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(io9)   You know that whole "universe will keep expanding forever" idea that cosmologists have been touting for years? Well, about that   (io9.com) divider line 91
    More: Interesting, universe, Cosmological Constant, cosmologists, observational astronomy, time and space, energy density, general relativity, Big Crunch  
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5156 clicks; posted to Geek » on 09 Mar 2014 at 11:30 AM (1 year ago)   |  Favorite    |   share:  Share on Twitter share via Email Share on Facebook   more»



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2014-03-09 11:38:20 AM  
Two guys change the cosmological constant and decide the universe will collapse?

Hold on science, I'm going to change the cosmological constant too.
 
2014-03-09 11:42:23 AM  
41,97778?
 
2014-03-09 11:44:28 AM  

Mytch: Two guys change the cosmological constant and decide the universe will collapse?

Hold on science, I'm going to change the cosmological constant too.


Okay, done. Let's see what happens to the Milky Way with my change to the cosmological constant. Someone call a journalist!

img.fark.net
 
2014-03-09 11:44:47 AM  
To be honest, I thought this was already the prevailing theory. Expansion (and all other processes) will use up all available energy basically until the universe is mostly entropy and unstable. It will then proceed to collapse and expand in decreasing pulses until the "crunch" (as the article calls it).
 
2014-03-09 11:45:05 AM  

Mytch: Two guys change the cosmological constant and decide the universe will collapse?

Hold on science, I'm going to change the cosmological constant too.


It is one of the few perks of being an astrophysicist. Not as great as the loads of nubile and rich women throwing themselves at you of course, but you can't have everything.
 
2014-03-09 11:46:20 AM  
Annnnnd rather than linking to the actual story, we get a link to gawker retards.


Link
 
2014-03-09 11:49:55 AM  
I guess attention whoring is a science now.
 
2014-03-09 11:50:12 AM  

Shotgun Justice: To be honest, I thought this was already the prevailing theory. Expansion (and all other processes) will use up all available energy basically until the universe is mostly entropy and unstable. It will then proceed to collapse and expand in decreasing pulses until the "crunch" (as the article calls it).


No. Due to the fact that gravity decreases drastically with distance, and that the rate of expansion is increasing, the crunch as you call it can't occur because gravity would be practically nonexistent.
 
2014-03-09 11:57:29 AM  
"This acceleration of the universe has only recently become measurable. According to such measurements, the universe's expansion rate was decelerating until about 5 billion years ago due to the gravitational attraction of the matter content of the universe, after which time the expansion began accelerating. According to the simplest extrapolation of the currently-favored cosmological model (known as "ΛCDM"), this acceleration becomes more dominant into the future." ---http://en.wikipedia.org/wiki/Metric_expansion_of_space

"Observations suggest that the expansion of the universe will continue forever. If so, the universe will cool as it expands, eventually becoming too cold to sustain life. For this reason, this future scenario is popularly called the Big Freeze." ---http://en.wikipedia.org/wiki/Future_of_an_expanding_universe
 
2014-03-09 11:59:16 AM  
I hope this is proven actually.  Psychologically the idea of renewal in a great crunch is much less disturbing than oblivion for everything that ever existed.
 
2014-03-09 12:00:59 PM  
I have never heard anyone suggest the universe will expand forever. I have only ever heard that it will expand until it collapses.
 
2014-03-09 12:05:00 PM  

Ambivalence: I have never heard anyone suggest the universe will expand forever. I have only ever heard that it will expand until it collapses.


Yeah, I'm not some kind of science person but that was my understanding too.  Like the universe is a giant accordion.  That "cosmic noise" that you hear about?  That's really just "Lady of Spain" being played very slowly.
 
2014-03-09 12:05:06 PM  
For those of you wondering, currently there is a problem with attributing vacuum energy as the cause of the cosmological constant. Essentially, the quantum mechanics side predicts an absolutely massive vacuum energy that doesn't really work well with most other calculations of the cosmological constant. So these reformulated GR in such a way as to basically ignore vacuum energy. The cosmological constant they predict is then very small (probably leftover from initial inflation), eventually to be overcome by gravity.
 
2014-03-09 12:05:19 PM  
I thought it was dissolving as it was expanding, like an air bubble released from the bottom of the ocean, breaking apart until it becomes one with the cosmic background radiation, but I do a lot of psychedelics.
 
