The Big Rip - new evidence for it?

[Shlibby]

Bulk viscosity is a factor now claimed to support the big rip scenario. Its nearly a year old, but an intriguing story nonetheless, as detailed in the guardian:

https://www.theguardian.com/science...ang-but-with-a-big-rip-how-the-world-will-end

and for any with access, physical review online:

http://journals.aps.org/prd/abstract/10.1103/PhysRevD.91.043532

being both a sci-fi fan and (almost predictably) a layman on, I am not well versed in the technical details. But I'm interested in subjects like this. Anybody knowledgeable enough to give any summations on whether this is just a rogue theory or a new, better one that fits the evidence?

 

[phinds]

I got as far as checking the Guardian's report and it has some very seriously incorrect statements so I stopped. Could be just the reporter's lack of understanding and the science behind it may not reflect his ignorance.

 

[rootone]

The article didn't suggest to me any new evidence.
'Big rip' always has been a possible scenario as have re-collapse and heat death.
It depends on what 'dark energy' is and how it behaves in the future, nobody can honestly claim that they know.
What does seem to be the case empirically though is that the rate of expansion has varied in the past, so it's possible that it might change again.

 

[Shlibby]

Thanks for the replies. I am not well versed in the subject. The big rip scenario makes me rather depressed about the future [if only the universe cared]. Could one of the previous posters, or perhaps someone else who agrees with them, summarize why this 'new' theory is not actually good evidence for the big rip?

 

[PeterDonis]

why this 'new' theory is not actually good evidence for the big rip?

A new theory, by itself, isn't evidence for anything. The only way to get actual new evidence is to make new observations or run new experiments. If the new theory makes significantly different predictions from the current ones about some new observation or experiment that you can make, then you can test it. But I don't see anything about that in the article.

 

[Shlibby]

The article says the new theory: "refines current models by finding a more consistent way to account for a property called bulk viscosity, a measure of a fluid’s ability to expand or contract. In this case, the fluid is the universe itself" The scientists involved claim that there new theory explains the data more effectively. Its far from flawless but still, wouldn't it be considered new evidence? And, what other evidence/s, against the big rip theory, would it have to go up against?

 

[PeterDonis]

The scientists involved claim that there new theory explains the data more effectively. Its far from flawless but still, wouldn't it be considered new evidence?

No, just a new theory that purports to explain existing evidence "more effectively". Developing such things is part of science, but it's not the "evidence" part.

what other evidence/s, against the big rip theory, would it have to go up against?

It's not a matter of evidence "against" the big rip vs. other models. All of the models in this category are huge extrapolations beyond our current evidence. It's more a question of which extrapolation "feels right" in the subjective opinion of various cosmologists.

 

[PeterDonis]

Btw, it looks like a preprint of the actual paper is on arxiv:

http://arxiv.org/abs/1409.4918

 

[George Jones]

Btw, it looks like a preprint of the actual paper is on arxiv:

http://arxiv.org/abs/1409.4918

This paper is a collaboration between a mathematician and two physicists. After experiencing the media attention generated by the paper, the mathematician wrote "Reflections on Science and the Media"

http://www.disconzi.net/Research/Science-and-media.pdf

which I think is rather interesting.

 

[phinds]

This paper is a collaboration between a mathematician and two physicists. After experiencing the media attention generated by the paper, the mathematician wrote "Reflections on Science and the Media"

http://www.disconzi.net/Research/Science-and-media.pdf

which I think is rather interesting.

Indeed. A very thoughtful discussion of the intersection of actual science and pop-science reporting, with, I think, the exception that he was overly generous towards the media.

 

[rootone]

. The big rip scenario makes me rather depressed about the future...

The main alternatives aren't great either, but then this about trillions of years in the future.

 

[Shlibby]

Ok, we're making progress. :)

It would be fair to say that the guardian article exagerates the new 'evidence' for the big rip, correct?
While were at it, is there a consensus, most popular view, on the ultimate fate of the universe, and if so, why is said theory believed to make the most sense?

