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131 comments

Use dark energy to get first post (-1)

Anonymous Coward | more than 3 years ago | (#36216564)

wwooooooo

I got it yes

Fuck yes

Bad pop-sci writing makes kittens sad (5, Informative)

Sneftel (15416) | more than 3 years ago | (#36216590)

here [swin.edu.au] is the actual press release, which (unlike that article) doesn't skip over what they actually did.

Re:Bad pop-sci writing makes kittens sad (5, Informative)

Dachannien (617929) | more than 3 years ago | (#36217002)

The press release is almost as bad, providing only one paragraph that actually mentions in extremely general terms what they did (something about observing galaxy and cluster distributions).

Also, the distinction not made here is that confirming the accelerating expansion of the universe is not the same thing as confirming the existence of dark energy. (And that's aside from "supporting evidence" not being the same as "confirming evidence".) There may be some other phenomenon at work here (e.g., something occurring off-brane and affecting our universe from outside, if the brane world theory turns out to be right), and observations of the structure of matter in the universe may not be sufficient to distinguish between dark energy and other possible phenomena.

Re:Bad pop-sci writing makes kittens sad (5, Informative)

Nadaka (224565) | more than 3 years ago | (#36217304)

That is exactly what dark energy is. Something that causes the universe to expand, but we really don't know what it is. It doesn't matter what specifically is, it is still called dark energy. Just like we have no idea what dark matter is, but it almost certainly exists.

Re:Bad pop-sci writing makes kittens sad (1)

mcneely.mike (927221) | more than 3 years ago | (#36217370)

it's like red matter, but only the klingons and vulcans have that. ;-)

Re:Bad pop-sci writing makes kittens sad (-1, Flamebait)

Anonymous Coward | more than 3 years ago | (#36217404)

Just like we have no idea what dark matter is, but it almost certainly exists.

Like God exists.

Re:Bad pop-sci writing makes kittens sad (1)

Joce640k (829181) | more than 3 years ago | (#36217716)

Not quite. Nobody's claiming that dark energy has any sort of intelligence or self awareness.

Re:Bad pop-sci writing makes kittens sad (1)

Archangel Michael (180766) | more than 3 years ago | (#36218116)

May Cthulhu strike you down for this heresy.

Re:Bad pop-sci writing makes kittens sad (2)

Nadaka (224565) | more than 3 years ago | (#36217758)

Our observations of the universe show that there is something affecting its structure on a massive scale. So we use dark energy and dark matter as placeholders until we can figure out what it is.

Now, if we were able to scientifically observe and quantify magic, resurrections, and the power of prayer? Then yes, it would be similar to saying "god" exists. But until you do that, the two are nothing alike.

Re:Bad pop-sci writing makes kittens sad (0)

Anonymous Coward | more than 3 years ago | (#36217924)

Do not underestimate the power of the Dark Energy.

Re:Bad pop-sci writing makes kittens sad (5, Informative)

Artifakt (700173) | more than 3 years ago | (#36218836)

If you use the term 'Dark Energy' for a place-holder of sorts, as many people popularising the concept still do, you're right, but the term has become more than that (which I guess leaves you semi-right) :-)

There are basically three, maybe four classes of hypothesis about dark energy.
1. There's an original set of hypothesis that was based on some estimates about the amount of normal matter in the universe and the amount of dark matter and dark energy there would need to be to make the universe just barely closed, based on the raw data astronomers had about 1994-95.
2. There's a second set of them, based on more current data, circa 2005-10. These are based on their being a lot more visible mass in the universe than we once thought in the 90's, but still a lot less (an order of magnitude, at the very least) than needed to close the universe. .They're also based on being able to rule out both some forms of undetected normal matter and possible types of dark matter. So we have some idea of what dark matter is, in that we now are sure it doesn't behave like most of those earlier models. In particular, we now are pretty sure dark matter doesn't pack together in the same way as normal matter - it won't 'schrunch down' to make something as compact as a star or a galaxy, but instead has a much shallower density gradient, forming huge clouds that are not much denser in their middles than near the edges. Unfortunately, almost none of the data seems to predict that dark matter is any of the hypothetical particles from various theories that seem likely in particle physics/quantum mechanics/string theory. Maybe it's a mixture of several, but that's a complex explanation and physicists are reluctant to go with that.
3. Maybe there's a simple explanation, one that requires only a single type of dark matter and a single force for dark energy..Maybe there's even a single theory.that will tie both of them together. But all the types of hypothesis considered for that role are in the area of far from mainstream physics. They all have a certain flakey side to them, almost like the electric universe hypothesis. (And no, I'm not saying that electric universe is a valid contender for a theory to explain dark energy - it does not appear to be at all - I'm just saying that the third group of hypothesis are every bit as strange as E.U.).
4. There's the occasional really weird hypothesis, that doesn't even worry about whether it predicts the universe is flat, doesn't seem to support a simple, single form of dark matter either, and is basically baroque in its elaboration, quirky in its math, and filled with ad-hoc assumptions where we are hoping that instead we will be able to derive some of the fundamental constants from simpler basics..There's a lack of elegant symmetry to the maths, and a certain amount of 'just because' to the underlying concepts. These models look like long-shots to most of the physics community, but if one of them gains traction, we would need to quit worrying about the relative flatness of the universe and why it might be expanding - for many of these models, expansion now doesn't necessarily mean the universe ever had an actual big bang, or an initial inflationary period either, and you can probably relax about the big rip too.

