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Hubble Builds 3D Dark Matter Map
astroengine writes "Dark matter can't be spotted directly because it doesn't interact with electromagnetic radiation (i.e. it doesn't emit any radiation and reflects no light). However, its gravitational influence on space-time can bend light from its otherwise straight path (a phenomenon known as 'lensing'). Using a sophisticated algorithm to scan a comprehensive Hubble Space Telescope survey of the cosmos, astronomers have plotted a map of 'weak lensing' events. Combining this with red shift measurements from ground-based observatories, they've produced a strikingly colorful 3D map of the structure of dark matter."
...but I fail to see the 3D that was promised by TFA.
I agree it's a nice picture but there seems to be no explanation as to what these colours actually mean, let alone any kind of conclusion drawn from what I presume to be "pockets of dark matter".
Anyone care to enlighten me?
The pic looks like the Zetarians.
Sig this!
looks photoshopped to me
If you mod me down, I will become more powerful than you can imagine....
...especially when you consider it's a picture of something that very possibly doesn't even exist.
There isn't any "scale bar" because you are not looking at something at any fixed distance! You are looking at (theoretically) blobs of stuff at various distances.
You could do it based on movement speeds. Things in the background of an image move slower than those in the midground when you change your position--If the thing in the background, a galaxy or something, moves in a strange way, then you can be sure it's being lensed. I'm not sure if the Earth moves enough for this to be useful, though, given the scale.
Conscience is the inner voice which warns us that someone may be looking.
looks like a My Little Pony pegasus got up there and jizzed all over the lens...
(To me still a imaginary excuse, based on the arrogance of not being able to admit that the math is wrong, but instead calling the universe wrong! ^^ [But a good {and compact!} explanation will of course change my mind.])
That might be something similar to what they told Einstein when he used his math to explain characteristics of nature that no one had witnessed.
I find the possibility of dark matter and energy kind of fascinating. Maybe it just a problem with their math - but then again, having huge amounts of mass in the universe be something other than what we experience every day adds a little mystery to it all.
Why are you letting these clowns ruin our country?
Sorta. As the earth goes around the sun, we do in fact get enough parallax to determine the distance to nearby stars. On the galactic scale, though, this doesn't work. The way they find lensing artifacts is that lensing doesn't just skew a single flat image of what we see, it might bend the same light source so it comes at us from different angles, producing multiple images of a single event. Something like this: http://en.wikipedia.org/wiki/Einstein_Cross
If they have good enough images with spectral plots for each pixel (which if they are using redshift to determine distance, they must have), I could see an algorithm being able to pick out which images are mirages, and therefore where the lensing matter must be.
... the disturbance I felt in the Force earlier. I thought I just had gas.
It's not arrogance; frankly, a true scientist is thrilled at the prospect of being proved wrong. It means they're answering some long-standing questions and posing countless new ones. Furthermore, the concepts of "dark matter" and "dark energy" are still only theories; scientists have yet to definitively prove the existence of these entities. These theories just happen to be the best explanations for what scientists observe.
The bottom line remains what osgeek above me said: it's easy for you to call the scientists who postulate dark matter "arrogant" considering it's something that has about as much impact on our daily lives as Einstein's Theory of Relativity does (which, when it was being proved, required very specific measurements to be taken, measurements that could only be gathered in a solar eclipse...how's that for completely unnecessary to quotidian life?).
No, right now we can't definitively prove that the 3D image referenced in TFA is indeed dark matter. But within the parameters of the current hypothesized model, that is what scientists believe to be pockets of dark matter.
"I'd just like to emphasise that taking a million years isn't a metaphor here..." -Rich Bradshaw
...how they know it’s lensing, and that the stars aren’t just positioned like that?
Sounds to me like you could never prove, which one it really is, until you fly behind that “dark matter”. (To me still a imaginary excuse, based on the arrogance of not being able to admit that the math is wrong, but instead calling the universe wrong! ^^ [But a good {and compact!} explanation will of course change my mind.])
When you see multiple images of the same object, it's lensing. This is, in fact, how gravitational lensing was first discovered. Check out this great wikipedia image of the effect: http://en.wikipedia.org/wiki/File:Einstein_cross.jpg. This is actually called strong lensing. TFA discusses weak lensing, which is a much smaller effect. That's detected by looking at very distant galaxies. Lensing changes the shape of galaxies such that there is a preferred orientation. If this orientation is statistically significant, i.e., too many galaxies are stretched in the same direction to be caused by normal physics, then it tells us that the weirdness is likely caused by lensing. Thanks to Hubble's ability to paint an incredibly dense picture of background galaxies, our statistics are based on a huge number of samples and we can trust them pretty thoroughly.
Awesome, right?
"I zero-index my hamsters" - Willtor (147206)
So luminiferous and aethereal! Almost magical like!
I'll go farther than that: I can remember how before the Hubble was launched, scientists didn't think we'd ever actually be able to observe the effect because it was too small to be imaged from any ground-based telescope.
