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Offline Steve West

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The age of the universe
« on: 09/02/2011 00:27:46 »
Hello.

I've got a question about the age of the universe.

O.K. so the universe is 13.7 billion years old and started at one infinitely dense point, however the larger the mass of an object, the more gravitational pull it exerts and therefore the slower time passes. So when the mass of the universe is around a very dense point, surely time would begin to pass very slowly and I'm guessing at the very beginning of the universe, stop. Is that right? If so, surely it doesn't make sense to give the universe an age, it would only be appropriate to say that it's been around an infinite amount of time.

Am I missing something here?

If your unit of measurement constantly changes, are you really measuring anything?



 

Offline Soul Surfer

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The age of the universe
« Reply #1 on: 09/02/2011 09:02:34 »
You are forgetting on very important point.  "we" are part of the universe and time always passes normally where "we"   (or any other we)  are  it is only when we look somewhere else that is a distance away that time passes differently.
 

Offline Pikaia

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The age of the universe
« Reply #2 on: 09/02/2011 11:50:49 »
The universe did not start as a point, it is infinite, and always has been. Also, the age of 13.7 billion years is the time since the Big Bang, but this might not represent the age of the universe, which may actually be infinitely old.

While it is true that time passes at a different rate depending on how deep you are within a gravitational well, the early universe was very uniform, so time would have elapsed at the same rate everywhere.
 

Offline peppercorn

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The age of the universe
« Reply #3 on: 09/02/2011 15:31:30 »
The universe did not start as a point, it is infinite, and always has been. Also, the age of 13.7 billion years is the time since the Big Bang, but this might not represent the age of the universe, which may actually be infinitely old.

Are you Sure about that?
 

Offline Pikaia

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The age of the universe
« Reply #4 on: 09/02/2011 16:02:42 »
Are you Sure about that?
Here is one theory in which the universe did not begin with the Big Bang.
http://www.scientificamerican.com/article.cfm?id=big-bang-or-big-bounce

The simplest model of the universe is infinite Euclidean.

http://www.astro.ucla.edu/~wright/cosmology_faq.html#RB

I am not sure about it, but I would be very surprised if the universe is finite in size, and almost as surprised if it began with the Big Bang.
 

Offline peppercorn

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The age of the universe
« Reply #5 on: 09/02/2011 17:19:42 »
I am not sure about it, but I would be very surprised if the universe is finite in size, and almost as surprised if it began with the Big Bang.

And your reason to prefer the concept of an infinitely old universe is?
Personally, whenever infinities crop up in physics I find them abhorrent - but that is just a subjective thing.  Having infinities doesn't seem very elegant.

Also, are you saying you would be 'almost' as surprised if our current observable universe was a result of a Big Bang event?  If not and you mean you're surprised that the whole thing started from a BB, then from your point of view this scenario would have to seem even more unlikely, wouldn't it?
 

Offline Pikaia

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The age of the universe
« Reply #6 on: 09/02/2011 18:58:03 »

And your reason to prefer the concept of an infinitely old universe is?
Personally, whenever infinities crop up in physics I find them abhorrent - but that is just a subjective thing.  Having infinities doesn't seem very elegant.
An infinite Euclidean universe seems more elegant to me than a finite universe, which would need a weird topology (or an edge, which would be even more inelegant).
Also, the universe can exist for an infinite time in future, so why not into the past?

I have never understood why people ever equated the Big Bang with the start of time - why should they represent the same thing?

That is why I like the theory described in the Sci Am article, with the Big Bang merely being a point of maximum density between a contraction phase and an expansion phase. There are other theories, but that is my prejudice.
 

Offline yor_on

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The age of the universe
« Reply #7 on: 12/02/2011 17:23:32 »
I agree with SoulSurfer. We all have a 'time' measured for us. In it we count durations and we expect those to exist after we're dead too. So we sure can count backwards to a 'start'. What we can't do is to decide what was before that point, even though some have theories about that too, well, at least I have a vague memory of some theoretical mathematicians trying to use what we know to define what might have been.
 

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The age of the universe
« Reply #7 on: 12/02/2011 17:23:32 »

 

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