Question regarding theory on accelerating universe

[Paul98]

well if we can see how fast different parts of the universe move at different times. We can plot them and see distance, velocity, and time. If the line tilts in one direction the universe is accelerating, in the other direction decelerating, and nether way the universe would be expanding at a constant rate.

 

[Biftheunderstudy]

Indeed, since we can look at the universe at different times by looking at galaxies that are farther and farther away, we can estimate the cosmological constant at that time. Thus, we don't have an estimate of the constant for only 100 years, but rather, billions of years.

 

[DrPizza]

Well if it's something we cannot know then WTF are people winning a Nobel Prize over it? It doesn't make sense.

The argument you're making is akin to saying this: "so, that astrophysicist got a Nobel prize for proving that life exists on a planet 85 light years away. Well, all he did is prove that life used to exist on that planet 85 years ago. For all we know, they could have destroyed their planet by now."

 

[William Gaatjes]

@William Gaatjes
What's going on in or on the sun that could affect the light we receive from Supernova that are nearby compared to those that are far away? Or the baryonic acoustic oscillations in the power spectrum of the CMB? Or gravitational lensing of galaxy clusters?

There is a lot of evidence, its kind of far fetched that something in the sun is affecting such different measurements to the exact same conclusion.

Well, i am not writing that the many selected measurements providing evidence for the expanding universe theory is an effect of the activity of the sun. What i do am thinking, is that i would not be surprised if within the measurements , there would be an influence that for example in the measured acceleration there would be a variance. Perhaps this is already compensated for , i do not know. I am just thinking that there might be some refraction and maybe even redshift & blueshift going on, on the border of the solar system. I am wondering if it will ever be possible to do such research. That is if it is ever possible to do such a large scale project that it would take at least 2 solar cycles (2 * 11 years). And then we would also have to take into account the delay because of traveling time and c. Perhaps it is possible to predict it with a computer simulation (magnetohydrodynamics) with various amounts of solar activity.

 

[Daedalus685]

Knowbody knows.

Well we don't know if there is anything 'outside' of space in the sense that the universe is a more complicated structure than what we currently can observe.

However, Dari is asking if space is expanding, which it is. There need not be any higher structure to the universe for the expansion to be happening.

The expansion even changes the orbit of the earth and the sun, there is what we would perceive as a pressure between all objects proportional to the space between them. This effect is far too small to currently measure on small scales though, but can be shown pretty well on larger scales.

 

[William Gaatjes]

Well we don't know if there is anything 'outside' of space in the sense that the universe is a more complicated structure than what we currently can observe.

However, Dari is asking if space is expanding, which it is. There need not be any higher structure to the universe for the expansion to be happening.

The expansion even changes the orbit of the earth and the sun, there is what we would perceive as a pressure between all objects proportional to the space between them. This effect is far too small to currently measure on small scales though, but can be shown pretty well on larger scales.

For a thorough understanding, we must repeat all experiments and recheck all laws of nature with current technology. I would not be surprised if something would turn up that would have a devastating effect on current theories and so called facts. Since we are inside a solar system ,we must first thoroughly research to understand what is going on here in our solar system and what effects it has on our measurements. That means long measurements over time. We will always experience what is going on in our solar system more stronger then what is going on light years away. Even if it is a incredibly huge event. I am not writing that there is nothing going on outside our solar system. I am writing that i doubt that the effects of our own solar system, that these effects are not always calculated into the measurements we find and the results we find and into the conclusions that we draw from those results. There are still a lot of assumptions made, also today as we speak. Prejudice. Lose the prejudice first to understand the universe. Learn to control that common human instinct. It is needed to be able to start, as a kickstart so to say. But after that a feedback mechanism is much more beneficial then a ballistic mindset.

 

[Dari]

The argument you're making is akin to saying this: "so, that astrophysicist got a Nobel prize for proving that life exists on a planet 85 light years away. Well, all he did is prove that life used to exist on that planet 85 years ago. For all we know, they could have destroyed their planet by now."

False. Astrophysicists are saying that the Universe is expanding NOW, not billions of years ago. The latter is factually correct while the former is speculative at best because it is impossible to know.

 

[Evadman]

False. Astrophysicists are saying that the Universe is expanding NOW, not billions of years ago. The latter is factually correct while the former is speculative at best because it is impossible to know.

You make my head hurt. Unless the cosmological constant changed, the universe is still expanding. If the cosmological constant changed, we won't know for a huge amount of time in the future by comparing gathered data over millions of years.

Is it possible that the cosmological constant changed? Yes. Is it likely knowing what we know now? No. The great thing about science is that the theory will be tested using new hypothesis's forever. If the theory doesn't hold up, the theory is modified. That 'flexibility' is the foundation of science.

 

[Dari]

You make my head hurt. Unless the cosmological constant changed, the universe is still expanding. If the cosmological constant changed, we won't know for a huge amount of time in the future by comparing gathered data over millions of years.

Is it possible that the cosmological constant changed? Yes. Is it likely knowing what we know now? No. The great thing about science is that the theory will be tested using new hypothesis's forever. If the theory doesn't hold up, the theory is modified. That 'flexibility' is the foundation of science.

How do I make your head hurt if you are basically repeating what I said? None of these events are a surety. My main point still stand in that the measurements are for events that occurred billions of years ago, not today. Therefore, it is not correct to say that the universe is expanding. It is correct to say that the universe was expanding billions of years ago and it may be expanding today but we don't know. Why is it so difficult to say this?

