Center of the Universe?

[thedarkshade]

Question:

 

I am not sure, but I think we might be better off defining things as "Rapid Expansion" instead of Explosion. It may sound redundant, but I personally think this is a big part of the misunderstanding of the process.

You got a point about this moo!

There was really no explosion, because it is often called "the ancient explosion". It's just the creation of everything from nothingness, followed by a Rapid Expansion that still goes on!

[Martin]

Question:

 

I am not sure, but I think we might be better off defining things as "Rapid Expansion" instead of Explosion. ... Martin, you're a physics expert --> is this right? and if so, isn't the definition "expanding" much better than "explosion"?

 

~moo

 

It sounds right to me, moo. I'm told that the misleading name Big Bang was first applied to expansion cosmology by Fred Hoyle, who preferred his own steady state model. It was originally a term of mockery or contempt---perhaps intended to discredit. It definitely gives the wrong mental image.

 

What we are talking about is simply the start of expansion. This is modeled in various ways---some models provide explanation as to why and how it got started, and others don't. At the moment there's not enough evidence to favor one over the others.

 

... creation of everything from nothingness, followed by a Rapid Expansion that still goes on!

 

I don't know of any scientific reason to claim that the Big Bang (defined as the beginning of expansion) was "the creation of everything from nothingness."

 

Anyone can choose to believe that as a philosophical or religious belief---but it is not part of science.

 

Indeed there are some cosmological models which only go back as far as the start of expansion and break down at that exact moment. They say nothing about that precise moment and don't go back any farther.

 

And there are other models which fit the data equally well, and which go back further. For instance to a contraction phase: offering explanation as to why and how the contraction turned around and expansion began. These may account for some features of the microwave background without needing to invoke an hypothetical "inflaton".

 

So there are models that break down, and models that don't, but at the moment there is no clear evidence to favor one over the other.

[thedarkshade]

I don't know of any scientific reason to claim that the Big Bang (defined as the beginning of expansion) was "the creation of everything from nothingness.

I think this makes logical sense, since the word before is absolutely meaningless when we refer to Big Bang.

What I'm trying to say is that (as I have read) the beginning lies in Big Bang. Our universe once was at that single zero volumed infinite dense point. It began right there.

[Realitycheck]

Sorry, i have been sick for a while.

 

alright this stuff (that martin has posted) has helped some. but there are still some unanswered questions, and i apologise. i understand that it is a hard subject to understand and you are doing your best and i appreciate it very much!

 

So, distances between stationary objects, are expanding. and i think, correct me if im wrong, were talking superlarge scale here, stationary objects being galactic clusters. lets see....im forming new understanding right now as im typing so its hard to figure out what i dont understand haha.

 

one quick question about expansion speeds. if distance A gives expansion speed B then does distance 2A give expansion speed 2B?

 

thats kinda leading to my question about something martin said, "expansion speeds are larger than c (for any distance 14 Gly or larger)"

 

is the reason for this the age of the universe? and what does this mean? if things 14 billion lys away are expanding faster than the speed of light does that mean we will never be able to see them?

 

and another thing i still dont understand (and maybe im not supposed to understand just accept) is still about the ?edge? of the universe and the lack there of. if everything is "expanding" in every direction, then the universe must be getting bigger. i dont even know what im trying to ask here since i dont understand heh. i mean, if you looked at the universe as a whole, even though thats not possible since there is no edges (right?) then if you looked the next second, because of expansion, the universe must be the whole +1, in the sence of size.... i guess....

 

i dunno if any of this stuff that i have said/asked makes any sence. i know it doesnt to me haha. i think i need to read up on those other form topics the poll thread martin posted about expansion and so on. but if anyone could help it would be nice i gotta go to class now

 

http://www.sciam.com/article.cfm?chanID=sa006&colID=1&articleID=0009F0CA-C523-1213-852383414B7F0147

 

What you should read is the Limeweaver article, as it will give you the clearest authoritative view on the subject. If a germ grew up to be a person, where would the grown-up person point to and call itself as a center? Your eyeball would say, "Well, I grew up out of a germ," and your pinkie would say, "Well, I grew up out of a germ," but the germ would no longer be the germ and there would be no place to point to. Granted, it did derive from a specific point in space and time, but it is really irrelevant. It just grew up into a universe.

 

As far as the edge of the universe is concerned, no one can really know for sure. The best way to think of it, in line with conventional theory, is that it is not space until the universe has grown into it. We can make theories and hypotheses, but there is really no way of confirming it right now, at least, so just think of it as the germ that grew into the universe and contains everything. There are theories about additional universes existing outside our own, but if we cannot even completely define our own, there is no point in hypothesizing others.

 

As far as expansion speeds are concerned, the universe is expanding at speeds greater than c, when taking into account the size of the universe as a whole. For instance, we know that the universe is approximately 14 billion years old. That means that any light produced that is 14 billion light years away would take exactly 14 billion years to get here. Any light produced from further than that distance would not be seen because it would not have arrived yet. However, we know that there are celestia farther than 14 billion light years away. Extrapolating from this data, we conclude that the universe must be expanding faster than the speed of light in order for it to be so much bigger, yet only partially viewable.

[Martin]

... the word before is absolutely meaningless when we refer to Big Bang.

...

 

How so?

 

Of course I know that before 2005 many people used to say that, but (as Roger Penrose remarked in a talk he gave at Cambridge that year) the situation has changed. Penrose was presenting his own model of what preceded.

 

With people regularly running models back in time before, how can you say time is absolutely meaningless?

 

The only context in which it is meaningless is if you limit yourself to the vintage 1915 version of General Relativity, which happens to break down at the start of expansion. It was in that context that people used to say that time stopped. It stopped because the model broke.

[thedarkshade]

No no Martin, listen.

 

We take Big Bang as the beginning of time and everything(or don't we?). So to say before the time began, then actually where does that before fit in? Not in time since time had not begun yet!

[Klaynos]

No no Martin, listen.

 

We take Big Bang as the beginning of time and everything(or don't we?). So to say before the time began, then actually where does that before fit in? Not in time since time had not begun yet!

 

Not any more we don't, times are achanging!

[Observer]

Let me give this a shot. Im young too and maybe can put it into better words for cmac.??

 

From what I gather from all the reading, the question of the "edge" of the universe is still unclear. This is probably a bad analogy, but take a baloon for example. Starts off small and gets "infinatly" bigger as air is added. It does not necessarily have a center because it is not expanding from one particular point. It is just expanding. And remember that a balloon can be any shape, not just a sphere.

 

It all made a lot more sense to me after watching the Big Bang Video on the YouTube link. So try that if you have not.

 

And also, I read this in one of the earlier posts, the universe is expanding in 4D??, so as time goes on, that is what is making the universe bigger (well dark energy is what is making it expand i think, but that is a different topic) So as time passes, the universe gets bigger, just like your ears get bigger as you age. ha.

 

And I think cmac is still trying to understand the whole light concept. Yes light can only travel at the speed of light. So there are things beyond our visibility, but that doesn't mean they aren't there. And noone is saying that there isn't.

 

Ok, if any of that is wrong, or if this makes absolutely no sense. Please don't hesistate to correct it. Im just taking a stabe at it based on what I've read here and on links, and some previous knowledge.