Slashdot Mirror
Astronomers Find Star-Less Galaxy
Wohngebaeudeversicherung writes "Astronomers have discovered a galaxy about 50 million lightyears away from earth that appears to be composed entirly of dark matter. This galaxy, dubbed VIRGOHI21 is rotating like a real galaxy, at speeds only explainable through massive amounts of matter, thought no single visible star could be detected."
I suggest we donate one of our stars. How about Ben Affleck?
...that I click on "Read More" to find out about matter that's invisible to us and all I get is:
"Nothing for you to see here. Please move along."
Brilliant.
"Backups are for wimps. Real men upload their data to an FTP site and have everyone else mirror it." -- Linus Torvalds
That's no galaxy, that's a space station!
Ah, so THAT's where all the indie movies are coming from.
Astronomers have discovered a galaxy about 50 million darkyears away from Virgo that appears to be composed entirly of light matter. This galaxy, dubbed EARTHHI21 is rotating like a real galaxy, at speeds only explainable through massive amounts of matter, thought no single dark mass could be detected."
MORTAR COMBAT!
Should't that be 50 million darkyears?
A feeling of having made the same mistake before: Deja Foobar
I've been getting that too, all morning long. I know it's offtopic but WTF?
Insert witty sig here.
What about black holes? Are they just saying there is no light being emitted?
wdd
I love the picture of the night sky with a big circle around a nondescript part. I looked at it was like "oicic."
Where primetime TV is actually entertaining?!
If someone says he and his monkey have nothing to hide, they almost certainly do.
No stars, and I bet the food is crappy as well.
... I submit that it be named the "Goatse Galaxy".
Trolling is a art,
It its comprised of large amounts of Dark Matter, how can they tell that its spinning?
... and in the DRM, bind them.
My quest is over! Bizarro world, I have found ye!
+1 Insightful, -1 Troll. What can I say, I'm an Insightful Troll.
Could there be a star producing waves outside of the renages we are trying to detect?
Evolution or ID?
Maybe the entire galaxy is surrounded by particles of dust from a long-destroyed supercomputer?
You probably shouldn't click this.
can't see but it is there and its all powerful, honestly !
dark matter is just another word for "we have no idea"
What the speed of dark is.
Hokey statistics and ancient misconceptions are no match for a good thought in your head, kid!
1913'Webster mentioned that "The term has recently been used for remote clusters of stars".
So I guess it will have to be updated.
Trolling using another account since 2005.
To think he thought the missing matter was the polystyrene used in packaging... ;)
One good turn - gets all the covers.
"The lab quickly retracted their findings, however, when it was learned that Marlon Brando paid $70M to orbit the Earth in a black space suit..."
It's made entirely out of dark matter? How will that affect my force points? I can't be really evil if the entire galaxy is dark!
i live there so fuck off
Aha! It's intelligent life! They must have engineered millions of Dyson Spheres over all the stars of their galaxy!
Do you like Japanese imports?
you know, i clicked on the link just to see if there was a picture of it...
yeah, i'm not thinking too quick today...
Isn't this what they've been telling us to look for for years now - the entire energy output of a galaxy caught and channelled for use by an intelligence that has spread throughout it's own galaxy?
Just a slight delay between the topic being posted and the actual content of the article, AFAIK.
Seems a little strange, but it's probably because of the massive amounts of traffic Slashdot gets.
~ Crummy
I'll believe it when I see it.
Microsoft!
Agile Artisans
Have the scientists concidered that maybe its just a stage 3 civilization that's getting ready to pWn us?
Maybe its just a bunch of Matrioshka brains...
Or just wussy dyson shells....
Since this guy was doing radio observations, he must have detected a weak radio signature for Hydrogen emission from this dwarf galaxy. A bulk of hydrogen gas (still dark matter) would look different from that of blackholes in radio.
Geez! Dark Matter!? Astronomers calculations don't add up, so they invent "Dark Matter" as book keeping. If these guys were accountants they'd be in prison.
My favorite part of the article: Someone thought that circling the invisible galaxy in the picture was a helpful move.
Personally, I think articles with discoveries this exciting need to be written with more enthusiasm
You are checking your backups, aren't you?
Shares for LenseCleaner Corp are sharply up in morning trading.
Sheesh, evil *and* a jerk. -- Jade
So, lots of mass and hot air, but no discernible light or stars.
Yeah, it sounds like pretty much every radio talk show host in the world.
52 Weeks, 52 Religions with John Hummel
Comment removed based on user account deletion
it's because GOD hasn't said "let there be light" yet...
So that's where the switch to turn off the internet's located...
Or a fishless school? A shipless starfleet nearby?
Seriously, a galaxy is a collection of stars. A starless galaxy is not a galaxy, else I have a starless galaxy in my drawer.
"Um, Bill? The lenscap is still on..."
We have clearly found the galaxy that the Romulan home-world resides within. Now if we can detect traces of ion trails that would reveal the cloaking......
.
-shpoffo
...and it doesn't require exotic quarks, leptons, or baryons to work.
Okay, that's an enormous (and highly unlikely) exaggeration, but I *have* thought of an interesting possibility. A Dyson Sphere surrounding several stars (or in a Type 3 civilization, an entire galaxy) would block visible light - the problem is it would glow in the infrared, so it wouldn't really be dark. Black holes are dark, but they tend to fling stuff around, and matter sucked into them gives off bursts of energy before they disappear.
The solution: a dark bubble. At the center of our galaxy there is a supermassive black hole, which is (according to some estimates) roughly three million solar masses. A civilization putting a bubble around it would have 1 (earth) gravity a little beyond the orbit of Pluto, perhaps 40-45 A.U. or so. The problem is that you still would need to stick some stars around it to supply energy, and a Klemperer rosette would be pretty noticeable.
Well, light falling onto a blackhole blue shifts, increasing its energy. Increase the bubble enough (remember, we're talking a civilization that can harness the energy of a galaxy), and the mass of the bubble itself starts to warp space around it. There comes a point where the size of the bubble and the mass that makes it up can be just under the Schwarzschild limit - a bit more massive and it would be a black hole - even without a central singularity. For humans, we'd want a bubble that has a surface gravity equal to earth's, and a blue-shifted energy equal to the average output from our sun.
As a back-of-the envelope calculation, using v^2=2*g*R, where v is the escape velocity, g is the gravitational attraction at the earth's surface, and R is the radius from the center of mass, and setting v=c (the speed of light) for the maximum size, you get a bubble with a diameter just a bit under a light-year across (354 light days, if I figured correctly). The surface area would be about 3 square light-years, 2.6 x 10^26 square kilometers, or 5.2 x 10^17 times the surface area of the earth. The mass would be equivalent to 1.5 trillion suns - roughly twice the mass of our galaxy. Assuming you use buckytubes as the material of choice, you'd have a shell 7000 kilometers thick of solid buckminsterfullerene.
Of course, this is the absolute maximum size and mass just before it becomes a black hole, so the actual construct would be a bit smaller and less massive, balancing surface gravity and blue-shifted energy hitting the surface. You'd also want to carve out mountain ranges and oceans for a bit of variety - a galactic Kansas would be kind of boring. For safety reasons, you would have to stick these bubbles in the empty space between galaxies, or just use all of the mass in one large galaxy (you'd have to be careful, though, to keep relativistic rocks from flying at the completed project). You'd have a sky that would look kind of like a slow-moving aurora, perhaps -- infrared would be shifted into visible light, visible stars would have their peak shifted to ultraviolet -- especially since the gravitational warping would slow down time considerably compared to the rest of the galaxy.
To detect them, you'd have to aim telescopes at the "empty" parts of the sky and see if there was any gravitational lensing. If something was there that was far too massive to be a neutron star but didn't have the characteristics of a supermassive black hole, that could be a sign of it. The largest ones would have the gravitational mass of a large galaxy, so if a supercluster appears to be missing a galaxy's worth of stars that stellar motions demand, it might not be exotic matter but instead bubbles of normal matter from some vast engineering project.
Of course, it might be too early in the evolution of the universe for a type 3 civilization to appear, or you might not be able to make a buckytube bubble big enough that would also support its own weight, so exotic forms of matter might still be necessary. One thing's for certain, though - a bubble like this would make Ringworld look as spacious as a phone booth.
