Is the Big Bang really the beginning?

[gib65]

I was just thinking: some theoreticions believe that the universe will eventually collapse under its own gravitational pull and result in a Big Crunch? Some of these theoreticions would go even further and postulate that after this Big Crunch, the universe will once again be in the same state it was in before the Big Bang, and so another Big Bang will occur. If this were true, then the universe is simply a perpetual series of Big Bangs and Big Crunches, and it not only makes sense to project this series into the future but into the past as well, which means that the most recent Big Bang was not the absolute beginning of the universe but only the beginning of the current cycle. In effect, it would mean that there isn't necessarily a beginning since this series could be retro-projected eternally. Is there any reasoning to this idea?

[mezarashi]

Personally I think that the whole question of what was there at the beginning of the universe is absurd. It's like the good old question what came first, the chicken or the egg, because you can keep asking questions. If the big bang was the beginning, you could ask, then what was before the big bang. What caused the big bang? How was the "universe" like before the big bang. If the big bang isn't, and it's part of a perpetual cycle of expansion and collapse, then the questions are, what started this cycle? When did this cycle begin? Will it ever end? What was there before this cycle started? Why did it start?

 

But back to the topic, there is a theory that predicts this endless expansion crush, string theory. String theory says that all the laws of the universe would remain the same if everything was inversed their planck length. Meaning that after the universe collapses to a size equal to the planck size, it would in fact "expand", because you can't tell. I'd personally like to believe in these perpetual cycle theories as well, although we don't know how true it all is

[Annemarie]

The universe could go three ways, due to the two major forces that are acting on matter on a macroscopic scale.

Firstly, if the universe is expanding quickly enough there will come a point when the gravitational force thats holding everthing together will not longer be able to, the universe will expand until even the atoms split apart. The point at which the universe started expanding was the big bang and continues for ever results in a universe which is a soup of particles at an equillibrium temperature. This is called an "open universe"

Scondly, the Universe may start slowing down in it's expansion, ie not enough kinetic energy to over gravity, and as you rightly stated we'll have a "big crunch", this is called a "closed universe"

Thirdly, kinetic energy and gravitational energy could reach equillibrium, i.e. no explosive ending just the universe chilling out, a "flat universe".

We will be able to find out which fate awaits us in a couple of thousand years, by tracking the universes expansions through red shitf.

Hubble (a very clever and inspiring man) founded a law to determine the age of the universe and its fate.

v = H r

v- Recessional Velocity H- Hubles Constant r- Distance

So from measuring the recessional vlocity of a star, you can calculate it's distance and the inverse of the Hubble Constant is the age of the universe. So the more measurements made the better the idea we have about it's age.

Once we know the universes age and it's expansion rate we can extrapolate the kinetic energy gained at the big bang.

The final state of the universe can be define by a constant w.

w is the ratio between the current density of the universe and the critical density, if w=1 the flat, w>1 closed universe and w<1 open.

Check out http://superstringtheory.com/cosmo/cosmo21.html and http://hyperphysics.phy-astr.gsu.edu/hbase/astro/hubble.html#c1 for more info

[Ophiolite]

[b']Is the Big Bang really the beginning?[/b]

You have definitely entered the area where science, philosophy and religion overlap.

[Johnny5]

I was just thinking: some theoreticions believe that the universe will eventually collapse under its own gravitational pull and result in a Big Crunch? Some of these theoreticions would go even further and postulate that after this Big Crunch, the universe will once again be in the same state it was in before the Big Bang, and so another Big Bang will occur. If this were true, then the universe is simply a perpetual series of Big Bangs and Big Crunches, and it not only makes sense to project this series into the future but into the past as well, which means that the most recent Big Bang was not the absolute beginning of the universe but only the beginning of the current cycle. In effect, it would mean that there isn't necessarily a beginning since this series could be retro-projected eternally. Is there any reasoning to this idea?

 

Nietzsche pondered it.

 

Time had a beginning, regardless of this theory, it wouldn't matter what cycle we were in now.

 

In order to even attempt to reason about time, and draw conclusions with certainty, one needs to start off with statements which are true, and known to be true.

 

How would anyone know there was a first moment in time?

 

I would suggest simply build up an axiomatic theory of time, and use that as an axiom.

 

It is possible to construct an argument in which you deduce that time had a beginning, but it's somewhat contrived.

