Big Bang Theory

[JustinW]

I have a problem, or it's just never been explained in a way that I understand, with the idea that there was darkness and then bang. The thought that there was a reaction so big that came from nothing or something so small. I'm curious though...could the bang just as easily have come from two objects colliding with so much force and mass. I know the scatter measurements of universes might not coincide with this, but there might be another explanation for that(even though I don't have one). Thoughts anyone.

[zerotwoone]

It is just two particles. Two particles predicting all of space when approaching One. But the collision doesn't necesarily have been huge or violent, just that the over all condition was changed. Imagine an Othello game. By placing just one piece on the board, you can change the entire complexion of the board.

 

 

[Light Storm]

I have a problem, or it's just never been explained in a way that I understand, with the idea that there was darkness and then bang. The thought that there was a reaction so big that came from nothing or something so small. I'm curious though...could the bang just as easily have come from two objects colliding with so much force and mass. I know the scatter measurements of universes might not coincide with this, but there might be another explanation for that(even though I don't have one). Thoughts anyone.

 

 

The big bang is an idea based around a singularity comprised of infinite mass that started the creation of the universe as we know it.

 

Hypothesis at best, and forever be.

 

Obviously there are many (myself included) who disagree.

 

 

[owl]

JustinW,

I started a similar thread awhile back in the Astronomy and Cosmology section, "Before the Bang... where did it all come from."

http://www.scienceforums.net/topic/55102-before-the-bang/page__p__591527__f

 

I'd be interested in your take on that conservation.

[StringJunky]

http://www.perimeterinstitute.ca/Outreach/What_We_Research/Cosmology_%26_Gravitation/

[owl]

http://www.perimeterinstitute.ca/Outreach/What_We_Research/Cosmology_%26_Gravitation/

The Essence of Cosmic Evolution

 

Astronomical observations indicate that the size of the universe – space itself – has always been expanding, and that matter and radiation contained in that space have always filled it more or less uniformly. As space expands, matter and radiation are spread more thinly. They become less dense and cool down, allowing more fundamental particles to "condense" into larger, composite particles – in much the same way water vapour condenses into droplets as it cools. This is the essence of cosmic evolution.

 

“As space expands,...”

 

The* assumption* here is that space is something that expands. Ontology asks what space is as an expanding “something.”

Objects in space move further apart as time elapses, but how does this translate into “space itself” (a supposed entity) expanding?

A sincere question. An honest answer would be appreciated.

[pantheory]

JustinW,

 

The Big Bang Theory (BB) name came from Fred Hoyle based upon his characterization of the original "fireworks" theory invented and named by Lemaître. Some years later this theory was re-explained and theorized by Gamow following the second world war. The physics which Gamow used at the time for this re-invigorated model was accordingly the atomic bomb, hence Big Bang. After a short time proponents of this model started disassociating it with an explosion. Now the original beginning is thought by many mainstream theorists to be only a hypothesis so instead the beginning of the modern BB theory starts with a hot dense field with no explanation of the beginning. This is the way that Wiki explains it:

 

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

 

Although the BB model is really the only discussed mainstream model, maybe a small but increasing number of astronomers and theorists are becoming disenchanted with the model because of some contradicting observations over the years leading to the Inflation, dark matter, and dark energy proposals. There have always been a number of non-mainstream theorists that have never accepted this model. I am one of those.

 

There are many different proposals now concerning the beginning of the universe, before the BB, multiverses, etc. So you can speculate here along with all the other mainstream ideas. You could study other models, and maybe someday you might wish to invent your own, other than just as speculation

 

owl,

 

The* assumption* here is that space is something that expands. Ontology asks what space is as an expanding "something."

Objects in space move further apart as time elapses, but how does this translate into "space itself" (a supposed entity) expanding?

A sincere question. An honest answer would be appreciated.

 

Let me provide you with some history as an answer for your question, which you probably already know.

 

Based upon the inverse square law of light concerning Luminosity Distance, there is a direct correlation between distances to galaxies and their observed redshifts. So accordingly the greater the redshift of a galaxy or other entity the increased probability of its distance.

