Study Claims To Provide First Direct Evidence of Dark Matter (theguardian.com) 72
An anonymous reader quotes a report from the Guardian: Nearly a century ago, scientists proposed that a mysterious invisible substance they named dark matter clumped around galaxies and formed a cosmic web across the universe. What dark matter is made from, and whether it is even real, are still open questions, but according to a study, the first direct evidence of the substance may finally have been glimpsed. More work is needed to rule out less exotic explanations, but if true, the discovery would go down as a turning point in the decades-long search for the elusive substance that is said to make up 27% of the cosmos.
"This could be a crucial breakthrough in unraveling the nature of dark matter," said Prof Tomonori Totani, an astrophysicist at the University of Tokyo, who said gamma rays emanating from the centre of the Milky Way appeared to bear the signature of the substance. [...] To search for potential dark matter signals, Totani analysed data from Nasa's Fermi Gamma-ray Space Telescope, which detects the most energetic photons in the electromagnetic spectrum. He spotted a pattern of gamma rays that appeared to match the shape of the dark matter halo that spreads out in a sphere from the heart of the galaxy. The signal "closely matches the properties of gamma-ray radiation predicted to be emitted by dark matter," Totani told the Guardian. Details are published in the Journal of Cosmology and Astroparticle Physics.
If Totani has seen dark matter at work, the observations suggest it is made from elementary particles 500 times more massive than the proton. But far more work is needed to rule out other astrophysical processes and background emissions that could explain the signals. Totani said the "decisive factor" would be detecting gamma rays with the same spectrum from other regions of space, such as dwarf galaxies. According to Prof Justin Read, an astrophysicist at the University of Surrey, the lack of significant signals from such galaxies strongly argues against Totani having seen gamma rays emitted from dark matter particle annihilation. Prof Kinwah Wu, a theoretical astrophysicist at UCL, urged caution, saying: "I appreciate the author's hard work and dedication, but we need extraordinary evidence for an extraordinary claim," he said. "This analysis has not reached this status yet. It is a piece of work which serves as an encouragement for the workers in the field to keep on pressing."
"This could be a crucial breakthrough in unraveling the nature of dark matter," said Prof Tomonori Totani, an astrophysicist at the University of Tokyo, who said gamma rays emanating from the centre of the Milky Way appeared to bear the signature of the substance. [...] To search for potential dark matter signals, Totani analysed data from Nasa's Fermi Gamma-ray Space Telescope, which detects the most energetic photons in the electromagnetic spectrum. He spotted a pattern of gamma rays that appeared to match the shape of the dark matter halo that spreads out in a sphere from the heart of the galaxy. The signal "closely matches the properties of gamma-ray radiation predicted to be emitted by dark matter," Totani told the Guardian. Details are published in the Journal of Cosmology and Astroparticle Physics.
If Totani has seen dark matter at work, the observations suggest it is made from elementary particles 500 times more massive than the proton. But far more work is needed to rule out other astrophysical processes and background emissions that could explain the signals. Totani said the "decisive factor" would be detecting gamma rays with the same spectrum from other regions of space, such as dwarf galaxies. According to Prof Justin Read, an astrophysicist at the University of Surrey, the lack of significant signals from such galaxies strongly argues against Totani having seen gamma rays emitted from dark matter particle annihilation. Prof Kinwah Wu, a theoretical astrophysicist at UCL, urged caution, saying: "I appreciate the author's hard work and dedication, but we need extraordinary evidence for an extraordinary claim," he said. "This analysis has not reached this status yet. It is a piece of work which serves as an encouragement for the workers in the field to keep on pressing."
It is pitch dark matter... (Score:4, Funny)
> TURN ON LAMP
The evidence for dark matter evaporates!
Re:It is pitch dark matter... (Score:4, Informative)
Re: It is pitch dark matter... (Score:1)
Re: It is pitch dark matter... (Score:5, Funny)
Does it mean... (Score:2)
...that we're no longer in the dark?
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If its true, then.... well yeah.
And we'll almost certainly get a better name for it than "Phrase which confuses non scientists into thinking scientists have an unprovable theory when scientists literally called it that to indicate that actually, they really dont have a theory yet, or more concisely 'dark matter' "
Re:Does it mean... (Score:5, Funny)
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Does it matter if you have 9 or 10 dollars, if all you want is to buy an ice cone for $3.50?
Does it matter if there are 9 or 10 parking lots if you know 5 of them are occupied, and you want to park your car?
Sometimes, 9 or 10 is a question of life and death. Are there 9 or 10 people in the burning building, and have we account for all of them rescued from the fire? Sometimes it is totally irrelevant.
Same with Dark Matter. If we want to account for
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Re:Does it mean... (Score:5, Insightful)
Or, as always... (Score:2)
...it could just be aliens. Or an alien bird shitting on the telescope.
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it's weather balloon radiation
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So that would explain the new human-lethal bird flu strain.
