The universe is expanding exponentially

[gib65]

I read at the following site:

 

http://www.pbs.org/wgbh/nova/elegant/view-glashow.html

 

that the universe is not only expanding but doing so at an accelerated rate! We're expanding FASTER as time goes on. Is this true? What kind of force is behind this acceleration? What will become of the universe?

 

PS - Scroll down to "Towards a unified field theory" in the link above where this is mentioned.

[ecoli]

wow, that guy really does not like the idea of a unified theory of everything.

[akahenaton]

wow, that guy really does not like the idea of a unified theory of everything.

 

 

which guy?

[CanadaAotS]

It isn't entirely unable to be proven, arent they looking for sparticles or something?

[[Tycho?]]

Yes, the universe is expanding at an accelerated rate. Nobody has a good reason why. The mysterious force causing this is called "dark energy" or sometimes the cosmological constant, and old relic of Einstiens original General Relativity equations. He added this constant so that a static universe would be possible. Once it was observed the universe was not static, he scrapped it.

[ecoli]

which guy?

Sheldon Glashow, they guy with whom the interview is with.

 

he says “I simply can’t imagine why any sane person would imagine, discuss, or mention, except insultingly, the concept of a theory of everything. It's a stupidity."

 

Was it not obvious who I meant?

[Severian]

I think I agree with everything that Glashow said in that interview (except for the bit about us 'proper' physicists being too old for the LHC).

[Mart]

We have no information about what the universe is doing except locally. Therefore to say it is expanding (or not) has no basis in observation.

[RoyLennigan]

We have no information about what the universe is doing except locally. Therefore to say it is[/b'] expanding (or not) has no basis in observation.

the basis of observation is that the redshift from radiation at the edge of the universe is increasing. that means that it is getting farther and farther away. actually, everything at a substantial distance is showing an increase in redshift, leading scientists to theorize that the distance between all objects in the universe is increasing.

[Mart]

Originally Posted by RoyLennigan

the basis of observation is that the redshift from radiation at the edge of the universe is increasing.

That radiation is fossil radiation. It tells us zilch about what is happening at "the edge of the universe" : it only tells us what was happening.

[bascule]

We have no information about what the universe is doing except locally. Therefore to say it is[/b'] expanding (or not) has no basis in observation.

 

I've never seen a hippopotamus. Therefore they don't exist.

 

That's some nice logic you have there.

[cpwmatthews]

How do we know the Universe is expanding and getting faster if we cannot see the edge of the Universe? That is presuming there is an edge to what could possibly be infinity; should that be possible.Are our planets getting further apart? Is the Universe expanding like an elastic band (faster at the end where motion is generated and slower at the other? Is our planet at the centre of the Universe? If not, who is to say that expantion is occuring uniformly everywhere in the Cosmos<

[Mart]

Originally Posted by bascule

I've never seen a hippopotamus. Therefore they don't exist.

That's your logic - not mine.

My point is that without evidence we can only assume that the present state of (distant) events is like their past states. This may or may not be a reasonable assumption.

If, many aeons ago, you had been a small insignificant mammal and some smart alec had said "I've never seen a hippopotamus. Therefore they don't exist." what would you have said?

[CanadaAotS]

"Can you eat one?" perhaps...

Then the other guy'd be like "But they dont exist... I am hungry though"

 

lol

[Locrian]

My point is that without evidence we can only assume[/i'] that the present state of (distant) events is like their past states. This may or may not be a reasonable assumption.

 

Of course it is. The primary evidence was observations of type Ia supernovae at various distances. These observations combined with the redshifting of the light demonstrate a difference in velocity based on distance and time. The results show very consistent patterns over time. To suggest that we cannot assume this pattern continues today is to suggest that the universe operated under very straight forward laws for billions of years and then suddenly stopped and is operating under different ones, for no reason.

[Mart]

Originally Posted by Locrian

to suggest that the universe operated under very straight forward laws for billions of years and then suddenly stopped and is operating under different ones

That's your suggestion - not mine.

