Inflationary Cosmology

Throughout most of these threads there have been multiple expalinations given for how exsactly the big bang "banged" and since many of these come from competing theories (and different members different interpretations of those theories) many of them seem confusing and conflicting.One of the most promising theories regarding the big bang is Inflation theory. This theory answers many of the tougher questions about the big bang especaily ones that are ofetn raised in a forum such as this includeing "what caused the big bang?" and "How can a singularity with almost infinite mass expand?" as well as other more obscure difficultyies regarding the big bang.I thought it would be usefull to have a discussion on this single interpretation of the big bang rather than a conglomoration of competeing big bang theories.I should also note that inflationary cosmology is not the only theory out there (after all that is the problem isn't it?) and observations may prove it wrong. I should also note that evedence contradicting inflationary cosmology do NOT contradict the big bang theory as inflationary cosmology exsists to adress issues WITH the big bang thoery.

I can provide a summery of the theory upon request, though it will take quite a while and will be drawn from popularized science (mostly from Brian Greene's "the fabric of the cosmos").Edited to add: and hopefully there are others who understand the theory, at least in part.This message has been edited by The Dread Dormammu, 10-29-2004 12:45 AM

Heh heh, there is a lot to cover I know. I guess I'm hoping that some of the physics buffs out there might be able to help out. I just to be able to provide some consistant answers to common creationist questions about the big bang.Perhaps if I limited the scope a little bit by proposing that inflationary cosmology provides these 3 solutions.1: Inflationary cosmology povides an explantion for what might have caused the big bang.2: Inflationary theory explains how an unimaginably dence universe can expand.3: Inflationary theory explains why the universe, on a large scale uniform and not "clumpy."

GULP!

One of the tougher problems with the big bang theory is that if the universe began as a singularity there doesn't seem to be a mechanisum for it to expand. However if Inflationary theory is correct The higg's feild fluctuations could provide just such an explaination.

Right! The discovery of dark energy was a big boost to inflationary cosmology becase it confirmend their suspicions that gravity can have a replsive as well as an attractive force. Furthermore the fact that dark enercgy contributed the needed 70% of the critical density for the universe halped make inflationary cosmology the best canidate to explain what happened moments after the big bang.

It's more that inflationary cosmology is able to look back farther than the standard big bang theory. Inflationary cosmology agrrees completly with big bang theory but big bang theory has some big questions to answer about what happened in the first few "moments" of the bang. Inflationary cosmology answers some of those those questions and as such looks farther back.For example we know that matter in the universe is spread out in a very uniform fashion, but not completely uniform, meaning that the universe is clumply enough so that it's not just a uniform mass of hydrogen atoms, but not so clumpy that it is just a mass of black holes. These might seem like extremes but if the inital conditions after the big bang were not almost perfectly ballanced both of these senarios are more likely than the foamy spread of superculsters. 30 years ago phyisists just threw up their hands and said, "Thats just the way inital conditions were" but now we think that this repulsive form of gravity called an inflaton (not incorectly spelled (unlike most of this post) imagine Glue-on or electr-on) feild made space in the first 10 to the -35th seconds expand by a factor of up to 10 to the 100th.The inflaton feild cut out at exsactly the same time throuout the universe so that matter should have been completely evenly dispersed. HOWEVER due the those pesky quantum uncertatnties it is impossible for an entire feild to cut out at EXSACTLY the same time. Now we can see how we have solved 2 problems with the standard theory: how to explain the universes (near) perfect distribution of matter, and how the universe got started expanding in the first place. Both questions are anwered with gravitys intensley powerful repulsive force, the inflaton feild.Incedentaly the scale of the expansion is enormous. To use Greene's metaphores; in that first razor thin breif period of time, space expanded in in a way that would be like scaling up a dna molicule to the size of the milky way, and that means that our OBSERVABLE universe, or our hubble volume, is only a tiny speck in the total universe. Greene compaires our hubble volume to a grain of sand compared with the earth (the total cosmos).This discription of a vastly huge universe actualy solves another problem dubbed "the flatness problem." It appears that our universe's space is flat. Again if things were just a little different it should have either a positive or a negative curve. Now if the universe is realy all that big it explains why our universe LOOKS flat, since it becomes harder and harder to tell if something really large is curved or not. For example, we can easly tell that a tennis ball is curved but unless you are far away from a PLANET-SIZED tennis ball, or are able to make some very precise mesurements you might think it's flat.So again this was just another one of those initail conditions that phyisisists had no explainaiton for, that inflationary cosmology can help to answer.

double postThis message has been edited by The Dread Dormammu, 10-29-2004 06:40 PM

double postThis message has been edited by The Dread Dormammu, 10-29-2004 06:39 PM

Another interesting consiquence of infaltionary theory is that the singularity at the beginning of the bang only needed to weigh about 20lbs and could still have produced all the matter in the universe.Though inflationary cosmology dosn't provide all the answers, a theory that requires such a small amount of mass to get started seems to be an improvement on the, "infinitely dence, infinitely massive, and we don't know where it came from", statement of standard big bang theory.This message has been edited by The Dread Dormammu, 11-01-2004 09:33 PM

Inflationary cosmology seems to indicate that our universe could have come from an earlyer universe. an Inflaton feild mines energy from gravity so that it produces extra matter.Ironicly this doesn't go against thermodynamics becase overall entropy still increases. So in effect our universe could have sprung into exixtance from a "proto universe" that was just as chotic and full of entropy as our own is now. all you need is a quantum fluxuation that produces an inflaton feild near in the same place as a singularity and BOOM new universe.

Yes, you are correct. In the examples given here the singularity and the field both exsist in a prior universe with it's own space.Srtictly speaking inflationary cosmology only adresses the big bang and not the universe that proceeded it however brane theory (using inflationary cosmology) posits that perhaps the universe was created when two negboring branes collided.So we haven't yet answered why there is something rather than nothing. Because we don't know about the prior universe or the neihboring branes.

It's true that we could not know much (if anything) about the prior universe, but I don't know what you mean about "photon decoupleing" are you talking about entaglement? If so I do not see the connection.If the 2 branes theory is correct we might be able to detect the nehboring brane. If gravity is capable of leaving our brane we might detect faint gravity waves in regions of our space where we do not detect matter. String theory predicts that perhaps gravity is so weak because it radiates out in more dimentions than, say, light. So it is theoreticaly possible to know some things about our neighboring brane (if it exsists).My initial feeling is that the prior universe would be distroyed or "pushed out of the way" by the new universe, but this is just speculation.

Well strings vibrate in the three extended dimentions plus the small ones. But what I was talking about with gravity is that most forms are "stuck" to our brane. Gravitons, on the other hand, seem to be free to leave our brane. Meaning they could radiate out to neigboring branes. I think you've got it backwards, our three primary spacial dimentions expanded. The other spacial dimentions didn't, they always stayed small.The only thing unique about the extra dimentions is their size, close to the plank scale. The three "extended" dimentions are either realy large, or realy small, depending on how you look at it (We can get into why if you want in future posts). The smaller dimentions stayed small and can be thought of as "normal." Our three larger spacial dimentions were the ones altered in the big bang.