Re:Bad pop-sci writing makes kittens sad (1)

Anonymous Coward | more than 3 years ago | (#36219430)

posting anonymous because i burned all my mod points in this thread. out of interest, would you care to provide any examples for (3) and (4)? i'd imagine that with (3) you're thinking things like chaplygin gases, but how about (4)?

you're also missing at least the following

1.5) The hypotheses between 1997 and 2005, which are very similar to the current hypotheses. Given that SN1a data came along in 1997 and the Lambda CDM model was pretty much immediately adopted as standard, with various "dark energies" soon postulated, you're missing a big chunk of time there. And given that WMAP1 came out in 2003, you're also missing the dramatic confirmation that WMAP1 brought with it.

5) Inhomogeneities, which can mimic some of the effects of dark energy. All the models that have been looked at so far are pure toy models and no-one is pretending that they're a valid model of the universe, but they're a proof of concept that local structure can have a significant effect -- and it would take an idiot to pretend that there isn't local structure near us.

6) An inaccurate model. It would also take an idiot to pretend that LCDM (or variations) isn't a superb model. It fits almost every prediction made thus far and frankly we have no serious competitor. But LCDM itself is "filled with ad-hoc assumptions", the most important of which is that we're pretending we know how to construct an average in GR. We don't and every attempt (probably including Zalaletdinov's) is gauge- or frame-variant. And yet we blithely say "the universe on average obeys a Robertson-Walker metric, so we plug it into the Einstein equations and...". Except that the average dynamics are not the dynamics of the average -- even if we can't perform the average we *can* say that! Likewise, the average geodesics are not the geodesics of the average. So we're definitely workign with the wrong model. Of course, any studies of this so far have been incomplete and tend to find corrections that act as curvature or dark matter and are frankly impossible to interpret, but even so...

WTF Grammar (5, Funny)

degeneratemonkey (1405019) | more than 3 years ago | (#36216596)

Last part of summary segfaults my internal parser.

Re:WTF Grammar (0)

Anonymous Coward | more than 3 years ago | (#36216836)

"Einstein is correct, as so far, usual."

best i can make out it should read:

"Einstein is correct, so far, as usual."

Re:WTF Grammar (1)

Kokuyo (549451) | more than 3 years ago | (#36216874)

Or:

Einstein is correct, as, so far, usual.

Very ugly either way...

Re:WTF Grammar (1)

robthebloke (1308483) | more than 3 years ago | (#36216952)

"So far, Einstein is correct, as usual."

Looks like a case of attack of the touchpad to me....

Re:WTF Grammar (2)

multisync (218450) | more than 3 years ago | (#36217072)

Or ...

"Einstein is correct, as usual (so far)."

Or ...

"Enstein is correct, as - so far - usual."

Or ...

"As usual, Einstein is correct. So far."

Re:WTF Grammar (1)

StikyPad (445176) | more than 3 years ago | (#36217920)

Except Einstein isn't usually correct. E.g., he didn't believe Heisenberg's uncertainty principle, and his first four proofs of E=mc^2 were flawed. It's just that his successes outshine his mistakes, so the latter are forgotten, as so far, usual.

Re:WTF Grammar (1)

Anonymous Coward | more than 3 years ago | (#36217950)

Or ...

"Is Einstein correct so far? As usual."

Or ...

"So, Einstein is far? Correct, as usual."

Or ...

"As Einstein, far is correct. So usual.

Or ...

"Einstein! Far is usual! Correct, ass."

Re:WTF Grammar (1)

Austerity Empowers (669817) | more than 3 years ago | (#36218138)

I think they call this grammar nazi baiting.

Re:WTF Grammar (5, Funny)

TheLink (130905) | more than 3 years ago | (#36216992)

That confirms the existence of dark grammar.

Re:WTF Grammar (0)

Anonymous Coward | more than 3 years ago | (#36217610)

Don't worry. It's not just you. I have to add a ppa to my repositories to allow my brain parse that

Einstein was right? (1)

m50d (797211) | more than 3 years ago | (#36216626)

Would that be when he called the cosmological constant "the biggest mistake of my life"?

(Not disagreeing with the result, but the einstein-fanboying in TFA is a little irritating)

Re:Einstein was right? (1)

austinpoet (789122) | more than 3 years ago | (#36216660)

fanboying einstein is better than fanservicing einstein

Re:Einstein was right? (0)

Anonymous Coward | more than 3 years ago | (#36216910)

Really? I'm sure with a haircut he'd be quite the grey fox.
even without the haircut... /giggles~

Re:Einstein was right? (1)

Nadaka (224565) | more than 3 years ago | (#36217346)

Haha.