Conditions change. Quasars are generally agreed to be very distant objects. But that is unlikely to be true. They were very distant objects. They existed at a certain time and then vanished - like dinosaurs - leaving just a fossil EM record.

To establish the constancy of a redshift at a given distance would require observations over a long period of time. Even then it would only serve to establish that the redshift had - in the past - remained constant.

[Locrian]

That's your suggestion - not mine.

 

No. Your suggestion is that our observations over a great deal of time have demonstrated that there is a pattern over a long period of time even up until recently, and yet we cannot assume that it is ongoing. This is the only interpretation that can be made from your posts.

 

To establish the constancy of a redshift at a given distance would require observations over a long period of time.

 

And all that requires it to view at farther distances. Since we have made observations at high distances - and that is what the study on supernovae was about, determining distances - we have also made observations over long periods of time.

[Mart]

Originally posted by Locrian

This is the only interpretation that can be made from your posts.

Let's try a little humility here. This is the only interpretation that you can make from my posts. I must have presented my ideas poorly.

Let's see if this helps. All data from the universe takes time to arrive on our doorstep. What this means is that the picture we have of the universe is "out of date" in the sense that events that appear to be happening have already happened. Nevertheless, we act as if they are happening now - that's their now. This is because as terrestrial creatures living our lives on a small scale we have had no practical need to take into account the time it takes for EM info to reach us. Hence our perceptual map is strongly biological and resists change and it is only relatively recently that it has been challenged by our conceptual maps.

Consequently, we are sorrounded by a perceptual map - which we call the universe - which strongly influences the way we conceptualise the universe. In short, it isn't like it looks to be! For example, there aren't quasars now in the universe - they're long gone - but their footprints still inform us to their previous existance. To speak of them as existing in the distance is OK as poetry but not as a reasoned account of their current existance.

The same goes for redshifts. If N-billion years ago the universe was thought to be expanding at a certain rate N (because data from that time supports that interpretation) it would be premature to assume that for the rest of time N would remain constant. And we have evidence that the rate of expansion decreases with time. Events from M-billion (M<N) years ago show redshifts which are less than the N-rate.

The above may not be crazy enough to be useful.

[Locrian]

If N-billion years ago the universe was thought to be expanding at a certain rate N (because data from that time supports that interpretation) it would be premature to assume that for the rest of time N would remain constant.

 

Firstly, no one suggests that N is constant. That's what this entire thread is about. You've said this a couple of times now and it doesn't make any sense.

 

All data from the universe takes time to arrive on our doorstep. What this means is that the picture we have of the universe is "out of date" in the sense that events that appear to be happening have already happened. Nevertheless, we act as if they are happening now - that's their[/i'] now.

 

No we aren't. By taking data at various distances we are taking data at various times. By taking data at ever smaller distances we can accumulate data and then see if a function can represent that data. Of course there are ones that do, and we can use them to determine what is occuring at this time. No one assumes that what is occuring far away is still occuring; on the contrary, the whole point of the entire issue at hand (the discovery in the late 90's that the universe is accelerating) is to use how things were to predict how things are. This is something that can only be done because we are well aware that things aren't now as we see them.

 

It is possible that the real issue you have here is one with science itself. That would make for an interesting philosophical discussion, but should be had in the appropriate forum. As for the science itself, when determining the rate at which space is expanding there is really nothing outside of standard physics principles used here.

[Mart]

Originally Posted by Locrian

It is possible that the real issue you have here is one with science itself.

No. I have no issues with science as a way of understanding the universe. My point is about the interpretation of data. I don't understand how data from the past can be used to say what the present state of a system is now - that's the system's now - unless their is an assumption that the system is essentially unchanging with time. It makes no difference to me whether more accurate measurements lead to the conclusion that the universe is accelerating because my beef is with the word is. I'm quite happy with the idea that at some time in the past the universe was doing this or that. The sticking point for me is that was is not is.

[Newfie]

We have developed other constants based on observations over small periods of time and can be mathematically proven, we don't have to sit on our asses, observing something until the end of time just to prove it to be constant.

