The Universe

[Professor Chaos]

Non-scientist seeking insight about the universe from some of our resident scientists and all-around experts on everything. (I'm looking at you, Choobus, ADT, AJF, and others.) Forgive me if/when I come across as stoopid here.

And please, please, correct me if I'm wrong about anything that follows.

When we speak about the "universe," we're technically speaking about the "observable universe." Mankind does not know whether the universe that we observe is all there is, 1/10th of what there is, 1/1,000th of what there is, or whether the universe is infinite.

The same applies to time. We don't know if there was a "before" the big bang or not. Isn't there one theory that there was a series of big bangs/big crunches before the big bang?

Anyways, is there a consensus in the scientific community that the big bang signifies the beginning of space/time? Based on logic, reason, and a very limited cosmological understanding, I tend to believe that matter, energy, and time have always existed, even before the BB. I would never purport to claim this as anything close to a fact, but I know of no evidence suggesting that time has had a beginning and that space has ends.

Am I way off base here? If not, why is the word "observable" almost never used in front of the word "universe?"

we do know that the universe is not infinite, but there is no telling what is outside of it. we really only know a little bit about what is inside of it.

http://antwrp.gsfc.nasa.gov/apod/ap050925.html

[Professor Chaos]

DontBeStupid wrote

we do know that the universe is not infinite, but there is no telling what is outside of it. we really only know a little bit about what is inside of it.

http://antwrp.gsfc.nasa.gov/apod/ap050925.html

Can you explain to me, a total dipshit on this stuff, how this explains that the universe is not infinite?

[nkb]

I'm surprised you did not include Xans in your list. He obviously has his science down (don't forget, he took HS physics).

An apology would be appropriate.

Meanwhile, I'm looking forward to some of the answers myself.

DontBeStupid wrote

we do know that the universe is not infinite, but there is no telling what is outside of it. we really only know a little bit about what is inside of it.

http://antwrp.gsfc.nasa.gov/apod/ap050925.html

Don't you mean that we know the known universe is finite?

For all we know, there could be an endless amount of universes out there that go on and on and on forever.

If I may be allowed to add to the stupid questions I have a couple on this subject as well.
As I understand it the universe is finite and unbounded like a ball I heard a theory that there could be other universes out there and that the big bang was essential our universe being sucked (obviously not intact) here from some place else. Is there any merit to that or did I understand it completely wrong or was the idiot box (TV late night science channel viewing) lying to me again?

Oh and is the universe bounded or unbounded I always get that confused and is it like a ball or does someone have a better analogy.

Oh oh and if it is like a ball could you in theory go all the way around it and end up back where you are now or is the ball analogy a bad one and that wouldn’t work?

Please use little words if you care to answer any of my questions I’m a science tard :P

Professor Chaos wrote

Non-scientist seeking insight about the universe from some of our resident scientists and all-around experts on everything. (I'm looking at you, Choobus, ADT, AJF, and others.) Forgive me if/when I come across as stoopid here.

And please, please, correct me if I'm wrong about anything that follows.

When we speak about the "universe," we're technically speaking about the "observable universe." Mankind does not know whether the universe that we observe is all there is, 1/10th of what there is, 1/1,000th of what there is, or whether the universe is infinite.

The same applies to time. We don't know if there was a "before" the big bang or not. Isn't there one theory that there was a series of big bangs/big crunches before the big bang?

Anyways, is there a consensus in the scientific community that the big bang signifies the beginning of space/time? Based on logic, reason, and a very limited cosmological understanding, I tend to believe that matter, energy, and time have always existed, even before the BB. I would never purport to claim this as anything close to a fact, but I know of no evidence suggesting that time has had a beginning and that space has ends.

Am I way off base here? If not, why is the word "observable" almost never used in front of the word "universe?"

I'm speaking from a position only slightly above that of a lay person, but I am willing to give it a shot.