Next come the assumptions and changing theory. First it was assumed that this increasing of redshifts with distance, is based upon a Doppler Shift implying that galaxies are moving away from us and from each other. The only basis for this assumption that I know of is that a Doppler shift is thought to be the most likely explanation for galactic redshifts, although there are a number of other possible explanations for them and no evidence to support this assumption.

 

Theorist long ago realized that they did not want to imply real motion of galaxies or even the relative motion of them, so they made another choice. Einstein proposed that space was "warped" by matter. They theorized that if space could warp then it also could seemingly expand. So secondly they assumed that space was expanding uniformly everywhere in the observable universe and theorized a cosmological constant to mathematically explain this expansion. Again the basis for this assumption is that it was thought to be the most likely explanation.

 

After some time they realized that a constant rate of the expansion of space could not explain certain cosmological problems such as the so called Horizon, Flatness, and other theoretical problems. To overcome these problems they theorized that a very quick expansion of space in the beginning could solve these problems and thereafter this Inflation of space epoch would end. The number of theories proposed were called Inflation Theories concerning the "superluminous" expansion of space and the universe along with it. Most theorist were satisfied with these explanations for maybe a decade.

 

Then in the 90's it was slowly realized that the present expansion of space did not seem to be constant over time based upon observations of type 1a supernova. But by changing the rate of the expansion of space they could explain what they were observing. So they proposed that the expansion of space and the universe was accelerating. This also did not last very long until they needed to explain even more distant observations of type 1a supernova which seemed to show that the universe via the expanding of space, first appeared to involve the decelerated expansion following Inflation, then afterward it started the accelerated expansion of space era at a redshift of about z = .6, which we accordingly are now in. This new theory they call Dark Energy, which is a variable expansion of space model.

//

Edited October 29, 2011 by pantheory

[Iggy]

There have always been a number of non-mainstream theorists that have never accepted this model. I am one of those.

I hope it isn't impertinent to ask, are you a theorist (a theoretical physicist for example) by occupation?

 

Next come the assumptions and changing theory. First it was assumed that this increasing of redshifts with distance, is based upon a Doppler Shift...

The first expanding models were those of Friedmann and Lemaitre. They were not "based upon a Doppler Shift". At least, I don't see how you could figure that. Redshift was the model's prediction (not assumption) that came from solving the line element for null geodesics.

 

Cosmological redshift is a function of scale factor and not a function of the relative velocity of the emitter at the time of the emission the way Dopper effect is. Here are some lecture notes making the same two points: The Friedmann-Robertson-Walker metric

 

Is your understanding different?

 

...implying that galaxies are moving away from us and from each other. The only basis for this assumption that I know of is that a Doppler shift is thought to be the most likely explanation for galactic redshifts, although there are a number of other possible explanations for them and no evidence to support this assumption.

The only basis for expansion is galactic redshift?

 

There are several predictions made on the basis of expansion (Tolman surface brightness, relic black body radiation, supernova time dilation, angular size of CMB anisotropies, abundance of light elements, etc) that have been confirmed.

 

I don't think "the only basis for this assumption" is fair.

 

Theorist long ago realized that they did not want to imply real motion of galaxies or even the relative motion of them, so they made another choice. Einstein proposed that space was "warped" by matter. They theorized that if space could warp then it also could seemingly expand.

Einstein didn't propose "warped space" to explain the motion of galaxies. Warped space is a necessary part of general relativity -- without it GR would only predict half of the correct deflection of light by the sun. That is to say, if locally straight lines near the sun remained straight to infinity then only half of the correct deflection would be predicted.

 

So secondly they assumed that space was expanding uniformly everywhere in the observable universe and theorized a cosmological constant to mathematically explain this expansion.

Maybe you misspoke or I misunderstand, but I'm quite sure the opposite is true. With no information either way, Einstein assumed the universe would be, or should be, static. After some preliminary modeling with his new theory he quickly determined that relativity doesn't want the universe to be static. He introduced the cosmological constant in an effort to make the model static, but it failed in that purpose for a couple different reasons.

 

Redshift observations came 13 years later.

 

The number of theories proposed were called Inflation Theories concerning the "superluminous" expansion of space and the universe along with it. Most theorist were satisfied with these explanations for maybe a decade.

