A map of the unseen unknown aka dark matter
May 27, 2021 2:51 PM Subscribe
Dark matter makes up about 27% of the universe, and its gravitational force is enough to mesh entire galaxies together in a structure known as the cosmic web. Now, scientists have created the largest ever map of this mysterious substance – and it could imply that there’s something wrong with Einstein’s theory of relativity.Astronomers create largest map of the universe’s dark matter
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The results are a surprise because they show that it is slightly smoother and more spread out than the current best theories predict.New dark matter map reveals cosmic mystery
The observation appears to stray from Einstein's theory of general relativity - posing a conundrum for researchers.
The results have been published by the Dark Energy Survey Collaboration.
Dark Matter is an invisible substance that permeates space. It accounts for 80% of the matter in the Universe.
New Dark Matter Map Reveals Hidden Bridges Between Galaxies
The XENON1T detector was filled with 3.2 tonnes of ultra-pure liquefied xenon, 2.0 t of which served as a target for particle interactions. When a particle crosses the target, it can generate tiny signals of light and free electrons from a xenon atom. Most of these interactions occur from particles that are known to exist. Scientists therefore carefully estimated the number of background events in XENON1T. When data of XENON1T were compared to known backgrounds, a surprising excess of 53 events over the expected 232 events was observed.Observation of Excess Events in the XENON1T Dark Matter Experiment
This raises the exciting question: where is this excess coming from?
All of this is way above my paygrade. Among you the more knowledgeable membership, riddle me this:
Dark matter slice of the total universe pie: 85% or 27%?
y2karl, dark matter makes up ~85% of the matter in the universe, but ~27% of the mass-energy content of the universe. The remainder is essentially all dark energy, with something like 5% being "normal" matter. Also, since the amount of dark energy is increasing over time, the universe will eventually be essentially 100% dark energy, with everything else being a rounding error.
posted by nosewings at 3:02 PM on May 27, 2021 [8 favorites]
posted by nosewings at 3:02 PM on May 27, 2021 [8 favorites]
the universe will eventually be essentially 100% dark energy
My new goth concept album.
posted by Abehammerb Lincoln at 3:05 PM on May 27, 2021 [13 favorites]
My new goth concept album.
posted by Abehammerb Lincoln at 3:05 PM on May 27, 2021 [13 favorites]
I miss physicsmatt at times like these.
posted by OHenryPacey at 3:07 PM on May 27, 2021 [9 favorites]
posted by OHenryPacey at 3:07 PM on May 27, 2021 [9 favorites]
Yikes -- so fast! Thanks nosewings!
Well, my appreciation of my insignificance as a material being has increased asymptomatically this afternoon.
posted by y2karl at 3:07 PM on May 27, 2021 [4 favorites]
Well, my appreciation of my insignificance as a material being has increased asymptomatically this afternoon.
posted by y2karl at 3:07 PM on May 27, 2021 [4 favorites]
You should spend more time looking at sponge cake.
posted by nickmark at 3:35 PM on May 27, 2021 [4 favorites]
posted by nickmark at 3:35 PM on May 27, 2021 [4 favorites]
Yes, but how will this affect the canonisation of Lady Diana?
posted by parmanparman at 3:35 PM on May 27, 2021
posted by parmanparman at 3:35 PM on May 27, 2021
I'm trying to understand the method, based on the third linked article. This seems very, very far from direct observation. Obviously we can't see the EM radiation from dark matter, that's why it's called "dark". But they aren't even observing light distortion directly?
From what I understand, this image comes from a machine learning model doing statistical inference on a bunch of data about dark matter distribution and galaxies. Except it's not even that; it's based on simulations of galaxies? How many assumptions are built in to making this thing?
I don't mean to denigrate the science, I'm sure these folks are world experts and it's way beyond my ability to evaluate. But it kind of feels like they're standing on top of a chair balanced on a step ladder on top of a circus ball.
posted by Nelson at 3:43 PM on May 27, 2021 [12 favorites]
From what I understand, this image comes from a machine learning model doing statistical inference on a bunch of data about dark matter distribution and galaxies. Except it's not even that; it's based on simulations of galaxies? How many assumptions are built in to making this thing?