2014-03-09 12:06:32 PM  

Ambivalence: I have never heard anyone suggest the universe will expand forever. I have only ever heard that it will expand until it collapses.


I have always heard described as a rubberband.  As in this Space.com article from 2004.

http://www.space.com/196-rubber-band-invoked-explain-dark-energy.htm l
 
2014-03-09 12:08:20 PM  
Cosmological question -- If the big bang came from a point of infinite heat and density, how would the universe look different if it were contracting towards said infinite point beyond the observable horizon?

Like if you were getting spagettified on the edge of a black hole wouldnt everything appear redshifted to you even though you were traveling towards a set point? Whats the difference between expanding forever and ever and shrinking to an infinite point? Are they the same thing in some sort of effect?

So the question of whether the universe is contracting or expanding is academic as it will look the same either way?
 
2014-03-09 12:08:33 PM  

Ambivalence: I have never heard anyone suggest the universe will expand forever. I have only ever heard that it will expand until it collapses.


Not disputing what you're heard but its hard to imagine your having paid attention to astrophysics in the past 20 years if you *haven't* heard the preponderance of not merely ever-expanding but rate-of-expanding-increasing evidence.  This has not been fringe science, its been the mainstream paradigm for decades.

I too would aesthetically prefer the concept of a cyclical bang-crunch universe but if to get there:

To address this problem, Kaloper and Padilla have slightly reformulated general relativity

Yeah, we've seen how well that's works for other scientists over the years.
 
2014-03-09 12:42:52 PM  
Bullshiat.
 
2014-03-09 12:44:10 PM  

Ambivalence: I have never heard anyone suggest the universe will expand forever. I have only ever heard that it will expand until it collapses.


I've never heard anyone suggest that the current view... that it looks like the universe is expanding forever... is wrong.
You must live in a different dimension.
 
2014-03-09 12:48:13 PM  

the opposite of charity is justice: To address this problem, Kaloper and Padilla have slightly reformulated general relativity

Yeah, we've seen how well that's works for other scientists over the years.


Yup. Unless you are a Q, you're not going to get much peer-review if you entire hypothesis is dependent on "Well, if you just make a 120-orders-of-magnitude change to part of the most successful astronomical theory in history, it all works!"
 
2014-03-09 12:50:01 PM  
Looks on hopefully

img1.fantasticfiction.co.uk

It's sad when a good "hard science" novel goes obsolete because of new science.
 
2014-03-09 01:31:35 PM  
Here's the wonderful thing about the term "universe" that the media happily skips over - the "universe" is defined by the number of stars we can see evidence of.
Stars, not space.

Furthermore, the formation of the 'universe' - the stars and galaxies that we see - is suggestive of the idea that a "universe" is just a galaxy, in macrocosm. Which is to suggest that even MORE light-years distant, there are other groupings of galaxies - "universes".

Ergo, to say that the local "universe" is collapsing is not really anything notable, except to say that gravity is a biatch.
 
2014-03-09 01:33:45 PM  

mikefinch: Cosmological question -- If the big bang came from a point of infinite heat and density, how would the universe look different if it were contracting towards said infinite point beyond the observable horizon?

Like if you were getting spagettified on the edge of a black hole wouldnt everything appear redshifted to you even though you were traveling towards a set point? Whats the difference between expanding forever and ever and shrinking to an infinite point? Are they the same thing in some sort of effect?

So the question of whether the universe is contracting or expanding is academic as it will look the same either way?


I'm not 100% sure this is exactly what you're asking, but there is no infinite point. The best way to envision this is to pretend that the three spatial dimensions are actually only two, so all of space is represented as a plane. Add one more dimension for that "space" to be curved through and now you have three dimensions in the analogy, which actually represent four. This surface can be curved in three main ways -- like a saddle (a "hyperbolic paraboloid") completely flat, or closed in a spherical type surface. A universe which eventually collapses on itself is the latter, the sphere-like surface. Consider that you live in the three-dimensional world represented by the surface of the sphere. If the sphere is big enough, it's very difficult for you to perceive the curvature from within -- it looks pretty flat. This is analogous to standing on the surface of the Earth and not being able to tell that the ground is curved.

