And yet it moves incorrectly.
Far out: Dark matter bridges millions of light-years long spotted between galaxies
Astrophysicists have for the first time spotted filaments of dark matter forming bridges between galaxies tens of millions of light-years apart. Dark matter – the ghostly substance that is thought to make up about a quarter of our universe – is strangely hard to find. Some physicists believe dark matter is made up of weakly …
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Thursday 13th April 2017 06:58 GMT AustinTX
The assumption that it's matter
Note that all they know is that these are regions which exhibit naked gravity without detectable source. Since matter is associated with gravity, they call it "dark matter". It's just as likely that it's something that gravity does on it's own. My own pet theory is that it's a displaced gravity field caused by the matter pulled into black holes.
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Thursday 13th April 2017 09:37 GMT Steve the Cynic
Re: The assumption that it's matter
"It's not a theory unless it fits into a framework of other observations,"
It *is* a theory - it explains (sort of, weakly, maybe) the observed phenomenon. It could use some more concrete manner of making predictions about other things we could observe, but it is a theory.
Without that capacity for prediction, it isn't a scientific theory because it cannot be falsified. General Relativity is specific enough that we can use it to predict how far light will bend and in which direction, and we can then do things to see if that actually happens.
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Sunday 16th April 2017 18:49 GMT Anonymous Coward
Re: The assumption that it's matter - It's a hypothesis.
It is 'an hypothesis' in some dialects of English, including the one you speak perhaps: almost certainly it is 'a hypothesis' in the dialects most commonly spoken now. Do you go to 'a hotel' or 'an hotel' for an example of another shift which is pretty much complete now (my grandfather would have gone to the latter, I go to the former).
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Monday 17th April 2017 01:04 GMT Leslie Graham
Re: The assumption that it's matter
You blasphemers.The Cosmic Star Goat is a recent usurper.
The one true God is the Flying Spaghetti Monster. May you be touched by His noodly appendage.
http://spaghettimonster.com/church-of-the-flying-spaghetti-monster-founded/the-gospel-of-the-flying-spaghetti-monster/
Repent.
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Monday 17th April 2017 09:39 GMT eldakka
Re: The assumption that it's matter
@Chemist
it's actually mass & energy that 'bends' spacetime AFAIK
Energy and mass are the same thing. Mass is (for want of a better or more scientific term) 'coalesced' or 'solidified' or 'concentrated' energy. They are different states of the same thing.
E=mc^2 therefore m=E/(c^2).
Therefore 1MJ of energy has 1000000/300000000^2 =1.11e-11 kg
Therefore stating mass bends space time is the same as stating energy bends space time which is the same as stating energy and mass bend space time. Therefore it is sufficient to just say "mass bends spacetime" or "energy bends spacetime" as the one, by definition, implies the other.
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Thursday 13th April 2017 18:14 GMT Anonymous Coward
Re: False false colours
"Surely the colour should be black where the density of dark matter is greatest?"
Transparent, surely? Black means energy is being absorbed which means that the substance is interacting with light. Dark matter is actually completely see-through. You can fire as many photons at it as you like but they will continue on their way even if very slightly deflected by gravity.
But "completely transparent matter" doesn't look nearly as snappy on grant applications. Unless it's for imperial clothing.
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Thursday 13th April 2017 13:41 GMT Alistair
Exhaust trails perhaps?
I keep hoping that the explanation is that this imbalance we're seeing is the pollution left behind by the far more advanced species transport devices. We're just slow getting to the party.
All that said, nice to see some data added to the pile so we can look at it in a different light.
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Thursday 13th April 2017 14:16 GMT Random Handle
Re: Exhaust trails perhaps?
>I keep hoping that the explanation is that this imbalance we're seeing is the pollution left behind by the far more advanced species transport devices.
Densely packed turtle coprolite? - can't help thinking this is research that would be better put on the backburner until more fundamental physics is addressed rather more locally.
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Thursday 13th April 2017 14:53 GMT Tikimon
It's the Dark Side, of course
Isn't it obvious? Dark matter and energy are the physical manifestations of the Dark Side of the Force. The early Sith were drawn to Dark Matter and Energy, and shaped themselves and their methods after them. Thus the Sith always work from the shadows, making sure their influence is never seen, their power carefully hidden. It's taken this long to even suspect the presence of dark forces and the Sith, it's clearly working for them.
Midichlorians on the other hand are needy little attention whores, you can sense them clean across the galaxy.
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Thursday 13th April 2017 15:15 GMT Draco
Had to look up what "Weak Lensing" is
Normal lensing effects would only be visible if we could "walk" around the lens noting the changes. Or if the lens moves between us and the object of interest.
Looking galaxy pairs 4.5 x 10^9 light years away seems to seems to preclude any possible use of one of those methods.
So the scientists have come up with "weak lensing". Essentially (if I correctly understand),
(1) we assume a uniformity across the galaxy pairs ("a spherical cow of uniform density") - except that they are not.
(2) if we sample the pairs and average them out then any differences (variance / noise) will be statistically reduced, leaving us with nice clean galaxy pair data.
(3) this nice clean galaxy pair data can them be compared against "real" galaxy pairs.
(4) this comparison will result in a difference.
(5) this difference will be attributed to gravitational lensing.
I will admit the theory behind weak lensing seems solid. Nevertheless, it doesn't sit well with my gut feeling which is saying that if you manipulate enough data and are looking for something, however weak, you are going to find it.
So if I had to ask a question (or two) about this, it would be: "Why couldn't the natural gravity between a pair of galaxies be responsible for the artefact observed instead of invoking a filament of dark matter?" And "Why should there be filaments of dark matter bridging galaxies?"
Hobo icon because I am not feeling terribly smart about all this.
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Thursday 13th April 2017 20:38 GMT danR2
All impossibilities been explored?
They've found something (pretty) dark that bends light paths. Is it filaments of helium? neutral hydrogen? Has it been mapped at 21 cm and nothing found? Just asking.
"How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth?" -Holmes
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Friday 14th April 2017 16:56 GMT mosw
Re: All impossibilities been explored?
"All impossibilities been explored?"
No.
I would assume their instruments and funding allowed them to conduct a very specific set of measurements that was motivated by some dark matter hypothesis. Others with access to different instruments and funding can follow up if they think it is worth investigating and try and identify what that matter is.
Until then it seems there is some matter that exists between the galaxies that they were otherwise not able to "see", aka dark matter.
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Friday 14th April 2017 03:09 GMT danR2
Re: Dark Matter? What about a worm hole?
A worm-hole is a tunnel of space-time itself, not a structure with extension through space. Distant from a worm-hole, all we (would) see is the hole part, a three dimensional analog akin to the hole you would plug a vacuum hose into in the wall for a central vacuum system. All the plumbing is hidden from view.
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Friday 14th April 2017 07:45 GMT perrenod
Dark matter or dark gravity
A significant observational achievement. It would have been interesting if in addition to their dark matter model, they had also applied the emergent gravity style model. A recent test with weak gravitational lensing using 33,000 galaxies compared both and found similar results. But emergent gravity (Erik Verlinde, additional gravity over and above Newton/GR at low accelerations due to dark energy - ordinary matter entanglement entropy interaction) could reproduce the results with fewer parameters.
More on emergent gravity here: https://darkmatterdarkenergy.com/2016/12/30/emergent-gravity-verlindes-proposal/ includes links to Verlinde's paper and the Brouwer et al. weak lensing study.
Biting the hand that feeds IT