I don't mean to denigrate the science, I'm sure these folks are world experts and it's way beyond my ability to evaluate. But it kind of feels like they're standing on top of a chair balanced on a step ladder on top of a circus ball.
posted by Nelson at 3:43 PM on May 27, 2021 [12 favorites]
it's easier in the tank of liquified xenon because you have some buoyancy to work with
posted by ryanrs at 3:56 PM on May 27, 2021 [5 favorites]
posted by ryanrs at 3:56 PM on May 27, 2021 [5 favorites]
Dark Matter is the bleedthrough gravitational effect of mass that exists in 'nearby' parallel universes; Change My Mind.
posted by bartleby at 4:17 PM on May 27, 2021 [11 favorites]
posted by bartleby at 4:17 PM on May 27, 2021 [11 favorites]
Also, since the amount of dark energy is increasing over time, the universe will eventually be essentially 100% dark energy, with everything else being a rounding error.
Kurzgesagt: The Final Border We Will Never Cross
posted by They sucked his brains out! at 4:30 PM on May 27, 2021 [2 favorites]
Kurzgesagt: The Final Border We Will Never Cross
posted by They sucked his brains out! at 4:30 PM on May 27, 2021 [2 favorites]
Dark matter is the weighty sins of the millions of alien races spread throughout the galaxy; Change My Mind.
posted by paper chromatographologist at 4:30 PM on May 27, 2021 [12 favorites]
posted by paper chromatographologist at 4:30 PM on May 27, 2021 [12 favorites]
Everything poops. The universe poops. There is no outside so the poop has to go inside. Dark matter is the poop of the universe; Change My Mind.
posted by Hairy Lobster at 4:40 PM on May 27, 2021 [15 favorites]
posted by Hairy Lobster at 4:40 PM on May 27, 2021 [15 favorites]
Change My Mind.
The mass, which looks like a replicator, "exists" in oodles at the universes center even our own Galaxy which suggests parallel universes 'bleed' in the center.
Iike a pack of chewels
posted by clavdivs at 4:41 PM on May 27, 2021
The mass, which looks like a replicator, "exists" in oodles at the universes center even our own Galaxy which suggests parallel universes 'bleed' in the center.
Iike a pack of chewels
posted by clavdivs at 4:41 PM on May 27, 2021
One day we may have a map with enough detail to see the tentacles.
posted by adept256 at 4:49 PM on May 27, 2021 [9 favorites]
posted by adept256 at 4:49 PM on May 27, 2021 [9 favorites]
I just finished reading The Three Body Problem trilogy and this thread is messing with my head 😳
posted by supermedusa at 5:05 PM on May 27, 2021 [2 favorites]
posted by supermedusa at 5:05 PM on May 27, 2021 [2 favorites]
They have also mapped the location of vast cosmic voids where the conventional laws of physics may not apply.Oh Guardian, never change. Pretty sure if I fact checked this I'd get the same result as when I fact checked their "vaccines only effective for a few months" story that was ran on a blatent misunderstanding of the Phiser vaccine study.
posted by joeyh at 5:09 PM on May 27, 2021 [8 favorites]
In my headcanon dark matter is like supports you add in to a model during 3D printing to hold the piece together as its printing. The ~beings~ who created the grande experiment that is our universe put it in to ensure the behavior and distribution of matter stars and galaxies that they wanted. For what ends, who really knows — we like to think it was all so they could create US (yay life) but the douglas adams angle is just as likely for now.
posted by wemayfreeze at 5:11 PM on May 27, 2021 [2 favorites]
posted by wemayfreeze at 5:11 PM on May 27, 2021 [2 favorites]
the universe will eventually be essentially 100% dark energy, with everything else being a rounding error.
wait... so we don't have to worry about the heat death of the universe any more but the DarkLord Energy?