Twinkle twinkle little star
How I wonder where you are.
Lightyears away in VIRGOHI21 so far
Oh why can't I see you, you naughty naughty star.
An Indian-American Hindu committed to non-violent thought/speech/action alarmed by the global explosion of radical Islam
...it's like a flea circus, but it's not a circus, and the fleas; they are stars. Seriously, they're there...you just can't see them. Now give me your money...err...I mean funding so I can, ummm, research this further.
It was easy to disprove the existence of aether with the Michelson-Morley experiment. Had that experiment not been possible it would have been very premature to jump to the conclusion that there is no aether. When it comes to dark matter, there is no easy experiment to disprove its existence and so it would be very rash to conclude that our understanding of gravity, which has worked extremely well for us for hundreds of years, is wrong.
We're going to have to find a new name for these dark matter aggregations, as they're definitely not galaxies. The root "gala" means "milk". Milk is white, and star-filled galaxies are generally whitish. Dark matter isn't.
This etymology lesson brought to you by the number 1 and the letter O.
Running another one of their Quagma experiments again.
Gonna get us all killed.
This just in - Researchers have diagnosed a new disease with no known symptoms !
Gotta love George!
Fuck you! I'm not getting on the plane, I'm getting IN the plane.
Perhaps the inhabitants of that galaxy don't want us accessing their sensitive data and have employed a matter firewall? Meanwhile we're like sitting ducks in the universe...
-"...bad old ideas look confusingly fresh when they are packaged as technology" - Jaron Lanier (Digital Maoism on Edge.o
Seriously, though.... Just because no light gets out doesn't mean no light is produced.
My Photography - http://ian-x.com
The Deathlings (comic) - http://thedeathlings.com
Dark Matter is matter that cannot be directly detected through emitted radiation. But you can detect it through its effect on surrounding bodies. The effect is usually gravitational.
The concept of Dark Matter evolved from the "missing mass problem". You can estimate the amount of mass in a cluster of galaxies based on the motions of other objects around the object in question. When you compare this mass to the mass based on the total brightness (visible mass) of the galaxy, you can find a huge discrepancy. This is the "missing mass".
Wikipedia provides more information.
Vivin Suresh Paliath
http://vivin.net
I like
Subscribers.
/., is inconvenience legit posters. If Malda wasn't so anal about having meta-discussions about the site somewhere on Slashdot, he'd know this.
$5 for 1000 pages. If you set it up so the subscription is 1 ad-free page per day, like me, you can be subscribed for more than two and half years for five bucks (I've gotten some gift subscriptions and at this rate I'll be subscribed for the next eleven years), which is great for trolls who only want to see stories early so they can get semi-relevant first troll posts into stories that get modded up long enough to cause problems and throttle legit discussion.
The "nothing to see here" means the story is up, but to try and keep the trolls away it can't be posted to for about 60 seconds after it's put on the front page (and, as a side effect, if the entire write up isn't on the front page, you can't read the whole story either).
Clearly it's just another failed attempt by Taco and friends to keep trolls out. It doesn't, I've gotten in two or three first post trolls that resulted in giant pissing matches despite the "Nothing to see here" crap, so all it does, like most of the other "anti-troll filters" on
Alito: A vote for Alito is a punch in the eye to put that bitch back in her place!
hmm, dark matter galaxy, yeah, fascinating, whatever. I can't BELIEVE Apple isn't shipping iPod minis and photos without FireWire cables!!!!!
Dear Slashdot: next time you want to mess with the site, add a rich-text editor for comments.
The preprint.
Dark matter by definition doesn't emit or reflect anything, then how on earth (literally?) did they discover radiation from this so called dark galaxy?
Now we know where all those lost socks end up.
12:50 - press return.
Don't they believe in flashlights in those parts? Damned hillbillies.
I mod down so you can mod up. Your welcome.
And it would be nice if Taco didn't sit at his computer to mod down so quickly, too.
Mostly random stuff.
If >75% of the universe is dark matter, won't most galaxies be dark? Now that we've discovered that dark matter "galaxates", or whatever we do. Unless dark matter's physical properties are less galaxational...
--
make install -not war
Am I the only one who thought of The F-Sharp Bell?
--Kimota!
Who moderates the meta-moderators?
So that's where all those missing socks, lost pens, and misplaced change ends up at!
The planets and moons and asteroids can be considered "dark matter".
From a distance, alone in space, nobody can see them. They do not glow, or burn or give off radiation of their own.
There are thousands and thousands of huge rocks floating around just our solar system that we don't know exist because we cannot see them directly.
Unlike a sun, they don't easily advertise their presence to obververs.
It is things like this that on a galactic scale really begin to add up.
We certainly don't know how much debris exists away from the comforting glow of a red hot sun, but we KNOW at least some exists.
liqbase
More detailed information can be found in the paper, which has been accepted for publication in a letter to the Astrophysical Journal.
Find it here.
It was a longhorn beta test. There was a big bang, and everything went dark.
It certainly is possible that "we don't know as much as we thought," but given what we do know, dark matter seems to be by far the most plausible.
First, it fits obervations well, and there is no particular reason to believe that we *can* see everything. There is certainly precedent (eg neutrinos).
While in themselves they are not reasonable candidates for dark matter, do we really have any strong observation evidence that the universe is not filled with iron basketballs? We certainly would have trouble seeing them directly... Iron basketballs aren't the only things we might miss, either.
Of course, there may both be dark matter and a misunderstanding of gravity.
As far as the cause of our difficulty being a misunderstanding of gravity, it seems unlikely: globular clusters do not show evidance of dark matter, but small compact dwarf galaxies do.
-Hil
Obligatory "farside" caption: "They knew they had the telescope pointed in the right direction, but forgot to remove the lenscap"
People who think they know everything are a great annoyance to those of us who do.
With all that Dark Matter, i bet all the inhabitants have Break Damage Limit equipped!
OH SNAP.
----------
somebody set up us the bomb.
"when the sun sets on the ghetto, all the broken stuff gets cold"
It was easy to disprove the existence of aether with the Michelson-Morley experiment
True, but before the Michelson-Morley experiment, it was impossiblet to disprove this fact. Until someone runs the "Richardson-O'Reilly" experiment, it'll be impossible to disprove dark matter too.
IANAA, but dark-matter sounds a bit like Tachyons, Anti-Time, and other Star Trekisms. But I hope it's true, I sure as hell don't want the universe imploding back in on itself.
Wer mit Ungeheuern kämpft, mag zusehn, dass er nicht dabei zum Ungeheuer wird. --Nietzsche
Oh.
Of course, such light should have a good trace of gamma radiation when it reachs us, so can't be... but could have been something interesting to find.
The science fictions possiblilites are endless.
BTW Galaxy of Terror (1981) was a kind of cool flick.
Sorry about the writing. Robot fingers, you know? Cliff Steele in DOOM PATROL #23
...our understanding of gravity, which has worked extremely well for us for hundreds of years...
Keep in mind that our understanding of gravity is that we have no clue what it is. However, our understanding of the effect of gravity has been working fine. The effect of gravity and gravity are two different things. It could very well be that there is absolutely no such thing as gravity and the effect of gravity is actually a side-effect multi-dimensional distortion, or subatomic radiation, or pure heavenly magic. That is why there is a 'theory of gravity' and a set of 'laws of the force of gravity'.
The previous comment is purposely vague and generalized, but all of the facts are completely true.
Looks to me like the King of all Cosmos is up to no good again.
They just changed their numbers, after the Paris Hilton "Shizzack".
"Flyin' in just a sweet place,
Never been known to fail..."
This is probably a simpler explanation:
http://www.electric-cosmos.org
If you read it all the way through you see that "Dark Matter" is just a hack to explain objects like this.
So it's pulling light in instead of spitting it out.
Perhaps time is even going backwards.
Mugbus anyone?
But now we're veering into philosophy.
The biggest difference is that models of real objects using fairly simple models of dark matter can match observations very well while reasonable ones without it do not seem to. Tachyons etc. do not seem to be of any help in explaining anything.
Of course models that match observations may still be wrong, and we just haven't thought up the correct one yet, but in this case it seems unlikely.
-Hil
How did they detect it if it has no stars?
