Age of the Universe + Dark energy/matter

[AccuJimmy]

Howdy, I'm new but the reason I joined the forum was the ask this question.

I don't really understand how the 13.7 billion year number was arrived at. It seems to me (and I know this is dumb and not scientific at all) that its not a large enough number. As I understand it, one of the factors in the equation comes from the deep field observations taken from the HST. Are the ancient globular clusters all "metal poor" to the degree that they "obviously" come from a time near the beginning of the universe?

Furthermore, the question of dark matter and how it relates to the age. Since we can't (or aren't) see(ing) beyond the 13 billion year mark, is it possible that the luminous matter beyond our visual scope makes up for the "missing matter" that was needed for the "large bang" to have occured in the first place?

Let me state that I believe in the observations that dark matter and energy exist, but is it possible that a simple miscalculation (or underestimate) in the amount of unseen matter makes up a greater proportion of said missing matter that is currently being filled by the dark matter hypothesis?

And finally... What is at the edge of the universe? Is there an edge? If space is flat there would have to be an edge right?

[Jens]

I think I can get this right, but I'm not a professional, so others may correct me.

I think the 13.7 billion figure comes from the Hubble value. Things that are further away move away more swiftly. So you can calculate backward from that and find when there appears to have been a singularity. You could imagine a similar thing for an explosion. If you look at the particles and see how fast they are going and how far away, you can estimate when the explosion took place.

And about the dark matter, one problem concerns the rotation of galaxies. When things orbit, their speed is dependent on the mass. So the stars in galaxies don't orbit correctly according to our understanding of galaxy. So the missing matter can't be beyond the edge of the universe.

What does the edge look like? It's a big black wall, and there are signs all over it reading "NO VISITORS BEYOND THIS POINT".

[astromark]

Jens said...
What does the edge look like? It's a big black wall, and there are signs all over it reading "NO VISITORS BEYOND THIS POINT".

As the local street kids have not been there yet the wall may still be clean.

I am unclear as to what you might see.
a universe behind you and void of nothingness in front.
or just more of the same.
By the time you arrive there it has expanded somewhat.
There is no edge. Just a expanding of space. Into infinity.

[Neverfly]

And finally... What is at the edge of the universe? Is there an edge? If space is flat there would have to be an edge right?

Note: This is as I understand and accept theory. I am not stating as absolute fact.

It is not flat. You would not be able to look past an "edge." The expansion occurs everywhere. Everywhere that is not bound by gravity.

Your question is similar to asking what you would see if you look over the edge of the earth. But the Earth is round- you would only see more Earth. Even though the Earth is not infinite- it can give the perception of being so.

Similarly, with the Universe, you would only see more Universe. However, this is a twisting and folding- the comprehension of Everything... In other words- to look past the universe would require something to be there.
So you could not look UP out past the atmosphere- you would still only see more of the same Universe.

[KKHS]

1. And about the dark matter, one problem concerns the rotation of galaxies. When things orbit, their speed is dependent on the mass. So the stars in galaxies don't orbit correctly according to our understanding of galaxy. So the missing matter can't be beyond the edge of the universe.

2. What does the edge look like? It's a big black wall, and there are signs all over it reading "NO VISITORS BEYOND THIS POINT".

1. As far as I understood it, it's is matter in side galaxies, that creates additional gravity. My "money" is in black holes (which is bad, since nothing get out from them, har har :-)

2. I realy don't believe the edge of universe is like a bottom of swedish swimming pool.

Since we can't (or aren't) see(ing) beyond the 13 billion year mark, is it possible that the luminous matter beyond our visual scope makes up for the "missing matter" that was needed for the "large bang" to have occured in the first place?

Well, no. As it's been told already, dark matter is matter that can't be observed exept by it's gravity, and it's inside galaxies, not outside observable universe (exept inside galaxies that are outside observable universe). As I said, it's most likely black holes, but that's my guess. It might also be "wild" particles and molecyles, that are smaller than light's wavelength. In anycase, it's matter that doesn't reflect or produce any light. And that has nothing to do with the "large bang" (I'm guessing it's big bang, but I might just missinteprete what you're meaning), or expansion of the universe, which is caused by dark energy. Though energy and matter are basically the same thing, it doesn't mean that dark matter and dark energy have anything to do with each other. Dark matter is matter that can't be seen, but has enough gravity to keep galaxies together, and dark energy is energy of the force that makes universe expand.

[AccuJimmy]

Wow. Thanks for the replies. I have to head to work at the moment but that will give me time to process a proper reply to the new questions that are forming in my noggin.

(large bang=big bang)(tryin' to be sly)

I guess I should have known that dark matter and dark energy weren't related.

Edge of the Universe.
My thinking was this -- think of the fireballs created by a nuclear explosion (as that's how I've always imagined the first moments of existance like a time-lapse vid of a nuke going off). As it expands there is an edge, no matter what or where the edge is. That's how I view the universe, we're inside a sphere of some sort. If there was a singularity 13b years ago that we can track back to, heading in the opposite direction, eventually, wouldn't you have to come to some sort of edge? (I know you couldn't actually get there in any sort of craft, but that's not what I'm getting at.)