[Locrian]

I don't understand how data from the past can be used to say what the present state of a system is now[/i'] - that's the system's now - unless their is an assumption that the system is essentially unchanging with time.

 

Why would you think the assumption is that the system is unchanging with time? You said earlier that the rate of expansion was constant. You suggested before that that someone thought redshift was constant. Why do you keep bringing up arguments that no one is making? I realize you aren't arguing for these, but I don't even see how they belong in the conversation, since absolutely no one has taken up those arguments.

 

If you don't understand how the observation of a system over time can lead to predictions for the system, then you are missing very basic fundamentals of physics. Maybe even fundamentals of science. Observation, theory and prediction are all basic scientific concepts that have been employed succesfully for several hundred years now.

[Mart]

Originally Posted by Locrian

If you don't understand how the observation of a system over time can lead to predictions for the system, then you are missing very basic fundamentals of physics.

Systems can be observed over periods of time and patterns can be established. Predictions can be made. Further observation can reveal the accuracy of the predictions. These "experiments" rely on repeatability. OK?

 

I think you're confused about "observations over time". There are two times to talk about when we're observing. The first and obvious time is that spent by us observing aspects, features, happenings of the universe. So in a fifty year period we can say that we observed this, that or the other. This may be what you mean by "observation of a system over time"

 

But there is a second time involved and that is the time of origin of the data that we access. It tells us only about past patterns. For example, there were (not are) as many ancient galaxies per unit volume of space as there were (not are) less ancient ones. (I have to keep emphasing the distinction between are and were because you just don't seem to get it.) But that tells us nothing about the density of galaxies now unless we assume that the pattern persists. We must rely on the fiirst type of time to decide this. The same goes for expansion. You may bleat that there is no reason to believe that such patterns won't persist but the universe is not constrained by your reasoning. Only time and observation will decide the issue.

[Davisaurus]

I think Mart and Locian are getting a bit carried away. Suffice to say that given our limited time of observational data, we can only project time forecast theories regarding cosmology by using observations in our universe at different distances and thus different times. I don't think anyone would say this model is guaranteed to be 100% accurate. However, short of waiting around for another 14 billion years, it is the best model that we can use.

 

So Mart, We can all see you in 14 billion years, and you can tell us whether the predictions using the existing models were reasonable assumptions. Till then we can all agree that there are no other models we can reasonably use.

 

Back to the topic at hand:

 

I guess I would call myself a speculative physics geek. So when confronted with the concept with a universe expanding at an increasing rate, I began to speculate. Everyone in the science community seems to think it is some sort of exotic 'dark matter' which no one can find. I think I have a simpler solution.

 

I read back in Scientific American a few years back about theories of infinite universes. One theory describes space-time as infinite in all directions. The speculation is that local universes burst into existence like bubbles in the bottom of the pot of boiling water. Randomly throughout spacetime. This means that in any direction at a sufficient distance is another local universe expanding similar to our own. These universes exist so far away that most would die a cold death before their expansion ever brought them into contact with each other.

 

Now assume that their are huge massive UNIVERSES, not just galaxies or stars, extremely far away in every direction. The gravitational pull of these universes, because of their astronomical masses would not be negligible despite their distance. Since they exist in all directions, the net effect should be to pull our universe apart at an increasing rate in every direction. No mysterious dark matter required.

 

Comments?

[Conceptual]

The data coming from the edge of the universe, which appears to be accelerating is actually data from 13 billions years ago. It is not what is happening today. Today's data from the edge of the universe will take 13-14 billions years to reach us. What we do know for sure is that the further back into time one goes (oldest transmitted data), the more the universe was accelerating. This makes sense since the original expansion from 13 billion years ago accelerated rapidly. Data that is closer to real time, i.e., from a billion years ago, shows very little red shift, indicting the modern universe has decellerated. The imaginary fifth force should be directed to help explain the potential beyond the original expansion. The fifth force is entropy. Entropy acts, tastes, and smells like a repulsive force but is not a force in the technical sense.