I know someone who wrote a fan service about Albert Einstein and Isaac Newton...

She is an odd one.

Re:Einstein was right? (1)

nedlohs (1335013) | more than 3 years ago | (#36217206)

TFA has that quote in it, so I guess you're doing einsteinfanboying if they are.

That is the core of the joke being made after all.

Re:Einstein was right? (1)

chemicaldave (1776600) | more than 3 years ago | (#36217606)

Doesn't make any less correct. I'm reading into it as "Oh, hey, whaddaya know. Looks like he was right." Which he has consistently been good at.

Re:Einstein was right? (4, Insightful)

bunratty (545641) | more than 3 years ago | (#36217706)

Yes. The reason that it was a mistake is that relativity predicts that the universe must be contracting or expanding. Because Einstein thought that the universe was static, instead of actually making the prediction, he added a fudge factor of gravitation repulsion that would keep the universe from collapsing under its own gravity. So he was wrong, because the universe is in fact expanding.

The reason it was the biggest mistake of his life is that adding gravitational repulsion to gravity produces an unstable equilibrium, so it would not have resulted in a steady state even if he was right. All matter would have had to have been equally distributed across the universe, and any perturbation would have caused local clumps that would collapse under gravity. So he incorrectly added his incorrect fudge factor. He was very, very wrong.

There's a reason he called it his biggest mistake. He made an obviously wrong prediction instead of correctly predicting the expansion of the universe. The fact that we now detect a repulsive force has nothing to do with Einstein's prediction except that it's also a repulsive force. It's just coincidence.

Re:Einstein was right? (1)

Talderas (1212466) | more than 3 years ago | (#36218064)

I'm a bit murky. I last read an Einstein biography about 8 months ago...

Was it that Einstein believes the universe wasn't expanding or that he capitulated to the common held belief that the universe wasn't expanding? In one case you had Einstein believing wrong and the other had Einstein kowtowing to the status quo.

Re:Einstein was right? (3, Insightful)

pclminion (145572) | more than 3 years ago | (#36218078)

Einstein saw it as a huge mistake, but it wasn't. Current evidence suggests that the value of the cosmological constant is not zero, it's some small positive number. If Einstein had not put the cosmological constant in in the first place, we wouldn't have been able to assign a value to it. His blunder was the assumption of a static universe, not a cosmological constant. The cosmological constant was a leap of physical intuition -- it has a value other than Einstein thought it should have, but so what? He was obviously a bit smarter than most of us :-)

Re:Einstein was right? (1)

Anonymous Coward | more than 3 years ago | (#36218502)

It's not *that* much of a leap of physical intuition. On the one hand if you look at relativity as a collection of partial differential equations it crops up inevitably as an integration constant that would otherwise be *assumed* to be zero. So in principle it's there at the outset and is just arbitrarily removed.

On the other hand if you view relativity in any other way the "cosmological constant" emerges one way or another -- as the constant term in a Laurent expansion of a more accurate Lagrangian density, or as a low-energy term coming out of some higher-energy modified gravity theory, or the basic identification which is as the energy of the vacuum itself. Getting the right *numbers* is tough, but that's a different matter; a constant term is fairly inevitable. And Einstein only got the "right" number by putting it in by hand, and his value was well out from the current observations and only of an equivalent order of magnitude because he wanted it to balance the universe while we want it to slightly accelerate it.

Move along (1)

dimethylxanthine (946092) | more than 3 years ago | (#36216640)

This is not the energy you are looking for...

Congrats to my kid's favorite band (0)

Anonymous Coward | more than 3 years ago | (#36216656)

Glad to see the Wiggles continue to break barriers and provide kids entertainment AND scientific research. They're the greatest thing Australia has ever given the world.

Einstein is correct usual! (0)

Anonymous Coward | more than 3 years ago | (#36216680)

Really folks, the tests your grade school teacher taught you are effective for examples such as these.

Einstein was wrong most of the time (1)

Anonymous Coward | more than 3 years ago | (#36216702)

Even if the percentage when he was right was a lot higher than most everyone on this planet. He made plenty of mistakes. Furthermore, stop thinking of him as an old man with the funny hair. He was still young when he did his important work, while most of the mistakes came later.

Re:Einstein was wrong most of the time (1)

Nadaka (224565) | more than 3 years ago | (#36217356)

Correct, at one time he was a young man with funny hair.

Re:Einstein was wrong most of the time (1)

UncleTogie (1004853) | more than 3 years ago | (#36220154)

Correct, at one time he was a young man with funny hair.

Are Y'oo Serious?

A bit of a stretch... (4, Insightful)

Eggplant Jeff (1859792) | more than 3 years ago | (#36216716)

Seems like TFA is slightly misleading though. They didn't confirm DARK ENERGY, they provided a bunch of data that confirms the universe is expanding AS EXPECTED PER CURRENT THEORY (and current theory uses dark energy to explain). It isn't like they built a dark energy detector and said "Wow, the readings are off the charts!"