As to your question on time, the concept of time is largely not understand before the big bang and most likely is a meaningless concept before the big bang. Time is intricately tied to the concept of space (i.e. space-time) and thus if space is entirely centralized into a singularity then time must also. The concept of time would not have had any real meaning until after the expansion.

The concept of the big bang/big crunch is a concept that has been progressively losing steam. The universe is expanding yet there is matter in the universe which will be affecting everything in the universe and so it seems like a very logical concept. However, the universe has in fact been speeding up in its expansion as opposed to slowing down, leading most people to believe that the universe won't likely reverse into a big crunch. There is a possibility that the universe could slow down, much in the way AJF described in a different thread using the backswing of a pendulum as an analogy, however this would require some force to instigate it. There is always the possibility that gravity might act differently in very long range interactions but as of now there is no evidence to suggest this.

As to the concept of eternal matter and eternal time, I am unaware of any consensus. My own preference, based on my sub par knowledge of the subject, is ground in the concept of quantum energy fluctuations. Essentially matter is rapidly created and destroyed by small fluctuations in potential. These occur on a quantum scale and so if the singularity acts on a quantum scale then it is possible that the singularity is the result of an energy fluctuation (note: Whether or not the singularity is more applicable to quantum or relativity is debatable).

There are certainly other ideas about the nature of the singularity and existence of matter, but really there isn’t, at least to my knowledge, one obvious or preferred theory.

[Choobus]

asking what happened before the big bang is like asking "what was your favourite colour before you were born?"

[Professor Chaos]

Choobus wrote

asking what happened before the big bang is like asking "what was your favourite colour before you were born?"

I know, but what do we know that leads us to believe that there was no "before" the big bang? I'm legitimately asking here, not disagreeing.

Can space exist by itself without matter or energy around?

--------------------------------------------------------------------------------


No. Experiments continue to show that there is no 'space' that stands apart from space-time itself...no arena in which matter, energy and gravity operate which is not affected by matter, energy and gravity. General relativity tells us that what we call space is just another feature of the gravitational field of the universe, so space and space-time can and do not exist apart from the matter and energy that creates the gravitational field. This is not speculation, but sound observation.

(source: http://einstein.stanford.edu/content...ty/a11332.html)

The issue* is, with everything collapsed down to a singularity, there isn't any gravitational field. Space and space-time, as noted above, didn't exist until the universe had expanded enough for a space-time continuum to form.

*I ain't no physicist.

[Choobus]

Professor Chaos wrote

I know, but what do we know that leads us to believe that there was no "before" the big bang? I'm legitimately asking here, not disagreeing.

The question makes no sense.

[Choobus]

ocmpoma wrote

The issue* is, with everything collapsed down to a singularity, there isn't any gravitational field. Space and space-time, as noted above, didn't exist until the universe had expanded enough for a space-time continuum to form.

that is incorrect. the problem is that ina singularity (or even just on a quantum length scale) the gravitational field is something quite different from what we usually mean when we talk about gravity: it is quantum gravity, and we aint be gots no quantum gravity theory yet so we do not know how to describe this situation. That does not mean that there is no gravitational field, only that it is some weird shit that doesn't act much like "normal" gravity

[Professor Chaos]

Choobus wrote

The question makes no sense.

Could you explain that to me like I'm a four-year old? What is the evidence that space/time has a beginning? I just want to understand this better.

[Choobus]

you're asking what happened before time. There was no before. I don't mean to sound like yoda but it doesn't make any sense to talk about the temporal order of non-temporal events.

ocmpoma wrote

blah blah blah

I stand (actually, I'm sitting) corrected.

That said, I'll go out on a limb again:

The evidence, Prof, for the lack of space-time and all the other wierdness of the quantum-sized universe, involves a lot of math that the vast majority of people could only have a chance of maybe possibly understanding well if they put in several years of rigorous study.


Richard Feynman: "If you think you understand quantum mechanics, you don't understand quantum mechanics."