Right, but I was under impression that you don't really care, wether it is possible to find right formula or not in some particular case.Chris Peterson wrote:With nature, such knowledge may be impossible.
What if "right" answer to those questions would result in better formula?
Not at all. The question of whether there is an underlying "truth" to the way the Universe works is fascinating. Above all, I care that the theories we derive are functional. If they serve to describe the behavior of nature they are doing their job, and science has done its job. In a very real sense, it does not matter if there are other theories that are equally effective at describing things.makc wrote:Right, but I was under impression that you don't really care, wether it is possible to find right formula or not in some particular case.
I agree! It says so much - In so little space.swainy wrote:Now there's a nice word.Chris Peterson wrote:indescribable
John Mather, along with George Smoot, won the Nobel Prize for his work on the Cosmic Background Explorer (COBE), the probe that first caught glimpses of fluctuations in the Cosmic Microwave Background (CMB) left over from the big bang. Those fluctuations are the product of the tiny, random, quantum fluctuations in the Universe immediately after the big bang, which are now visible in the large scale structures of the current Universe, as they produced clusters of galaxies and filaments of dark matter. For his talk at the Lindau Nobel Laureates Meeting, Mather took the audience on both a short history of the Universe, and a history of how we've come to understand it.
Mather started out with some background on the Big Bang — although he said he preferred the term used in a Calvin and Hobbes strip, the "Horrendous Space Kablooie." (We'll continue to use Big Bang for now.) He described how, in the early 1920s, Alexander Friedman applied Einstein's equations to the Universe, and figured it must be expanding. Einstein asked his friends, who told him the Universe couldn't be expanding, so he added the cosmological constant in order to preserve the static universe that everyone thought existed.
Friedman died a few years after and, within a year, Hubble published his famous paper, providing evidence of an expanding universe. ("In the same year we learned that the economy could collapse, we learned that the Universe is expanding," Mather quipped.) Mather showed Figure One of Hubble's paper, with red shift (and therefore speed) rising with a galaxy's distance from the Earth.
Once a consensus formed around the Big Bang model, things went through a bit of a slow period. Information on the stability of free neutrons let theorists calculate the expected elemental abundances of hydrogen and helium, and later, the existence of the CMB was predicted, but there wasn't any obvious way to detect it until Penzias and Wilson's famous experiment at Bell Labs found the faint hiss of the CMB. Now, according to Mather, a dedicated high school student could probably manage it. About one percent of the snowflakes you see when you tune a TV in between channels, Mather said, can be ascribed to the CMB.
A useful failure
Mather started his work on the CMB back in graduate school. He said the idea for COBE "came from the failure of my thesis project," which was meant to measure the CMB via balloon-borne instruments. As that work was failing, NASA put out a request for projects, and COBE was born. Its ability to match CMB measurements with theory, immortalized by xkcd, COBE started off a new era of cosmology.
Mather briefly described our current understanding of the Universe. A tiny fragment of a (possibly infinite) collection of material started expanding at a pace faster than light as a false vacuum decayed into a true one. Within fractions of a second, matter and antimatter annihilated, leaving a tiny bias towards matter. As inflation apparently went missing for billions of years, a steady expansion of space time and gravitational effects produced the Universe we now see. But about 5 billion years ago, inflation returned as the expansion of space-time started to accelerate. "We call the cause of this acceleration dark energy, which means we do not have any idea what it is," said Mather.
Right now, we're on version seven of the data produced by COBE's successor, WMAP. And we've now got a model for the Universe that incorporates dark matter and dark energy called ΛCDM that matches the curves returned from WMAP just as well as early inflationary cosmology theory produced a curve that matched COBE.
swainy wrote:And Now, I find yet another reason for our (Seemingly-delusional) expansion. Get your head around this Guys.
http://www.dailygalaxy.com/my_weblog/20 ... -says.html
This doesn't address the reason for expansion at all. The theory seems to take its existence at face value (there is certainly nothing "Seemingly-delusional" about it). What these guys are suggesting is that IF you assume time is slowing down, the well observed apparent INCREASE in the rate of expansion (which is generally attributed to dark energy) would look the same without an actual acceleration. It's an interesting idea, but nothing to get too excited about until it starts proposing methods by which it could be tested or falsified. Until then, the current theory remains the best explanation.swainy wrote:And Now, I find yet another reason for our (Seemingly-delusional) expansion. Get your head around this Guys.
http://www.dailygalaxy.com/my_weblog/20 ... -says.html
Its the under-lined part of this, that interests me Chris. Quote:Chris Peterson wrote:This doesn't address the reason for expansion at all. The theory seems to take its existence at face value (there is certainly nothing "Seemingly-delusional" about it). What these guys are suggesting is that IF you assume time is slowing down, the well observed apparent INCREASE in the rate of expansion (which is generally attributed to dark energy) would look the same without an actual acceleration. It's an interesting idea, but nothing to get too excited about until it starts proposing methods by which it could be tested or falsified. Until then, the current theory remains the best explanation.swainy wrote:And Now, I find yet another reason for our (Seemingly-delusional) expansion. Get your head around this Guys.
