Thread: Explain this whole "Big Bang" thing to me

I know the ideas behind it, of course, but specifically I was wondering about something I read the other day. It was a typical religion argument, and someone asked what came before the big bang. The answer given was something like "Time didn't exist before the Big Bang, so it's not a question that can be answered". Not verbatim, but that's the gist. So, my question should be obvious by now - how does it work? My mind is having trouble imagining a time where... well, there wasn't any time.

I'll try to explain how I understand it using the Penrose and Hawking theory - apologies if I mix something up, as I don't have the book handy.

Anyways, imagine something called the "past light cone" - the tip/vertex of the cone is you, the observer, looking at distant galaxies which are really the universe in an earlier time. Why? because time travels at a finite speed. Time in this cone is represented in the vertical direction and the space directions are represented horizontally.

So, as you travel down the cone. first you see the galaxies as they appear recently, even lower are galaxies as they were billions of years ago, then you have some background radiation and finally matter density which makes our light cone bend in, circularly, meeting at a point called the "Big Bang Singularity."

Now, our cone is actually pear shaped. As the light bends inward, towards itself, sooner or later (in a finite time though ), the cross section of the light cone goes down to zero; therefore the matter trapped in this past light cone is stored in a region/space whose boundary is 0 - hence, there had to be a beginning to time, according to the theory of general relativity.



Actually this theory does argue for the Church/religion/whatever as it does give a bases to the moment of "creation."


Cheez, I'm sure you can get Hawkins paper describing this whole thing somewhere on the net, it was a pretty big deal way back when, and I think they even got a considerable amount of money for it

Originally Posted by axon

I'll try to explain how I understand it using the Penrose and Hawking theory - apologies if I mix something up, as I don't have the book handy.

That was a good explanation. Time does not flow in a straight line and I belive Hawking used the analogy that asking what happend before Big Bang is like asking what lies north of the north pole.

Well, what about the theory that mankind in the distant future creates the universe that we are in today(circular creation, man exists because man made himself). Thus, there really is no beginning of time.

Actually this theory does argue for the Church/religion/whatever as it does give a bases to the moment of "creation."

Not really... It says rather... "We don't know."

While it doesn't directly contradict some of the premises of many religions, neither does it support them.

Cheers

Originally Posted by MadCow257

Axon there is a problem. It explains nothing, nada, zilc, nin. And why did they get money for that? It's like asking what's beyond the edge of the universe. There is no answer. Creationists can't say what existed before God, and evolutionists can't say what existed before time. Both of us just have to make some unscientific leap. Its unavoidable. Why don't people realize that?

Or perhaps just admit that we don't know.

Originally Posted by MadCow257

Axon there is a problem. It explains nothing, nada, zilc, nin. And why did they get money for that? It's like asking what's beyond the edge of the universe. There is no answer. Creationists can't say what existed before God, and evolutionists can't say what existed before time. Both of us just have to make some unscientific leap. Its unavoidable. Why don't people realize that?

they proved it mathematically according to the general theory of relativity - if you want the mathematical proof search for it online or at your library.

I just wanted to answer Cheez's question, so don't hold me responsible for what I wrote. The question was: why does Big Bang support that time did not exist before the "bang" - so I've written the explanation given by Hawkin - so do with it as you please.

Not really... It says rather... "We don't know."

While it doesn't directly contradict some of the premises of many religions, neither does it support them.

no, that theory made many creationists very happy, as it did support the idea that the universe has a beginning. At one point there is nothing, and at the beginning of time there is "something".

If you think about it...... what do you think created the primordial ooze that well..... banged. There are a terribly large amount of signs pointing towards the existence of a god.
Vanilla Ice's theory as seen on the surreal life is totally moronic. He says there is a god BUT we come from another more advanced planet. If I could meet I would ask him 1 thing. Why the hell we would get so dumb all of a sudden. His theory is just full of holes as is the theory of evolution.

I prefer the pressure theory. Basically, when you accurately expand the equations for gravitation, pressure becomes a source of gravity. In the everyday world, it's insignificant. In the early days of the universe with very little entropy, everything was very tightly bunched together such that the pressure term of the gravitation equations was much more significant than the 'regular' terms from gravitation. The thing is, the pressure term of gravitation induces a repulsive force, where normal gravity (following newton's laws for macroscopic objects) is an attractive force (it induces a pull).

So, basically, the theory suggests that gravity caused the big bang. Because it is gravity, and not some other mysterious unknown entity (gravity obeys the speed limit of the universe, the speed of light) the big bang acts as a single well defined event with respect to absolute space time (as opposed to basing it off of relative time or whatever).

Originally Posted by Darkness

I prefer the pressure theory. Basically, when you accurately expand the equations for gravitation, pressure becomes a source of gravity. In the everyday world, it's insignificant. In the early days of the universe with very little entropy, everything was very tightly bunched together such that the pressure term of the gravitation equations was much more significant than the 'regular' terms from gravitation. The thing is, the pressure term of gravitation induces a repulsive force, where normal gravity (following newton's laws for macroscopic objects) is an attractive force (it induces a pull).

So, basically, the theory suggests that gravity caused the big bang. Because it is gravity, and not some other mysterious unknown entity (gravity obeys the speed limit of the universe, the speed of light) the big bang acts as a single well defined event with respect to absolute space time (as opposed to basing it off of relative time or whatever).

The one complication I see is the unification of the forces "early" on after the big bang. For there to be repulsion, there must be a repulsive force but gravity isn't (unless of course, you found something with negative mass).

It was my understanding, when I read my source, which I don't have handy, that to get the total force of gravity, you basically take a bunch of different terms to get an accurate answer...sort of like expanding a taylor series or something like that. But, the pressure term from gravity is sort of like the term from the 1000th derivative which is usually small, except for in certain instances (I realize the taylor series isn't the best example).

So, unless I read my source wrong, yes, pressure does contribute to gravity, and yes, it creates a repulsive gravity. Of course, every classical text book defines gravity as being attractive, but I was reading a book about string theory, which isn't a classical text book.

Of course, every argument is flaky in the sense that we can't really prove much of anything. I'm regurgitating some fancy ideas I would have never thought of.

A better argument against my response is that I didn't even touch upon the problem of *where* the matter came from, only how it expanded

The pressure theory also contributes to this idea of an expanding universe (a universe that may be expanding at an increasing rate, as opposed to expanding only to someday collapse...it again deals with balancing the attractive component of gravity with the repulsive component of gravity, where the outskirts of the universe becomes so distant from ordinary mass that the pressure term of gravity becomes dominant and repels it away).