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 RocketMan_Len
Joined: 7/5/2006
Msg: 69
how is the universe expanding?Page 5 of 6    (1, 2, 3, 4, 5, 6)
^^^^^

Better check your facts...

1 - the Steady-State Theory has *not* replaced the Big Bang in regards to the beginning of the universe. Quite the contrary - continuing observations tend to support the Big Bang event.

2 - the Universe is *not* expanding at a constant steady rate... measurements indicate that the rate of expansion is accelerating.
 stargazer1000
Joined: 1/16/2008
Msg: 70
how is the universe expanding?
Posted: 1/18/2010 5:21:56 AM

When we look deep into space we are ‘looking back into time’. 13 billion years I think, now the further we look the faster we see the acceleration. OK, but surely that has to be switched on a time graph. Plotting acceleration with the age of the universe shows it slowing down over time not accelerating. If we could view the whole universe all in the same time frame what would we see? I mean the edge of the visible universe some 13 billion years ago is expanding beyond the speed of light…but what is it doing today? The universe isn’t expanding around us here on earth right now, is it the same in every point in the universe just that the information hasn’t got to us, and why aren’t the stars moving apart across the plane of view, surely the expansion should be 3 dimensional? And not just in the line of sight.


I can try...

When you look further out into the universe, you are looking closer and closer to the "beginning." Galaxies appear less organized, smaller and more of them. Incidentally, distance is measured by "redshift." The further away a galaxy is, the redder the galaxy appears due to the doppler effect.

Conversely, of course, nearer galaxies are less red shifted and more organized.

What's happening at the "edge" of the universe? No one knows. Essentially, the earliest moments of the big bang - that moment of inflation in which the universe expanded faster than the speed of light - likely set the geometry of the universe and thus is beyond our visible horizon.

Our current understanding of the accelerated expansion of the universe results from studies involving Type 1A supernovae. They are a "standard candle" for cosmic distances since their particular mechanism allows them to brighten to a standard brightness. Kind of like using a 100W lightbulb to judge distance in a football field. Now this tells us that, taking all other considerations into account, then galaxies at certain redshifts should have Type 1A supernovae at a certain brightness. However, it was discovered that they were actually dimmer than they should be. And that the distribution was not the expected power-over-time distribution but showed a sharp increase several billion years after the big bang (as denoted by the CMB, by the way).

In answer to your question, yes, the universe is expanding around us even now. And studies done take samples from all over the sky so basically in all four dimensions. What is not known (but is theorized) is what is causing that expansion to accelerate. Also what is not known is the final fate of our universe, although that too is theorized. As for what the universe is expanding "into," again, not known. It's not an illegitimate question. It's just not clear how we would be able to observe it.

Locally, gravity still holds sway. So gravity still holds our galaxy together and even pulls together the local group. However, on cosmological scales, the average expansion direction is outward.

Hope that clears it up.
 stargazer1000
Joined: 1/16/2008
Msg: 71
how is the universe expanding?
Posted: 1/18/2010 6:24:49 AM

What I am after is an explanation of how you know 13 billion light years away/ago that the universe is not only still expanding but accelerating when that information hasn’t got here yet?


Well, the fact that the information hasn't reached us yet is one reason.

Furthermore, the fact that you're looking further out into the universe means you're also looking "backward" in time. And the fact that cosmologists have discovered that the more contemporaneous galaxies within, for instance, the nearest 50 million light years is moving faster than galaxies in the past, say 3 billion years after the big bang.


Just because it was expanding faster in the past doesn’t mean that it is expanding anymore. Look at the facts, early universe, fast expansion, the older it gets the slower the expansion rate…so why say that it is getting faster?


That's not a fact, that's an assumption. Again, the evidence indicates that, in fact that the expansion has speeded up (independently verified by different teams of cosmologists, by the way). The evidence is the redshift detected from Type 1A supernovae being dimmer than they should be. Why it's expanding faster is an area of investigation.