If this flu acquires human-human transmission (which other bird flu strains have developed at various times ; it's obviously not a difficult thing to acquire), how is RFK Jr going to deal with it? Vaginal douches and Ivermectin? horse tranquilizer to overdose?
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It's more likely to get that engineering in America.
Asia in general and China in particular have had due respect for the lethality of respiratory viruses for a long time. I remember wondering about the Oriental habit of wearing respiratory masks in public places through the 2000s and 2010s - and it's largely down to their reasonable concerns about SARS (2004 to 2006) and then MERS (2012 to 2021).
No, I'd expect any lunatic gene engineering to take place in a Texas garage, performed by an anti-vaxx campaigner
Dark matter, you say? (Score:4, Funny)
I'll believe it when I see it.
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Apparently you'll need to be able to see gamma rays to be able to see it.
If.. (Score:3)
its emitting gamma rays, then its not dark.
Re:If.. (Score:5, Funny)
Indeed, now it's not dark matter, but instead the matter previously known as dark.
Re: If.. (Score:4, Funny)
Re:If.. (Score:5, Interesting)
It it suggested that dark matter rarely interacts with normal matter but when two dark matter particles smash together they can generate gamma rays.
From the New Scientist These hypothetical particles are fiendishly difficult to detect because they interact so rarely with regular matter, but theorists predict that they should occasionally self-annihilate, disappearing and producing a flash of high-energy radiation in the form of gamma rays. [newscientist.com].
Since we know nothing about it (Score:1)
... other than it responds to gravity, there could be an entire alternate universe consising of dark matter stars, planets etc hidden in plain site and perhaps dark energy could be some form of alternative EM radiation that only interacts with dark matter - dark light if you will - that said dark stars emit.
Re:Since we know nothing about it (Score:5, Interesting)
We know it weakly interacts electromagnetically, which means one of the ways in which it is posited planets form, initially via electrostatic attraction of dust particles, isn't likely to work. This means dark matter will be less "clumpy" and more diffuse, and less likely to create denser conglomerations that could lead to stellar and planetary formation.
What this finding does suggest, if it holds true, is that some form of supersymmetry, as an extension fo the Standard Model is true. Experiments over the last 10-15 years have heavily constrained the masses and energy levels of any supersymmetry model, so it would appear that if this is the case, it's going to require returning to a model that some physicists had started to abandon.
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It also suggests that as time goes by, dark matter will decay into normal matter (photons). Rather slowly, however.
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I don't see how that follows from MightyMartian's post. Care to elaborate?
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And the reason there couldn't be some kind of dark electrostatic force which dark matter interacts with is? There could be an entire gamut of forces unknown to us that only interact with dark matter.
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"If there is, it is extremely weak, below the scale of Higgs interactions, on the scale of gravity"
And you know this how? Where is the proof that these forces can't exist given we have no way to measure them?
"The best fit to the data is a particle that doesn't interact with baryonic matter or itself."
Since when? The CBR gives no such indication, just a general indication of the spread of baryonic matter in the early universe. It says nothing whatsoever about dark matter.
Re: Since we know nothing about it (Score:2)
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But we do not yet know
(IIUC, there is a finite nonzero coupling constant between *any* two QM fields)
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there could be an entire alternate universe consising of dark matter stars, planets etc hidden in plain site
ObSF: Photino Birds [fandom.com].
Re:Blind idiocy. (Score:4, Insightful)
Nobody except you claims that dark matter explains everything. Nobody except you expects it to explain everything.
There is an observed phenomenon that requires explanation. Nobody knows what the explanation is, nobody has seen it, only its effects have been observed, so they call it "dark".
It is not a marketing term, there is nothing being marketed. It does not imply that the people studying it know what it is, quite the opposite, the term was chosed precisely because they say they do not know what it is.
It is not a religion. The observed phenomenon (the inexplicable velocity of the outer parts of some galaxies) is observable. You don't need to believe anything for it to be there.
And because science is all about discovering things that nobody has discovered yet, and about figuring stuff out, and then publicly sharing what has been found, so that others can verify or disprove the findings, there is the expectation that someday somebody will figure out what that dark matter stuff really is, and the likes of you will have to find some other strawman.
Until then, scientists will keep sciencing the science. For the benefit of all, even you who doesn't contribute anything other than wasting everyone's time and air with your nonsense.
Re: Blind idiocy. (Score:5, Informative)
Just a small nit to pick: it's not just about the behavior of galaxies.
The anisotropy that we observe in the cosmic microwave background could also be explained by the existence of matter that is not directly visible, aka dark matter.
One of the issues with the "modified Newtonian dynamics" approaches is while it explains the galaxy observations, it doesn't explain the CMB observations. That doesn't necessarily mean that it's wrong, of course. But dark matter fits the observations of multiple discrepancies (galaxy behavior and CMB anisotropy and more), so most cosmologists think that dark matter is the more likely explanation.
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There is an observed phenomenon that requires explanation. Nobody knows what the explanation is, nobody has seen it, only its effects have been observed, so they call it "dark".