Congressman (skeptical): Well, I dunno...I don't really see anything there.
Astronomer: Oh, one moment...let me circle it for you!
Congressman: Yes, yes I see it!
Astronomer: Now I was wondering, Congressman...how much additional funding might we get for this discovery?
Congressman: Hm. I'm not sure we have additional funds for such an admittedly amazing find. Now, if you had TWO dark matter galaxies, we'd have something to discuss.
Astronomer (uncapping pen): Funny you should mention that...
This is exactl what one may expect to see with a type III civilization... Funny how nobody thinks o investigate on these lines...
where managers come from!
*BA-BOOM BING*
Thanks for coming out, enjoy the fish.
...with my tax return?
IRS Auditor: We've added up all of the income your employers have reported for you and it is much greater than what is reported on your tax form. How do you explain that.
Me: While you can usually detect income through tax forms, some types simply don't register. I believe that it is called...dark income.
IRS Auditor: I believe that it is called...tax evasion.
Me: gulp...
http://news.bbc.co.uk/2/hi/uk_news/wales/south_eas t/4288633.stm
--- This
http://arxiv.org/abs/astro-ph/0502312
Do you emit radiation? No? Then you're made of dark matter.
For great justice.
"But all your emitter and collector are belong to me!"
I agree that it is scientifically suspect. It is up to the DM advocates to describe a feasible experiment that could disprove their theory. If they don't then their theory is non-scientific.
Once you go black, you never go back.
We have secretly replaced these Slashdot mods' sense of humor with a rusty nail. Let's see if they notice!!
Some common objections to dark matter I constantly see whenever the topic comes up on Slashdot:
...
Can't dark matter just be brown dwarves or black holes or something? Why do scientists postulate crazy exotic invisible particles?
Dark matter is postulated to come in two kinds, Massive Compact Halo Objects (MACHOs) and Weakly Interacting Massive Particles (WIMPs). MACHOs are things like brown dwarves, etc.; WIMPs are the new kind of matter. We have already detected some MACHOs through gravitational microlensing experiments (looking for them by how they gravitationally deflect light). But if all the dark matter were MACHOs or something else mundane and baryonic, we would have detected more of them by now. That leaves WIMPs. Also, MACHOs and WIMPs have different physical properties (e.g., they cluster differently, and thus seed the formation of the large-scale galactic clusters we see today in different manners), and an all-MACHO universe doesn't cluster right, though it works out if you let some WIMPs into the mixture.
Ordinary neutrinos don't do the trick, either; we evidently need some new kind of particle. We don't know what WIMPs are, but some have postulated axions, neutralinos or other supersymmetric particles, WIMPZILLAs, solitons, sterile neutriono (that only interact gravitationally),
Dark matter is unscientific; it can't be tested or falsified.
Dark matter theories can be tested indirectly by observing the different predictions they make for galactic rotation curves, early-universe structure formation, cosmological expansion, etc. Already such observations have excluded a number of dark matter theories. And there are experiments underway that try to directly detect them, similarly to how we detect neutrinos.
Dark matter is just epicycles all over again, a fudge factor to preserve a wrong theory of gravity.
Once upon a time, irregularities were noted in the orbit of Uranus. It could have been postulated that the laws of gravity were wrong. Instead, it was postulated that an unseen bulk of matter was perturbing Uranus's orbit. Eventually, that bulk of matter was seen: the planet Neptune.
On the other hand, once upon a time, irregularities were noted in the orbit of Mercury. It was postulated that maybe a new planet caused them (Vulcan), but that turned out to be wrong; instead, a new theory of gravity was needed (general relativity).
The moral: you can attempt to explain away the observations with either dark matter or a new theory of gravity; both are scientifically valid approach. The problem with the latter is that it has proven extraordinarily difficult to produce a modified theory of gravity that is consistent with all observations, whereas there are dark matter theories that appear to do the job. Believe me, scientists don't ignore the possibility of a new theory of gravity any more than they ignore the possibility of a new type of matter; it's just that new theories of gravity don't seem to work as well as new theories of matter in explaining the observations.
What about MOND?
MOdified Newtonian Dynamics is the leading candidate for a non-dark matter alternative, modifying the laws of gravity. (Note that this page is by MOND's inventor, and may be biased.) However, it has had trouble with a number of observational tests; you can search the astro-ph arXiv for critiques of MOND. In particular, although it seems to work for galactic rotation curves, it's hard to get it to also work for cosmological expansion and structure formation. It's also very difficult to make it into a theory compatible with observed tests of relativity.
What about Bekenstein's MOND theory?
Bekenstein recently proposed a relativistic version of MOND called
We may be seeing a chunk of heavier elements but these are left over from the big bang.
Sorry about the writing. Robot fingers, you know? Cliff Steele in DOOM PATROL #23
Yeah, I don't think "look" is the right word here.
From the article "In the Virgo cluster of galaxies, they found a mass of hydrogen atoms a hundred million times the mass of the Sun. The mysterious galaxy has been called VIRGOHI21."
But the first thing about Dark Matter is that it cannot be detected by it emitted radiation!!!
A real stealth galaxy. I wonder how big the cloaking device must be
http://www.dieblinkenlights.com
Now, real physicists, good physicists, will acknowledge (at least if you back them into a corner) that "dark matter" is not a concept of a real, existent *thing*. As in, we don't really have reason to believe in a magical material called "dark matter". The statement that "scientists have discovered a galaxy of dark matter" is kind of a wrong way of talking about it. Scientists have discovered that there equations don't work out quite right unless they suppose there's matter where they aren't detecting matter. So, if they assume that there's other undetectable matter somewhere in the area, doing certain things, our model works better.
However, poor physicists and science media people pick up on this and start imagining invisible planets populated by invisible people, and we get stories like, "scientists discover DARK MATTER!" You gotta love how these things are always phrased like that, too. It's never, "this particular scientist, Dr. Whateverhisnameis, has made certain readings and theorized bla-bla-bla." It's always "scientists" as a whole have "discovered" bla-bla-bla. Apparently, all scientists everywhere agree. "THEY" have "PROVED" bla-bla-bla as soon as someone somewhere makes some other reading that comes *close* to a value expected by the bla-bla-bla theory. So yadda-yadda-yadda, now geeks are standing around the water cooler trying to sound smart by talking about the invisible dark-matter planets.
To rectify this injustice, the master tapes to all seven seasons of Star Trek: Voyager will be dumped there as soon as the copyright runs out.
>>dark matter is just another word for "we have no idea"
Wow, get a grip. 1), dark matter is not visible to the eye, but neither are x-rays. Invisible != Undetectable.
2), dark matter is not "all powerful." I can't even guess what you meant to imply. It's conjectured that dark matter exerts a force, not that it flies around like a genie granting wishes.
3), dark matter is just another word for "we found an anomaly, and our observations lead us to believe this model may explain that anomaly."
4) extra irony points for accusing science of using a "god of the gaps" approach because they discovered something new and put a name to it and are researching it. Clue on line 1, calling AC, clue on line 1.. please pick up.
Parent is a perfect example of reactionary political slop masquerading as relevant opinion. I sure hope the AC was just trolling, because if that's genuine ignorance, I fear for the future of our species. One redeeming quality though.. I'm sure our friend the AC didn't realize this, but implying that dark matter is a foil for ignorance by comparing it to god (can't see but it is there and its all powerful, honestly !) implies that the AC thinks god is a foil for ignorance. (I know he didn't use the word "god" explicitly, but what else could he be referring to? Root? :) doesn't fit.)
Once again an offtopic comment with no redeeming intellectual or informational value is modded +interesting by conservative mods who just want to rub their creationist, anti-rationalist views in the face of a technocratic forum. Mod parent down, down doobee down, doo wa.
"A witty saying proves nothing." ~Voltaire
"d'Oh!" ~Homer
http://www.artchive.com/artchive/M/malevich/b_circ le.jpg.html
See down there in left corner! Liers!
maybe not visible radiation...
"Maggie call Aquaman!!!"
The astronomers say it is hard to study the universe's dark, hidden objects because of the Earth's proximity to the Sun
So why isnt there a project to send a telescope to the edge of the solar system and a couple of other space relays to send the photos back to us?