The superluminal expansion of space is not limited to inflation. For example, the Lambda-CDM model is superluminal at z > 1.4

 

Then in the 90's it was slowly realized that the present expansion of space did not seem to be constant over time based upon observations of type 1a supernova. But by changing the rate of the expansion of space they could explain what they were observing. So they proposed that the expansion of space and the universe was accelerating. This also did not last very long until they needed to explain even more distant observations of type 1a supernova which seemed to show that the universe via the expanding of space, first appeared to involve the decelerated expansion following Inflation, then afterward it started the accelerated expansion of space era at a redshift of about z = .6, which we accordingly are now in.

The recent reintroduction of the cosmological constant meant that the universe would first decelerate then accelerate in expansion. It was never the case, and no one ever believed, that the cosmological constant meant that the deceleration parameter was always negative. It means (and meant) that there is deceleration until the onset of acceleration.

 

This new theory they call Dark Energy, which is a variable expansion of space model.

The rate of expansion has always been variable. The big bang has never been a freely coasting universe. Without the cosmological constant the rate of expansion will slow either indefinitely (if the universe is open) or it will slow to a stop and re-collapse (if it is closed). With the cosmological constant the rate of expansion will decelerate until Omega-Lambda gets big enough and Omega-M gets small enough for the cosmological constant to be the dominant factor and it starts accelerating.

 

That is my understanding.

[DrRocket]

I have a problem, or it's just never been explained in a way that I understand, with the idea that there was darkness and then bang. The thought that there was a reaction so big that came from nothing or something so small. I'm curious though...could the bang just as easily have come from two objects colliding with so much force and mass. I know the scatter measurements of universes might not coincide with this, but there might be another explanation for that(even though I don't have one). Thoughts anyone.

 

You have misconstrued the big bang hypothesis.

 

Based on what has been observed and general relativity Hawking and Penrose showed that the universe in the distant past was extremely dense and highly curved. The theory actually predicts that spacetime is singular, which in this case means that timelike geodesics cannot be extended indefinitely into the past -- i.e. there is, within the context of general relativity, no "before" the big bang.

 

This is generally taken to mean that general relativity is not a fully accurate model all the way back to t=0. It is thought that the model is pretty good from about t= +10^-33 sec onward. No one has the slightest what happened at t=0.

 

But the big bang WAS NOT an explosion of matter within space over some brief period of time. The big bang represents an initial point or surface (a Cauchy surface) in the spacetime manifold of general relativity from which everything subsequent to it has evolved (according to the laws of mechanics). It was essentially the beginning of both time and space.

 

There may eventually be other explanations, probably arising from a future theory that can combine both gravitational and quantum phenomena. No such theory currently exists, but there is a lot of ongoing research -- and a lot of speculation in the popular literature.

 

General relativity is sufficiently well supported that the basic idea of the big bang is on solid footing, so long as you don't try to go all the way to t=0. There are a lot of finer points yet to be resolved, and lots of room for further research. But there is little point in arguing against the basic idea.

 

You would do well to read the "Cosmo Basics" thread. http://www.scienceforums.net/topic/33180-cosmo-basics/

 

You would also do well to ignore the bull that some folks will try to feed you.

[truedeity]

no one can understand the big bang theory.

[StringJunky]

“As space expands,...”

 

The* assumption* here is that space is something that expands. Ontology asks what space is as an expanding “something.”

Objects in space move further apart as time elapses, but how does this translate into “space itself” (a supposed entity) expanding?

A sincere question. An honest answer would be appreciated.

 

I don't know enough yet to have an opinion on the nature of space...I just follow the theories and hypotheses, in the time that I have, that are available within conventional astro-cosmo research as pointed at by physicists here. Unless I decide to take up the required advanced math as a hobby it's highly unlikely that I will ever be adept enough to form a realistically viable opinion of my own.

 

The OP should have asked this question in the Astro Cosmo section imo and got the conventional view first rather than open themselves to potential confusion and misinformation from other people's personal ideas in Speculations. Their question is Astro/Cosmo 101 and Dr Rocket pointed justinw to the right place in Cosmo Basics. My link was given in the same spirit...a quick conventional overview of the BB and Relativity's problems with it.