Anyway, to go back to your post, if the universe is sphere-like, and you're on the surface, there really isn't a center. Any point on the surface of the sphere looks pretty much the same as any other. If the sphere itself is shrinking, again, no place looks different than another -- there is no "center" to the surface, and what you perceive is your surroundings are getting closer to you. Someone elsewhere would see the same basic thing. In this analogy, a collapsing universe is like a balloon having the air let out.

There is a difference between the sphere inflating and contracting that should be visible. At large enough distances, everything should be traveling away in the first instance and towards you in the second.
 
2014-03-09 01:46:16 PM  
My personal belief based on no scientific knowledge is that the universe is both infinitely large and small. Our scientific assumptions are based only on what we can see. This is no different than believing the earth is flat because we can't see over the horizon. This is why theories keep changing as our ability to see further into space or further into the building blocks changes.
 
2014-03-09 02:01:50 PM  
I just hope I am here to see it, whichever way it goes.
 
2014-03-09 02:06:20 PM  
I always wondered about the collapsing universe from a light-speed standpoint. Since gravity, like everything else, is limited by the speed of light, how could it even reach the light energy that flies away from its source? Black holes give off light because light is going fast enough to escape their intense gravity. Wouldn't it be impossible to reach that light and energy that was released? How would that collapse not lead to a heat death eventually anyway?

Sorry if this is crude and very incorrect. I'm not an astrophysicist so a lot of that report went way over my head.
 
2014-03-09 02:06:38 PM  
Ka is a wheel.  :/
 
2014-03-09 02:07:30 PM  

mikefinch: So the question of whether the universe is contracting or expanding is academic as it will look the same either way?



Not so.  While expanding, everything is red-shifted.  While contracting, everything will be blue-shifted.
 
2014-03-09 02:10:53 PM  

mikefinch: Cosmological question -- If the big bang came from a point of infinite heat and density, how would the universe look different if it were contracting towards said infinite point beyond the observable horizon?

Like if you were getting spagettified on the edge of a black hole wouldnt everything appear redshifted to you even though you were traveling towards a set point? Whats the difference between expanding forever and ever and shrinking to an infinite point? Are they the same thing in some sort of effect?

So the question of whether the universe is contracting or expanding is academic as it will look the same either way?


It's an interesting question.  There should be a few things we would observe which might suggest this though. Such an instance would require all observable matter to be spaghettifying towards a singularity.  The most obvious observation is that if we were to look beyond that singularity, all matter would be blue-shifted.  Presumably, this case relies on us not being able to [reliably] observe matter at that distance. In this case, we can assume that while matter in front of us would be accelerating an a faster pace than us, and matter behind us would be accelerating a slower pace than us, there would still be a spherical plane of matter which would be accelerating parallel to us towards the singularity.  This would mean that there would be a plan of matter that is moving closer to us due to it being roughly on the same sphere of collapse towards the singularity.
 
2014-03-09 02:24:09 PM  
Astro-philosophers, really. The guys working at either end of the size scale have been a major brain sink for the past couple of decades. The vaccum energy of space? Anyone figure out a way to use it? Higgs Boson? Any idea about isolating an object from the Higgs field so we can see about breaking the speed limit?

I suppose it's better than them all going to Wall Street to be quants until the blow up some sector of the economy. Again.
 
2014-03-09 02:27:20 PM  

Mytch: Two guys change the cosmological constant and decide the universe will collapse?

Hold on science, I'm going to change the cosmological constant too.


The rationale behind it is actually pretty much legit and actually quite an interesting take on the problem, even in the brief form presented.

So... not sure why you're going with mockery on this one.  Tweaking constants and using different base-models is pretty much the preferred way to work out the mechanics behind things too large for lab-scale or too complex for current analytical technology.
 
2014-03-09 02:40:58 PM  
Well I don't know about all that, but someone once told me that time is a flat circle.
 
2014-03-09 02:47:53 PM  

The Gentleman Caller: Well I don't know about all that, but someone once told me that time is a flat circle.


If you get the opportunity...
 
2014-03-09 02:49:07 PM  
Too bad it clashes with observational evidence.  Does their hypothesis reconcile the fact that the expansion of the universe is actually accelerating?
 
2014-03-09 02:52:03 PM  

Jim_Callahan: Mytch: Two guys change the cosmological constant and decide the universe will collapse?

