what is the big bang theory?

I am under the impression that this is what the theory states:Somewhere between 18 and 20 billion years ago, all of the matter in the universe was compressed into a tiny space no larger than the dot on a page. This dot spun faster and faster until it exploded, thus creating the Universe and everything in it.Is there anything more to it?

A single spinning point isn't a very good analogy. While the specifics of the Big Bang theory are not known precisely, the evidence does tend to point to all of known existance radiating from a single point, where it would have been somewhere in the order of 12-20 billion years ago (in many cases, we're dealing with very distant objects, so it is hard to pinpoint). As far as I am aware, the most precise estimate currently is around 13.7 billion years ago. Likewise, there appears to be a "maximum age" on the oldest types of stars - we can't find anything in space that should be older than this time.Why did it occur? There are many theories as to why it would have occurred; most are still at a speculative level. One such possibility lies in quantum ("vaccuum") fluctuations. Are you familiar with the Casimir effect? The effect occurs when you have two plates very close to each other, but not touching. The plates experience a force pushing them together. This is due to vaccuum fluctuations. In vaccuum fluctuations, two particles can come into existence, so long as they promptly destroy each other and leave the net effect on the universe as having no energy change. If the space between two plates is small enough, it makes it hard for this to occur on the inside, leading to increased pressure on the outsides. Vaccuum fluctuations also can cause black holes to slowly "evaporate". One theory for the big bang involves these fluctuations creating an amount of energy in a single location large enough that it cannot annihilate itself quickly enough, leading to a supermassive "detonation" of sorts.(if I misspoke on anything, someone please correct me, it's been a while since I read up on the topic. ).------------------
"Illuminant light,
illuminate me."

The Big Bang was not strictly speaking an explosion - certainly not of matter into space like a supernova. It was an (and is ... the universe as currently existing is a continuation of the same event) expansion of the whole of space-time itself, dragging the matter and energy of the universe along with it. The entire universe started as a volume much smaller than a pixel on your monitor. I may not be aware of some new theory, but to my knowledge the universe itself isn't spinning.Alan

I'm afraid that is mainly the product of Kent Hovind's imagination.It is one of the reasons he is not taken seriously.Last I heard the univers was thought to be a few billion years younger (13.5 billion years old, IIRC).The singularity contained no matter at all. It did not spin, nor did it explode as such. The Big Bang represents an expansion of space,filled with energy which condensed into particles which form the basic constituents of matter.

Ima confused : (First off, for the people who said there WAS a "dot" how was this dot formedPaulK,so the "singularity" didnt contain any matter at all? didnt spin or explode either?So then.... this "expansion of space." what caused it? and where did this energy come from : (

If I say something like the Higgs field of the supercooled false vaccum lost energy via quantum tunnelling then you could quite rightly complain that I was throwing incomprehensible jargon at you (actually I don;t guarantee that I've used the jargon entirely correctly but what I wrote is very close to one explanation)Cosmology is a very complicated subject. If you really want to try to understand it I suggest you go to The Book Nook forum and enquire after the best books. Alan H. Guth's _The Inflationary Universe_ is the one I used above, and it does go into more detail than most. But there are a lot of books with good reputatiosn that I haven't even read on the subject. And that's just the books which are aimed at the ordinary public - there's a lot more to know, but obviously it's more difficult to understand.

Are you sure that is what the big bang theory is because in textbooks and big bang web pages they say it was an explosion????? The other people explained the big bang differently.------------------
"I AM THE MESSENJAH"contact me for any reason at: messenjahjr@yahoo.com

An explosion is a non-technical term, so it applies in a general way, but is very misleading.An "explosion" is usually a sudden expansion of matter into space.The Big Bang is more properly thought of as an expansion of space itself.The intuitions one have with regard to "explosions" are inappropriate for the Big Bang.

Personally I think our Knowledge of the universe is not good enough to get how it started if it even started... Personally I have a few Problems with Big Bang.... its hard to explain if anyone even understands it..... I truly don't think we should try to figure out where it came from yet. there is no point. we are still trapped on this little Mud Ball. Until we can see the universe how can we Know what it is or how it came to be? I don't think anyone should Point to anything yet that includes Gods, Big bang etc.... we simply do not have Enough information[This message has been edited by DC85, 09-03-2003]

It is frequently called an explosion but the term isn't accurate. An explosion is an expansion of matter in space-time. The BB was a creation/expansion of space-time itself.------------------
No webpage found at provided URL: www.hells-handmaiden.com

Yes, I am sure. It may well be that many books use the term "explosion" loosely, but the Big Bang was very different from an ordinary explosion.

As for the alleged spin of the singularity: something can only spin relative to the surrounding spacetime. Since spacetime exists only after the Big Bang, one cannot speak of something spinning before the Big Bang. For that matter, one cannot even speak of 'before the Big Bang'. The universe itself also cannot be said to be spinning, for that would imply the existence of spacetime outside it, relative to which it would be spinning. If there was spacetime outside the universe, it would not rightly be called 'the universe', in the sense of 'everything there is'.On the other hand, there are new theories about the concept of a 'multiverse', of which our universe is only one of the constituents. In these theories, the universe is just that part of the multiverse we can observe. If those theories are in any way connected with reality, then a universe might spin after all, although we could never know it.------------------
"In the beginning the Universe was created. This has made a lot of people very angry and been widely regarded as a bad move." - Douglas N. Adams

There is a lot of confusion with the big bang, mainly because of 2 concepts: a. the expansion of space and b. the singularity. For one, the concept of empty space expanding isn't natural. After all, how something we can't see, touch or feel have any physical existence at all? Most tend to visualize a ball of matter flying apart or expanding into this empty space instead. But this view is incorrect. In GR, space is a property of a very physical gravitational field, and can indeed expand. In the big bang model, it is the empty space in between galaxies that expands. If we wind the clock back on this cosmic expansion, we'll find that the universe becomes much more dense and hotter. In such a state, galaxies would not exist, and only very basic elements could. Tracing the expansion back to a maximum state of density is the beginning of time.Which brings us to the second problem, the singularity. This is where Hovind's silly spinning dot comes from. If GR is correct on all scales, then with some assumptions it can be mathematically shown that the universe must begin in a singular state. This singularity is a point of zero volume and infinite density. It is not a dot, pixel or anything else. It is a mathematical point, and most cosmologists probably do not think it has anything to do with reality. Why? Well go back to the assumption that GR can accurately describe space on all scales. If the gravitational field (spacetime itself) is actually quantum field, then GR is not going to provide any useful description. Most working on developing a theory of quantum gravity expect the singularity to be replaced by something of finite density.Once the singularity is removed, then the question "how small did our visible universe start off as?" becomes valid. But keep in mind that's only asking how big the visible universe is, not the entire universe itself. Oddly enough, the big bang theory is compatible with an universe of infinite size. In the case of the big bang, in the beginning the universe would be infinitely dense at each point, but the overall size was, and always will be, infinite. Only a finite universe gets smaller as we approach the beginning. If that is indeed the case, additional data on intitial conditions (as well as a quantum theory of gravity) will be required to know what that size was.So as you can see, there is a. no dot b. no spinning dot either.

A little thinking reveals that the Big Bang is impossible and could never have happened. When matter is compressed above a certain density then its gravity becomes so strong that it prevents the escape of any matter or energy, including light. Had all the matter in the universe once been collected in a singularity, then even if space were originally the same size and expanded rapidly from there, matter could not expand to fill that space because of gravity. I know the evidence points to all matter being contained in a singularity at one time in the distance past, but the universe must have had some other origin.--Percy

ugh! This stuff gives me a headache... but it sure is interesting.