 

The article on Quantum Gravity from the same site as I linked before mentions some possible quantum descriptions of what space is.

Edited October 29, 2011 by StringJunky

[owl]

Pantheory:

Theorist long ago realized that they did not want to imply real motion of galaxies or even the relative motion of them, so they made another choice. Einstein proposed that space was "warped" by matter. They theorized that if space could warp then it also could seemingly expand.

 

Why deny the motion of galaxies as observed, moving away from each other?

Regarding Einstein’s proposal, it does not address the ontological question, “What is space?”, that it can be warped and expand.

 

I've been told quite often here that such ontological questions as "what is it?" do not much concern physicists/cosmologists. Yet it remains an honest and sincere question in my mind. Is there no possible answer? The rest of your post could only make sense to me if the above were answered.

Thanks for your efforts.

Grammar edit.

Edited October 29, 2011 by owl

[himoura]

i accept the big bang and think its the correct model. Inflation theory however still has some major hurdles to overcome despite its wide acceptance.

 

(from wikipedia criticisms of inflation theory)

 

In order to work, and as pointed out by Roger Penrose from 1986 on, inflation requires extremely specific initial conditions of its own, so that the problem (or pseudoproblem) of initial conditions is not solved: “There is something fundamentally misconceived about trying to explain the uniformity of the early universe as resulting from a thermalization process. […] For, if the thermalization is actually doing anything […] then it represents a definite increasing of the entropy. Thus, the universe would have been even more special before the thermalization than after.”^[93] The problem of specific or “fine-tuned” initial conditions would not have been solved; it would have got worse.

 

A recurrent criticism of inflation is that the invoked inflaton field does not correspond to any known physical field, and that its potential energy curve seems to be an ad hoc contrivance to accommodate almost any data we could get. It is significant that Paul J. Steinhardt, one of the founding fathers of inflationary cosmology, has recently become one of its sharpest critics. He calls ‘bad inflation’ a period of accelerated expansion whose outcome conflicts with observations, and ‘good inflation’ one compatible with them: “Not only is bad inflation more likely than good inflation, but no inflation is more likely than either. … Roger Penrose considered all the possible configurations of the inflation and gravitational fields. Some of these configurations lead to inflation … Other configurations lead to a uniform, flat universe directly –without inflation. Obtaining a flat universe is unlikely overall. Penrose’s shocking conclusion, though, was that obtaining a flat universe without inflation is much more likely than with inflation –by a factor of 10 to the googol (10 to the 100) power!”^[94]

[pantheory]

I hope it isn't impertinent to ask, are you a theorist (a theoretical physicist for example) by occupation?

I have been a part-time theorist for more than 50 years; see pantheory.org

 

The first expanding models were those of Friedmann and Lemaitre. They were not "based upon a Doppler Shift". At least, I don't see how you could figure that. Redshift was the model's prediction (not assumption) that came from solving the line element for null geodesics.

Hubble wrote a paper concerning an apparent correlation between galactic redshifts and their distance based upon their luminosity. He mentioned a Doppler shift as being one possible cause of the observed galactic redshifts. Friedmann, Lemaitre, and others had realized than Einstein's cosmological equations could lead to a number or non-static solutions. Some of these solutions could lead to a contracting universe, other solutions to an expanding universe, and some to a static universe with inclusion of a constant, and still others could lead to a changing expansion and contraction rates or any combination thereof. It was realized that all of these possible solutions could not be valid.

 

Upon hearing of Hubble's observations concerning a correlation between galactic redshifts and distances, Lemaitre hypothesized that if the redshifts were Doppler shifts (recession velocities), then the universe could be expanding and if so then it could have started at a single point. He included the solutions to Einstein's equations that lead to an expanding universe and called this new theory the "fireworks" theory. His published paper suggested that there was a "premordial atom" that started the entire universe via its explosion. Other solutions to the Einstein equations were also published about the same time. Upon analyzing the physics of this fireworks theory a number or theoretical problems were thought to exist so this theory never gained much favor during these times.

 

http://en.wikipedia....Big_Bang_theory

 

Cosmological redshift is a function of scale factor and not a function of the relative velocity of the emitter at the time of the emission the way Doppler effect is. Here are some lecture notes making the same two points: The Friedmann-Robertson-Walker metric

 

Of course this is present-day theory

 

Is your understanding different?