Ok if I was born on a planet 13 billion light years away (still inside this big bang) and looked deep into space at where Earth should be, would I see expansion of the universe faster than the speed of light, if I can why can’t I see Andromeda flying away from us near to the speed of light now on Earth?


If the expansion was occurring faster than the speed of light, then you wouldn't be able to see anything. It would be outside your visual range.

As for Andromeda, it's part of the local group and only 2 million light years away and actually getting closer. Again, in the local group, distances are close enough that cosmological expansion is overcome by local gravity. However, looking beyond the local group and cosmological expansion is the primary thing you're going to observe.


Conversely when on the planet, are all the other planets rushing away from me faster than the speed of light or will there be no expansion except over distance/time away from me? If so is this the same at every point instantaneously across the universe? In which case the universe is not expanding today but was in the past.


All the other planets in our solar system? No. All the other planet in our galaxy? No, but we're not directly observing those planets. We're directly observing their stars. And they're bound to our galaxy by its combined gravity.

Does the universe exist contemporaneously to us? Of course. However, we're constrained on the information we can get about it by the speed of light. Even the information from your computer screen is delayed by a femtosecond or two. And the observations to date indicate that the universe not only continues to expand but has accelerated.

Is it possible that all expansion of the universe has stopped? Hypothetically. But look at the problem with that. Something would have to act to stop all expansion that, at one point speeded up, all at once. Or, at the very least, move across the universe at the speed of light, since that is the fundamental speed constraint within our universe. But since we have no observational evidence for such a force, and there would be evidence of it, unless is started in the past million years, it would be pure conjecture. A "what if" thing.
 stargazer1000
Joined: 1/16/2008
Msg: 72
how is the universe expanding?
Posted: 1/18/2010 6:46:12 AM

What is happening 13 billion light years away (distance) NOW? Not 13 billion years ago but today?


Okay, and I'll try and answer as simply as possible.

Specifically? Likely the same kinds of things that are happening right now. Because the laws of the universe are, well, universal. So if you could somehow sidestep that pesky whole "nothing travels faster than light" rule, you would likely see galaxies and planets much as they would appear. However, since it's 13 billion light years away, we can't view "now" there. We can only observe "then" there.
 JustDukky
Joined: 7/8/2004
Msg: 73
how is the universe expanding?
Posted: 1/18/2010 6:52:57 AM
13 billion light years ago (time) the universe was expanding near to the speed of light.

...or perhaps much faster.

What is happening 13 billion light years away (distance) NOW? Not 13 billion years ago but today?

It's impossible to know...the information won't reach here for 13 billion years....I'll probably be retired by then and more concerned about the expansion of my gut.
 stargazer1000
Joined: 1/16/2008
Msg: 74
how is the universe expanding?
Posted: 1/18/2010 6:56:23 AM

Exactly, so how can you claim that the universe is still expanding today? when all you have is information from the past.


Conversely and hypothetically, how can one propose the universe isn't still expanding since you haven't seen any evidence for it having stopped? Additionally, since we already have evidence for expansion occurring, can you come up with a reasonably plausible mechanism for it stopping?
 stargazer1000
Joined: 1/16/2008
Msg: 75
how is the universe expanding?
Posted: 1/18/2010 7:24:40 AM

Exactly, you cannot say either way, only by making observations on what is going on around you today can you say. All we can say is that as universal time goes by the rate of expansion gets smaller or as you look back in time so it gets faster.


So what you're seeing is that we're not seeing the effects of the big bang "now" so...what? All cosmological scale structures in the universe have stopped expanding why? How? Without actual observational evidence to back that conjecture, that's all it is. Conjecture.

You see, the power graph shows an acceleration at a point AFTER the big bang. So, at some point, something in the universe hit the accelerator pedal. Consequently, the overall evolution of the universe is expansion from a single event, accelerating to close to present day...or at least within the last 10 million years or so. Again, without actual observational evidence to the contrary, then it really is a non-issue.