 

[pw38]

How do I make your head hurt if you are basically repeating what I said? None of these events are a surety. My main point still stand in that the measurements are for events that occurred billions of years ago, not today. Therefore, it is not correct to say that the universe is expanding. It is correct to say that the universe was expanding billions of years ago and it may be expanding today but we don't know. Why is it so difficult to say this?

I think you're trying to win an un-winnable argument and I don't really understand why. If the smartest cosmologists and astrophysicists can't satisfy you with an answer that you will accept why on Earth would you expect anything different on some random technology board? We've already answered your question numerous times but you won't accept it.

The issue is an error in assumption on your part. You assumed they "know" or have said they know when in fact it's never said for sure that anyone knows. It's assumed as such because of how we understand math and physics. No more, no less.

edit

Also, think about it like this. We can measure galaxies millions and billions of light years away. We can measure phenomenon within those galaxies that happened millions and billions of years ago. As the same phenomenon happen in our galaxy and the resultant measurements yield the same results for those stars much much closer to us it can be assumed with a high degree of certainty that what was happening back then is still happening now. The simple fact that as gravity has less of an effect on each galaxy there's no doubt that they're speeding away from each other at faster and faster speeds. To believe otherwise requires a bigger leap in logic than the one you're proposing is being use in this case.

 

[Dari]

I think you're trying to win an un-winnable argument and I don't really understand why. If the smartest cosmologists and astrophysicists can't satisfy you with an answer that you will accept why on Earth would you expect anything different on some random technology board? We've already answered your question numerous times but you won't accept it.

The issue is an error in assumption on your part. You assumed they "know" or have said they know when in fact it's never said for sure that anyone knows. It's assumed as such because of how we understand math and physics. No more, no less.

edit

Also, think about it like this. We can measure galaxies millions and billions of light years away. We can measure phenomenon within those galaxies that happened millions and billions of years ago. As the same phenomenon happen in our galaxy and the resultant measurements yield the same results for those stars much much closer to us it can be assumed with a high degree of certainty that what was happening back then is still happening now. The simple fact that as gravity has less of an effect on each galaxy there's no doubt that they're speeding away from each other at faster and faster speeds. To believe otherwise requires a bigger leap in logic than the one you're proposing is being use in this case.

Bigger leap, huh?
http://www.bbc.co.uk/news/science-environment-15791236

How's that for a bigger leap? Goes to show that your fundamental assumptions can be wrong.

 

[silverpig]

There is no conflict between an expanding universe and the big bang theory, that same theory was used, rather, to model the expanding universe.

An accelerating universe was, in part, predicted by Einstein with the inclusion of a cosmological constant in his theory of general relativity (which he then retracted due to his personal beliefs that the universe should be static).

No one likes the idea of dark matter or dark energy, but they are ways of trying to understand cosmology without having to know the exact details of the composition.

Actually I think it was the other way around. He included the constant to make the universe static (otherwise it should collapse in on itself due to gravity). Once Hubble found that the universe was expanding, Einstein retracted the constant.

 

[silverpig]

False. Astrophysicists are saying that the Universe is expanding NOW, not billions of years ago. The latter is factually correct while the former is speculative at best because it is impossible to know.

By that logic it is impossible to say that the sun exists NOW. All you can say is it existed 8 minutes ago and "we'll see what happens"...

 

[Dari]

By that logic it is impossible to say that the sun exists NOW. All you can say is it existed 8 minutes ago and "we'll see what happens"...

That is true as well. But comparing 8 minutes to billions of years is ridiculous from a pragmatic point of view. Also, thankfully, we have other means to determine the existence of the sun, mainly gravity, which may or may not be instantaneous (I don't know). But determining whether or not the universe is expanding is dependent upon information that is billions of years old (not 8 minutes) and theory that was just formulated within the last 100 years.

 

[pw38]

Bigger leap, huh?
http://www.bbc.co.uk/news/science-environment-15791236

How's that for a bigger leap? Goes to show that your fundamental assumptions can be wrong.

Did you not read the very first sentence in the article? I guess whatever allows you to ignore what everyone else has told you so far though. Have fun, I really can't keep repeating what we've already told you.

 

[Dari]

Did you not read the very first sentence in the article? I guess whatever allows you to ignore what everyone else has told you so far though. Have fun, I really can't keep repeating what we've already told you.

The team which found that neutrinos may travel faster than light has carried out an improved version of their experiment - and confirmed the result.

What is your point?

 

[Biftheunderstudy]

Actually I think it was the other way around. He included the constant to make the universe static (otherwise it should collapse in on itself due to gravity). Once Hubble found that the universe was expanding, Einstein retracted the constant.

Ooops, my bad. This is actually what I meant, but I see from my post that I actually typed the opposite

 

[pw38]

What is your point?

It awaits independent confirmation. Fermilab is going to run the experiment next year. If they find the same results, then well, we might be onto something.

Regardless, you're still arguing a point that although pretty certain, can't obviously be totally confirmed and you're wanting to know how they are so certain while not understanding that they are never certain. That's the beauty of the scientific process. What we go with as accepted theory, if proven wrong, will be swept aside and new theory generated and tested. Why argue such a minute point? Just because you disagree with it? Well, congrats to you. Run some experiments yourself and give us a working theory on why you disagree. Otherwise it just seems you're wanting to argue for arguments sake.

 

[Onceler]

The universe burst forth faster than the speed of light then slowed and now is moving faster than it was when it was slowed.