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IANAAstrophysicist, but my understanding is that a point source, such as a black hole, would create a strong lensing effect. These observations are of a weak lensing effect that indicates a diffuse source of gravity.
The dark matter doesn't bend light. The gravity from the dark matter bends light.
Actually, it does exist. Frankly, I'm fucking sick of posting the same links over and over, so why don't you just go to Wikipedia and read about the Bullet Cluster. There is simply no question, now, even among MOND proponents: there is weakly interacting matter out there, and we have no idea what it is.
I actually submitted a story on this exact same topic back in 2007. The only thing new they seem to have now is a nicer picture, the article seems much lighter than the original article I linked to three years ago. The new article doesn't seem to indicate any new science that has developed since then, not even links or mentions of any new publications updating the findings in 2007, or even mentions of the scientists who are behind this work...
Qu'on me donne six lignes écrites de la main du plus honnête homme, j'y trouverai de quoi le faire pendre.
"I'll note: this has nothing to do with dark matter. As it happens, 90% of the matter in the Universe is in a form that emits no light, but affects other matter through gravity. We know it exists ... locally, in nearby galaxies and clusters of galaxies, too. This new result doesn't affect that, since the now un-hidden galaxies are very far away, like many billions of light years away. They can't possibly affect nearby galaxies, so they don't account for dark matter."
"Laugh while you can a-monkey boy!" - Dr Emilio Lizardo
"These theories just happen to be the best explanations for what scientists observe."
Exactly! Dark matter and dark energy are just tags for unexplained phenomena that appear to have similar properties to matter and energy. They are not simply mathematical entities, they are phenomena that can be observed but cannot (yet) be explained with our mathematical models. This is no different to any other physics, Newton didn't discover gravity he discovered it could be described with maths.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
Is it me, or did that pic give anyone else a TOS flashback where they meet some energy-based alien that fucks with the ship?
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...is totally normal matter, but invisible for us because it is located in another universe? I am not a physicist so my idea might be totally wacko, but ages ago I watched the BBC documentation 'The elegant universe'. One of the string theories explained there proposed that the reason gravity is so weak compared to other major forces is that the 'strings', which are responsible for gravity have the ability to migrate into parallel universes. Therefore we always feel only a fraction of the gravity mass 'produces'. <--- Please be lenient with my very unscientific wording. :-)
So when I saw this documentation I always wondered, when 'our' gravity migrates into other universes, shouldn't also migrate gravity from other universes into ours? I wondered if this theory was true, how would a black hole in a parallel universe look like here?
So maybe, if we had the ability to fly to those places where hubble located the 'dark matter', we would find nothing. The space is curved there for no apparent reason. It is actually because of normal matter in a parallel universe.
or put another way, the dark matter doesn't bend light -- it bends space. (!)
~.~
I'm a peripheral visionary.
The language was asking for it.
The article dated "March 26, 2010":
http://news.discovery.com/space/hubble-3d-map-universe-dark-matter.html
has a source dated 25-Mar-2010::
http://www.spacetelescope.org/news/html/heic1005.html
with this quote which explains everything:
The data was old, the analysis and imaging is new.
The 'Links' at the bottom include the new paper, and the old study. The old press release dated "7-errNoSuchMonth-2007":
"News Release heic0701 - First 3D map of the Universe's Dark Matter scaffolding"
http://www.spacetelescope.org/news/html/heic0701.html
Is the one described your original article:
http://news.bbc.co.uk/2/hi/science/nature/6235751.stm
The question I have is why so many people are so antagonistic to the very notion of dark matter, routinely calling the people who suggest it... "arrogant" and the like.
Personally I think the AC (perhaps unintentionally) nailed it -- it's part of a larger anti-science movement that considers the conclusions of science confusing, uncomfortable, or politically unattractive, and therefore seeks to discredit not just the particular theories but science in general. They do this by dressing up their ignorance with a thin veneer of scientific criticism in order to paint the professional scientists as the ones who are arrogant, ignorant, and arguing out of belief not evidence or reason.
Dark matter gets singled out because it sounds weird (especially if you know nothing about it) and like scientists are just making things up (especially if...). And if they're just making that up, then maybe they're just making up global warming, or evolution, or the age of the earth.
Even if they aren't against any of those particular theories, it's still just part of a general anti-science trend where people start with their conclusion -- the scientists are wrong because I don't understand them and I'm so smart that's not possible unless they're wrong -- and then work backwards to the kind of posts you see here. Accusing scientists of arrogance and dogmatism.
I mean look at the GP. They says it's "dogmatic in the extreme" not to admit that non-baryonic matter violates the law of gravity, clearly demonstrating that they are arguing out of ignorance and a belief that dark matter theory can't be true. The hypocrisy is astounding.
The world makes me sad. But data like this makes me happy. It's an exciting time in physics no matter what the doubters say and I can't wait to see where it leads.
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