Re:A bit of a stretch... (1)

Henriok (6762) | more than 3 years ago | (#36216828)

If they had built such a detector, wouldn't they the charts be calibrated to about the expected amount of dark matter?

Re:A bit of a stretch... (0)

Anonymous Coward | more than 3 years ago | (#36216902)

If they had built such a detector, wouldn't they the charts be calibrated to about the expected amount of dark matter?

Probably yes, but that misses the point. "Wow, the readings are off the charts!" is just something you have to say from time to time if you're a serious scientist.

Re:A bit of a stretch... (1)

Dyinobal (1427207) | more than 3 years ago | (#36217074)

Everyone knows the standard detector only goes up to nine thousand. The Dark Mater was clearly over nine thousand if it was off the charts.

Re:A bit of a stretch... (1)

Dynetrekk (1607735) | more than 3 years ago | (#36217264)

Don't you mean, 11 [xkcd.com] ?

Re:A bit of a stretch... (1)

amRadioHed (463061) | more than 3 years ago | (#36218948)

Don't you mean, 11 [youtube.com] ?

Fixed that for you.

Re:A bit of a stretch... (1)

berashith (222128) | more than 3 years ago | (#36217284)

what if dark matter goes all the way up to eleven?

Re:A bit of a stretch... (1)

marcosdumay (620877) | more than 3 years ago | (#36219086)

That may be the reason it goes off the charts. Calibrating it for dark matter will make it quite wrong for detecting dark energy.

(a) current theory (2)

bill_mcgonigle (4333) | more than 3 years ago | (#36216978)

and current theory uses dark energy to explain

The most popular current theory does - there are competitors as well. But, yeah, this is useful because those working on all the theories can keep on going, knowing that they're more likely to be on the right track than they were yesterday.

Re:A bit of a stretch... (0)

Anonymous Coward | more than 3 years ago | (#36217024)

As far as I know, "dark energy" is another name for the accelerating expansion of the universe, not a mechanism. To make a simple analogy, it's a bit like if they said "we measured gravity!" and you replied "no, you've measured things falling to the ground". Well duh, that's what call gravity.

Re:A bit of a stretch... (1)

khallow (566160) | more than 3 years ago | (#36217648)

This is correct. They aren't claiming there is some sort of unseen energy. That's just the name that stuck. If they're seeing an expanding universe, they're seeing "dark energy".

Re:A bit of a stretch... (4, Insightful)

mangu (126918) | more than 3 years ago | (#36217054)

They didn't confirm DARK ENERGY, they provided a bunch of data that confirms the universe is expanding AS EXPECTED PER CURRENT THEORY (and current theory uses dark energy to explain).

You inverted cause and effect. There's no theory for the expansion of the universe by itself, dark energy is a theory that was created to explain the *measured* expansion. The problem with it is that it's ad hoc, dark energy is not predicted by any other effect that we have observed.

The press release was skimpy on details, but if I got it right it has demonstrated that dark energy is a good fit to the observed distribution of visible mass in the universe.

Re:A bit of a stretch... (0)

Anonymous Coward | more than 3 years ago | (#36217406)

Well, that depends on your definition of energy. Stuff moving faster means there's extra energy, and the fact that they didn't build dark energy detector only confirms that it's dark. :P

Re:A bit of a stretch... (0)

Chemisor (97276) | more than 3 years ago | (#36217426)

If you instead propose that the universe oscillates in size, then it would become obvious that expansion will first be accelerating then decelerating, sinusoidally. Dr.Randall Mills proposes that the acceleration is caused by the stars "burning" matter into energy, uncurving space. Eventually matter will all turn to energy or black holes, black holes will over time capture all the energy and by becoming more massive will cause space contraction. Then something magical will happen and the black holes will explode and become matter again, restarting the cycle. According to Mills, the cycle ought to take about a trillion years. While his other theories have not been particularly successful, I think he's much closer to the target here than the mainstream "dark energy" crowd.

The Wiggles?? (1)

Gumbercules!! (1158841) | more than 3 years ago | (#36216718)

I guess the Wiggles [wikipedia.org] are really taking their child education program seriously.

You spelt Wiggles wrong, btw.

Re:The Wiggles?? (1)

OzPeter (195038) | more than 3 years ago | (#36216858)

I guess the Wiggles [wikipedia.org] are really taking their child education program seriously. You spelt Wiggles wrong, btw.

I wish I could find the reference, but I remember a few years ago of an astronomer(?) calling some celstial objects B1 and B2 after Bananas in Pyjamas. So the Wiggles are justplaying catchup.

Re:The Wiggles?? (1)

L4t3r4lu5 (1216702) | more than 3 years ago | (#36217184)

Further evidence of a music career preceding physics [wikipedia.org]

Seriously, though; The music industry can keep Blue.

But does it proof the dark energy existence ? (2)

nithril (2191466) | more than 3 years ago | (#36216740)

Ok It seems they proof the universe was expanding at an accelerating rate. But does/why it proof the dark energy existence ?