http://www.dailygalaxy.com/my_weblog/20 ... -says.html
Yes. That's what they said. That's what I said. Nothing at all about expansion, only about the apparent change in rate of expansion.swainy wrote:"Currently, astronomers are able to discern the expansion speed of the universe using the so-called "red shift" technique. This technique relies on the understanding that stars moving away appear redder in color than ones moving towards us. Scientists look for supernovae of certain types that provide a sort of benchmark. However, the accuracy of these measurements depends on time remaining invariable throughout the universe. If time is slowing down, according to this new theory, our solitary time dimension is slowly turning into a new space dimension. Therefore the far-distant, ancient stars seen by cosmologists would from our perspective, look as though they were accelerating".
Not necessarily. No obvious changes in gravitational theory at all. No changes in the physics of cosmological redshift. It might impact the interpretation of other measurements of high-redshift objects.And what other implications would come from this? Remember the redshift conversation we had?
But if Time is slowing down, What of gravity (which I talked about months ago) Light. More or less everything Huh?
1 second per second.swainy wrote:What I want to know is, just how fast was Time running 10 billion years ago?
I didn't notice before how old this work is- almost three years. And just about the only references to it are in pop science magazines and blogs. The actual paper is here, and doesn't seem to say quite the same thing as the popular interpretations. It is dense, and based on several layers of speculation on top of speculation. And there doesn't seem to be any followup or much in the way of interest from other researchers. Like so much in string theory, it seems much more about playing mathematical games to demonstrate what could be possible under an assumed set of conditions than it is about actually providing likely explanations for anything.swainy wrote:Here's some more info on the paper that was published,
http://www.wired.com/wiredscience/2007/ ... ists-time/
Based on my reading of the above paper, and on modern physical theory, I'd say the answer, with a high probability of being correct, is that it was running exactly the same speed as it does now.What I want to know is, just how fast was Time running 10 billion years ago?
A shape-shifting fifth fundamental force could neatly explain the mystery of dark energy – and some other puzzling astronomical observations
ASK A cosmologist for a potted history of the universe, and it might go something like this: the cosmos began some 13.6 billion years ago with a big bang, exploding from a pinprick of searing heat and incredible density. Since then, it has been cooling and expanding: at first exponentially fast, but soon at a more measured, steady tempo.
At that point our friendly cosmologist might give voice to a little embarrassment. Because if measurements of the distance to faraway supernovae are to be believed, around 5 billion years ago the universe's expansion started to accelerate again. We don't know why. A mysterious "dark energy" permeating space is generally fingered as the culprit. But while this entity apparently flings galaxies apart with gusto, it has never been seen or produced in the lab and seemingly does not interact directly with light or matter on Earth or elsewhere. Such undetectability runs counter to the stuff of science.
Or are we just overlooking evidence that is already there? Some inconsistencies in recent astrophysical observations, easy to dismiss as blips if taken on their own, might invite a startling conclusion when looked at together: that the cosmos is suffused by a fifth force in addition to the canonical four of gravity, electromagnetism and the strong and weak nuclear forces. What is unusual about this force is that its range changes according to its environment - a cosmic chameleon that might just explain the mysteries of dark energy.
No, no, it's true, I saw it on Futurama. And you know that you can trust Futurama on subjects of astronomy.Ann wrote:As a non-religious person, I regard the Big Bounce hypothesis as a mixture of religious ideas and wishful thinking.
I think the idea that a big crunch would be followed by a big bang is fairly natural and intuitive. Imagine naive (non-relativistic) picture of the "end times" of a collapsing universe, where all galaxies converge towards a central point following an inverse Hubble law. If we assume that each galaxy just coasts through the center as per Newton's First Law, without interacting with the other galaxies doing the same simultaneously, we end up immediately after the crunch event with a universe full of galaxies moving away from each other following a Hubble law, which more or less matches the era we find ourselves in now.Ann wrote:(I can't say that many professional astronomers seemed to be confident that a Big Crunch was coming or that it would give rise to a new Big Bang or a new habitable universe,
Hm, I get a somewhat opposite impression. A lot of the early emotional resistance to the big bang idea came from atheists who felt that the idea that the universe has existed for only a finite time sounded too much like creationism. If the universe was created 15 gigayears ago, there must have been a Creator, nyet? And because only stupid people think there was a Creator, the universe must have been around forever, and we have to find a way to explain the observations without concluding that time started at that point. Ergo: a bouncing universe!And if good people die and go to Heaven, why shouldn't our good universe die and rise again and go to Big Bang-Heaven? And why shouldn't a new Big Bang produce a universe just like ours, only perhaps a little better?