 

[phinds]

It would be fair to say that the guardian article exagerates the new 'evidence' for the big rip, correct?

yes

While were at it, is there a consensus, most popular view, on the ultimate fate of the universe, and if so, why is said theory believed to make the most sense?

Continued expansion leading to heat death, because that fits the current model and there is currently no evidence to the contrary.

 

[Shlibby]

Thank you; I am getting less depressed about the big rip so far :D Even in light of this new 'theory', what overall is the specific reason/s for heat death being the most likely possibility?

Also, though this might be a bit off-topic, the youtubian enlightenment revalates that Michio Kaku is enthusiastic about travel to another universe being possible for a very advanced civilization, such as humanity might be in the future (wish I could find all the videos, but has a lot to do with negative energy, wormholes and the like). What would others here say about that? Just wishful thinking, or plausible, even if far out humankind's current range?

 

[phinds]

Thank you; I am getting less depressed about the big rip so far :D Even in light of this new 'theory', what overall is the specific reason/s for heat death being the most likely possibility?

Exactly what I said. Continued accelerating expansion.

Also, though this might be a bit off-topic, the youtubian enlightenment revalates that Michio Kaku is enthusiastic about travel to another universe being possible for a very advanced civilization, such as humanity might be in the future (wish I could find all the videos, but has a lot to do with negative energy, wormholes and the like). What would others here say about that? Just wishful thinking, or plausible, even if far out humankind's current range?[/QUOTE]Kaku has been widely, and in my view deservedly, panned here for some time now due to his going way too far in his attempts to popularize science. He is not to be taken seriously.

 

[Bandersnatch]

what overall is the specific reason/s for heat death being the most likely possibility?

In the currently-favoured model of evolution of the universe, the difference between big rip and heat death depends on whether dark energy is in the form of a cosmological constant, or something that varies in time (e.g. 'quintessence'). Dark energy being the thing responsible for accelerated expansion. In both cases expansion accelerates, but in the latter case the growing (if it's growing) dark energy influence leads to gradual overcoming of local gravitational, and later intermolecular an nuclear forces (i.e., 'ripping' everything apart).

To distinguish between the two, we have to rely on observations of rates of recession of distant objects. We try to fit the models to these observations, and decide which is a better match.

As far as I'm aware of the developments in the field, there is no sufficient evidence that dark energy varies with time, but the observations relied upon are still imprecise enough to permit both explanations in principle. The steadily increasing precision of observations narrow down the possibilities towards constancy (read: the model with the cosmological constant remains a good-fit to the data), so if the dark energy is to vary, it would do so slowly.

 

[phinds]

... Michio Kaku is enthusiastic about ...

Kaku is enthusiastic about things he is not familiar with (to put it charitably). Examples:

http://rationalwiki.org/wiki/Michio_Kaku

http://bigthink.com/ideas/26680

http://scienceblogs.com/pharyngula/2011/02/16/why-do-physicists-think-they-a/

 

[Shlibby]

Phinds, why is the continued accelerated expansion not evidence for a big rip? If it keeps expanding faster, isn't that more consistent with the big rip than the big freeze?

Bandersnatch. So you're saying that evidence shows dark energy does not vary over time, and, this is evidence for the big freeze, correct? And, are there any specific projects, or technologies that, given current rates of progress, will significantly increase our precise knowledge on this issue, such as new computers, sattelites, measurement devices, etc. ?

 

[phinds]

Phinds, why is the continued accelerated expansion not evidence for a big rip? If it keeps expanding faster, isn't that more consistent with the big rip than the big freeze?

No, there is so far no evidence at all that gravitationally bound systems such as galactic clusters will be affected by it and that would be necessary for the big rip.

Really, I think you would be better served by reading some basic cosmology than asking random questions on an internet forum. Once you've got some basics under your belt things will make more sense and many of your questions will evaporate. Of course, there will be new ones to take their place.