Also, to further boggle the mind, the actual expansion of the universe in the first few nanoseconds actually exceeded the speed of light and may even be continuing. Again, not a violation of the laws of physics for within the universe since it is the entire universe we're talking about.
 stargazer1000
Joined: 1/16/2008
Msg: 76
how is the universe expanding?
Posted: 1/18/2010 7:45:49 AM

What? not sure if I understand what you just said. We can see the big bang now as it happened 13 billion light years ago because we are 13 billion light years away (in fact at any point in the universe we would be 13 billion light years away, hence a singularity). So what, well it shows the universe expansion is slowing down, if it was accelerating then the hubble constant would have a - sign in front of it and as the universe started off at +SoL accelerating would give up a reading of?


Um...no.

You are missing a significant point, specifically, that the acceleration began AFTER the big bang. So, in fact, the evidence is quite the opposite of what you're proposing. And, since this is from the cosmologists themselves, I'm going to take their word on it.

Unless you've actually had some telescope time on Keck, Gemini or the Hubble you haven't told us about. And have some actual observations that you'd like to share. Otherwise, as far as I can tell, you're playing word games to justify a notion that you like over the actual science. Nothing more.
 stargazer1000
Joined: 1/16/2008
Msg: 77
how is the universe expanding?
Posted: 1/18/2010 8:04:08 AM

This is the whole point, where are you getting that it is accelerating


Ask a cosmologist. They have better data. However, since the cosmologists doing the science say that evidence exists for an accelerating universe, I'll go with it.

Hey, this seems to be your opportunity to prove your point. You're the one insisting the universe is slowing down. Why don't you fill in those numbers to prove your point?


there was nothing before the big bang!?!


That's a separate question.
 stargazer1000
Joined: 1/16/2008
Msg: 78
how is the universe expanding?
Posted: 1/18/2010 8:32:47 AM

Actually NO, all I was asking was can anyone explain how they come to the conclusion that the universe is accelerating. If they can then I all well and good, so far, not so good. I am not insisting that it is slowing down, just want to know how people come to the conclusion that it is accelerating. If there's plenty of evidence at least throw me a bone here.


Or is it that you don't understand how the evidence was derived? Because I tried to explain it with the references to Type 1A supernovae which is the phenomenon was observed.


So why mention it then? significant point you said?


I don't recall mentioning no "before" but if you can give me the direct quote, I'll certainly try to address it.
 stargazer1000
Joined: 1/16/2008
Msg: 79
how is the universe expanding?
Posted: 1/18/2010 9:46:30 AM
All they are doing is getting a fix on distances, as you rightly said, redshift also does this. However, how do you go from knowing how far away and how old it is to concluding that the universe is expanding.


Okay, let's try this again. What causes doppler shift? Does the pitch of a car's engine change when it's standing still? No? Why?

Yes, redshift is used as a distance scale. However, we would not have redshift if the universe were static. What is measured is the rate of expansion. And what was found was that the power rate was not constant but had an increase at a set time back in the earlier universe.

Since Type 1A supernovae were found to be dimmer than they should have at that point, it means that something else is in play. Again, an acceleration.

Frankly, I don't understand the problem you're having with this. The science is sound. What stake do you have in a non-expanding, non-accelerating universe?


No you do not have to directly say something to make an implication. We can only ever be talking about AFTER the big bang because there is no before, why say acceleration is after the big bang...everything happened after the big bang because...there was no before.


If it was not said, then it is not part of the discussion. What you choose to infer from statements I made is irrelevant to the discussion at hand. However, since we don't have any information about a 'before' of the big bang, we can make no statements about it either way.

And since we are talking about this universe and this universe exists as the result of a 'big bang,' then how else might we refer to cosmic evolution since then?


Let me just ask you one more question...
Given that the radius size of the observable universe at 14gpc, won’t that make the ‘expansion rate’ at 10,388,000 km per sec? about 34x faster than the speed of light?