posted by sammyo at 5:12 PM on May 27, 2021 [1 favorite]
wait... so we don't have to worry about the heat death of the universe any more but the Dark
posted by sammyo at 5:12 PM on May 27, 2021 [1 favorite]
The ~beings~ who created the grande experiment that is our universe put it in to ensure the behavior and distribution of matter stars and galaxies that they wanted.
wemayfreeze, you might enjoy the short story The Janitor on Mars if you haven't read it yet.
posted by paper chromatographologist at 5:17 PM on May 27, 2021 [3 favorites]
wemayfreeze, you might enjoy the short story The Janitor on Mars if you haven't read it yet.
posted by paper chromatographologist at 5:17 PM on May 27, 2021 [3 favorites]
"There are more things in Heaven and Earth, Horatio, than are dreamt of in your philosophy..."
posted by jim in austin at 5:27 PM on May 27, 2021 [1 favorite]
posted by jim in austin at 5:27 PM on May 27, 2021 [1 favorite]
RIP the Dark Matter TV show. It was so awful I loved it.
posted by adept256 at 5:42 PM on May 27, 2021 [10 favorites]
posted by adept256 at 5:42 PM on May 27, 2021 [10 favorites]
@Nelson : The simulations were used to train a machine learning model that maps from observations from positions and velocities of galaxies to the underlying distribution of dark matter. They then applied that model to real observations of galaxy locations and flows to make their dark matter map.
The challenge here is that the method should only give really accurate results if the simulations you are training on faithfully replicate the mapping from matter density to galaxies in the real universe. Simulations are getting better all the time but you should definitely take that with a grain of salt; there are lots of simplifying assumptions that need to be made if you want to simulate galaxy formation in a large-volume mock universe that we know are imperfect.
posted by janewman at 6:02 PM on May 27, 2021 [7 favorites]
The challenge here is that the method should only give really accurate results if the simulations you are training on faithfully replicate the mapping from matter density to galaxies in the real universe. Simulations are getting better all the time but you should definitely take that with a grain of salt; there are lots of simplifying assumptions that need to be made if you want to simulate galaxy formation in a large-volume mock universe that we know are imperfect.
posted by janewman at 6:02 PM on May 27, 2021 [7 favorites]
The basic idea of the method is sound, though: galaxies should form where the dark matter density is high (as the dark matter dominates the mass and hence the gravity), so when we map locations of galaxies we are effectively mapping where the dark matter is concentrated. You can calibrate some aspects of that mapping based on how fast galaxies are flowing towards the denser regions (as again those flows are driven by gravity, and hence primarily by the dark matter). People have been applying these basic ideas for >25 years (though the technique has been out of fashion for a while).
posted by janewman at 6:05 PM on May 27, 2021 [3 favorites]
posted by janewman at 6:05 PM on May 27, 2021 [3 favorites]
I'm enthralled and utterly befuddled. Science is neat.
posted by MiraK at 6:45 PM on May 27, 2021 [4 favorites]
posted by MiraK at 6:45 PM on May 27, 2021 [4 favorites]
I would like to take this opportunity to point out the book "The Disordered Cosmos
A Journey into Dark Matter, Spacetime, and Dreams Deferred" by Chanda Prescod-Weinstein, a book about a lot of things including the term "dark matter", race, intersectionality, gender and gender identity, and also physics! Just started reading it, it covers intersections I never even thought of, let alone have read anything about in this way. Looks fab!
posted by Rufous-headed Towhee heehee at 6:49 PM on May 27, 2021 [8 favorites]
A Journey into Dark Matter, Spacetime, and Dreams Deferred" by Chanda Prescod-Weinstein, a book about a lot of things including the term "dark matter", race, intersectionality, gender and gender identity, and also physics! Just started reading it, it covers intersections I never even thought of, let alone have read anything about in this way. Looks fab!