Since I was actively theorizing at the time, I first recall when I read the idea of the expansion of space idea instead of their being recession velocities, about the early 1960's. At the time there were many opposed to the idea and there still are, although now they are great minority.

 

http://arxiv.org/PS_...0/0310214v2.pdf

 

The only basis for expansion is galactic redshift?

 

There are several predictions made on the basis of expansion (Tolman surface brightness, relic black body radiation, supernova time dilation, angular size of CMB anisotropies, abundance of light elements, etc) that have been confirmed.

 

I don't think "the only basis for this assumption" is fair.

There may be other assertions and so-called evidence or support concerning tests for the expansion of the universe other than galactic redshifts, but I am presently am unaware of any.

 

 

Einstein didn't propose "warped space" to explain the motion of galaxies.

Nor did I say that he did. He said that space warps surrounding matter which accordingly is the cause of gravity.

 

Warped space is a necessary part of general relativity -- without it GR would only predict half of the correct deflection of light by the sun. That is to say, if locally straight lines near the sun remained straight to infinity then only half of the correct deflection would be predicted.

This is true but if space can warp then it also could seemingly expand. It this idea space was not simply just the distance between matter.

 

Maybe you misspoke or I misunderstand, but I'm quite sure the opposite is true. With no information either way, Einstein assumed the universe would be, or should be, static.

This is true because observations of that time seeming to confirm this static condition and was Einstein's reason for adding a "cosmological constant" to his cosmological equations.

 

After some preliminary modeling with his new theory he quickly determined that relativity doesn't want the universe to be static.

I think this statement is wrong.

 

He introduced the cosmological constant in an effort to make the model static, but it failed in that purpose for a couple different reasons. Redshift observations came 13 years later.

This is true.

 

The superluminal expansion of space is not limited to inflation. For example, the Lambda-CDM model is superluminal at z > 1.4

This is true but some Inflation models propose the beginning as being millions of times faster than light.

 

 

The recent reintroduction of the cosmological constant meant that the universe would first decelerate then accelerate in expansion. It was never the case, and no one ever believed, that the cosmological constant meant that the deceleration parameter was always negative. It means (and meant) that there is deceleration until the onset of acceleration.

 

The rate of expansion has always been variable. The big bang has never been a freely coasting universe.

For almost 40 years the rate of expansion of the universe was believed to be constant. It is called the Hubble Constant.

 

Without the cosmological constant the rate of expansion will slow either indefinitely (if the universe is open) or it will slow to a stop and re-collapse (if it is closed).

Without Einstein's cosmological constant most believed that expansion could go on forever, but some thought that the this rate of expansion could slow down and eventually stop and the contraction could take place, a Big Crunch.

 

With the cosmological constant the rate of expansion will decelerate until Omega-Lambda gets big enough and Omega-M gets small enough for the cosmological constant to be the dominant factor and it starts accelerating. That is my understanding.

With the inclusion of Einstein's cosmological constant to account for what is presently believed to be Dark Energy, the rate of the expansion of the universe is thought to be currently accelerating forever in the future. If this constant is accordingly a variable as some believe, then the rate of expansion could change again.

 

Of course for some cosmological models where there is a different explanation for cosmological redshifts like mine, neither space nor the observable universe is accordingly expanding.

Edited October 30, 2011 by pantheory

[owl]

Pantheory,

Just a reminder...

Please answer my post 12 above...

"...it remains an honest and sincere question in my mind."

[pantheory]

Pantheory:

 

Why deny the motion of galaxies as observed, moving away from each other?

Regarding Einstein's proposal, it does not address the ontological question, "What is space?", that it can be warped and expand.

 

I've been told quite often here that such ontological questions as "what is it?" do not much concern physicists/cosmologists. Yet it remains an honest and sincere question in my mind. Is there no possible answer? The rest of your post could only make sense to me if the above were answered.

Thanks for your efforts.

Grammar edit.

Thanks for the reminder owl I had forgotten your valid comment and question.

 

Why deny the motion of galaxies as observed, moving away from each other?