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
According to the article, the object in question does, in fact, contain plenty of baryonic matter. In fact, it contains 100 million solar masses of hydrogen - that's how it was detected.
Why hasn't this gravitationally bound collection of hydrogen (plus possibly nonbaryonic other stuff) collapsed to form significant numbers of stars? Isn't this really bizarre?
To quote an old college friend, "The Michelson-Morely experiment was flawed, since the Case Quad is the center of the universe, and the experiment was performed too close to the center to be able to measure any perceivable aether drift."
Another 42 reference... VIRGO - Half Is 21
I'm not sure that's the right way of saying it. Ether is a very old idea intended to deal with a couple questions. For example, what is there in "empty space". It's sometimes used as a term in natural philosophy and is actually not necessarily intended, in concept, to be a physical material in the sense that we think of "matter", but has been supposed to be a whole lot of different things.
That having been said, there was a time when people tried to use the concept of ether to explain the behavior of light. They supposed that light was nothing other than waves passing through this "ether", which they believed was some sort of a physical material. This idea had many problems, but one of the benefits of this explanation was that it would explain why light traveled at a constant speed. Imagining light as wave in a medium was also useful in understanding many behaviors of light, including refraction, reflection, and the famous double-slit experiment.
OK, so it was supposed that light's constant speed was a result of passing through ether that was stationary, and the speed that a wave travels can be determined through certain aspects of the medium, including rigidity of the particles and distance between particles and such. So if ether was the medium of light, and therefore the speed of light was constant through the medium (relative to the medium), then we would be able to determine how fast we're moving, relative to the motion of the medium, by careful measurements of the speed of light. This was the intention of the Michelson-Morely experiment.
However, what the Michellson-Morley experiment demonstrated was that light's constant speed was constant *regardless* of the context of the observer. In essence, the medium would need to be stationary to everyone all the time, no matter what their velocity was. What this proved was not that "there was no ether", but that explaining light as waves in ether was *insufficient* to explain the consistency of the speed of light.
Here is the accepted Astrophysical Journal Letter regarding this discovery.
http://xxx.lanl.gov/abs/astro-ph/0502312
(Note: Be on guard for confusing astronomical conventions, like measuring almost everything logrithmically with decreasing numbers representing increasing brightnesses.)
To sum up: Astronomers discovered a large mass of rotating Hydrogen gas towards the Virgo Cluster. From the gas dynamics they were able to estimate the mass of the system, and found it to be comparible to the mass of a galaxy. When they went to look at the optical light given off by stars, they found they couldn't find nearly the amount they should for a normal galaxy, hence the 'star-less galaxy' title.
Current Cold Dark Matter (CMD) models of galaxy formation predict that these 'star-less' masses of dark matter should exist in the universe. While other candidates have been discovered in the past, this is the only (currently) viable candidate now known. If it holds up to subsequent analysis, it will provide observational support for the CDM formation models.
A few quick points --
- Dark matter is simply non-luminous matter (matter that does not emit light at any wavelength).
- Yes, black holes are a form of dark matter (baryonic).
- No, this is not an 'anti-matter' galaxy.
- Current Dark Matter theories lean towards it having a non-baryonic source (i.e. not being made up of 'normal' matter).
Furthermore, Hawking radiation is inversely proportional to the mass of the black hole. In order for the amount of Hawking radiation to exceed the cosmic microwave background (CMB) radiation, the black hole must have a mass significantly less than our sun. A super-massive black hole would emit a miniscule fraction of the CMB, and hence would be black for all intents and purposes.
Ben Hocking
Need a professional organizer?
Photons (light) do not possess charge. The photon has no antiparticle (or, you could say, it is its own antiparticle). It is a 'real neutral particle', with zero spin, electromagnetic charge, weak charge and strong charge.
The World Wide Web is dying. Soon, we shall have only the Internet.
Actually Dark Matter has been seen visually. In fact there were recent claims that it's existance was "proven" by visual inspection correllating to the already observed gravitational effects and predicted existance.
How?
By observing supernova. The immense amount of light given off by a super novae explosion actually illuminates this "Dark Matter" which is merely diffuse hydrogen uneavenly spread throughout the universe and allows us to actually see parts of it for a small period of time. "Proving" the existance of Dark Matter is one of the many things the Hubble is credited with being responsible for.
There have also been many other forms of indirect evidence that have all pointed to the same conclusion over the past 2-3 years.
The certainty of the existance and the makeup of what Dark Matter is made a giant leap in the confidence level in recent years and can be talked about with a lot more certainty that you are giving it.
Now as to the subject of Dark Energy...
Contrary to popular belief, coding is not all free blow-jobs and beer. Those things cost MONEY!
The Death Star doesn't put off much light.
As in "How long does it take for a management chain to pass the blame"
You have obviously not been keeping up with the astronomical science that has been done in the last 3-4 years or you would realise how insanely ignorant that coment is.
"... This galaxy, dubbed VIRGOHI21 is rotating like a real galaxy, at speeds only explainable through massive amounts of matter, thought no single visible star could be detected."
You thought wrong.
Why am I on Slashdot? I'm bored. Why am I bored? I'm on Slashdot.
The dark matter at the heart of astrophysical research is not diffuse hydrogen, but something more exotic. Hydrogen is not sufficient to account for the phenomena dark matter is invoked to explain.
Dark matter had been seen, many many times now.
It's existance both theoretically and observationally is not suspect at all at this point. It's composition is in fact also now very well known.
It's exact distribution and method of distribution is currently weak though.
Dark galaxy? Did they perhaps find this:t .html
http://www.candydirect.com/bars/Milky-Way-Midnigh
huh? you define gravity as the singular instance of an apple falling? It seems perhaps you're using a definition of the word that doesn't correspond to common usage. Most people consider gravity to be a universal force that causes each particle of matter to attract every other particle of matter in a relationship corresponding to the mass of the particles and the inverse square of the distance between them. According to Newtonian physics, which was where the concept was originally formulated, this would result in an Apple falling, roughly, from your hand towards the earth, given that the Earth is the most massive and closest body around.
However, a singular instance of an apple traveling toward the earth, or even a thousand instances, is insufficient demonstration that "gravity exists".
Insufficient data for a meaningful answer.
Who said that the hydrogen was diffuse? What the Hubble showed is that the hydrogen is a lot LESS diffuse than previously thought! It is not just evenly spread out throught the universe, it exists in huge dense, well comsicly dense, clouds in numbers that were not known to exist before.
Current observed behavior of interstellar hydrogen now put it at explaining about 80% of the "missing mass" of the universe.
So all that is left is 20% unknown at this point, and disconveries of things like dark galaxies and other dark structures may be source for closing out that last 20%.
As boring as that might seem to some...
Half the leptons.
Same great taste!*
Light galaxies.
*The photons sorta shine out your fourth point of contact. Minimal interaction.
emt 377 emt 4
Maybe they just have a galaxy-cloaking device, they don't want visitors.
Very false. We have some idea of what the MACHOs are, but we're just guessing about the WIMPs.
Perhaps it is a time-reversed galaxy. So, instead of emitting photons, it absorbs them.
But, I wanted socialized health insurance!
It was easy to disprove the existence of aether with the Michelson-Morley experiment
Like interpretations of so many classic physics experiments taught in high school and college, that interpretation is somewhat simplistic. The Michelson-Morley experiment showed that the observed speed of light did not depend on the state of motion of the observer.
That does exclude simple models in which light propagates exactly analogous to sound. But it excludes few other models. In particular, there are models of an "aether" that can account for those observations, and Lorentz actually believed in those when he developed the equations that form the basis of Einstein's theory of special relativity. People just didn't adopt that view because Einstein's explanation seemed simpler.
at times also known as the simple lack of a sense of humour.
I think I'll stick to AC comments.
Mostly random stuff.
The question is, once we account for all the "normal matter", will we have enough "normal matter" to account for the gravitational effects we see (according to our current understanding of gravity). Many scientists say, according to their estimates, no, which then still requires a place-holder of "dark matter". However, in this sense, rather than "dark matter", we might call it, "that unknown thing which we don't know what it is but somehow causes these unexplained gravitational effects". Or maybe we could all it, "WTF?! matter". "Dark matter" sounds catchier, though.
The galaxy is so new that the light from the stars hasn't reached earth yet. That could be fun.