posted by Rufous-headed Towhee heehee at 6:49 PM on May 27, 2021 [8 favorites]
Dark matter is the stuff that exists all around us that we can't pick up with our measly five senses and the world is so much richer and layered than we realize, change my mind
posted by EarnestDeer at 6:53 PM on May 27, 2021 [3 favorites]
posted by EarnestDeer at 6:53 PM on May 27, 2021 [3 favorites]
If I have seen far, it is because I have stood on the shoulders of a giant standing on a chair balanced on a step ladder on top of a circus ball.
posted by biogeo at 7:18 PM on May 27, 2021 [26 favorites]
posted by biogeo at 7:18 PM on May 27, 2021 [26 favorites]
Looking back at @Nelson's comment I think I should clarify my comments: they only are relevant to the third link (which is not really related to the Dark Energy Survey results).
DES doesn't measure motions of galaxies; rather, their constraints come from combining measurements of gravitational lensing (the small distortions of shapes of background objects due to the gravitational influence of matter in the foreground) and galaxy clustering. Similarly, though, the goal is to probe both the gravitational influence of the dark matter (in this case, via the mass maps that come from lensing) and the relationship of galaxies to dark matter (via the observed galaxy clustering and its relation to the mass maps) by having multiple probes that depend on both.
posted by janewman at 7:38 PM on May 27, 2021 [1 favorite]
DES doesn't measure motions of galaxies; rather, their constraints come from combining measurements of gravitational lensing (the small distortions of shapes of background objects due to the gravitational influence of matter in the foreground) and galaxy clustering. Similarly, though, the goal is to probe both the gravitational influence of the dark matter (in this case, via the mass maps that come from lensing) and the relationship of galaxies to dark matter (via the observed galaxy clustering and its relation to the mass maps) by having multiple probes that depend on both.
posted by janewman at 7:38 PM on May 27, 2021 [1 favorite]
It's super easy to specify the wrong loss function for an ML model and end up with something too smooth. ("Haha, sure, L2, why not?") My bet's on ML bug, rather than general relativity is wrong...
posted by kaibutsu at 7:47 PM on May 27, 2021 [4 favorites]
posted by kaibutsu at 7:47 PM on May 27, 2021 [4 favorites]
I mean, in some versions of string theory, I think it's L11.
posted by biogeo at 8:05 PM on May 27, 2021
posted by biogeo at 8:05 PM on May 27, 2021
dark matter makes up ~85% of the matter in the universe, but ~27% of the mass-energy content of the universe. The remainder is essentially all dark energy, with something like 5% being "normal" matter.
Doesn't that essentially make what we understand as the universe the anomaly, and dark energy/matter is the normal?
posted by kirkaracha at 10:11 PM on May 27, 2021
Doesn't that essentially make what we understand as the universe the anomaly, and dark energy/matter is the normal?
posted by kirkaracha at 10:11 PM on May 27, 2021
wait... so we don't have to worry about the heat death of the universe any more but the Dark Lord Energy?
Dark energy is the thing causing the expansion of the universe to accelerate, so it's the thing that will eventually cause heat death.
Doesn't that essentially make what we understand as the universe the anomaly, and dark energy/matter is the normal?
One interesting thing about dark energy is that it's extremely homogeneous; i.e., any two unit volumes anywhere in the universe have basically the same amount of dark energy in them. This is to say that dark energy can't have any kind of structure. So while there's much more of it (in joules) than there is of us, we're much more complex---and, from a certain point of view, much more interesting.
The situation with dark matter is, on this topic at least, less clear. It does clump, but we don't know exactly what it can "do"---as far as we can tell, it doesn't seem to interact via any force except gravity (hence the "dark" moniker---we can't see it).
posted by nosewings at 10:25 PM on May 27, 2021 [5 favorites]
Dark energy is the thing causing the expansion of the universe to accelerate, so it's the thing that will eventually cause heat death.
Doesn't that essentially make what we understand as the universe the anomaly, and dark energy/matter is the normal?
One interesting thing about dark energy is that it's extremely homogeneous; i.e., any two unit volumes anywhere in the universe have basically the same amount of dark energy in them. This is to say that dark energy can't have any kind of structure. So while there's much more of it (in joules) than there is of us, we're much more complex---and, from a certain point of view, much more interesting.