Re:But does it proof the dark energy existence ? (1)

Anonymous Coward | more than 3 years ago | (#36216790)

It does prove (again) that there is something that causes accelerating expansion, they call it dark energy because they don't know what it is.

Re:But does it proof the dark energy existence ? (1)

nithril (2191466) | more than 3 years ago | (#36216906)

Something or maybe equation is .. wrong ? There is no dark matter nor dark energy, just incomplete/incorrect equation.

Re:But does it proof the dark energy existence ? (1)

The_Wilschon (782534) | more than 3 years ago | (#36218036)

Yes. This is correct. The Einstein field equations without a cosmological constant fail to describe the universe. Thus those equations are incorrect or incomplete. However, when we add a cosmological constant, the resulting equations do correctly describe the universe. We don't know, on a microscopic level, what sort of effect produces the term in the equations called the cosmological constant, but we do know some very general features of what sort of microscopic phenomena could produce that term. More specifically, an amount of energy which is proportional to the volume of space would produce a cosmological constant term. Since we know with a reasonable degree of certainty that a) the phenomenon in question is an energy type phenomenon, and b) it does not appear to couple to the photon, it is a form of energy which is "dark", and we call it "dark energy".

I really wish that this "dark matter and dark energy just mean scientists have no idea what they are talking about" meme would die. It simply isn't true. There are some very specific things that we don't know about dark matter and dark energy. There are a lot more things that we do know about them.

Re:But does it proof the dark energy existence ? (1)

david_thornley (598059) | more than 3 years ago | (#36218702)

So you know, for example, that there is nothing that has mass and doesn't interact with photons? How do you do that, divine revelation?

And, yes, the current theories don't work with observable matter and energy, much as pre-quantum physics couldn't account for things like black-body radiation. When that happens, physicists come up with wacky "what-if" ideas, such as the idea that light (known to be a wave) could only come in packets of a certain "size". Other physicists start playing with those ideas, and finding other things the ideas could explain, predictions of what we could observe under the ideas, and ways in which we could test those ideas to see which have promise and which don't.

It turned out that black-body radiation wasn't explained by classical physics, but required some of the basics of quantum mechanics. It turned out that the differences between Mercury's predicted and observed orbit weren't due to another planet inside Mercury's orbit (named "Vulcan"), but were evidence of some really strange ideas called General Relativity. To a physicist of the 19th Century, quantum mechanics and general relativity would have seemed far wackier than, say, matter and energy that can't be observed using modern observation techniques.

Re:But does it proof the dark energy existence ? (0)

Anonymous Coward | more than 3 years ago | (#36216854)

F = m x a

Re:But does it proof the dark energy existence ? (1)

pclminion (145572) | more than 3 years ago | (#36217864)

Ok It seems they proof the universe was expanding at an accelerating rate. But does/why it proof the dark energy existence ?

Because dark energy is defined as a substance (quantity, thing, whatever) that causes accelerated expansion of the universe.

It sounds goofy but this is legitimate in science, especially physics. For instance, what is a wave function? Well, it's the variation over time and space of "some quantity". What quantity? What IS it? We don't know, however, we can do math on it and arrive at specific predictions which are confirmed by experiment. Nobody to this day knows what "it is" with respect to the wave function, yet we all accept that it's a legitimate thing, mathematically at least.

Re:But does it proof the dark energy existence ? (1)

The_Wilschon (782534) | more than 3 years ago | (#36217986)

Dark energy refers to a specific general relativistic situation. While we don't know why that situation occurs, we have done measurements (including this one) confirming that the particular inputs we put into the equations of GR reproduce the characteristics of the universe to within theoretical and experimental uncertainty.

There are lots of ways that one could construct an alternative theory that would also describe a universe expanding at an accelerating rate that would not agree with our observations. The fact that our observations (and in particular the new observations of the WiggleZ experiment) agree with the particular theory called "Dark Energy" (or more accurately the Lambda-CDM model) and disagree with lots of other potential theories is the subject of the article.

Einstein is always right (0)

Anonymous Coward | more than 3 years ago | (#36216886)

Because history is written by the winners.

Re:Einstein is always right (1)

robthebloke (1308483) | more than 3 years ago | (#36216968)

Awesome! I can't wait to see the history of the 21st century according to Charlie Sheen!

Educational Songs (1)

VorpalRodent (964940) | more than 3 years ago | (#36216900)

When I was a kid, TV shows had songs about the alphabet and counting. Apparently, The Wiggles [wikipedia.org] are doing children's edutainment about theoretical physics? Wow...

Re:Educational Songs (5, Funny)

drinkypoo (153816) | more than 3 years ago | (#36217010)

When I was a kid, TV shows had songs about the alphabet and counting. Apparently, The Wiggles are doing children's edutainment about theoretical physics? Wow...

The cat in the box goes 'round and 'round...
Round and round
Round and round
The cat in the box goes 'round and 'round...
Now let's see if it's dead!