The previous poster. But it doesn't matter.
No, that is way, way wrong. Even taking interstellar hydrogen into account leaves 80+% of the matter unexplained.
TFA says this object is "a mass of hydrogen atoms a hundred million times the mass of the Sun."
It may be unusual that none of this hydrogen has ignited in a fusion reaction, but that doesn't change the fact that hydrogen atoms are baryonic matter, quite common here on earth. (There are quadrillions of them in my body right now.)
Later, TFA says "according to cosmological models, dark matter is five times more abundant than the ordinary (baryonic) matter that makes up everything we can see and touch."
So this object is "dark" in the sense that it doesn't emit visible light, but it's not Dark Matter.
Or am I missing something here?
That that is is that that that that is not is not.
pi=sigma{n:0-infinity}[(1/16)^n][(4/(8n+1))-(2/(8n +4))-(1/ (8n+5))-(1/(8n+6))]
All this talk of light and dark is making me think that the universe is one big experiment in racism. Why can't we have fuschia-years or mauve-matter?
ObTopic: no one wants to lend credence to the "below our threshold for detection" statement that someone else posted earlier? It may be possible that the stars are simply too dim...no?
I cracked it! All this "dark matter" is actually space craft that are using cloaking devices. Duh.
They should call this galaxy the "Romulan Galaxy" just on principle. Show some respect to our cloaked overlords.
Authority questions you. Return the favor.
No, that's absolutely incorrect. When scientists talk about dark matter they really do mean some actual stuff, not just a problem with gravity. We do have plenty of reason to believe in this magical material (too many for me to list here in fact, short list of acronym soup: BBN, CMB, LSS).
There are quite a few models for what dark matter could be, many motivated by our theories of particle physics.
If you want to learn more, here is an excellent review on the subject, written at a very basic level.
Essentially all you need is a massive particle with a very low probability of reaction (cross section). There are people who are trying to use techniques similar to neutrino detection to find evidence of actual dark matter particles (come back in 5-10 years and we may have detected dark matter particles).
We may also be able to see gamma rays from dark matter particle annihilation at the center of our galaxy, or at the centers of dwarf satellite galaxies (the Milky way may be difficult, the signal would be higher, but you also have confusion with other high-energy sources).
Doug
Venn ist das nurnstuck git und Slotermeyer? Ya! Beigerhund das oder die Flipperwaldt gersput!
PS I'd love to do a poll among random people on your "Most people consider gravity to be..." statement to see how many actually agree. I certainly don't thing that the facts that (1) gravity effects every type of matter and (2) gravity follows an inverse square law are actually built into the meaning of the word 'gravity'. For example someone might find a type of particle that doesn't attract other particles and that wouldn't force us to change our usage of the word. Sure, physicists would have a bit of work to do but even they would probably continue to call gravity 'gravity'.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
I know a Romulan Bird of Prey using a cloaking device when I see one.
Authority questions you. Return the favor.
...I'm just wondering how anybody whose overriding interest is apparently astronomy chose an alias like 'Wohngebauedeversicherung'.
What about household insurance interests the submitter so deeply?
You're right. Obviously the astronomers involved made all this stuff up. They haven't got a preprint of a their report to Astrophysics Journal posted on the web, or anything like that. And popular science journalists would never try to get cute with the pictures they choose to go with their articles. I mean that just doesn't happen.
Though the BBC is a reputable source and usually gets their facts straight, they're not to be mistaken for a peer-reviewed journal. A two-hundred-word article isn't going to have a full complement of figures and supporting data--and it shouldn't be expected to.
Mods--the parent post is funny at best; not insightful. I have this amusing mental image of a bunch of drunk astronomers drawing random circles on star charts and saying, "Okay, this week we'll tell them there's dark matter here. Suckers."
~Idarubicin
So where is the false color image of this galaxy?
The availability or otherwise of a false color image reflects only on how the researchers chose to present their data; has no bearing whatsoever on the existence of the galaxy. In this particular case, it would in fact be unusual to present a false color image, since radio data are more commonly illustrated using contour maps.
How do they know it's rotating like a galaxy?
From the radio observations, which pick up 21cm emission from cold, neutral hydrogen gas. Doppler shifts of the 21cm line allow them to establish a rotation curve for the galaxy.
They haven't shown any sort of evidence of the real matter they claim to have detected.
No, in fact they have presented evidence for the real matter (neutral hydrogen), in the form of the 21cm emission.
To post a picture of empty space and say it's full of dark matter is just stupid.
No, it's quite significant: based on the radio emission, we would expect a population of stars, that would show up in the optical image. The actual absence of these stars, as evidenced by the 'empty space', is the whole reason that this is news.
I think the only dark matter this article shows is in the astronomers head.
By totally misunderstanding every aspect of the story, you have effctively stood up in front of the /. community, and loudly proclaimed 'I'm dumb as shit'. Congratulations.
Tubal-Cain smokes the white owl.
They don't even have a Starbucks.
Weeks of coding saves hours of planning.
> it would be very rash to conclude that our understanding of gravity,
> which has worked extremely well for us for hundreds of years
You exaggerage -- significantly. Until Newton, one of the prevailing ideas
was that gravity drew everything in the universe toward one central point.
(This goes back to Aristotle, if not further...) I _suppose_ you could call
Newton "hundreds of years ago", but it's not very many hundreds. Quite aside
from that, our understanding of gravity has been revised significantly in the
last hundred years; Newton's basic equation is still more-or-less correct, but
it doesn't explain everything or cover all of the edge cases; furthermore, it
doesn't work at all at the particle level.
Our _basic_ understanding of gravity is _basically_ correct, but there is
definitely still stuff about gravity that we don't know or understand.
As for "dark matter", there's dark matter and then there's dark matter. This
particular discovery is far enough away that it's not terribly hard to explain;
we'd only be able to "see" it if it were radiating light, so it could
_potentially_ be perfectly ordinary matter that just doesn't happen to
be doing that. Perhaps it's not grouped up into stars the way the matter
here is, for instance -- a ring of roughly uniform density, or something
along those lines.
Or it could be something else. Point is, we don't know.
Cut that out, or I will ship you to Norilsk in a box.
Now we know where Samus kept popping off to through those damned portals.
End of lesson. You may press the button.
As far as a scientist is concerned, gravity is only an explanation of effects. Consider atoms: To a scientists, atoms "exist" insofar as the idea of atoms allows correct predictions about effects we observe in the physical world (from chemistry to the signal from a electron microscope). As you claim, the theory of gravity (currently General Relativity) allows us to make good predictions about the physical world, so a scientist can say "gravity exists". It doesn't make a lot of sense to treat it differently in that respect from the other fundemental forces.
Now, you may be addressing some metaphysical idea of existence, that is seperate from effects on the physical world. I just want to be clear that that is quite separate from the question of whether gravity exists in the scientific sense, to which the answer must be yes. Of course, the weird thing about the scientific notion of existence is that new data may show us that something actually does not have quite the properties we thought or that only something that approximates it actually exists. In the case of gravity, we know that there must be corrections to the way we understand it now in order to account for quantum effects, but the most reasonable way to view this is then to say that gravity exists, but we don't entirely understand the nature of it yet.
"You call it a new way of thinking; I call it regression to ignorance!" -- Operation Ivy
a decaffeinated galaxy??
What I find most interesting about the "dark galaxy" is that it's got plenty of hydrogen but it somehow has not managed to form stars.
Sustainability and energy independence essay
Random question--
I recently read this idea that the universe might be curved back on itself...that light that seems to be from a "long long long way away" might actually be from "here", but a long time ago. Is there any evidence for or against the universe being a closed system like that? Is this idea taken seriously by anyone of repute?
SO YOU'RE GOING TO DIE: The Comic for Dealing with Death
This is a good point - it's quite possible we don't understand gravity (especially in the case of dark energy!). However, there turns out to be a lot of evidence for dark matter (galaxy rotation curves, gravitational lensing, structure formation, the microwave background, etc.), and it turns out that it's hard to come up with a model without dark matter that explains all of these observations. Dark matter is, in a very real sense, the simplest interpretation of this data. There are some earlier posts of mine (and otheres) that talk about this evidence in more detail.