By calling the "phenomenon" matter, you are positing that some sort of material exists. That is a step too far. That is why you and the scientific community gets so much push-back and derision. People like you are asserting that a physical material exists without any, ummmm, material proof... which is what science is based upon. "Show me the money".
There is something going on. Something that we can not explain. To invent the concept of a new type of matter, while a reasonable process to follow, is a step to
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You do realise that the first evidence for dark matter was found (and published) in the 1930s, well before anyone but Goddard's most optimistic liquid-fuelled rockets got off New Jersey potato fields.
No, you're an AC. You probably don't know that.
Your ignorance doesn't make it untrue.
This whole concept has always bothered me. (Score:3)
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If it reacts only to gravity, it should clump together with ordinary matter.
It should not clump - that would require it to interact with ordinary matter to lose orbital energy. Instead it just passes through, with gravity of the earth or the sun being the only force affecting its trajectory.
[...]So why is not all around us on earth? Why is it only found in the depths of space? What excludes it from our everyday experiences?
It probably is all around us, but does not interact with regular matter a lot. The depths of space are huge, so even at a low density, there can be a lot of dark matter swirling about around galactic nuclei.
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The Sun, all stars, galaxies, formed by ordinary matter self gravitating into a volume where it's components interact with each other. With ordinary matter that implies a confining pressure produced by gravity, and a resisting pressure from the particles interacting with each other and not being able to share the same volume.
As a "RetiredChemist", you should recognise that situation from deriving the "Ideal Gas Laws" from Newtonian dynamics of particles and Van der Waal's expression for the volume of gas mo
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It probably is all around us, but does not interact with regular matter a lot.
It appears not to at solar system scales. Because we can plot the trajectory of a satellite to intercept an object beyond the orbit of Pluto without considering its effects. But at galaxy scales, it distorts the effects of gravity and galactic rotation sufficient to be easily observable.
Magic stuff, this dark matter. It knows when to be there and when not to.
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27% of the cosmos is not insignificant. Unless it is distributed very unevenly. So now your theory has to explain that.
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Gravity tends to clump stuff up.
But not the same way luminous matter (the "standard" stuff) clumps up. The mass distribution needed to explain spiral galaxies assumes that this "dark matter" remains at the periphery of the galaxy, keeping the rotational velocities constant as one moves away from the galactic center. So now, dark matter has to be something that doesn't interact with gravity (or curved space-time) the same way normal matter does. It curves space-time like normal matter does. But it isn't pulled into the gravity well (space
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The mass distribution needed to explain spiral galaxies assumes that this "dark matter" remains at the periphery of the galaxy, keeping the rotational velocities constant as one moves away from the galactic center.
Umm... no?
If you're going to be convinced that people are making shit up, at least get things right about what they're making up: maybe sit down with Kepler's law, a pencil, and Gauss' law?
If you do so, you get the ad hoc model [wikipedia.org] that matches observations in most galaxies pretty well. That's very not constant, and in fact very centrally peaked, because the radial velocity distributions are only constant in the outer reaches. It's the density distribution that provides the gravity to make the radial veloci
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ahh wait, I see. You're still thinking that somehow Dark Matter isn't in the solar system. It can be (and probably is), at the same density needed to mess with the rotation of the galaxy. However, (tiny density)x(tiny solar system volume)=not enough mass to show up in orbital dynamics. On the other hand, (same tiny density)x(galaxy sized volume) adds up to way more dark matter than "normal" matter in our galaxy.
Just because we don't know what the stuff is doesn't mean we don't see it doing stuff. And it
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Re: This whole concept has always bothered me. (Score:3)
Certainly it could orbit the earth, but the orbit could easily pass through the earth since it does not interact. The reduced gravity from earth while it is below the surface will mean the orbit wonâ(TM)t be an ellipse and i think it would be unstable.
An eloquent way... (Score:2, Insightful)
... to say "O RLY?"
"I appreciate the author's hard work and dedication, but we need extraordinary evidence for an extraordinary claim," he said. "This analysis has not reached this status yet. It is a piece of work which serves as an encouragement for the workers in the field to keep on pressing."
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I don't think you understand the process of science. That is the appropriate reaction to any initial claim. An initial observation needs to be repeated by others, and the data that justified the initial claim should be reanalyzed by others to see if they agree with the interpretation. Then arguments ensue. Eventually people "pretty much" come to an agreement.
Sometimes the arguments last for decades.
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And sometimes they're terminated by funerals.
Researcher Has Direct Evidence Of Dark Matter (Score:2)
Idiotic breathless summary (Score:2)
For those who don't follow this kind of thing for a living, this exact signature was investigated ~10 years ago, Dan Hooper
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If the primordial dark matter is clumpy, then you don't necessarily need millisecond pulsars. The radiation could be clumpy because two clumps of dark matter are slowly passing through each other.
With so little evidence, you can make almost anything fit.
Extraordinary Claims require Extraordinary Proof (Score:2)
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