Hold on science, I'm going to change the cosmological constant too.

The rationale behind it is actually pretty much legit and actually quite an interesting take on the problem, even in the brief form presented.

So... not sure why you're going with mockery on this one.  Tweaking constants and using different base-models is pretty much the preferred way to work out the mechanics behind things too large for lab-scale or too complex for current analytical technology.


There abstract points to why. ("A slight revision of general relativity can avoid an enormously large (and observationally inconsistent) cosmological constant, assuming that our Universe eventually collapses back on itself."

This means they first assumed that the universe will collapse back upon itself (despite this being not being supported by either the current model or current observations) and then re-engineered the constant to support their assumption.
 
2014-03-09 02:55:37 PM  

pchouky: There is a difference between the sphere inflating and contracting that should be visible. At large enough distances, everything should be traveling away in the first instance and towards you in the second.


But my point is that if the big bang spawned from a point of infinite density and heat then wouldnt it also contract to an infinite point? Instead of a balloon think of the universe as falling into a giant black hole...

indy_kid: mikefinch: So the question of whether the universe is contracting or expanding is academic as it will look the same either way?


Not so.  While expanding, everything is red-shifted.  While contracting, everything will be blue-shifted.


Thats my point -- from the point of the observer on earth everything in the universe would look like it was red shifted. If i fell into a black hole feet first my feet would fall in faster than my head. I would get stretched out -- even though i would be being crushed; observationally all the bits of my body would be getting farther and farther apart.... So all we can tell is that the universe is accelerating around us. To say that its expanding or contracting is misleading because we will never be able to observe this from a neutral frame of reference...

From our point of view exploding and crushing is going to look the same...
 
2014-03-09 02:57:33 PM  
So is Pluto a planet again? We simple minded farkers want to know!
 
2014-03-09 03:09:39 PM  

MrBallou: Looks on hopefully

[img1.fantasticfiction.co.uk image 250x403]

It's sad when a good "hard science" novel goes obsolete because of new science.


Tau?.

img4.wikia.nocookie.net
 
2014-03-09 03:18:18 PM  

CygnusDarius: MrBallou: Looks on hopefully

[img1.fantasticfiction.co.uk image 250x403]

It's sad when a good "hard science" novel goes obsolete because of new science.

Tau?.

[img4.wikia.nocookie.net image 640x425]


It's SCIENCE, biatches.

upload.wikimedia.org
 
2014-03-09 03:24:27 PM  

Mytch: Presumably, this case relies on us not being able to [reliably] observe matter at that distance. In this case, we can assume that while matter in front of us would be accelerating an a faster pace than us, and matter behind us would be accelerating a slower pace than us, there would still be a spherical plane of matter which would be accelerating parallel to us towards the singularity. This would mean that there would be a plan of matter that is moving closer to us due to it being roughly on the same sphere of collapse towards the singularity.


But looking past a singularity is like looking into a black hole. It ends the observable universe at its horizon. And the best examples of red shift can be seen at the farthest reaches of the universe while the andromeda galaxy is infact blue shifted towards us (but that could just be because our galaxies are kinky for each other...)
 
2014-03-09 03:29:21 PM  
slightly reformulated general relativity such that the cosmological constant is  the historical average of the matter energy density in the universe

Can you say kludge?  I know that you can.
 
2014-03-09 03:37:51 PM  

MrBallou: CygnusDarius: MrBallou: Looks on hopefully

[img1.fantasticfiction.co.uk image 250x403]

It's sad when a good "hard science" novel goes obsolete because of new science.

Tau?.

[img4.wikia.nocookie.net image 640x425]

It's SCIENCE, biatches.

[upload.wikimedia.org image 132x31]


And I'm guessing it works.

/Biatches
//Yes, I actually love the science-based memes
 
2014-03-09 03:45:50 PM  

Begoggle: Bullshiat.


Ah, yes, the same words that were used by critics of such quack theories as:

Avogadro and his theory on chemical combinations
Mendel and his observations on genetics
Sammelwise and his sanitation practices
Margulis and her endosymbiotic theory

Congratulations.  Just like all of those critics, I am sure you have already analysed the problem thoroughly and perhaps conducted experiments of your own to discredit it,
 
2014-03-09 03:51:27 PM  
Sciency stuff.  I might have to read this thread later.
 
