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New Evidence for Open Universe
Observations made by the Hubble telescope have produced evidence that the universe is full of "dark energy", stuff that has mass but does not emit nor block light, and that a disregarded theory first postulated by Einstein about "negative gravity" is actually valid. If true, this would provide firm evidence that the universe will not collapse in a "big crunch" but will expand indefinitely. See the SF Chronicle, New York Times, MSNBC, or CNN for stories (the Chronicle story is the best, IMHO). For background information, you may want to check out the cosmology FAQ or more information about negative gravity. (Update: 04/04 11:03 AM by michael : A couple of people have pointed out that this write-up is inaccurate; I'm not going to try to correct it, but read the comments for more information.)
This leaves you with a singularity that exploded for no apparent reason and existed for no apparent reason. Where did it come from? Why did it explode?
How complex do things have to get before "God did it" becomes the best explanation?
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For full disclosure, I am a physics graduate student working in the astronomy department at Berkeley. Although I am not a cosmologist, I heard the latest on the supernova searches from one of the key investigators yesterday at an informal brown bag lunch. As a regular /. reader, I thought I would put in my own two cents worth of corrections and additional info.
First, the existence of a cosmological constant is NOT at all news. Prior observations by both the LBL group doing observations of supernovae type Ia (group page) and the BOOMERANG group doing observations of the cosmic microwave background (group page) verified the existence of a cosmological constant several years ago.
Second, as a previous poster has stated, the geometry of the universe is NOT necessarily open.
See especially this informative figure which shows the allowed region of parameter space based on both the SNIa and the BOOMERANG results. As you can easily see, the combined results are consistent with a flat universe with a cosmological constant, but the flat universe is a critical case, and one cannot exclude either an open or closed universe.
Third, what IS new is the detection of an extremely distant SN at redshift z = 1.6. The discovery, made largely by Adam Riess, who is now at the Hubble Space Telescope Institute, was largely serendipitous; it was detected in the Hubble Deep Field, and a number of prior observations allowed Riess to piece together a light curve from which he could infer the intrinsic luminosity. The NEW results are remarkable for two main reasons :
1) Critics have argued that a thin smattering of grey dust in intergalactic space could mimic the effect of a cosmological constant (ie, for a fixed redshift, objects seen are dimmer not due to an acceleration of the expansion of the universe, but instead due to obscuring dust along the line of sight, where the dust must absorb equally well at all frequencies). However, at very high redshift, the relative contribution of matter is higher, and so objects seen are BRIGHTER than what one expects in a freely coasting universe. This is not the trend predicted by the simplest dust model. So the recent evidence is one further advance for the non-zero cosmological constant model.
2) At such high redshifts, clocks appear to be moving faster because of the relative expansion of the universe since then (a photon wavelength is stretched out, but c remains constant, hence the photon frequency is also slowing in time in the universe, as are all clocks). The high redshift SNIa light curve exhibits this general relativistic time effect, and one cannot make sense of the curve without correcting for it.
Science, like Nature, must also be tamed, with a view turned towards its preservation.
It's not silly to explain it away - if the explanation is testable, then it's a valid concern. If you're a good experimentalist, you can *always* come up with a better explanation than "bad physics" - especially because you know the portions of your research that were hacks - and there are *ALWAYS* hacks. :) So if you can't find a problem with your experiment that might explain something, honestly, you're fooling yourself. It might be that all of the explanations you can come up with are crap - I'm not suggesting that any experimental effect can be explained away - I'm just saying any good experimentalist can come up with problems with their own experiment, even if they're not real.
Anyway, take something from my field: in the 80s and 90s, a bunch of experiments all seemed to confirm that the positron fraction in cosmic rays increased at high energies. This made no sense - and fundamentally you don't want to believe it at all. But they all confirmed it, until the next class of experiments came along and showed "oh, wait, you didn't have good enough rejection."
The fact is that in a good experiment, they should've immediately guessed "um, we might not have good enough rejection" and in fact, some of them did suggest that, and that's what led to the better experiments. It might've been that what they saw was real, and their concerns were baseless, but they came up with the concerns, which is the important part.
I agree that the fact that several groups got consistent answers is suggestive, but far space astrophysics relies on far too many assumptions to suggest redefining physics on a small scale until you get a huge swath of data to back it up. Everyone nowadays seems to be hinting in every talk and paper that I read that "evidence is mounting for a cosmological constant": no. Evidence is mounting for a systematic problem in our data regarding the expansion of the universe. The fact that it MAY be explained by a cosmological constant is unimportant. The cosmological constant is a 'fudge factor' in these cases: you can't disprove it because you can fit it to the data. The fact that you can fit it to all the data just says that the experiments are all measuring the same thing precisely - not necessarily accurately.
It was a psuedo-mistake. It was thrown in because it *can* exist.
Historically it was set to zero because it doesn't look pretty in the equations, but there's no reason it should be zero, and in fact, current astronomical observations say that it's probably not zero.
Of course, I'll state my opinion flat out and say that I think the astronomical observations are flawed in the first place, for many fundamental reasons (especially the supernova observations. Trust me. Supernovae are anything *but* reliable observations). I've seen too much duplicity in reporting of astronomical data (see also the Hubble Constant war) to believe anything 'surprising' like this.
It's possible, but the researchers IMHO are trusting their own data too much to suggest something like this. Start from the assumption that the cosmological constant is zero, then try to see if there's anything in your data that would explain the problem OTHER than a cosmological constant. If you can't find anything, you're a bad scientist - talk to some other ones and get some ideas. Check those ideas, check your instruments, run the experiment again. Repeat. Only when you've exhausted everything you can think of can you say "well... we might want to consider a cosmological constant."