The situation with dark matter is, on this topic at least, less clear. It does clump, but we don't know exactly what it can "do"---as far as we can tell, it doesn't seem to interact via any force except gravity (hence the "dark" moniker---we can't see it).
posted by nosewings at 10:25 PM on May 27, 2021 [5 favorites]
I was going to say something similar to @nosewings -- "normal" matter is the part of the universe that does interesting things, so that's why we care about it most. You can simulate a universe with just dark matter + dark energy pretty easily, as you just need to worry about gravity; once ordinary matter enters the picture it gets a lot harder.
The main candidates for dark matter do have interactions besides gravity, though -- the weak force, in the case of WIMPS (Weakly Interacting Massive Particles, hence the name), or interactions with electric and magnetic fields in the case of axions. Those interactions are so weak we can generally get by without having to simulate them, though.
posted by janewman at 10:50 PM on May 27, 2021 [2 favorites]
The main candidates for dark matter do have interactions besides gravity, though -- the weak force, in the case of WIMPS (Weakly Interacting Massive Particles, hence the name), or interactions with electric and magnetic fields in the case of axions. Those interactions are so weak we can generally get by without having to simulate them, though.
posted by janewman at 10:50 PM on May 27, 2021 [2 favorites]
MetaFilter: it's easier in the tank of liquified xenon
posted by chavenet at 1:29 AM on May 28, 2021 [5 favorites]
posted by chavenet at 1:29 AM on May 28, 2021 [5 favorites]
"The results are a surprise because they show that it is slightly smoother and more spread out than the current best theories predict."
Am I the only one imagining a gigantic spatula?
posted by Nancy Lebovitz at 5:16 AM on May 28, 2021 [1 favorite]
Am I the only one imagining a gigantic spatula?
posted by Nancy Lebovitz at 5:16 AM on May 28, 2021 [1 favorite]
This thread is what happens when you try to get your science from newspapers and press releases.
posted by heatherlogan at 6:47 AM on May 28, 2021 [4 favorites]
posted by heatherlogan at 6:47 AM on May 28, 2021 [4 favorites]
Well, my appreciation of my insignificance as a material being has increased asymptomatically this afternoon.
Er, asymptopically to be sure....
Damn you, autocorrect, damn you!
posted by y2karl at 12:16 PM on May 28, 2021 [4 favorites]
Er, asymptopically to be sure....
Damn you, autocorrect, damn you!
posted by y2karl at 12:16 PM on May 28, 2021 [4 favorites]
Which is a word I learned when I read G. Harry Stine's article Science Fiction Is Too Conservative in the May 1961 issue of Analog a mere sixty years ago.
posted by y2karl at 12:34 PM on May 28, 2021
posted by y2karl at 12:34 PM on May 28, 2021
The main candidates for dark matter do have interactions besides gravity, though -- the weak force, in the case of WIMPS (Weakly Interacting Massive Particles, hence the name), or interactions with electric and magnetic fields in the case of axions.
I'm no expert, but I've wondered whether that's because, if it turns out that dark matter only interacts gravitationally, then there's simply no hope of us ever knowing anything about it.
posted by nosewings at 2:49 PM on May 28, 2021
I'm no expert, but I've wondered whether that's because, if it turns out that dark matter only interacts gravitationally, then there's simply no hope of us ever knowing anything about it.
posted by nosewings at 2:49 PM on May 28, 2021
If it only interacts gravitationally, that may be everything there is to know about it.
posted by biogeo at 3:35 PM on May 28, 2021
posted by biogeo at 3:35 PM on May 28, 2021
Dark matter is the toxic gunk that builds up when my mind hasn't been changed recently. Change my mind.
posted by It's Raining Florence Henderson at 4:35 PM on May 28, 2021 [9 favorites]
posted by It's Raining Florence Henderson at 4:35 PM on May 28, 2021 [9 favorites]
Dark Matter is all the thetans hiding from Xenu; Change My Mind.
posted by lock robster at 5:25 PM on May 28, 2021 [2 favorites]
posted by lock robster at 5:25 PM on May 28, 2021 [2 favorites]
@nosewings: it depends how massive the dark matter is. Primordial black holes that formed during the Big Bang do remain a candidate for the dark matter. They only interact gravitationally (if they have zero electric charge), but they can have observable signatures. This is how we've ruled out most possible masses for black holes as dark matter, in fact (obligatory xkcd).