This observation, if confirmed, could be one of the best evidences yet that dark matter is real, physical "stuff". Visible galaxies and clusters form in the middle of large dark matter halos, which act as "seeds". Cosmologists have always predicted that there should be some population of these halos that never accumulate enough visible stuff to be visible. The discovery of such a "dark halo" is a fairly impressive confirmation of the theory. It's possible to believe that gravity can be modified to change rotation velocities in a galaxy, but it's hard to imagine such a modification producing effects where no real matter exists!
Parents point of view is not the most common, but that doesn't make him a troll.
Does anyone else find it ironic that the Cheshire radio telescope found something that cannot be seen?
*click**beep**beep* Scotty, One to Mod up!
Let's send both of these nutbars out there.
Sadly, it appears that VIRGOHI21 was a casualty of the Photino Bird's campaign against baryonic matter.
I hope someone gets the reference.
HI is hydrogen-iodide/iodic acid. definately *not* neutral stuff.
Nope. No number N would be sufficient. Apples going towards earth could be explained by some law that makes apples go towards earth. There were ancient theories that talked about tendencies either "downward" or "toward the center", neither of which were really gravity, especially when considered this tendency was paired-with/opposed-by a tendency that forced things into circular motion. The sheer fact of apples moving towards the ground, even if we wanted an explanation for why apples *always* go toward the ground, could be explained by a law that "apples are attracted to ground". That's not gravity.
When people talk about gravity, whether they know it or not, whether they like it or not, they are referring to the universal gravitation from Newton's theories of physics. For it to be gravity, it requires more than that apples attract ground, it requires that matter attracts matter, and it requires the sort of rules that comprehend the fact that the pull of the sun is less of an influence than the pull of the earth (which has to do with distance) and the fact that the earth pulls the apple greater than your hand does (which requires mass).
If they're talking about "things go down", well, in fact, that is not the same as gravity. Part of the reason things go down, after all, is air-pressure. You know, not everything goes down. Helium balloons go up, planes go up, and birds go up.
"dark matter is five times more abundant than the ordinary (baryonic) matter that makes up everything we can see and touch." - FTA
... dose this seem odd to anyone else or am i just totally mis redaing this?
Ok so this sounds to me then like it is saying that dark matter makes up 5/6 of all matter in the universe five times more than baryonic:
Since 5x + x = 100% of matter where x = baryonic quantity -- so 6x = total matter matter so there fore dark matter is 5/6 ~ 83% and baryonic is ~ 17%.
This seems like a disproportionally high amount of dark matter in the universe to me. I mean, Duh, right you look in the sky at night and you see little stars in huge mass of black but I still just can't fathom that only 17% of all matter is not dark matter
You can read the full story at New Scientist - there are some interesting disagreements between the astronomers about whether this really is the first dark galaxy
It was easy to disprove the existence of aether with the Michelson-Morley experiment.
Have you seen the experimental apparatus for detecting gravity waves? It's almost the same experiment, just to a much greater precision. Thanks to scientific progress, we'll call it "gravity waves" instead of "ether waves" when the speed of light is seen to be different in orthagonal directions. I find it very amusing. (Yeah, yeah, the theory is a lot better, but you have to admit it's funny.)
Socialism: a lie told by totalitarians and believed by fools.
This "new" galaxy, how old is it really? It's hard to tell, but a perfectly valid question, since if it is possible to detect it's age I wouldn't be surprised if it is going to be older than Big Bang.
Why? - Well, if we scale down Big Bang to firework size (Think of those spherical explosions you see in fireorks.) If one explodes before another you will see the stars of the first one first, but even though the stars has stopped glowing, the particles remains. Figure that "our" Big Bang isn't the only one that has occured.
What if this galaxy is the remains of some Big Bang that occured much much earlier than about 13 billion years ago. (give or take a few :-) ) This will put some theories completely upside down. Are we going to have a new Big Bang, and in that case when?
This discovery is at least one example of the situation where reality is stranger than fiction. (I haven't seen any story based on the idea of a galaxy completely of dark matter.)
If builders built buildings the way programmers wrote programs, then the first woodpecker would destroy civilization.
There quite a few theories of what dark matter could be, along with the theory that we're just wrong about gravity. What experiment could be performed to distinguish between these theories? If you understand the current science, please do explain.
Socialism: a lie told by totalitarians and believed by fools.
Hmmm. Might this be the "back door" of a super-massive black hole in a parallel Universe.
...that dolphins are unintelligent. It merely raises questions about the intelligence of the other creatures involved.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
"Okay, this week we'll tell them there's dark matter here. Suckers."
Well, the GPP does have a point, even if it's the BBC that flubbed it. Make with the cool pictures if you want more funding, Mr Scientist Man!
Socialism: a lie told by totalitarians and believed by fools.
It would be much more efficient to construct a single Dyson Sphere over the entire galaxy. It would also be a lot more aesthetic, as the view would be rotating.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
So, is the term baryons short for "Barry Manilons", a physics concept inspired by the famous singer/songwriter? It would explain much about Life, the Universe and Everything.
Earth is pre-Type I; Sagan apparently calculated us at about 0.7 on the Kardashev Scale.
//Information does not want to be free; it wants to breed.
I question it to the extent I simply don't believe in it. I think the Israeli explanation that gravity falls off slower than one over r squared at big distances is more likely, and the Pioneer anomalies give it some support. Much as I hate to lose the first ever universal law, I think this makes more sense.
I am trolling
"Oh My God, it's *not* so full of stars!!!"
To distinguish between dark matter theories and alternate gravity theories, you need a specific model of each. Then you make predictions with them: if you assume such-and-such kind of particle with so-and-so properties, what does that predict for galactic rotation curves, structure formation, cosmological expansion, etc. And if you assume thus-and-such force law for gravity, what does that predict? Then you see if all those predictions agree with observations or not. Already, such observations have ruled out some models of dark matter, as well as virtually all alternative theories of gravity that have been proposed.
Also, direct detection of dark matter would certainly be a smoking gun, although it may not be possible. But searches are underway.
It is already known that simply modifying the exponent in the Newtonian force law is insufficient to provide an alternative to dark matter; it doesn't agree with observations. (At least, not without postulating an altered exponent and dark matter on top of that, which doesn't really help!) MOND is a better attempt at modifying the force law, but it has more problems than dark matter at this point.
You've just describe the scientific method, which I'm sure is useful for some readers, but I was hoping for somehting a little deeper. :)
Are there then models of dark matter which specify how the non-baryonic particles were formed, and how they come to be distributed, without the freedom to simply arrange the particles however you need to to make the numbers work out? Any links to descriptions of said theories?
Socialism: a lie told by totalitarians and believed by fools.
My God, it's full of... no, wait, not really... oh well...
Larry Niven has this explained: Dyson Spheres. Each star is surrounded by matter so that all the available star's energy is utilized.
The other night upon the stair,
I saw a star that wasn't there.
It wasn't there again today,
I wish, I wish it'd go away...
Of course there are specific models of dark matter. There is a vast literature. Search the Harvard ADS database for thousands of papers. Formation of these particles is often tied to inflation, and there are lots of early-universe gravitational clustering models to determine structure formation. People don't simply arrange dark matter how they see fit; typically, quantum fluctuations during inflation are postulated to generate density fluctuations during reheating, which seed structure. All kinds of predictions can be made. For instance, if you postulate that all the dark matter is neutrinos, you get a "hot dark matter" scenario in which the particles zip around so fast, they don't stay in one place long enough to produce enough clustering of matter. Thus, you need a component of cold dark matter, etc. Elsewhere in this thread some people have posted links to FAQs and tutorials and such on dark matter. You should read them.
This would qualify as a Kardashev Type III civilization.
But don't suggest this to the astronomers or astrophysicists because they are so friggen sure that the universe is *dead* and nothing they observe could be explained by the activity of advanced technological civilizations... They obviously haven't read any of the work by the Lineweaver group pointing out that 75% of the stars in the galactic habitable zone are older (in some cases much older) than the Sun. [Ref: astro-ph/0401024].
Roll the open source and nanotechnology development efforts forward by a few hundred million years and project what the universe would look like...
The link next to the text... Find out more about what is going on in south east Wales
This galaxy is in south east Wales? Why did it take so long to find it?! Oh right, cause it's dark.
