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Published by Tormod
04-13-2008
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Scientific American has taken it all-out and headlined this on their March issue frontpage:
The End of Cosmology?
An accelerating universe wipes out traces of its own origins
Full article available online:
The End of Cosmology?: Scientific American
I am going to read through it but I have to admit I was a bit surprised when I read the headline. If anything, if cosmology wipes itself out then my guess it is would be instantly recreated...because what is cosmology but the search for origins and a philosophical understanding of our relationship to the universe? I don't see that ending any time soon.
Thoughts? |
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Re: The End of Cosmology
I think they're just saying that any evidence (that a civilization might use to deduce a cosmology) will be unavailable in the distant future.
Think how lucky we are now!
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Re: The End of Cosmology
Yeah see that was my point. Cosmology isn't dependent on evidence IMHO. Only when it's coupled with astronomy and made into a science does it require scientific evidence. Cosmology has been around for a long time without needing any evidence apart from the observed movement of the sun, the moon, the planets etc...  |
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Re: The End of Cosmology
Well okay, yes, I guess folk cosmologies could still proliferate; I was just thinking of science based cosmologies. I read the article over a month ago, so I'm just going on vague feelings here.
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A "soft" expansion event horizon 100 billion years from now
I’ve gotten a couple of issues behind in my SciAm reading (which I credit partly to the crappiness of my handheld viewer, which takes so long to render/”turn” a pdf file page that I can get distracted and do something else  ), so hadn’t read this 3/2008 article until hearing about it in this thread.
It’s the kind of science article its most recognizable author, Lawrence Krause of “The Physics of Star Trek” fame is famed for: conventional science put into popular terms to explain a sound but startling, and not widely discussed, scientific idea. Krause, a real career astrophysicist, is a “rock star” among popular science writers, and with the collaborators and whatever publishing support folk his fame puts at his disposal, puts together a SciAm article as beautiful as any – the “night sky of Earth zero, 5 billion, 100 billion, and 10 trillion years from now” art alone is spectacular, poster-worthy stuff.
What the article is getting at with its provocative yet scientifically sound and well-explained title is that if, as present best models suggest, the rate of the metric expansion of the universe continues to increase, the amount of information available in any volume of it will steadily decrease. In astronomy terms, this decrease will result in fewer distant galaxies being visible to present-day, or even advanced future telescopes, as increasing numbers of them come to lie outside of an expansion-defined event horizon – though nearby, gravitationally-bound galaxies will move closer together, forming eventually a globular “supergalaxies” of the only practically visible stars to observers within them. Models predict this will occur much faster than the exhaustion of light element “star fuel” results in the end of the stelliferous era, so in about 100 billion years – about 8 times the current age of the univers - stars and physics will be pretty similar to how they are now, but their arrangement in space and the observable sky dramatically different.
It’s important to note that this “expansion event horizon” is “soft” compared to others, such the gravitational event horizons associated with black holes. Light from distant galaxies isn’t prevented from crossing it, but redshifted so greatly it’s not practically observable, ultimately to a point where its wavelength is greater than the event horizon, and fundamental physics dictates that the probability of a photon of such light interacting with anything is negligible, and any such detections almost certainly lost in the “noise” of nearby stars (though I can think of a few interesting observatory designs for such an era). As Krause and Scherrer note, astronomy won’t quite be impossible – it will be possible, for example, to use chains of spacecraft to extend the practical radius of observation far beyond the event horizon – but it will be much more difficult than it is now. A newly emerged intelligence like our own, coming to have technology like ours, might be unable to scientifically conclude that anything lies beyond their local supergalaxy.
Of course, all these predictions of far future events depends on our present-day theories and models being correct and complete in enough significant details, so may turn out to be dramatically wrong. But you can only scientifically predict with the science you know, and I think Krause, Scherrer, and other proponents of these predictions do a good job of it. My major criticism of this article is that, uncharacteristically for Krause, it sometimes skimps on numbers. For example, nowhere in it do they provide even a rough estimate of the number of stars in the theorized 100-billion-years-from now supergalaxy. |
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Re: The End of Cosmology
There are some conceptual problems with the acceleration expansion of the universe. First, the data we receive from far distances is not real time data, but historical data. This implies if an object is billions of light years away, and we receive its signal today, all we can say is billions of years ago this object was accelerating. It tells us nothing of today, since the signal of what is happening today, will take billions of years to reach us. If it pulled a u-turn 1 billion years ago, we can't know this from the historical data, since this data is too old to tell us anything about it more recent history. It is ancient history data of a time long past.
One of the models to describe the expansion of universe, compares the space-time expansion to an expanding bubble or foam where everything is expanding relative to each other. If we assume this is true than the closet data should be the same as the more distant data. While the closest data should be the closest to us in real time, i.e., less historical. The question is, does the closest data show the same level expansion-acceleration? The closet galaxies are actually blue shifted or contracting toward us. This data is less historical, so based on the bubble expansion relative to galaxies, it should be closer to the real time nature of the universe, and less biased by ancient history of or what had been.