Again, thanks to everyone.

EDIT: actually "edge" isn't the best term I guess, "wall" is perhaps more accurate

[Neverfly]

The misnamed theory may be giving you the wrong impression.
The theory is about an expansion- more so than explosion.

[Cougar]

Howdy, I'm new but the reason I joined the forum was the ask this question.... I don't really understand how the 13.7 billion year number was arrived at.

Well, you've gotten a number of rather partial and some speculative answers. There are actually a number of lines of evidence that go together to bring us the 13.7 billion year number. They are all touched on in this Wikipedia article.

1. the WMAP results give us a good estimate of the matter-energy content of the universe, thus the curvature parameter, which tells us that the space of the universe is generally flat.
   
2. The Hubble constant, which isn't exactly constant, tells us the expansion rate, which we can basically run backwards and get the universe's age, after correcting for the variation in rate due to the matter-energy content and the newfound cosmological constant, which causes the expansion to accelerate at later times. We get a good estimate for all this using observations of Type Ia supernovas.
   
3. We get verification of our estimates on the age just by estimating the age of the oldest stars, white dwarfs, etc. There do not appear to be any objects out there that are older than 13.7 billion years, even though the lifetime of a typical white dwarf could very well be much older. But they aren't.

It seems to me (and I know this is dumb and not scientific at all) that its not a large enough number.

You don't seem to realize how big 13 billion really is! I suppose that's just a side-effect of being exposed to Bush economics....

As I understand it, one of the factors in the equation comes from the deep field observations taken from the HST.

Actually, no. The Hubble Ultra-Deep Field does seem to show that galaxies have evolved in the past 10 or so billion years; and it shows that our best long exposure cannot see any objects farther than 12 or so billion lightyears away, which offers some kind of verification of our current age estimate; but I don't know that the HUDF gives us a direct estimate of the age of the universe....

Are the ancient globular clusters all "metal poor" to the degree that they "obviously" come from a time near the beginning of the universe?

Well, as Wiki says,

Although it appears that globular clusters contain some of the first stars to be produced in the galaxy, their origins and their role in galactic evolution are still unclear. It does appear clear that globular clusters are significantly different from dwarf elliptical galaxies and were formed as part of the star formation of the parent galaxy rather than as a separate galaxy. However, recent conjectures by astronomers suggest that globular clusters and dwarf spheroidals may not be clearly separate and distinct types of objects.

Furthermore, the question of dark matter and how it relates to the age. Since we can't (or aren't) see(ing) beyond the 13 billion year mark, is it possible that the luminous matter beyond our visual scope makes up for the "missing matter" that was needed for the "large bang" to have occured in the first place?

Nope. There are also a number of lines of evidence that yield estimates for the amount of dark matter. See this Wiki article, which points out....

The observed phenomena consistent with dark matter observations include the rotational speeds of galaxies, orbital velocities of galaxies in clusters, gravitational lensing of background objects by galaxy clusters such as the Bullet cluster, and the temperature distribution of hot gas in galaxies and clusters of galaxies. Dark matter also plays a central role in structure formation and galaxy evolution, and has measurable effects on the anisotropy of the cosmic microwave background. All these lines of evidence suggest that galaxies, clusters of galaxies, and the universe as a whole contain far more matter than that which interacts with electromagnetic radiation: the remainder is called the "dark matter component".

Let me state that I believe in the observations that dark matter and energy exist, but is it possible that a simple miscalculation (or underestimate) in the amount of unseen matter makes up a greater proportion of said missing matter that is currently being filled by the dark matter hypothesis?

Well.... our estimates are constantly being revised as new observations come in. But, as in all of science, we seem to be getting closer and closer to the answers, and it's unlikely there has been any major "miscalculation."

And finally... What is at the edge of the universe? Is there an edge? If space is flat there would have to be an edge right?

Not at all. We're not really sure about the topology of the universe. As pointed out, the surface of a sphere is 2-dimensional, and it has no edge. The shape of the universe could possibly be a 3-dimensional counterpart to that type of situation.....

[AccuJimmy]

Thanks Cougar.

I've read the age Wiki before but just couldn't get my mind to absorb the concepts, you've done a good job at honing in on my exact problems. I now get the age concept and why its a pretty good estimate. Thanks too for clarifying the Deep Field images confusion I had.

You don't seem to realize how big 13 billion really is! I suppose that's just a side-effect of being exposed to Bush economics....

I do and I don't I guess. I've heard/seen/read that there are stars out there that are 150b light years away, we'll never see them because they're so far away space keeps expanding so the light has to travel further and further and it can never 'catch' us. No problem there. Yet something about that concept just doesn't sit well with me. I'm not sure I'll ever fully get it.