The lights are out but is there anyone at home?
This really very interesting. What is it? Is a galaxy of long dead stars? If it is normal matter why has it not formed stars? A giant black hole.
Is it emitting in X-RAY, Gamma, IR?
See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
OH NO!! It's a Deathstar!! Be careful of the dark side or bring out the evil!!
...is it faster than the speed of lint? I know its not faster than Ludicrous Speed.
Read my short stories - You won't regret it.
...if anybody out there has the technology to cloak an entire freakin' galaxy. We are so toast.
Is it just my observation, or are there way too many stupid people in the world?
And if we define hunger as lack of food, then the speed of hunger must be equal to speed of food?
A little bit too simple for my taste.
I do not think the word "theory" means what you think it means. A scientific theory is a thesis that has been proven by numerous experiments, has many peer-reviewed papers published exploring it, and is generally accepted as "truth" by the scientific community.
A (layman/religious) "theory" is a guess that could be disproven at any moment, and which has no basis in fact, except the coincidental.
Now then, when we debate a scientific theory, we know there is a large body of work that supports the theory. We can reference it, and we can reproduce the experiments. When we debate a religious theory, it generally comes down to who can shout the loudest, because there are NO reproducible experiments, and precious-few peer-reviewed papers (How many angels can dance on the head of a pin? Discuss.)--certainly not in any respected journals.
As for the desirability of "testing religious theories" there is really no point. As one of my profs put it, If someone comes to you with a 'proof that any angle can be trisected', it doesn't matter how long the proof, how elegant the introduction, how many sources cited, or how clear the abstract. There is no point in reading it, because you know somewhere, buried deep in the discussion, there is a tiny error that renders the entire proof meaningless.
Yeah, right.
Decades of work has indicated more than three ways to make QM compatible with GR, including: string theory (AKA M-theory), twistors, and loop quantum gravity (LQG). However, it is suspected by some that, just like St. Patrick would tell us, these three are actually different facets of the same underlying reality. (Just like different interpretations of QM don't actually produce different predictions.)
Ben Hocking
Need a professional organizer?
Scientists have discovered the source of Dark Matter and energy in the universe.
/. dupe posts...
/. editor.
Dark Energy is what comprises
and Dark Matter is what is between the ears of every
Check journal for info on Anti-TextBook, an idea by me.
But right now, cosmology is at a particular, historically characterizable point, when a lot of different speculations can theoretically be proved or disproved, but in practice we can't build the equipment. We could theoretically attain the enegrgies needed to show unification between the strong nuclear and electroweak forces, but we'd have to build a particle accelerator that stretches across Jupiter's orbit. We could theoretically pick which Superstring or "M" theories looked the most promising and throw out a thousand competitors, but we'll have to wait for 500 of those 18 month doublings under Moore's law before we can actually build a computer fast enough to process the data.
The Epicycle model didn't get questioned much, until it got so elaborate that it wasn't just 3 epicycles to explain Mars' apparent motion, it was 50 or so. The more we accumulated accurate observations, the more it became obvious Occam's Razor mattered. Eliptical orbits didn't look obviously simpler than a primitive version of the epicycle theory, but did look obviously simpler than its elaborated version.
This goes back to that pesky tangent on religion. When the gap between thoretically provable and practically provable gets large enough, what's the difference? "I'm not making a leap of faith here, it's a scientific prediction! It can be proved! No really! I just need the entire resources of the human race for the next 30,000 years at my personal beck and call, and I'll prove it!"
There's a lot of observed evidence that supports the claim physics, and particularly cosmology, is in the middle of one of those dreaded paradygm shifts. (Ha, got to use that overused word and actually need it - Mad props to Me!).
In other words, it would be very rash to conclude that our understanding of gravity is wrong, based solely on its predicting Dark Matter, but when you add in the evidence in other areas, the idea is starting to look just a trifle less rash.
Who is John Cabal?
... can be found at http://www.theregister.co.uk/2005/02/23/galaxy_dar k_first/
Intelligence and a healthy sense of self-preservation are two very different things. At least the dolphins don't seem to slaughter eachother the way we do.
I've read many of them. There's seems to be an amazing amount of "science validated by computer models built using that science" going on here. Great for spotting logical inconsistancies, I'm sure, but as an engineer I prefer not to dine on the menu.
Heck, I'd settle for a mechinism explaining how much-faster-than-light expansion occured - but only for a little while, just enough to make all the numbers come out the way they need to. What inputs drive the speed of universe expansion, or for that matter caused it in the first place, let alone accellerated it (but only breifly).
Socialism: a lie told by totalitarians and believed by fools.
Only if there were something that was bright enough to be seen behind it. There has to be something for a massive object to lense before it can be observed.
HA! I just wasted some of your bandwidth with a frivolous sig!
Oh really? Well, as long as you're accusing scientists of incompetence, why don't you name names and cite the papers with this circular reasoning?
That's the domain of inflationary cosmology. With the advent of WMAP, we're finally approaching a point where we can rule out many classes of inflationary models, and the one that's most supported right now is plain vanilla de Sitter type inflation, with a cosmological constant. That puts a lot of constraints on what the inflaton can be, but we still don't know -- more tests are being devised. As for what caused the universe to expand in the first place -- the Big Bang -- may never be known. I don't know what your "but only briefly" comment means; the accelerating expansion is still going on.
...You should just be glad he didn't post pictures of the the Tubgirl supernova.
*shiver*
HA! I just wasted some of your bandwidth with a frivolous sig!
Only on Slashdot will you see calculations for accelerating a Dyson sphere with starlight so you can go visit your girlfriend in another part of the galaxy.
People on Slashdot who can calculate the acceleration effects of starlight on Dyson spheres do not have girlfriends. Sorry.
HA! I just wasted some of your bandwidth with a frivolous sig!
Those romulans are cloaking their entire galaxy!
It's the other way around, 80% has been explained.
It's Dark Energy that is still the bigger mystery.
OK, I'll do it.
Single-star dyson spheres: number_of_stars*4*pi*radius^2
where radius is the radius you build the sphere at. number_of_stars is something like 10^11
Galaxy dyson sphere: 1*2*pi*8_kiloparsecs^2
16 kiloparsecs is given as the approximation of the galaxy in question's diameter. I'm using 2*pi*radius^2 since you can build a flattened spheroid... spiral galaxies are pretty flat.
n.b. 1 parsec = 3.1x10^16 m
1 earth-sun distance (astronomical unit) = 1.50x10^11 m
so surface area of case 1 over case 2 is
radius^2*7.3x10^-8
where radius is in astronomical units. So, if you take a pretty conservative case and build your sphere at the same distance the Earth is at, then you have to use about 10^7 times more material to build a galaxy sphere. (I'm sure with most stars you could build it a lot closer, and live on the outside)
Still, interesting idea, and I agree totally that it would be prettier. It might have a problem with stars hitting it though...
Anyway, to get a little more on-topic, it's impossible in this case since astronomers detected hydrogen in the galaxy, they just haven't observed any stars. So the stars could be covered, the whole galaxy couldn't be.
Slashdot - Mutual Assured Discussion
Hell the dark matter has even beem mapped!
For gods sake people, just google for Dark Matter and do a little catching up! Your college astronomy classes you had 5-10+ years ago has now left you with completely out of date information! Hell even 2+ years ago...
No, that's simply incorrect. Dark matter is still unexplained, and dark matter outweighs regular matter by 5-to-1. The mass-energy content of the universe is about 5% normal matter, 25% dark matter, and 70% dark energy. The latter two, 95% of the total mass-energy content of the universe, are still unexplained -- there are theories for what they might be, but nobody knows.
Dark matter has been "mapped" assuming that certain dark matter models are correct, as opposed to alternative theories of gravity or whatnot. I'd definitely bet on dark matter, but it's not a foregone conclusion. And that still doesn't change the fact that we don't know what 80% of the matter in the universe actually is, even though we know where it is and how much of it there is.
Not to mention that dark matter has been both seen visually during white dwarf and supernova explosions recently and actually mapped out in some areas of space.
Except that "Gravity" is the effect. That's it. The word "Gravity" is not a cause in itself, except as an affect on other things.