I believe there is no evidence other than the redshifts themselves to support the idea that galaxies are moving away from each other or that space is expanding. My own model is over 50 years old, at pantheory.org, and instead proposes the diminution of matter to explain galactic redshifts. I also propose reasons for this alleged very slow diminution. So in my model the observable universe is not expanding. But the point concerning this thread is that space expanding is an assumption based upon no other evidence that I know of other than galactic redshifts. There are many other possible explanations for these observed redshifts.

 

Regarding Einstein's proposal, it does not address the ontological question, "What is space?", that it can be warped and expand.

I agree with you. In my own model space is nothing more than the volume that matter and field (the ZPF) occupies, an extension of matter and nothing more.

 

I've been told quite often here that such ontological questions as "what is it?" do not much concern physicists/cosmologists....... Is there no possible answer? The rest of your post could only make sense to me if the above were answered. Thanks for your efforts

I agree with you 100% that all the "where, what, when, how, and why, etc. questions are all valid, and that all must have a logical explanation to them that at least would be understandable by at least some knowledgeable persons reading such answers. I disagree with those that contend that such questions are solely metaphysical or philosophical. I think that you are of a similar opinion

Edited November 1, 2011 by pantheory

[Iggy]

I have been a part-time theorist for more than 50 years; see pantheory.org ...

 

 

The rate of expansion has always been variable. The big bang has never been a freely coasting universe.

 

For almost 40 years the rate of expansion of the universe was believed to be constant. It is called the Hubble Constant.

The Hubble constant isn't constant. It changes over time depending on the deceleration parameter. There were a few other basic misunderstandings about cosmology in your reply that make me wonder how you are using the word "theorist".

[pantheory]

The Hubble constant isn't constant. It changes over time depending on the deceleration parameter.

Hi Iggy,

 

For about 40 years the universe was thought to be expanding at a constant rate called the Hubble constant. Here is a link.

 

http://www.eso.org/~...rs/EPN/epn.html

 

This idea started to change in the early 90's based upon studies of type 1a supernovae that could not be explained by standard cosmology at that time. The authors of the study, Riess and Pulmutter, suggested that the observations could be explained if the universe's expansion rate was accelerating. This interpretation lasted until about 2001 when even further supernova brightness seemed to be explainable if the universe then was expanding at a decelerating rate. Today standard-model cosmologists now believe the rate of expansion of the universe varies over time.

 

There were a few other basic misunderstandings about cosmology in your reply that make me wonder how you are using the word "theorist".

Here is the website concerning my history as a theorist in cosmology and theoretical physics.

 

http://www.pantheory.org

//

Edited November 28, 2011 by pantheory

[Iggy]

Hi Iggy,

 

For about 40 years the universe was thought to be expanding at a constant rate called the Hubble constant. Here is a link.

 

http://www.eso.org/~...rs/EPN/epn.html

Not only does that link fail to support what you are saying, it repeats precisely what I said,

 

The world models are characterized by two parameters: the current rate and the deceleration of the expansion. The first parameter is called the Hubble constant after Edwin Hubble, who discovered the cosmic expansion in 1929. The other parameter describes the change of the expansion and depends on the energy density and the curvature of the universe.

 

Before the discovery of acceleration, everyone assumed that the deceleration parameter was positive (that's why it's called deceleration and not acceleration parameter)

 

I can quote wikipedia if that would help,

 

The value of the Hubble parameter changes over time either increasing or decreasing depending on the sign of the so-called deceleration parameter...

 

It was long thought that q was positive, indicating that the expansion is slowing down due to gravitational attraction. This would imply an age of the universe less than 1/H (which is about 14 billion years). For instance, a value for q of 1/2 (once favoured by most theorists) would give the age of the universe as 2/(3H). The discovery in 1998 that q is apparently negative means that the universe could actually be older than 1/H.

http://en.wikipedia.org/wiki/Hubble%27s_law#The_.E2.80.98ultimate_fate.E2.80.99_and_age_of_the_universe

 

It is impossible to be competent in cosmology while not knowing that the rate of expansion changes even without lambda. Anyone who has used the friedmann equation would have to know that.

 

People used to think the universe was decelerating, now they think it's accelerating. Sorry you believed otherwise.