I expect that all of those signatures would also be there for a dark matter particle of the same mass (to start off with, one would expect that a pointlike particle of given mass with no other observable properties would have an event horizon and act like a black hole of the same mass, gravitationally).
posted by janewman at 5:41 PM on May 28, 2021
I expect that all of those signatures would also be there for a dark matter particle of the same mass (to start off with, one would expect that a pointlike particle of given mass with no other observable properties would have an event horizon and act like a black hole of the same mass, gravitationally).
posted by janewman at 5:41 PM on May 28, 2021
Mixing matter and dark matter is like mixing pesto and antipasto.
posted by kirkaracha at 6:51 PM on May 28, 2021 [3 favorites]
posted by kirkaracha at 6:51 PM on May 28, 2021 [3 favorites]
Yeah, gee, I wish physicsmatt were still around. :-(
posted by Don.Kinsayder at 6:57 PM on May 28, 2021 [1 favorite]
posted by Don.Kinsayder at 6:57 PM on May 28, 2021 [1 favorite]
Dark matter is the weighty sins of the millions of alien races spread throughout the galaxy; Change My Mind.
I never got past grade ten physics but I'm pretty sure weight is a meaningless measure the instant you clear the earth's orbit. Mass on the other hand ...
posted by philip-random at 7:24 PM on May 28, 2021
I never got past grade ten physics but I'm pretty sure weight is a meaningless measure the instant you clear the earth's orbit. Mass on the other hand ...
posted by philip-random at 7:24 PM on May 28, 2021
weight is a meaningless measure the instant you clear the earth's orbit
Nope, not when we're talking about sins. Ask Maat.
posted by paper chromatographologist at 8:19 PM on May 28, 2021 [2 favorites]
Nope, not when we're talking about sins. Ask Maat.
posted by paper chromatographologist at 8:19 PM on May 28, 2021 [2 favorites]
So many questions. Is dark matter alive?
posted by otherchaz at 5:52 AM on May 29, 2021 [1 favorite]
posted by otherchaz at 5:52 AM on May 29, 2021 [1 favorite]
And can we kill it?
posted by Spathe Cadet at 7:15 AM on May 29, 2021 [2 favorites]
posted by Spathe Cadet at 7:15 AM on May 29, 2021 [2 favorites]
More importantly, can it be et?
posted by OHenryPacey at 9:33 AM on May 29, 2021 [2 favorites]
posted by OHenryPacey at 9:33 AM on May 29, 2021 [2 favorites]
Dear MetaFilter, I recently discovered there is about 10^-16 grams of dark matter in my house which I think has been sitting untouched for about 14.8 billion years. Can I still eat it?
posted by biogeo at 3:26 PM on May 29, 2021 [6 favorites]
posted by biogeo at 3:26 PM on May 29, 2021 [6 favorites]
I had a goldfish that was all black, a bit shy and had big boggley eyes. Massive Astrophysical Compact Halo Object, or MACHO was the name. Any visiting astronomer or astrophysicist, and we had a few, would be invited to try and find all the missing dark matter in our MACHO containment unit.
Har har I’d say, This one is real. And here they are, still looking for all that dark matter.
posted by zenon at 10:10 PM on May 29, 2021 [2 favorites]
Har har I’d say, This one is real. And here they are, still looking for all that dark matter.
posted by zenon at 10:10 PM on May 29, 2021 [2 favorites]
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posted by y2karl at 3:00 PM on May 27, 2021 [7 favorites]