Really Slashdot (2)

JamesP (688957) | more than 3 years ago | (#36216924)

WTF has Einstein to do with this?!

Of course studies of dark energy are deeply conneted to general relativity. But don't throw names like you pretend you know what you are doing.

This is becoming ridiculous, this is like "Well, I drove 100Mi at 50MPH and it took 2 hours, looks like Newton is right again"

Cosmological Constant (5, Informative)

bill_mcgonigle (4333) | more than 3 years ago | (#36217038)

WTF has Einstein to do with this?!

I assume TFS was referring to the cosmological constant [wired.com] - some have figured that Dark Energy is the mechanism behind the lambda* in Einstein's equations.

*someday Unicode will work on Slashdot...

Re:Cosmological Constant (1)

MozeeToby (1163751) | more than 3 years ago | (#36217908)

Einstein added the cosmological constant because he felt at the time that the universe should be steady state, it shouldn't have an identifiable end. The cosmological constant was meant to exactly cancel out the force of gravity at cosmological scales so that the universe could effectively last forever. We know now that this is most likely not the case, eventually the expansion will accelerate so rapidly that individual subatomic particles will be torn to pieces by it. So really, Einstein was right in that there is a cosmological constant (and do note that he changed his mind later and removed it from the equations), but he was very much so wrong about what the value of the constant would be and the effects that it would have on the universe.

Re:Cosmological Constant (1)

marcosdumay (620877) | more than 3 years ago | (#36219174)

As far as I know, Einstein added the cosmological constant because the equations he was solving hod true for any value of it. Then he choosed some value different from zero because he wanted to make the universe static.

Re:Cosmological Constant (0)

Anonymous Coward | more than 3 years ago | (#36219794)

...

*someday Unicode will work on Slashdot...

Judgement Day [cnn.com] came and went. If we don't have unicode on Slashdot by now, it's simply not coming...

Re:Really Slashdot (0)

Anonymous Coward | more than 3 years ago | (#36217628)

Wow, you're so smart. Maybe we should throw out Relativity and just listen to you ramble.

Time dilation (0)

Anonymous Coward | more than 3 years ago | (#36216972)

Is it true that as the universe expands, it becomes less gravitationally dense, as a result light travels faster and gives the appearance the expansion is accelerating?

Re:Time dilation (0)

Anonymous Coward | more than 3 years ago | (#36218074)

no.

do you really think that cosmologists since 1921, basing the model on relativity and postulating a metric from which they can derive the propagation of light rays and therefore everything that affects them between source and observer, would have overlooked it while you, a squirt on slashdot who's never touched relativity or cosmology, noticed it?

face it, the people studying this know what they're doing. no-one sat up one morning shouting 'I MUST ADD DARK ENERGY INTO THE UNIVERSE'. they sat up late one night and said 'what the FUCK?' when they did and redid their calculation (which automatically includes, as i say, all the effects of gravity and the evolution of the universe on light propagation) and then did it again more times to convince their extremely sceptical collaborators who then redid it themselves before finally deciding that they hadn't made a mistake and should probably publish.

Re:Time dilation (2)

MoralHazard (447833) | more than 3 years ago | (#36218236)

Couple of problems with that:

  * Gravitationally-induced time dilation is a local effect--the degree of dilation for an observer depends on the strength of the local gravitational field at that observer's location. And while the universe's expansion does contribute some ongoing changes to the local gravity field strengths at every point throughout the universe, the size of those changes is miniscule compared to the absolute strength of even the earth's gravity at the planet's surface. The observed effects of lambda (cosmological constant, dark energy, whatever) are a whole lot bigger.
  * Time dilation works opposite to your description, i.e., the GREATER the local mass density (and therefore the more intense the local gravitational field) the faster time will move relative to the rest of the universe.
  * Einstein's GR includes the relativity of time and space in the model, as specific terms OTHER than lambda. Lambda is the part of the model that *cannot* be explained by anything else we already know about.

I know, I know: IHPBT. I needed something to do while my coffee was cooling.

Re:Time dilation (1)

BertieBaggio (944287) | more than 3 years ago | (#36218812)

IHPBT? Isn't that the code in Doom 1/2 for infinite ammo? *grin*

More Accurate Description (5, Informative)

Lluc (703772) | more than 3 years ago | (#36217092)

A team of Australian researchers has observed 200,000 galaxies, confirming existing theories about the expansion of the universe. These theories require an unobserved force known as dark energy to account for the expansion of the universe versus contraction that is predicted due to gravitational forces. Dark energy and dark matter have not yet been observed or measured in any way.

Re:More Accurate Description (0)

Anonymous Coward | more than 3 years ago | (#36217480)

A team of Australian researchers has observed 200,000 galaxies, confirming existing observations about the expansion of the universe. It seems to be expanding while physicists were expecting it to contact under the effect gravity. They have not one bastard clue as to why this is the case, but find they can get funding from research councils if they talk about dark things: like dark matter, dark energy and the dark side.