 

Also, Stephen Hawking recently tried to prove that time had a beginning using umm, oh yeah... using the concept of imaginary time, but the problem with that boils down to using square root of -1.

 

No matter how you look at it, the negation of the fact that time had a beginning, leads to a multiplicity of contradictions. But you need a highly sophisticated pre-developed, axiomatic theory of time.

 

Regards

 

PS: Here is one idea i had, but eventually decided the argument was too complex to carry out mathematically...

 

Imagine everything running in reverse, from right now. Visualize the planets reversing their spins, and moving backwards along their orbits, broken things coming back together, go back more and more.

 

If we take current macroscopic astronomical observations seriously, as we go more and more back into the past, relative to now, things will be getting closer and closer together. Perhaps a computer could be used to project how far back in time all of the material was concentrated into one mass.

 

Now comes the idea, but as I said it's too complex to prove useful.

 

Eventually, there would come a condition of the universe, at which the reversal of motion would cause some problem. Like, for example, the temperature of the supermass approaches infinity if there was no first moment in time. Something along these lines.

 

But you aren't going to deduce the answer this way, for a lot of reasons.

 

But my point is, time did have a beginning, how you argue that fact is up to you.

[bascule]

In inflationary cosmology the "beginning", whatever it may be, happened before the Big Bang...

[ydoaPs]

anyone who thinks that the big bang was the begining of the universe doesn't understand the theory.

[gib65]

But my point is' date=' time did have a beginning, how you argue that fact is up to you.[/quote']

 

I don't quite get your reasoning. Are you saying that time has a beginning simply because you hold it to be axiomatically true, and that's that? You mentioned some contradictions, like heat approaching infinity, but I fail to the reasoning behind this.

[Johnny5]

I don't quite get your reasoning. Are you saying that time has a beginning simply because you hold it to be axiomatically true, and that's that? You mentioned some contradictions, like heat approaching infinity, but I fail to the reasoning behind this.

 

Here is my reasoning...

 

I can develop symbolic logic, design it to terminate at the statement:

 

There is at least one moment in time A, such that for any moment in time B, if not(A=B) then A before B.

 

The statement above is almost pure first order logic, and sentential calculus.

 

But exactly when, in the course of me actually contriving this argument, do I in reality "realize the conclusion, which im busy contriving" is true???

 

And if it truly is a deductive argument, then the argument form has to be a valid argument form, such as modus ponens. Which means the argument runs somewhat like this:

 

Suppose I know that the following 5 statements are true

 

1. if A then B

2. if B then C

3. if C then D

4. if D then E

5. If E then (there is at least one moment in time X, such that for any moment in time Y, if not(X=Y) then X before Y)

 

So all 5 of these statements I could know, but without also knowing a sixth

 

6. A

 

I cannot draw the conclusion that time had a beginning.

 

So this begs the question what statement 'A' do I already know, which I could use to reach the conclusion that time had a beginning deductively?

 

These are logistical problems in logic, and so the rationally best thing to do is to design an axiomatic system of time, with the following axiom:

 

1. There is at least one moment in time A, such that for any moment in time B, if not (A simultaneous B) then A before B.

 

As long as your other axioms are consistent with this axiom, the system you develop will be free from contradiction, and the very fact that time really had a beginning, will mean that your system will coincide with ultimate temporal reality.

 

Regards

[Annemarie]

I don't think religion has anything to do with physics, personally I think when the two mix it generally has bad concequences. Also when physics mixes with anything except what it naturally should.

[gib65]

Johnny5,

 

There are 2 ways to interpret your logic formula, and I'm trying to figure out which one you mean. I'll use A and E as the universal and existential quantifiers (since I don't have access to special symbols here ). The 2 ways are:

 

1) ExAy(if not(x=y) then x before y.)

 

2) AyEx(if not(y=x) then x before y.)

 

The difference is subtle but crucial, and in fact they are saying the opposite of one another in the context of the question: Does time have a beginning?

 

1) says that there is at least one point in time such that for all other points in time not equal to itself, it comes before them.

 

2) says that for each point in time, there is at least one point other than itself that comes before it.

 

1) suggests there is a first point in time, whereas 2) suggests there is none. 1) suggests that there is a "first" point for which all other points in time (not itself) come after it - there is no point in time that comes before it. 2) suggests that for any given point in time, there is some time before it - 11:00 comes before 12:00, 10:00 comes before 11:00, 9:00 comes before 10:00, and so on ad infinitum.