The artificialness of the inflationary model of which I speak is the idea that, about the time the strong force seperated, the inflation rate was briefly many many times higher than at the time of recombination. "The universe needs to be a certain size at recombination for the CMB data to make sense, but that size is too big for the CMB temperature to have equalized across the universe, so let's just assume this convenient very rapid inflaiton before that, to make everything work out." There's no mechanism to explain why that would happen, it's a bag on the side of the theory.
OK, I'll admit that occasionally when someone says "for this model to be consistant, we'll just assume this very odd thing about the universe" they're right, but far more often it's not the universe that has the problem.
However, I don't totally discount this oddball ad-hockey because it did make some predictions that MAP seems to be confirming.
Socialism: a lie told by totalitarians and believed by fools.
We don't even know if the current cosmological expansion has anything to do with early-universe inflation. Right now, the leading candidate for cosmological expansion is the ordinary cosmological constant. If so, early-universe expansion is unrelated that, taking place by an entirely different mechanism (the slow roll of an inflaton field). I don't see what your problem with the inflaton is. In fact, it's so easy for inflatons of one type or another to crop up in high-energy physics, that the problem is perhaps not why there was rapid inflation in the early universe, but why it stopped -- the so-called "graceful exit" problem. But that has been solved within a wide class of models too, and there are a number of quite natural candidates for inflaton fields.
Where is the ad-hocery?
All Cardiff Uni Physx, Comsc & Engin students (maths too if you fancy the walk), lets go and give Drs Davies & Minchin a hearty slap on the back tomorrow...
er, I can't be bothered to go find my Cosmos notes to find where Doc Davies' office is... ask someone, I'm sure they'll be happy to point you to the directory of staff offices.
How do they know it does not contain any stars? After all...would not a star made of "dark matter" be radiating the so called "dark energy?" Why does stars made of dark matter have to radiate visible energy?
SELECT * FROM User WHERE Clue > 0
0 rows returned
This article describes studies of intergalactic gas 150 times hotter than the sun. Such gas is difficult to detect because it can only radiate at ultraviolet wavelengths:
http://www.space.com/scienceastronomy/missing_matt er_030212.html/
"A worthy cause has never been harmed by the truth" - Gandhi
- I have a great model for the big-bang theory: it's inconstsiant with the observed redshift of distant galaxies, but I'll just add this "cosmological constant" and it will be fine.
- I have a better model, and we don't need that mysterious cosmological constant, so out it goes.
- Better measurements call for a better model, it doesn't quite account for the redshift of distant galaxies, so welcome back cosmological constant!
- Hmmm, all the observed matter and expected dark matter still doesn't quite make things work out, lets add "dark energy" to explain the cosmological constant!
- Wow, great CMB data but it appears that the cosmological constant isn't quite, ummmm, constant. Yeah, can someone come up with a model for brief hyper-inflation real quick? And I don't mean Jimmy Carter.
I'm not convinced the inflation theory is wrong, but please excuse my skepticism given the track record!Socialism: a lie told by totalitarians and believed by fools.
Actually, just saw another interesting article on the subject. Hubble photogrphed two colliding spiral galaxies. They were in a position such that one should have been able to see the behind galaxy through the empty spaces in the spiral arms of the front galaxy.
:) There is supposed to be a satellite launch in a few years to try to detect some of the other dark matter theories, if some of these theoretical exotic particle theories are correct, then we should be able to detect them with the right equipment.
Only, you couldn't. The "empty space" between the spiral arms was completely black. Meaning that they were filled with interstellar "dust". Much more dust that was thought to exist there.
The amount of real matter just went up and dark matter went down as there is now known to be a lot more mass in simple matter contined, invisibly, within galaxies than was previously thought.
There is a lot of speculation on what the "other" dark matter is, but so far, everytime any real "dark" matter is actually found, it seems to always turs out to be... plain old matter that was not known to exist in a certain place or in a certain way.
As for your question, yeah, well it'll just take time, at some point it may all be accounted for, or not, well see
Contrary to popular belief, coding is not all free blow-jobs and beer. Those things cost MONEY!
This AC is correct... he didn't deserve to be modded down, and I probably didn't deserve my +5, Interesting.
That that is is that that that that is not is not.
How much crap do we have to roll up in balls to repopulate this galaxy with stars?
You mention that we "don't understand gravity as well as we think we do," but last time I checked.... gravity doesn't REPEL objects.
... get this... negatively damped. If you go through calculations of the Energy-Momentum tensor for the system, the pressure holding the system in is exactly 1 times the negative of the energy density. In other words, the equation for this state mandates that there is a form of energy in the universe which has a negative equivalent gravitational effect.
The greatest evidence for "dark matter" comes not from an astrophysicist necessarily, but rather from scalar field theory in physics.
Using a very well known differential equation for cosmological inflation:
phi ddot + 3H phi dot + V' = 0
where H is the Hubble constant and the middle term refers to damping, we can see that our observable universe is
Physicists pretty uniformly refer to this effect as "dark matter." There is credence given to it amongst the physics community because with simple field theory calculations of this sort, the entirety of Maxwell's E/M equations and all of classical Lagrangian mechanics can be derived fairly easily on a page or two. Dirac derived relativistic quantum field theory from this as well. So, seeing as the most fundamental branches of physics: classical (E/M), relativity, and QFT are a stone's throw from one another in this formalism, people take it seriously. Also, if you do a very simple observation of fluid dynamics on rotating disc-like galaxies, you will find the equations yield the entirely wrong answer. For:
del . (del p / rho) = del (omega^2 r rhat) - del^2 U
where p is pressure, rho is mass density, omega is angular velocity, r is radius from the center of the rotating frame, and U is gravitational attractive energy. This yields very bad results and since the data we can collect is quite accurate, as well as the terms in the model being about as general as they come, it is a powerful indicator of something wrong, something which an attractive force (e.g. gravity) can't account for in the cosmological equation of state.
of the existence of black cats in coal cellars at midnight.
They say the first thing to go is your penis. Well, it's either that or your brain. I forget which...
Thanks for straightening me out. Not enough sleep, pulled up an old link and read it too fast.
Cheers. :-)
"A worthy cause has never been harmed by the truth" - Gandhi
Everybody knows that dark is what happens when something fills up with light. (By the way, I googled the poor bastard I just linked to. Do your worst.)
For years, we all knew that lightbulbs emit light. Science has now proven this false. Lightbulbs, and other sources of light suck in darkness. In fact, when a lightbulb becomes full of dark, it stops working and has a dark spot on it. Candles are an even better example, since the wick clearly turns black as it is progressively exposed to dark.
Dark also has mass, which causes it to generate heat from friction as it is sucked in. Because lightbulbs are made of clear glass, the dark can go in easier than it can for a candle and there is less heat. For this reason, you don't want to touch a candle while it is sucking dark.
Maybe if the new Dr. Who gets in a budget crunch, they can spend a season trapped in a "dark galaxy".
A few flashlights, and some metallic wrapping paper and they're all set.
WwWWWwwWWWwwWoOoOOoOOOOooOOo
DaAaAAaAaARrkkKK GaaAAaaAaAAAaAaalxyyYyYyyy...
Please do not take this post into account.
that the comments about this are so ass-headed that I actually feel compelled to read the article.
Bill Moyers: Theocrats and ideologues in charge of US government. Moyers: For the first time in our history, ideology and theology hold a monopoly of power in Washington. Theology asserts propositions that cannot be proven true; ideologues hold stoutly to a worldview despite being contradicted by what is generally accepted as reality. When ideology and theology couple, their offspring are not always bad, but they are always blind. And there is the danger: voters and politicians alike, oblivious to the facts.
"A witty saying proves nothing." ~Voltaire
"d'Oh!" ~Homer
They've discovered my illegal garbage dump.
This is not the sig you're looking for.
I got some dirt on the actual techniques they used to find the galaxy.
Bob: Ok, hand me that picture.
Dave: But how do you know..
Bob: Look, just hand me the freaking picture.
Dave: Okay, okay!
Bob: Now, all we need to do is draw a little oval with a dashed line, like so.. voila! Instant invisible galaxy.
Dave: Is that an invisible Paris Hilton?
Bob: I'll be damned, that girl's got more pictures floating around than the royal family.
https://www.eff.org/https-everywhere