The "bad scientist" comment up there implied that a good scientist can always come up with a problem in his/her experiment that will cause a systematic error, not that a cosmological constant is inherently bad.
I don't know. IMHO they haven't done enough checking yet to convince me. Supernova data doesn't convince me - they're way too variable, and they are NOT standard candles, regardless of what anyone tells you.
It's been ported to Lisp and is an Emacs package. Just type M-x big-! and start your own universe.
First of all, these data do _not_ suggest that the universe is open, but rather that it is flat. This is a key cosmological difference.
Secondly, dark energy does _not_ have mass (you're probably thinking of dark matter). Dark Energy is thought to be (by some) the vaccuum energy density of the universe. At the current time, it appears that dark energy is accelerating the outward motion of the universe. This, in fact, is what the supernova observations are showing: given our expansion rate now, we would expect the supernova to be moving away from us more quickly than the actual motion we observe. This suggests that the universe was expanding more slowly in the past than it is now; that is, the universe is accelerating in its expansion.
Because it adds to the overall energy density of the universe, however, it is thought to suggest that it makes the universe flat, cosmologically speaking.
I couldn't tell if you were experimenting with poor-man's cryogenics or looking for the orange sherbet.
http://antwrp.gsfc.nasa.gov/apod/
Today's Astronomy Picture of the day is all about this, too. It's got a bunch of links at the bottom for people wanting to read more.
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Too late, SGI already has a trademark.
Can your IM do this?
Why do you need a purpose? The "purposes" you list for other discoveries seem like they were concocted after the fact to justify it for people who prefer to believe in a supreme being guiding the Universe.
If you really need a purpose, here's one: to provide us with a challenge. If the Universe continues to expand indefinitely, there will be a time when the average density of the Universe is low enough that the formation of news stars becomes unlikely, and the fuel for those stars will begin to be burned up. Survival of the human race will be almost impossible in those conditions. The fight to survive will be the last remaining challenge for a race that will have had more than enough time to uncover a set of physical laws that describe the Universe. We'll need something to do.
- W. Blaine Dowler
http://www.bureau42.com
Great ! Does that mean I can change its source and recompile it ?
It was a psuedo-mistake. It was thrown in because it *can* exist.
It was not a mistake to include it, not even a pseudo-mistake. At least in hindsight :-) And I don't mean from an observational viewpoint; from a fundamental theoretical viewpoint, you EXPECT there to be a cosmological constant term. Here are just two reasons:
The problem since the seventies has not been to explain why the cosmological constant is not zero (since you wouldn't naively expect it to be), but why it is so CLOSE to zero; that is, why does the universe have some approximate symmetry that keeps the cosmological constant so small, despite what would otherwise be its natural inclination to be large.
Observations made by the Hubble telescope have produced evidence that the universe is full of "dark energy", stuff that has mass but does not emit nor block light,
Your dark energy explaination is actually the definition of "Dark Matter". Dark energy is the repulsive force in space that accelerates the already spreading galaxies.
Another theory that supports this "Dark Energy" is the theory of a second sun Nemesis
Good quote, too many chars. Seriously, the slashdot 120 char limit sucks!
can be found here:
Blast from the Past: Farthest Supernova Ever Seen Sheds Light on Dark Universe
... and some more information, why this should tell us, that the universe is expanding faster.
I don't know about anybody else, but did anyone else say "whew" when you read this? I was always worried that if, by some miracle, cryogenics was ever perfected and we could live forever, we would be stilted by a crunching universe (not a terribly fun way to die). At least now we have some extra time.
- I don't care if they globalize against free speech. All my best free thoughts are done in my head.
The cosmological constant, which provides a repulsion on the cosmological scale, was famously declared by Einstein to be the biggest mistake of his life. However, it has been known for many decades now that the it is a very valid part of the theory - it's not so much a fudge factor as a constant of integration.
A common misconception, left over from decades of cosmology textbooks which implicitly assumed a zero cosmological constant (equivalently, no dark energy). These textbooks all make the equation that closed geometry = universe recollapses, open geometry = universe expands forever, flat geometry = borderline case.
In fact, if you have a cosmological constant (or dark energy), you can have a closed univere which expands at an accelerating rate.
The best evidence about the geometry of the universe currently comes from cosmic microwave background observations, which suggests that the geometry is *flat*. The supernova evidence suggests that the expansion of the universe is accelerating.
It is a mistake to state that an eternal expansion, or an accelerating expansion, is an "open" universe.
-Rob
Ok so my postings so far for the day will come to a halt, but I figured this should be included in the topic, or... You could just read it anyways...
Two British astronomers have counted up to 20 "free floating" planets, drifting in the constellation of Orion. They told the National Astronomy Meeting in Cambridge yesterday that they had identified the "signature" of water vapour in the infrared spectrum of faint points of light in the Orion nebula. This is a vast cloud of gas and dust 1,300 light years from Earth, but visible as the middle "star" in the sword of the constellation of Orion.
Read on
360 degrees of Karma
In fact, this really means that I doubt what the scientists say on this matter very much. Everything else in nature has a greater purpose and direction, a manifest destiny if you will, whether it be evolution or consciousness or even life itself. Scientists have always prided them on showing the point of life since the days of Euclid, through Newton (who was a very spiritual man) and onwards.
The entire body of science points towards there being a directional purpose to life. This discovery flies in the face of everything we have learned, and I for one am sceptical. Not until they show the higher purpose (multiuniverses?) will I be convinced of this.
You know exactly what to do-
Your kiss, your fingers on my thigh-
You know exactly what to do-
Your kiss, your fingers on my thigh-
I think of little else but you.