 

It sounds to me like you mean to imply 1), but then you are right that you need a statement A to arrive at such a conclusion, and therein lies your problem (at least, I'm inclined to believe). I don't think you'd ever find such a statement. For me, 2) is intuitively true. Of course, this is all in the context of the never-ending-cycle-of-big-bangs-and-crunches. If the big bang WAS the begining of time, space, and all matter and energy, with nothing preceding it, you may very well find your statement A after all.

[Ophiolite]

You have definitely entered the area where science, philosophy and religion overlap.

I don't think religion has anything to do with physics, personally I think when the two mix it generally has bad concequences. Also when physics mixes with anything except what it naturally should.

And physics has very little to do with the 'time' that gib65 is talking of, before the big bang, or within the repetitive cycle of big bangs and big crunches that preceded the current Universe. That area (currently) cannot be properly investigated by physics: we can use physics principles to speculate on possibilities, but we cannot (currently) test such speculations - therefore they are, in essence, unscientific. Philosophy (Johhny5 brings in Nietzsche) and religion have at least as much to say about this area, currently, as physics.

[Johnny5]

Johnny5' date='

 

There are 2 ways to interpret your logic formula, and I'm trying to figure out which one you mean. I'll use A and E as the universal and existential quantifiers (since I don't have access to special symbols here ). The 2 ways are:

 

1) ExAy(if not(x=y) then x before y.)

 

2) AyEx(if not(y=x) then x before y.)

[/quote']

 

I meant what I said...

 

There is at least one moment in time X, such that for any moment in time Y, if not (X=Y) then X before Y.

 

So that is one above. Using special symbols, we have this:

 

Let Á denote the set of moments in time, and let us restrict the domain of discourse to this set only. Thus, the existential and universal quantifiers refer to elements of this set only in what follows.

 

To formulate the statement that time had a beginning using FOL, we write this:

 

[math] \exists X \forall Y[ \neg(X=Y)\Rightarrow \text{X before Y} ][/math]

 

Translation: There is at least one X an element of Á, such that for any Y an element of Á, if X is a different element of Á than Y, then the following statement is true:

 

X before Y

 

Proving there is only one such element of Á is left as a theorem.

 

So that is what I mean. I do not mean (2), i mean (1), in the manner that I have explained.

 

Here is your translation of (1):

 

1) says that there is at least one point in time such that for all other points in time not equal to itself, it comes before them

 

You translated = as equal to.

 

This will raise some questions as to what is meant by two elements of Á being equal.

 

There is a simple answer to that, which has to do with simultaneity being an equivalence relation on Á. But I will let that come out naturally. For right now where we are is good.

 

Now, let me analyze (2):

 

[math]\forall Y \exists X [ \neg(X=Y)\Rightarrow \text{X before Y} ]

[/math]

 

Let me translate. For any moment in time Y, there is at least one moment in time X, such that if X is different from Y, then X comes before Y.

 

That is not what I meant.

 

It sounds to me like you mean to imply 1), but then you are right that you need a statement A to arrive at such a conclusion, and therein lies your problem (at least, I'm inclined to believe).

 

Yes you are correct, I am referring to 1.

 

In fact, to say that time did not have a beginning, i would formulate that as follows:

 

[math] \neg \exists X \forall Y[ \neg(\text{X simultaneous to Y})\Rightarrow \text{X before Y} ][/math]

 

Which is equivalent to:

 

[math] \forall X \exists Y[ \neg(\text{X simultaneous to Y}) \text{and} \neg (\text{X before Y}) ][/math]

 

Which is equivalent to:

 

 

[math] \forall X \exists Y[\text{Y before X}] [/math]

 

Translation: Given any moment in time X, there is at least one moment in time Y, such that Y before X.

 

The temporal logic which I am using, is based upon the fact that the following statement is necessarily a tautology:

 

[math] \forall X \forall Y[\text{X simultaneous Y or X before Y or Y before X}][/math]

 

Undefined binary relation on Á: before

 

Definition: For any x,y elements of Á

X simultaneous Y if and only if (not(X before Y) and not(Y before X))

 

Using nothing but first order logic, and the definition above, you can prove that the following statement is necessarily a tautology:

 

[math] \forall X \forall Y[\text{X simultaneous Y or X before Y or Y before X}][/math]

[gib65]

GOT IT!!!

[uncool]

Johnny, I challenge you to prove your statement (that is, that there exists a moment x etc.)

-Uncool-

[zaphod]

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