Re:More Accurate Description (1)

blueg3 (192743) | more than 3 years ago | (#36217532)

Dark energy and dark matter have not yet been observed or measured in any way.

Measuring the expansion of the universe is measuring dark energy. Perhaps you meant that they haven't been directly measured (that is what the "dark" implies, after all), although there are problems with that adjective: most things in physics these day are only ever indirectly measured.

Re:More Accurate Description (1)

Anonymous Coward | more than 3 years ago | (#36218266)

If it's a force, why is it called energy? Shouldn't it be Dark Force, or Dark side of the Force?

Re:More Accurate Description (1)

marcosdumay (620877) | more than 3 years ago | (#36219210)

1 - Dark energy is the name of whatever causes the universe to expand.

2 - A team of researches confirm that the universe is expanding.

1 & 2 -> A team of researches confirm that dark energy (whatever it is) exist.

Dark Magnetism (0)

Anonymous Coward | more than 3 years ago | (#36217126)

If there's dark energy and dark matter, is there also dark magnetism?

A non-physicist wonders....

Scientific Method (0)

Anonymous Coward | more than 3 years ago | (#36217232)

I may be wrong, but doesn't science only support a theory/hypothesis etc? I remember my professor ripping on some people because they confirmed Bandura's learning theory. He said that you can never confirm something in science, only support it.

not news (-1)

Anonymous Coward | more than 3 years ago | (#36217316)

This is not news! Do a google search for Dark Suckers.

Presumption of static images (1)

Drethon (1445051) | more than 3 years ago | (#36217488)

So we've basically taken a snapshot of the universe (since the time span we've been observing is a minute fraction just compared to a planet, much less the universe) and made definite measurements of movement from this still picture. I don't know, something always sounded wrong about this...

Re:Presumption of static images (1)

ThatMegathronDude (1189203) | more than 3 years ago | (#36217820)

Measurements of galactic movement are based on the fact that all other galaxies have a redshift, i.e. they are moving away from us and the doppler effect has shifted their light frequency toward the red end of the spectrum.

Re:Presumption of static images (0)

Anonymous Coward | more than 3 years ago | (#36217940)

Well, not /all/. M31, for example, is blueshifted. ;)

Re:Presumption of static images (1)

Drethon (1445051) | more than 3 years ago | (#36218028)

Which is great but have we ever correlated redshift to distance or speed with actual observations or just mathematical models? I'm all for mathematical models but when they don't have actual observational support I wonder a tad...

Re:Presumption of static images (1)

locofungus (179280) | more than 3 years ago | (#36218288)

It's a multifaceted calibration.

There are stars with predictable brightnesses that are close enough to exhibit parallax.

Those same stars in other galaxies then give us a distance to other galaxies.

There are other events, supernovas etc that are known to have an upper limit in brightness. From that we can estimate distances to far away galaxies.

Or we can use redshift to estimate the same distances.

Of course there are wide error bars. But it's not just a random guess.

And what is this "mathematical models without observational support". The whole point of a mathematical model is that it explains observations. There are two types of model - empirical, where the model agrees with the observations but we don't understand why the model should agree (the early atomic emission spectroscopy results fell into this category) and physical, where the model is based around our understanding of the underlying physics, those same atomic spectroscopy models are now physical models given that we now understand emission spectra based on the ideas of atomic number, electron shells etc

Tim.

Re:Presumption of static images (1)

Curunir_wolf (588405) | more than 3 years ago | (#36218470)

Which is great but have we ever correlated redshift to distance or speed with actual observations or just mathematical models? I'm all for mathematical models but when they don't have actual observational support I wonder a tad...

There are a number of techniques for determining distance based on relative luminosity (stars classed Cepheid variables were originally used by Hubble to determine the distance of objects). The technique originally used to determine that the expansion of the universe was actually accelerating used Type Ia supernova, which pretty much all have exactly the same luminosity. Since the luminosity of those objects is a known quantity, the distance is easily determined. So, yes, there is plenty of observational evidence, both of the expansion, and that the expansion is getting faster, not slowing.

Re:Presumption of static images (0)

Anonymous Coward | more than 3 years ago | (#36218184)

OH MY GOD YOU'RE RIGHT EVERY COSMOLOGIST EVER BORN IS TOTALLY WRONG!!!!!111111111111!!!!

STOP THE PRESSES, IDIOT SLASHDOTTER DISPROVES RELATIVTY

Retard. Do you *seriously* think that generations of people smarter than either of us (and I *am* a cosmologist) would be wasting their time if it was so easy for someone to come along and say "But it's a static photograph!!!! LOL."

A) It's not a static photograph. The CMB is a photo of the universe aged 100,000 years... and to actually predict something that looks like it you need a seriously carefully tuned model of hte universe. That tuning then tells you masses about the age of the universe and its evolution and lets you *predict* other things which we cna go and observe. Those other things are much later on in the universe. So *this* survey was looking at things when the universe was maybe 9 or 10 BILLION years old. How static is that????? LOL 100,000 years = 10,000,000,000 years!!! IDIOT SLASHDOTTER DISPROVES NUMBER THEORY!!!!!!111eleven!!!