Edited November 29, 2011 by Iggy

[pantheory]

Not only does that link fail to support what you are saying, it repeats precisely what I said,

 

Before the discovery of acceleration, everyone assumed that the deceleration parameter was positive (that's why it's called deceleration and not acceleration parameter)

 

I can quote wikipedia if that would help,

 

http://en.wikipedia....of_the_universe

 

It is impossible to be competent in cosmology while not knowing that the rate of expansion changes even without lambda. Anyone who has used the friedmann equation would have to know that.

 

People used to think the universe was decelerating, now they think it's accelerating. Sorry you believed otherwise.

I agree that they now believe the expansion rate of the universe was and is variable, but this is not what they asserted prior to the early 1990's.

 

Cosmology is in turmoil. The standard model of a few years ago has recently been abandoned and replaced by new ideas. The reasons for this dramatic change are new measurements of the geometry and the matter contents of the universe. The new model implies a dynamical age of the universe that accommodates the oldest known stellar objects, but raises the need for a dark energy component, which is not readily explained within the current particle physics theories.

 

This quote from the 2001 article and link that I posted for you states that the standard model a few years prior to 2001 was quite different. Starting in 1980 was the first Inflation hypothesis, about the same time the dark matter idea was being seriously analyzed.

 

The general changes to the Big Bang model since about 1948 (Gamow) went like this:

 

--The original BB expansion of the universe was believed to be constant after beginning times, hence the words Hubble constant means a constant rate of expansion as formulated as a constant recession velocity designated as H₀ in the Hubble distance formula. It you can understand the Hubble formula then you can understand what I am saying.

 

http://hyperphysics....tro/hubble.html

 

Some thought that this expansion rate might be slowing down over time (which would have necessarily changed the Hubble Formula if valid) but there was no accepted evidence to support this proposal.

 

--next came the criticisms concerning the perceived Horizon and Flatness problems. These problems seemed to be serious enough to change the theory. Hence the Inflation hypothesis was formulated which most believed in one form or another, solved many of the perceived problems. So the general Inflation idea was added to the BB model including the various versions of it as possibilities.

 

--about the same time came the failure of general relativity, the mathematical foundation of the BB model, to predict the orbital velocities of stars in our galaxy, along with other spiral galaxies rotation rates, and also velocities of galaxies in a cluster. All considered this a monumental problem so theory again needed to be changed. To account for this discrepancy between theory and observation the dark matter hypothesis was proposed. Most also agreed that this theory change could solve the observational problems if dark matter existed.

 

--next the observations of type 1a supernova seemed to contradict the Hubble formula. The closest galaxies concerning their redshifts seemed to be farther away than the Hubble formula could allow. Eventually this problem became serious enough that a new force was proposed, dark energy -- which was later added to the standard model. The most widely held idea was that of Einstein's cosmological constant being dark energy, but instead of it being a constant rate of accelerated expansion, observations concluded that it needed to be a variable changing the expansion rate, which we now call lambda.

 

--next it was realized as a great problem that a BB beginning could not be explained mathematically concerning Einstein's cosmological equations, so a BB beginning was put aside and now the BB beginning is considered just an hypothesis by many or most theorists today. After the very beginning accordingly resulted in a hot-dense universe that the BB model now begins with. No more 10^{-43 sec} after the bang this happened, then that happened, etc.

 

http://en.wikipedia....Big_Bang_theory

 

 

Now the model is called the Lambda, CDM, Inflation model of Big Bang cosmology, or similar words to that effect.

 

It is impossible to be competent in cosmology while not knowing that the rate of expansion changes even without lambda. Anyone who has used the friedmann equation would have to know that.

(your quote)

 

The proposal that the expansion of the universe is variable after the proposed Inflation era, originally came from the study of type 1a supernova by Pulmutter and Co. as they relate to the Hubble distance formula, and were not derived from Friedmann's expanding universe solution to Einstein's cosmological equations.