Let me give an analogy. We have three astronauts each with a watch that are all set at the same time. We also have a fourth watch which we will leave on the earth at mission control. We give them each the same project which is to build a shelter that will take one month. The first astronaut we place on the moon, the second on Mars and the third on one of Jupiter's moons. Each astronaut sets up a camera to show their progress. At exactly the same time on their watches, JAN 1, 2056 at 12 noon, they all begin their projects. Because of the time delay of the video signal, the person on the moon will appear to start first and the person on one of Jupiter's moon will appear to start last.
We know they are all in synch because they are all wearing the same hi-tech watch which has been certified to keep perfect time. But the time delay in the video signal is creating the illusion their watches are off. The uniform expansion of space-time assures all the watches are the same. Our best bet to assure we are observing the real time and not historical progress due to signal time delay, is to focus ourself on the astronaut on the moon, since his progress is closest what they are all doing in synch time.
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Re: The End of Cosmology
To All
Maybe what that article means is an 'end' to Cosmogony (BBT) rather than cosmology.
The cosmology is protected by the 'Laws of Conservation' like the SSU. So it cannot end.
The BBT does not comply and so it is not protected. Ha ha.
Mike C
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The Hubble flow and the relativity of simultaneity
Quote:
Originally Posted by HydrogenBond
There are some conceptual problems with the acceleration expansion of the universe. First, the data we receive from far distances is not real time data, but historical data. This implies if an object is billions of light years away, and we receive its signal today, all we can say is billions of years ago this object was accelerating.
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No simple bolometric or spectroscopic data can directly reveal that an object is accelerating, only the radial component of its velocity. Hence Hubble's law makes no statement about a relationship between distance and acceleration, only between distance and velocity.
It’s also critical to note that Both the simple signal time HydrogenBond mentions, and these more complicated factors, are included in theoretical models of the universe. These models are complicated, but mathematically rigorous, not reliant on intuitive satisfaction.
As has been noted in many threads, claims like the following
Quote:
Originally Posted by HydrogenBond
It tells us nothing of today, since the signal of what is happening today will take billions of years to reach us.
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strongly contradict the relativity of simultaneity, a essential concept of modern physics. The concept that spatially separate events absolutely do or do not happen at the same time or on a particular order, though intuitively appealing, is ultimately meaningless and unhelpful.
Quote:
Originally Posted by HydrogenBond
The closet galaxies are actually blue shifted or contracting toward us. This data is less historical, so based on the bubble expansion relative to galaxies, it should be closer to the real time nature of the universe, and less biased by ancient history of or what had been.
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As the article that started this thread describes, nearby galaxies are blue shifted because they are gravitationally bound, tending over billions of years to grow closer together until an entire local supercluster of galaxies becomes a “supergalaxy”, not because data about them is “less historic”. Redshift observation clusters of galaxies so distant that the light we are currently receiving from them was emitted when they were billions of years younger than our galaxy show similar movement. There is no “bias” of these very old images of the universe: other than the population of stars in them containing more metal-poor population II and III stars than our galaxy, the fundamental mechanical nature of physics evidenced by the motion of these distant, ancient galaxy clusters is not much different than our nearby, young cluster.
The Krause and Scherrer article does not address skepticism of the widely accepted theory of the metric expansion of space, but rather shows a surprising consequence of it. If you reject mainstream cosmology, the article has, IMHO, very little of interest to offer you – though I still recommend it on the merit of the prettiness of its illustrations (available, unfortunately, only in the sciamdigital.com and print versions). |
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Re: The End of Cosmology
Quote:
Originally Posted by Tormod
If anything, if cosmology wipes itself out then my guess it is would be instantly recreated...because what is cosmology but the search for origins and a philosophical understanding of our relationship to the universe? I don't see that ending any time soon.
Thoughts?
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I agree Tormod,
The first sentence says it all, in all its truthful glory.
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One hundred years ago a Scientific American article about the history and large-scale structure of the universe would have been almost completely wrong.
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Has anybody collected any empirical evidence to verify this factoid and can we just assume that today everything is almost completely right? It would be interesting to see some figures on the relationships of the scientific 'truths' of periods of time 100 years apart and their relative realities.
After all, we then might be able to tell if our universe of scientific knowledge is actually expanding, if the limits are being restricted/falsified/countered (contracting) by the 'anti'/fallacious scientific knowledge that we know it contains, or if only large parts of it are disappearing (or are about to dissappear) down their own black hole of localised hubris. |
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Last edited by LaurieAG; 04-15-2008 at 12:06 AM..
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Re: The End of Cosmology
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In short, it erases all the signs that a big bang ever occurred. To our distant descendants, the universe will look like a small puddle of stars in an endless, changeless void. What knowledge has the universe already erased?
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This view goes as far as these event horizons, information is lost to our present observations past these points, however this view is not taking in to account that our point of view will not remain static in space time for the next few billion years.
One constant in the universe is that information and energy in the universe is constantly evolving and moving though a series events in space time.
We can assume from observations of the cyclical nature of energy and information that our view point will also pass though many yet unseen event horizons. |
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