A good one to ask that question to would be Bob Berman of Astronomy Magazine. Not being a mathematician, I really cannot answer that effectively without considerably more research.

However, since the "edge" of the universe has likely left our observable frame of reference since it exceeded the speed of light, how much it does is not a question anyone can answer.

 stargazer1000
Joined: 1/16/2008
Msg: 80
how is the universe expanding?
Posted: 1/18/2010 9:59:51 AM

No but it does change pitch as it is comming towards me, so why did it stop 2 billion years ago.


Which is not what the science is saying. Hence the use of the word "accelerating."


Why do you think there is aome agenda here? just want to know how people are ariving at these conclusions


Observation with really big telescopes.
 stargazer1000
Joined: 1/16/2008
Msg: 81
how is the universe expanding?
Posted: 1/18/2010 10:19:57 AM


Which is not what the science is saying.


yes it is.


No, it's what you think it should say.


So no real fact to present to back up your contention.


Sadly, my telescope is a very limited 8" Schmidt-Cassegrain so is not up to the standards of say 10-metre Keck where these observations are being made. And since I'm not a cosmologist, I'm going to go with what they have to say on the subject. But hey, the information is there if you are inclined to actually look.

Of course, if you think you know more than what actual cosmologists who actually do the science, then more power to you. Have fun.
 stargazer1000
Joined: 1/16/2008
Msg: 82
how is the universe expanding?
Posted: 1/18/2010 10:48:31 AM

I have but sadly they tend to avoid the real questions and no I do not know more, I am asking questions if you haven't spotted it, not giving answers.


They give the answers they can based on what they have. Now, whether or not you are willing to accept their answers is quite another matter. However, let's look again at this:


Given that the radius size of the observable universe at 14gpc, won’t that make the ‘expansion rate’ at 10,388,000 km per sec? about 34x faster than the speed of light?


Where did you get that number? 14 billion parsecs? That's over 40 billion light years in radius. Or did you mean diameter? Maybe that is a problem with your math right there.

But hey, don't take my word for it. Try contacting these guys:

http://www.cfa.harvard.edu/supernova//HighZ.html
 stargazer1000
Joined: 1/16/2008
Msg: 83
how is the universe expanding?
Posted: 1/18/2010 12:12:31 PM
Well andy, if you don't think I "know what I'm talking about," perhaps I'll leave you to find your own answers. Unless, of course, you attempting to bait an entire debate on the legitimacy of modern physics, cosmology, astronomy, astrophysics, etc.

I mean, I could attempt to talk about cosmological scale, etc., but apparently my 30 years of actually studying astronomy is not up to your particular standard. What actually constitutes an "answer" to you remains to be seen.

Not that you've offered any of your own. Hey, questions are fine. But I notice that you don't actually offer any real information of your own to counter the argument. Like evidence for a "slowing" universe, especially after I offered you the current state of understanding regarding an accelerating universe.
 stargazer1000
Joined: 1/16/2008
Msg: 84
how is the universe expanding?
Posted: 1/18/2010 12:18:14 PM
WHY can't there just be vacum, or nothing? And, it being a vacum, how can nothing expand? Unless you mean that the physical objects are going further apart. If that is the case, than all that if happening is that they are re-arranging themselves further apart from each other.


Indeed, space is a vacuum. However, spacetime itself the physical underpinning of how the universe is structured. It's why you get things like gravity waves and frame dragging. The former has yet to be observed. Preliminary data from Gravity Probe B has detected the second geodetic effect. It also effects the orbit of Mercury and high-density objects like binary pulsars, for instance.
 stargazer1000
Joined: 1/16/2008
Msg: 85
how is the universe expanding?
Posted: 1/18/2010 12:22:45 PM

I don't recall mentioning that you don't "know what I'm talking about," but if you can give me the direct quote, I'll certainly try to address it.


Okay.


But you are right I do need to talk to someone who does know what they are talking about!