 

[Shlibby]

I appreciate your enduring my uninformed curiosity. Having little exposure to formal education on the issue, I'm not sure what sources to start with. Any particular book titles, or even links to webpages, written with layperson comprehensibility included would be a good start, with the caveat that i can get some reasonable measure of enlightenment on scientific appraisal of the big rip specifically. It is the one that, by far, has my curiosity piqued.

Just so we're clear--and rest assured this will be last randomly-blurted inquiry--gravitationally bound systems, such as galactic clusters, are *not* being affected by the accelerated expansion of the universe, as would be necessary for the big rip, correct?

 

[PeterDonis]

why is the continued accelerated expansion not evidence for a big rip?

Because accelerated expansion, by itself, does not lead to a big rip. It leads to a big freeze. To get a big rip, you need, roughly speaking, accelerated expansion whose rate of acceleration itself keeps accelerating, corresponding to the density of dark energy increasing with time (as opposed to the rate of acceleration being constant, as it is with a cosmological constant). As Bandersnatch said, so far we have no evidence to support the density of dark energy increasing with time, or for rate of acceleration of the expansion increasing. So the current best fit model is constant dark energy density and a big freeze, not a big rip.

 

[Bandersnatch]

So you're saying that evidence shows dark energy does not vary over time, and, this is evidence for the big freeze, correct?

In layman's terms, yes. But, be careful with the word 'evidence' here. As it is with any observation of a lack of an effect, you'll never know whether there is no effect, or whether your measurements are just not precise enough (there being no such animal as a perfect measurement). I.e., it looks like it doesn't vary so far, but maybe we're just not looking carefully enough yet.
That's why the big rip scenario cannot be ruled out, and that's why people are still working on its theoretical aspects as in the paper referred to in this discussion.

And, are there any specific projects, or technologies that, given current rates of progress, will significantly increase our precise knowledge on this issue, such as new computers, sattelites, measurement devices, etc. ?

Sure, this is an ongoing process, and the precision is constantly getting improved. In the area of observations, for example, we had the now-concluded mission of the WMAP satellite, the PLANCK satellite, no longer collecting measurements, but whose data are still being analysed, the ongoing BICEP/Keck experiments, and the soon to be launched JWST orbital observatory.

 

[phinds]

I appreciate your enduring my uninformed curiosity. Having little exposure to formal education on the issue, I'm not sure what sources to start with. Any particular book titles, or even links to webpages, written with layperson comprehensibility included would be a good start, with the caveat that i can get some reasonable measure of enlightenment on scientific appraisal of the big rip specifically. It is the one that, by far, has my curiosity piqued.

The big rip is no longer discussed by serious physicists as far as I know so you'd probably have to look for the kind of pop-science book that is best shunned. I'm not really the right person to ask about that though and perhaps one of our more informed members will answer. If that doesn't happen, start a new thread with a subject line something like "best cosmology books for a beginner?" or better yet, do a forum search. This question has come up before.

In fact, MOST questions have been asked here before, generally MANY times, so a forum search is always a good idea when you have a new question. For example, see the list of threads at the bottom of this page.

Just so we're clear--and rest assured this will be last randomly-blurted inquiry--gravitationally bound systems, such as galactic clusters, are *not* being affected by the accelerated expansion of the universe, as would be necessary for the big rip, correct?

Yes, that is exactly what I just said.

I recommend the link in my signature.

 

[Bandersnatch]

The big rip is no longer discussed by serious physicists

I don't think it's fair to say that. Just look at the paper referred to in the OP. Searching for 'quintessence', or even 'big rip' in arxiv is also indicative.

 

[phinds]

I don't think it's fair to say that. Just look at the paper referred to in the OP. Searching for 'quintessence', or even 'big rip' in arxiv is also indicative.

Fair enough. I apparently misspoke.

 

[Chronos]

Variable speeed of light theories remain not entirely 'disproven', but, also enjoy zero justification. I view this as little more than cannon fodder for scifi writers.