 

Remember. the BB model could be considered only one single theory in it's whole, that I believe will be entirely replaced, maybe within a couple of decades after the James Webb goes up. Of course that's just me , but I expect the theory to keep changing until then. The next thing that I expect to change is the asserted age of the universe. Since they can now "play with" changing expansion rates of the universe, they can now propose that the universe could now be much older. I think this will soon happen within maybe a couple of years after the James Webb goes up. I also expect a number of unintentional false claims that dark matter has been found, dark energy, Big Bang neutrinos, etc.

Edited November 29, 2011 by pantheory

[owl]

Thanks for the reminder owl I had forgotten your valid comment and question.

...(Edited)...

I agree with you. In my own model space is nothing more than the volume that matter and field (the ZPF) occupies, an extension of matter and nothing more.

 

How is space an "extension of matter" rather than just the absence of it?

I agree with you 100% that all the "where, what, when, how, and why, etc. questions are all valid, and that all must have a logical explanation to them that at least would be understandable by at least some knowledgeable persons reading such answers. I disagree with those that contend that such questions are solely metaphysical or philosophical. I think that you are of a similar opinion

 

Yes.

[pantheory]

owl,

 

How is space an "extension of matter" rather than just the absence of it?

I'll be very brief since this is a Big Bang thread. I believe space is best defined as the volume which matter and field collectively occupies. This excludes/ eliminates hypothetical space that one might consider that might exist outside the bounds of matter and field. The same thing applies to the similar definition that: space is a limited extension of matter. (i.e. that the extension is limited to the volume that matter collectively occupies but not beyond the extension of the ZPF.)

 

The "absence of matter" is a cool definition but it includes an infinity of "potential space" beyond the extension of matter and field (if their extension is finite in volume), which I believe is an unnecessary theoretical complication. Of course the definition of space should include distances between designated matter, as well as areas or volumes encompassed by designated matter. Any more discussion between us on this matter I think should take place in a related past or future thread of yours or mine , or both ? We both have enough related old threads, I think, without needing a new one, if you wish further discussion.

//

Edited November 29, 2011 by pantheory

[owl]

owl,

 

 

I'll be very brief since this is a Big Bang thread. I believe space is best defined as the volume which matter and field collectively occupies. This excludes/ eliminates hypothetical space that one might consider that might exist outside the bounds of matter and field. The same thing applies to the similar definition that: space is a limited extension of matter. (i.e. that the extension is limited to the volume that matter collectively occupies but not beyond the extension of the ZPF.)

 

The "absence of matter" is a cool definition but it includes an infinity of "potential space" beyond the possible extension of matter and field (if it is finite), which I believe is an unnecessary theoretical complication. Of course the definition of space should include distances between designated matter, as well as areas or volumes encompassed by designated matter. Any more discussion between us on this matter I think should take place in a related past or future thread of yours or mine , or both ? We both have enough related old threads, I think, without needing a new one, if you wish further discussion.

//

Agreed. No intention to "hijack" this thread. I suggest my "Is philosophy relevant to science?" thread in philosophy, where "What does infinite space mean?" will be an on topic question.

[pantheory]

Agreed. No intention to "hijack" this thread. I suggest my "Is philosophy relevant to science?" thread in philosophy, where "What does infinite space mean?" will be an on topic question.

 

Got it

[Iggy]

The original BB expansion of the universe was believed to be constant after beginning times, hence the words Hubble constant means a constant rate of expansion as formulated as a constant recession velocity designated as H₀ in the Hubble distance formula. It you can understand the Hubble formula then you can understand what I am saying.

H₀ means "the Hubble constant today". Only one type of Friedmann universe has a Hubble constant that remains constant over time:

 

 

It is [latex]\Omega_M = 0[/latex]. An empty universe. See Carroll 1992 for an example of that graph explained before the discovery of acceleration.

 

 

By the way, the hubble constant is called a 'constant' because it is a proportionality constant between distance (at some point in time) and velocity (at the same point in time) -- not because it is constant over time. I understand how that could be confusing, but that's exactly why websites bother to say:

 

The value of the Hubble parameter changes over time

-wikipedia

 

...the Hubble "constant" is not really constant because it changes with time and therefore should probably more properly be called the "Hubble parameter"...

-Hubble Law

 

It's a simple misunderstanding . The big bang has never been about constant expansion. You won't find any sources saying that. It is not, as they say, a freely coasting model.

Edited November 29, 2011 by Iggy