2014-03-09 04:00:41 PM  

BKITU: Yup. Unless you are a Q, you're not going to get much peer-review


I still wouldn't trust that guy after he plugged a strange laptop into the internal network.

i.telegraph.co.uk
 
2014-03-09 04:06:16 PM  
Make up your mind, science! I've got to have a good number for the caterers...
 
2014-03-09 04:30:01 PM  
Underwater Bystander: Black holes give off light because light is going fast enough to escape their intense gravity.

Nope, once light crosses the event horizon it can't escape.  Black holes spin, and their mass drags the surrounding spacetime along with it.  This makes the atoms collide with high energy, which releases X-Rays.  Some of the X-Rays head into the black hole, others head out into the galaxy.  The spinning black hole also has a hefty magnetic field, which can channel the xrays into jets at the poles.

/ Not an astrophysicist
// Don't even play one on TV
/// On the internet, nobody knows you aren't an astrophysicist
 
2014-03-09 04:31:02 PM  

Cpl.D: Too bad it clashes with observational evidence.  Does their hypothesis reconcile the fact that the expansion of the universe is actually accelerating?


No, but the existing theory doesn't currently reconcile with observations of the cosmological constant. Other theories reconcile the observed acceleration, this theory reconciles the observed cosmological constant.

It should be noted that the authors aren't coming out and claiming that they've suddenly discovered how the universe *really* works, they're claiming that they've found a theory that is consistent with this one little piece of evidence that other people haven't been able to work out yet (at least not in a stable universe).


Mytch: There abstract points to why. ("A slight revision of general relativity can avoid an enormously large (and observationally inconsistent) cosmological constant, assuming that our Universe eventually collapses back on itself."


That's not the author's abstract, that's a synopsis that someone else wrote (poorly). The paper doesn't assume a collapsing universe, the collapse is a consequence of their formulation of GR.


mikefinch: But my point is that if the big bang spawned from a point of infinite density and heat then wouldnt it also contract to an infinite point? Instead of a balloon think of the universe as falling into a giant black hole...


Ultimate contraction is not a foregone conclusion. The first thing you have to understand is that when people talk about a contracting universe, they don't mean that gravity merely pulls all of the matter in the universe back into one spot (i.e. an enormous black hole). They literally mean that the total space available in the universe is fluctuating.

We suspect that there are several forces "inflating" the universe, and several forces "deflating" the universe. The ultimate destiny is determined by whether or not those inflationary forces are greater than, equal to, or less than the deflationary forces. Right now we know that the universe is inflating, and that the rate of inflation is increasing (i.e. the expansion of the universe is accelerating).

The truth is that people haven't fully quantified all of those inflationary and deflationary forces, and they don't fully understand how they all interact. As others have pointed out, the most accepted view right now is that inflation will continue forever, but there are problems with that theory, problems with all the other theories, so we don't really know with great certainty that we have it all figured out.
 
2014-03-09 04:44:43 PM  

mikefinch: pchouky: There is a difference between the sphere inflating and contracting that should be visible. At large enough distances, everything should be traveling away in the first instance and towards you in the second.

But my point is that if the big bang spawned from a point of infinite density and heat then wouldnt it also contract to an infinite point? Instead of a balloon think of the universe as falling into a giant black hole...

indy_kid: mikefinch: So the question of whether the universe is contracting or expanding is academic as it will look the same either way?


Not so.  While expanding, everything is red-shifted.  While contracting, everything will be blue-shifted.

Thats my point -- from the point of the observer on earth everything in the universe would look like it was red shifted. If i fell into a black hole feet first my feet would fall in faster than my head. I would get stretched out -- even though i would be being crushed; observationally all the bits of my body would be getting farther and farther apart.... So all we can tell is that the universe is accelerating around us. To say that its expanding or contracting is misleading because we will never be able to observe this from a neutral frame of reference...

From our point of view exploding and crushing is going to look the same...


I thought the universe is inflating, not expanding. It's not actually stretching out, only the space between things is increasing over time.
 
2014-03-09 04:45:52 PM  
Has anyone studied how many times scientists have reversed their view on expansion vs. how often they reversed their view on eggs being healthy or not
 
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