B) Working from CMB+Supernovae -- again, 100,000 years compared to maybe 10bn years -- you can make predictions for the wavelength that should be there in the galactic distribution. Lo and fucking behold you go looking at that wavelength and you find it. What more do you want? Cartwheels in the fucking sky? An observation is made, a theory is built to fit the observation, the theory is cross-checked and supplemented by further observation, and then predictions are made that can be tested. The predictions are tested and found to be in superb agreement with observation. What's wrong here?

Nothing to see here (2)

Jeremi (14640) | more than 3 years ago | (#36218012)

Slashdot posts these articles about dark energy every 6 months, but nothing ever makes it to consumers. Let me know when Dark Energy generators are available at my local Home Depot, then I'll be interested.

Re:Nothing to see here (0)

Anonymous Coward | more than 3 years ago | (#36219038)

Consumer level dark energy generators are 5-10 years away.

Pushing by negative pressure? (0)

Anonymous Coward | more than 3 years ago | (#36219220)

Re dark energy:

Can anyone explains how the Universe expansion can be accelerated by a dark energy that has the property of negative pressure?

Naively positive pressure pushes away, so negative pressure should attract ???

Such bullshit (1)

Latinhypercube (935707) | more than 3 years ago | (#36219396)

There are other conclusions to the same observations. Rather than inventing and invisible 73% of the the universe.
How about, we don't understand gravity properly at galactic scales (MOND theory)..
Or how about, there is an near infinite universe BEYOND OUR OBSERVABLE universe, that influences and attracts the matter in ours.

Re:Such bullshit (0)

Anonymous Coward | more than 3 years ago | (#36219836)

Hey, if we're talking "such bullshit" how about we start calling out idiots on Slashdot who think they've got the answers to everything.

Come on then Latinhypercube, let's see you

1) Understand gravity properly at galactic scales -- and just name-dropping MOND isn't good enough because MOND is, as Milgrom is very happy to point out, purely phenomenological. There's nothing to understand and no reason to do what he did -- it's totally arbitrary and just fits the results. It's not even *defined*; it includes a function which is postulated to have certain limiting values for "high" and "low" accelerations with respect to another, arbitrarily chosen, acceleration. So how about you contribute to actually understanding gravity at galactic scales. If you're so in love with MOND, how about finding a way to apply it to clusters, because as startlingly successful as it is on galactic scales, it sure as fuck doesn't work on cluster scales. Or how about you apply it to cosmology... no, wait, you can't because it's inherently a Newtonian theory (that's the "N" in MOND in case you weren't aware) and can't be applied on scales approaching the Hubble scale because to do so violates causality quite horribly. So give us a generalisation of MOND to use on cosmological scales. And make it a bit less ad-hoc and ugly than Bekenstein's scalar/vector/tensor theory which included a host more arbitrary functions which were thrown in simply so that the low-energy limit was MOND.

2) Show how this "near-infinite universe" (an unsupported assumption, by the way, albeit one that I'd agree with) "influences and attracts the matter in ours" when it's BY DEFINITION outside of our horizon and cannot influence us without breaking causality. Build a proper, quantitative, predictive theory that explains how this hidden matter in a near-infinite universe outside our horizon is producing effects that mimic dark energy -- and, since you raised MOND one has to assume, the absolutely unrelated dark matter. Dark matter would be a particular triumph since it's present on small scales as well as large.

In all events, I demand

a) A CMB angular power spectrum for temperature, E mode polarisation and the cross-correlation which fits the WMAP data *at least as well as* Lambda CDM.
b) A matter power spectrum that fits the SDSS and, now, WiggleZ, *at least as well as* Lambda CDM.
c) A Hubble diagram that fits the supernova data

because unsubstantiated "theories" are totally useless. This is physics so we need testable predictions. Give me observables. And then give me a unique signature -- a firm prediction for the B mode polarisation of the CMB, for example, or the bispectrum of the galaxy cluster distribution.

No? You can't do this? Fucking shut up then and leave it to the professionals, who *have* thought of all of this before and *have* tried to test it, regardless of what you might believe.

Dark Energy/Matter Podcast by Cornell University (0)

Anonymous Coward | more than 3 years ago | (#36219514)

I came across this podcast by the Ask an Astronomer group at Cornell University, that has a great discussion of the difference between Dark Matter (Episode 1) and Dark Energy (Episode 2). Both are about 8 minutes into the podcast. Though, only the first episode is on iTunes until the end of this week, they said.

Their podcast is here: tiny.cc/AAApodcast
Their website (which also has a ton of Dark Energy/Matter questions) is here: curious.astro.cornell.edu

Re:Dark Energy/Matter Podcast by Cornell Universit (1)

thermalgreen (2192080) | more than 3 years ago | (#36220130)

Cool!

Now you see... (1)

Chris Mattern (191822) | more than 3 years ago | (#36219540)

...the *power* of the dark side.

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