As a non-religious person, I regard the Big Bounce hypothesis as a mixture of religious ideas and wishful thinking.
If you really want to... that's pretty much my point, Henning. The bouncing universe seems to be one that many people want, so some astronomers may try their best to oblige them. Demand and supply, you know... where there is a demand for something, some people will do their best to supply it.Henning Makholm wrote: In retrospect, somebody probably ought to have asked themselves where all the entropy of the incoming universe would go during the process, but there are all sorts of ways to think around the Second Law of Thermodynamics if you really want to.
You are talking about Fred Hoyle, aren't you? He was a famous atheist with many strange ideas. I don't think he is very represtentative of atheists, certainly not of modern-day atheists.Hm, I get a somewhat opposite impression. A lot of the early emotional resistance to the big bang idea came from atheists who felt that the idea that the universe has existed for only a finite time sounded too much like creationism. If the universe was created 15 gigayears ago, there must have been a Creator, nyet? And because only stupid people think there was a Creator, the universe must have been around forever, and we have to find a way to explain the observations without concluding that time started at that point. Ergo: a bouncing universe!
Yes, today the Big Bounce seems to be a pretty religious idea.Today of course, the dominant mode of emotional resistance to the big bang seems to come from religuous people who dislike it simply because it is a different story from the 7-day Genesis.
Sorry, bystander. I was out of line.Please leave religion, or lack thereof, out of the discussion, Rule #14.
Not much, because it depends on the Universe collapsing in a Big Crunch. That idea made sense before observations demonstrated with a fair degree of certainty that the expansion rate of the Universe is increasing, and therefore it will not ever collapse.Ann wrote:Religion aside, does anyone know how much support the Big Bounce hypothesis (which postulates that our universe is going to undergo collapse and then rise again, phoenix-like, from the ashes of the Big Crunch) receives from professional astronomers of today?
That's a bit uncharitable. Would those astronomers not be able to want things for themselves? The Second Law sounds pessimistic enough on its face that I really cannot fault the theorist who wants to find a way around it.Ann wrote:If you really want to... that's pretty much my point, Henning. The bouncing universe seems to be one that many people want, so some astronomers may try their best to oblige them. Demand and supply, you know...Henning Makholm wrote: In retrospect, somebody probably ought to have asked themselves where all the entropy of the incoming universe would go during the process, but there are all sorts of ways to think around the Second Law of Thermodynamics if you really want to.
Not that I know of. The name doesn't ring any particular bell. (Untill I googled. It probably should have, but I'm bad with names).You are talking about Fred Hoyle, aren't you?
I was not implying that that the (un)reasoning I described was representative of "atheists" in general. I would sooner claim that readheads have a uniform opinion about building codes.I don't think he is very represtentative of atheists, certainly not of modern-day atheists.
I don't think the Big Bounce itself even has enough serious advocates today that trying to generalize about their motivation is very enlightening. It is unattractive from a scientific point of view (because of thermodynamics and GR), and it doesn't go far enough for those who're willing to disregard scientific evidence for religious reasons. (If you want a 7-day genesis, you'll want to avoid the big bang altogether, not precede it by an earlier universe).Yes, today the Big Bounce seems to be a pretty religious idea.
Hmm, I thought we were covered by "Focused, polite discussion of concepts such as creationism and "intelligent design" which bear direct relevance to astronomy and science, for the purposes of conversing about and addressing misconceptions." It's not as if Ann and I are trying to convert each other ...bystander wrote:Please leave religion, or lack thereof, out of the discussion, Rule #14.
Perhaps that is how you see it, but you should distinguish this philosophical viewpoint from the scientific one, which rather strongly suggests the Universe will continue to expand forever- an idea that is not at odds in any way with any fundamental scientific concepts, or even with many naturally observed phenomena at our scale.beyond wrote:The Universe, to me, will expand untill it stops and then it will just stay there in an expanded state, just like everything else that is animated(living?)does.
Bare with it, it will come to my point. 1 of 5Henning Makholm wrote:Hmm, I thought we were covered by "Focused, polite discussion of concepts such as creationism and "intelligent design" which bear direct relevance to astronomy and science, for the purposes of conversing about and addressing misconceptions.
Actually it is not at odds with what i said either, at least the way i see it. It could be that as far as human-kind is concerned, the Universe will never reach it's fully expanded state.Chris Peterson wrote:Perhaps that is how you see it, but you should distinguish this philosophical viewpoint from the scientific one, which rather strongly suggests the Universe will continue to expand forever- an idea that is not at odds in any way with any fundamental scientific concepts, or even with many naturally observed phenomena at our scale.beyond wrote:The Universe, to me, will expand untill it stops and then it will just stay there in an expanded state, just like everything else that is animated(living?)does.
