.

WHERE "DARK ENERGY" COMES INTO ALL THIS.

O.K., at first all this pretty much matched what we could see through telescopes etc.

The b.b. had produced a vast cloud of expanding hydrogen gas that, because it wasn't PERFECTLY homogenous, started clumping up into galaxies and stars as it continued to expand.

So now one of two things would happen in the long term (as in billions of years from now).

1) The big bang expansion had SO much inertia behind it that this cloud of clumped up galaxies and stars would continue to expand forever, getting cooler and thinner, as it went. Eventually even individual stars would get so far apart that you wouldn't even see any other stars in the night sky. The night sky would just be black. Eventually even the stars, all of them, would burn-out, cool, and the entire universe would under go what was termed "heat death".

2) The big bang's expansion DIDN'T have enough inertia to keep expanding forever. Eventually, just as in that first example I gave of the stray atom shooting away from a gas cloud, the expansion would run out of steam (momentum), stall, and the entire universe would start to fall back into what was referred to as "The Big Crunch". Eventually all mass and energy would be compressed back into a single point to produce another Big Bang, and this process would repeat for all time - Big Bang, stall, Big Crunch - Big Bang, stall, Big Crunch - Big Bang, stall, Big Crunch, and that would repeat for all time because since energy can't be created or lost, and there was no place for the energy to go, this process would repeat - literally - forever.

So the BIG question a few decades ago was - WHICH IS IT? Big Crunch leads to Big Bang and repeat for all time? Or Heat Death?

The answer lie in measuring - to a very exact degree - how quickly the expansion of the universe was slowing.

If the expansion was slowing quickly - that would imply Big Crunch.

If the expansion was not slowing quickly enough - that would imply Heat Death.

So with much better instruments those measurements were made and, once the results were in...

IT HIT THE FAN BIG TIME BABY!

Turns out, to literally EVERYONE'S amazement, the expansion wasn't slowing at all, IT WAS ACCELLERATING!

Something HAS to be powering that accelerated expansion. For now it's being called "Dark Energy". And "Dark Energy" ISN'T just a fudge factor or a cheat. It's VERY real, it's right there in front of our eyes. We didn't expect to see this - but hey - it's RIGHT THERE in front of us. We can't just ignore it. It's effects can be clearly seen, and measured, and analyzed, but this is a very new wrinkle in things nobody expected to have to grapple with. It's just a new piece of the puzzle to be placed in the picture. But for now, and just for now, NOBODY knows where Dark Energy comes from - yet.
 
  • #28
Science is hard. The universe is complicated and happily accommodates some very strange rules. It confuses everyone, CG, not just you. There are no iron clad answers for questions such as yours, just probabilities. I don't believe you have waded far enough into this swamp to realize how deep it might be. Handwaving is usually perceived as a cry for help in these parts.
 
  • #29
ChristianGolfer said:
Given the benefit of every doubt, the best thing a big bang could form is an expanding cloud of gas

That's useful...

Please explain your model, because all of the Big Bang models I've heard are suck. I'll be open minded...

I'll believe that you will be open minded when I see some experimental evidence of it :-)

Right now, the experimental evidence of your posts suggests someone with a closed mind and some sort of axe to grind.

As far as some information on the big bang goes, one of my favorite websites is Ned Wright's cosmology tutorial.

But that is probably a bit advanced for where you seem to be at, you might try reading through the FAQ instead.

http://www.astro.ucla.edu/~wright/cosmology_faq.html

I'm not sure if that will answer your "question", because so far you haven't asked one.
 
  • #30
Talk Origins also has a good overview, at a non-technical level: http://www.talkorigins.org/faqs/astronomy/bigbang.html" [Broken]. The section Common Misconceptions about the Big Bang is succinct, and has a number of good referneces.
 
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  • #31
Alright, can someone please give me a simple lists of steps in what happened in the Big Bang. You guess obviously know the theory front to back, could you please just give me a general overview. Honestly, I'm 16 years old, number one in my class, number one on the golf team, Vice President of NHS, and Vice President of the class. I have a lot of work to do every day when I get home from school, and really don't have the time to look through the links you guys have given me. The only reason I looked into this Big Bang stuff at all is because I did a physics project on it entitled "The physics of creation". Please...
 
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  • #32
If you've got the time to come here and argue about it, you've got the time to read information from the links posted so far.
 
  • #33
ChristianGolfer said:
... Honestly, I'm 16 years old, ...

It all becomes clear now :smile:
 
  • #34
How is it quicker to read something here than elsewhere? The information you've been pointed towards is more complete and carefully constructed than a quick post from someone here would provide. Given the responses you have given to the explanations we have already taken the time to give, it dosn't encourage spending a more lengthy amount of time explaining things to a greater depth.

If you want to understand things more deeply you will have to invest some time and effort in it. There is no way to short cut this fact that anyone else here can provide.

We are happy to answer questions, but when the answers are ignored and the same questions are fired back again patience runs thin.
 
  • #35
A bright, but cocky, 16 year old, probably with a strong religious upbringing, what to recommend...

One place to start reading might be:

http://map.gsfc.nasa.gov/m_uni.html
http://map.gsfc.nasa.gov/m_uni/uni_101bb1.html
http://map.gsfc.nasa.gov/m_uni/uni_101bb2.html
http://map.gsfc.nasa.gov/m_uni/uni_101bbtest.html

I'm giving multiple links rather than 1 because the site navigation is a bit funky.

And you might find it interesting that LeMaitre, often called the "Father of the Big Bang", was a Jesuit monsignor. So if you are experiencing some personal religious issues (not that it's really any of our business), you might find it interesting that the father of the Big Bang was a Jesuit.

Note that different people here know different things and are at different educational levels. I, for instance, am more interested in General Relativity than cosmology, but I've been dragooned to this forum to help keep an eye on it while our moderator, Space Tiger, works on his thesis.

As you get older than 16, you may one day start to appreciate that not everything can be explained in 200 words or less. Furthermore, you may someday be in the position of trying to explain to your 16 year old son that a) you don't know everything b) you do know things that he doesn't (not that he'll believe you) and that c) communicating across the generation gap can be difficult.
 

1. How do cosmologists observe the expanding universe?

Cosmologists use a variety of tools and techniques to observe the expanding universe, including telescopes, satellites, and computer simulations. They also study the cosmic microwave background radiation, which is a remnant of the early universe, to gather information about the expansion.

2. What evidence supports the theory of an expanding universe?

There are several lines of evidence that support the theory of an expanding universe, including the redshift of light from distant galaxies, the observed distribution of galaxies in the universe, and the cosmic microwave background radiation. These observations all point to a universe that is expanding.

3. How does dark energy play a role in the expanding universe?

Dark energy is a mysterious force that is thought to be responsible for the accelerating expansion of the universe. It is believed to make up about 70% of the total energy in the universe and is thought to counteract the gravitational pull of matter, causing the expansion to accelerate.

4. What is the fate of the expanding universe?

The fate of the expanding universe is a topic of ongoing research and debate among cosmologists. Some theories suggest that the expansion will continue indefinitely, while others propose that it will eventually slow down and possibly even reverse. The ultimate fate of the universe is still unknown.

5. Are there any unanswered questions about the expanding universe?

Yes, there are still many unanswered questions about the expanding universe, such as the exact nature of dark energy and the ultimate fate of the universe. Cosmologists continue to study and gather evidence to better understand the mechanisms driving the expansion and the implications for the future of our universe.

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