Hmmm....
 stargazer1000
Joined: 1/16/2008
Msg: 86
how is the universe expanding?
Posted: 1/18/2010 12:53:30 PM

I think that we can agree that space is a vacum, or just plain simply put, nothing. I think the problem is the definition of "expanding". Nothing can't expand, since there is nothing to expand, so what leaves you with is the re-location of the stars, planets, space gas, etc, further apart from each other.

Sometimes the simplest answer is correct. I think that too many people are trying to apply too many theories that have yet to be full explainded or observed.


So Einstein was wrong, then, was he? And every experiment proving the bending of spacetime from Eddington onward is wrong too? Hmmm.... Interesting.
 stargazer1000
Joined: 1/16/2008
Msg: 87
how is the universe expanding?
Posted: 1/18/2010 1:47:50 PM

And, correct me if I am wrong, but the whole discussion of space is mostly theoretical, is it not? If so, how can one come to exact conclusions?


Well, again, we could get into the distinction from laymen's understanding of the word "theory" versus the actual meaning of the word, but that's been done to death.

As for conclusions....it's a little thing called evidence. Hence, my references to Eddington, Gravity Probe B, Mercury, etc.


However, if there is nothing, that is different than the bending of spacetime


Is it? Why? Why isn't spacetime a "thing" unto itself?
 CountIbli
Joined: 6/1/2005
Msg: 88
how is the universe expanding?
Posted: 1/18/2010 1:48:07 PM
I haven't read all the replies but it looks like this thread got derailed very quickly. The question was what the universe is expanding into. To answer this we need to step back a little to get some mathematics involved (I'll try to make it as painless as possible). Warning: This response is almost as long as a typical post by Scorpionmover

Let's start simple with two points, A and B, on a line. The distance between them is just |B-A|, where | | is the absolute value. This definition doesn't work so well when we get into 3 dimensions, so we can modify it somewhat. Let's suppose we have two points A(x, y, z) and B(t, u, v). The distance between them is sqrt[(x-t)^2 + (y-u)^2 + (z-v)^2], where sqrt means square root. This reduces to the previous expression in one dimension, so we haven't fundamentally changed the definition of distance.

We can further generalize this definition of distance by introducing some coefficients.

d=sqrt[a(x-t)^2 + b(y-u)^2 + c(z-v)^2]

Why would we introduce these coefficients? For one thing, if we're using a coordinate system besides the Cartesian coordinate system (for example spherical coordinates where we have a distance, a latitude, and a longitude) we have to introduce these coordinates in order to get consistent results across different coordinate systems. Obviously the choice of coordinate system shouldn't change distance.

We can generalize even further by allowing cross terms into the definition of distance. For example there might be a term like f(x-v)^2 in that sqrt operation.

We can collect all these coefficients into a special matrix called the metric tensor. This metric tensor is crucial for the mathematics of General Relativity. The metric tensor basically tells us how to define distance. GR contains two rather nifty generalizations of this metric tensor. First of all, the coefficients can be functions of position so that the very definition of distance depends on where you are in the universe. This is basically what is meant by non-Euclidean geometry. Second of all, GR takes place in 4 dimensions, with the fourth dimension being time.

GR consists of a complicated mathematical relationship between this metric tensor and the amount of energy/matter present. From a physical standpoint this metric tensor represents gravity. But the metric tensor also tells us what distance is.

So finally we can answer the OP. Asking what the universe is expanding into is a meaningless question. I think the question probably comes from thinking about expansion like a balloon blowing up (a common analogy, but one that is horribly misleading). The universe is not expanding like a balloon, which needs to expand into something. Instead, the very definition of distance is changing over time.

On the question of extragalactic redshift, this has nothing to do with the Doppler effect. This is because the galaxies are not moving away from each other. Remember, the universe itself is not getting bigger and carrying galaxies with it (they are not like dots on the surface of a balloon). What's happening is that the very definition of distance between galaxies is changing. The extragalactic redshift is a gravitational effect not a Doppler effect. Caveat: there are small local motions that the galaxies undergo which cause Doppler shifting (which can be redshift or blueshift), but this is separate from the extragalctic redshift.