I'm still going to hunt for my answer as to what's at the edge. I think I'm confused about the whole "flat vs. curved" idea of space. To me, if its flat, there has to be an edge. If its curved (and correct me if I'm wrong, some data points to it definitely NOT being curved) I can understand why there is no edge.

Can my confusion on that idea come from what Neverfly pointed out? The idea of rapid expansion vs. an explosion? Here's how I think about those concepts. If it was a "bang" (ie. explosion) I point back to my previous example of a huge fireball that just keeps going. No matter how you look at a fireball, and no matter how big it would be, it still has an edge. Now, the rapid expansion makes sense to me because what is "outside" the edge doesn't actually exist, just as time didn't exist before the big bang. Dark energy just keeps creating space, apparently at an ever increasing rate. (correct?)

But even that idea is a little hard to swallow. Where is the dark energy? How does dark energy differ from steady state theory, which I don't think anyone really accepts anymore? (I suppose the difference is dark energy is creating empty space, steady state said matter was being created.) Yet they do feel somewhat analogous.

How far off base am I now?

[Cougar]

I'm still going to hunt for my answer as to what's at the edge.

Helpful might be mathematical physicist-cosmologist Janna Levin's quirky little book, How the Universe Got Its Spots.

I think I'm confused about the whole "flat vs. curved" idea of space. To me, if its flat, there has to be an edge.

Take a flat piece of paper. Connect two opposite edges to make a cylinder. Then connect the two "circle" ends to make a donut shaped object.... No edges!

[KKHS]

Take a flat piece of paper. Connect two opposite edges to make a cylinder. Then connect the two "circle" ends to make a donut shaped object.... No edges!

Oh dear god! I just remembered that episode in Simpsons, where Homer told Stephen Hawking at Moe's about his theory of donut shape universe :-)

[Cougar]

It's all in the topology.

[AccuJimmy]

Thanks for the heads up on the book, I added it to my Amazon shopping list and the next time I order something its first on my list.

[Ari Jokimaki]

I'm still going to hunt for my answer as to what's at the edge. I think I'm confused about the whole "flat vs. curved" idea of space. To me, if its flat, there has to be an edge. If its curved (and correct me if I'm wrong, some data points to it definitely NOT being curved) I can understand why there is no edge.

It seems to me that you are thinking flat universe in exactly correct way. If universe is flat, it is not curved. But the thing that you are missing relating to your question about the presence of an edge is that if Big Bang universe has flat geometry, it didn't start as one tiny point, it was infinitely large already at the beginning. See this page for details. I'm sure you see that there's no edges in infinitely large universe. In flat geometry case, the usual story about starting from a tiny point and then expanding to current size is only about the observable universe. Unfortunately, this point is very poorly presented in popular literature which then causes this confusion.

[AccuJimmy]

It seems to me that you are thinking flat universe in exactly correct way. If universe is flat, it is not curved. But the thing that you are missing relating to your question about the presence of an edge is that if Big Bang universe has flat geometry, it didn't start as one tiny point, it was infinitely large already at the beginning. See this page for details. I'm sure you see that there's no edges in infinitely large universe. In flat geometry case, the usual story about starting from a tiny point and then expanding to current size is only about the observable universe. Unfortunately, this point is very poorly presented in popular literature which then causes this confusion.

Unfortunately your link didn't work. But I get the gist somewhat of your point. It was infinitely large at the point of the big bang?

If that is true, I don't understand how dark energy creates more space. If the universe was large but without mass until the big bang, why do we need dark energy to explain the formation of space? Wouldn't matter just be filling up what's already there? Of course that doesn't make sense when you consider the increase in the rate of expansion of space, thus dark energy again makes sense.

I tend to figure things out by talk or writing out my ideas. It generally bothers most people.

Now my question becomes -- is there any observation that supports the idea that the space the universe exists in was infinitely large before the moment of the big bang? (it seems too much like string theory to me, something that I've yet to be convinced of)

[Ari Jokimaki]

Unfortunately your link didn't work.

It seems to work for me. The website was probably down when you tried it.

But I get the gist somewhat of your point. It was infinitely large at the point of the big bang?

Yes, if the geometry of the universe is flat.

If that is true, I don't understand how dark energy creates more space...

Sorry, I haven't been following dark energy related things at all so I can't help you there.

Wouldn't matter just be filling up what's already there?

Matter is not expanding, the space is, so matter is not filling up anything. It's actually other way around in my opinion; things start with huge matter/energy density and when space expands, the matter/energy density becomes lower, so actually space overall is becoming more empty, not full.

Now my question becomes -- is there any observation that supports the idea that the space the universe exists in was infinitely large before the moment of the big bang? (it seems too much like string theory to me, something that I've yet to be convinced of)

Not actually observation but logical trail of thought: if universe is flat, it makes sense to assume that it's infinitely large, because otherwise it would have edges somewhere. If universe is flat and infinitely large now, and if the rate of space expansion is finite, then the universe had to be infinitely large always, because you can't get infinitely large from something finite with finite growth rate during finite time period.