Hopefully this clears things up for those who managed to make it to the end.
 stargazer1000
Joined: 1/16/2008
Msg: 89
how is the universe expanding?
Posted: 1/18/2010 1:54:56 PM

On the question of extragalactic redshift, this has nothing to do with the Doppler effect. This is because the galaxies are not moving away from each other. Remember, the universe itself is not getting bigger and carrying galaxies with it (they are not like dots on the surface of a balloon). What's happening is that the very definition of distance between galaxies is changing. The extragalactic redshift is a gravitational effect not a Doppler effect. Caveat: there are small local motions that the galaxies undergo which cause Doppler shifting (which can be redshift or blueshift), but this is separate from the extragalctic redshift.


Except....we are talking expansion of spacetime between galaxies which is spreading the wavelength of light between two points spreading apart. The term Doppler shift is commonly used by cosmologists. Are you saying they're wrong in the name of the very tool they use?

As for what the universe is expanding "into," again, there are cosmologists who are asking that very question and trying to find answers. Then there are those who are looking into possible "collision" points between our universe and, perhaps neighbouring universes.

So what am I missing?
 CountIbli
Joined: 6/1/2005
Msg: 90
how is the universe expanding?
Posted: 1/19/2010 4:46:45 PM


Except....we are talking expansion of spacetime between galaxies which is spreading the wavelength of light between two points spreading apart. The term Doppler shift is commonly used by cosmologists. Are you saying they're wrong in the name of the very tool they use?


The short answer: Yes. Longer answer: http://scienceblogs.com/interactions/2007/03/redshift_basic_concepts.php



As for what the universe is expanding "into," again, there are cosmologists who are asking that very question and trying to find answers. Then there are those who are looking into possible "collision" points between our universe and, perhaps neighbouring universes.

So what am I missing?


Until we find one of these other universes all they're talking about is science fiction.
 stargazer1000
Joined: 1/16/2008
Msg: 91
how is the universe expanding?
Posted: 1/19/2010 5:17:48 PM

The short answer: Yes. Longer answer: http://scienceblogs.com/interactions/2007/03/redshift_basic_concepts.php


Well Count, after some additional research, I stand corrected. Thank you.

Actually, I am curious to know what your degree is in. Are you working in this field, related or just an area of interest?


Until we find one of these other universes all they're talking about is science fiction.


Certainly more in the realm of conjecture, however, one that many are taking it seriously which is why they are actively looking for some kind of theoretical model that can serve as a basis for experiment/observation to find 'em.
 CountIbli
Joined: 6/1/2005
Msg: 92
how is the universe expanding?
Posted: 1/20/2010 12:17:18 AM


Actually, I am curious to know what your degree is in. Are you working in this field, related or just an area of interest?


I have a BS in physics and a MS in mathematics, but I've never worked in those fields. The jobs just weren't there when I graduated and 15 years later my degrees aren't worth the paper they're written on.
 JustDukky
Joined: 7/8/2004
Msg: 93
how is the universe expanding?
Posted: 1/20/2010 4:25:29 AM
Did you go into math/physics for a job...or because you loved it? I suspect the latter, simply because it appears you've "kept up" and haven't forgotten everything. If you didn't enjoy it, you probably would have forgotten. Still, I noted a bit of disparagement in your post, so I thought I'd drop a couple of trite comments that appear to apply:


I've never worked in those fields.

If you do what you love, you'll never work a day in your life.

15 years later my degrees aren't worth the paper they're written on.

If they are important to you, who cares what anybody else thinks they are worth?

The basest of all treasures is money. It isn't worth the paper it's printed on, but everyone seems to value it. If nobody else values your degree, it's because money can't buy it. Its value can't be exchanged and must stay with you. The treasure is yours to keep.

Now have a beer & kill a few brain cells... It always works for me...
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