New Dark Matter Map Reveals Cosmic Mystery (bbc.com) 52
New submitter rundgong shares a report from the BBC: An international team of researchers has created the largest and most detailed map of the distribution of so-called dark matter in the Universe. The results are a surprise because they show that it is slightly smoother and more spread out than the current best theories predict. 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.
Using the Victor M Blanco telescope in Chile, the team behind the new work analyzed 100 million galaxies. The map shows how dark matter sprawls across the Universe. The black areas are vast areas of nothingness, called voids, where the laws of physics might be different. The bright areas are where dark matter is concentrated. They are called "halos" because right in the centre is where our reality exists. In their midst are galaxies like our own Milky Way, shining brightly like tiny gems on a vast cosmic web.
According to Dr Jeffrey, who is also part of a department at University College London, the map, clearly shows that galaxies are part of a larger invisible structure. "No one in the history of humanity has been able to look out into space and see where dark matter is to such an extent. Astronomers have been able to build pictures of small patches, but we have unveiled vast new swathes which show much more of its structure. For the first time we can see the Universe in a different way."
Using the Victor M Blanco telescope in Chile, the team behind the new work analyzed 100 million galaxies. The map shows how dark matter sprawls across the Universe. The black areas are vast areas of nothingness, called voids, where the laws of physics might be different. The bright areas are where dark matter is concentrated. They are called "halos" because right in the centre is where our reality exists. In their midst are galaxies like our own Milky Way, shining brightly like tiny gems on a vast cosmic web.
According to Dr Jeffrey, who is also part of a department at University College London, the map, clearly shows that galaxies are part of a larger invisible structure. "No one in the history of humanity has been able to look out into space and see where dark matter is to such an extent. Astronomers have been able to build pictures of small patches, but we have unveiled vast new swathes which show much more of its structure. For the first time we can see the Universe in a different way."
I think the BBC is going a bit far... (Score:5, Interesting)
saying these voids" are "where the laws of physics might be different".
While the astrophysicists may not understand how the current laws apply in this location or, more intriguingly there may be new laws at play that they don't understand, I don't think that they are saying that in this region of space the laws are different from everywhere else. Their EFFECTS might lead to a different outcome than what they expect but are the laws themselves different? That's something completely ... different.
I mention this because I think it's been a principle since Newton(!) that all the laws of physics work the same everywhere in the universe. Now there has been some talk about changes over time, such as maybe the force of gravity weakening on cosmological time scales, but I don't think there's been much serious conjecture about the laws being different at different locations. Of course some laws are much more relevant at different SCALES (like I believe the strong force only "works" over very short distances) but it should behave this way the same everywhere in the universe.
I think there was a science fiction book where a spaceship was stranded in a place where the force of gravity was billions of times stronger. So stars could form and ignite with relatively small clumps of hydrogen and even people had their own gravitational "attraction". This place I think, was only reached by going through a portal to another universe (and it is fiction of course).
Actually if the laws of physics DON'T apply the same everywhere in the universe, would it be the same universe? I mean isn't that a good definition of a universe, where all the laws of physics apply uniformly?
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AIUI, the actual idea is that the voids may be expanding at a different rate than the rest of us.
However, a week doesn't go by without someone claiming they think they've found evidence for "new physics". I treat the announcements as ads for their new paper, or PR press releases for the institution they work for.
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The trouble is the BBC is mainly a bunch of journalists whose main training is to ask "And how does that make you feel?", which unfortunately means they lack the skills to understand anything like physics, maths, logic, err, you name it.
Re: I think the BBC is going a bit far... (Score:1)
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The trouble is that entirely too many people sincerely believe that things are different now.
Hint: while they didn't call it "click-bait" a century or six ago, what passed for "news" then was just as sensationalist then as now....
Re: I think the BBC is going a bit far... (Score:2)
Iâ(TM)m just a slashdotter, but I thought it was reasonably understood that the âoelawsâ of physics are different inside the event horizon of a singularity.
Terminology [Re: I think the BBC is going a bit... (Score:3)
Iâ(TM)m just a slashdotter, but I thought it was reasonably understood that the âoelawsâ of physics are different inside the event horizon of a singularity.
Some minor correction: for reference: an event horizon is a region of space in which gravity forms a one-way surface: matter (and energy) can flow through it one way, but not the other. An event horizon is not a singularity (unless you are using the wrong coordinate system).
There is a singularity at the center of a Schwartzschild black hole, but that singularity is not the event horizon.
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Did my comment not convey that? I'm asking for clarity. My understanding is that the event horizon is the practical, functional boundary of a singularity, not the singularity itself ("the event horizon *of* a singularity").
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Did my comment not convey that? I'm asking for clarity. My understanding is that the event horizon is the practical, functional boundary of a singularity, not the singularity itself ("the event horizon *of* a singularity").
They're different types of things. Event horizons can exist without a singularity; whether singularities can exist without an event horizon is an open question (Penrose's "cosmic censorship" hypothesis says that they can't. Some counterexamples exist, but it's unclear whether they could be formed in the real world.)
"Raft" [Re:I think the BBC is going a bit far...] (Score:3)
I think there was a science fiction book where a spaceship was stranded in a place where the force of gravity was billions of times stronger.
Raft, by Stephen Baxter. One of his earliest novels.
A lot of his early work looked at cosmology and advanced physics. (His work has mostly moved on to other themes, although from time to time he does return to the Xeelee sequence,)
So stars could form and ignite with relatively small clumps of hydrogen and even people had their own gravitational "attraction". This place I think, was only reached by going through a portal to another universe (and it is fiction of course).
Actually if the laws of physics DON'T apply the same everywhere in the universe, would it be the same universe? I mean isn't that a good definition of a universe, where all the laws of physics apply uniformly?
If the laws of physics don't apply the same everywhere in the universe... then there needs to be a law about where the laws of physics apply, and which laws apply in which regions.
And that law would apply everywhere....
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Dark matter (Score:3)
Can be thought of as a function you need to add on order to make models meet expectation.
This is preferred, at least for me, as it means I don't have to care if you've actual matter, MOND, Emergent Gravity or even some combination of these and not just one. It's a function, not a why.
So far, so good, so what?
Loud guitars notwithstanding, that doesn't strike me as a MOND map. I'd expect MOND to be organized more like contours and less like a random dot stereogram. I'd like to hear the thoughts of other Slashdotters on that, as I know there are MOND fans here.
But a smooth random distribution might be problematic for matter fans, too. If it is the same everywhere at thus level, it would have zero impact on large scales. It should only matter at much smaller scales, right? At the scale shown here, the resultant force after you've added everything up must be very close to zero everywhere.
Doesn't gravity cause halos? (modified..) (Score:3, Insightful)
Dark Matter is no more "proven" than modified gravity, or gravity acting differently at larger distances.
The laws of physics are modified for very small distances, why can't gravity act differently (less/more) at large distances?
This obsession with Dark Matter is not very scientific. "But it works if you add in Dark Energy!" *eye roll*
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> why can't gravity act differently (less/more) at large distances?
What's the need? Einstein based models have been very effective with strong predictive power for many decades. The idea that there are far more planets in interstellar or intergalactic space is a potent one, they'd be dense and cold, thus nearly indetectable at even modest intragalactic distances. And we do keep discovering more of them in our interstellar region. Another working theory is that quantum black holes do _not_ evaporate from
Re: Doesn't gravity cause halos? (modified..) (Score:2)
Perhaps this time I'll finally be wrong.
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Re: Doesn't gravity cause halos? (modified..) (Score:1)
Re:Doesn't gravity cause halos? (modified..) (Score:5, Informative)
This obsession with Dark Matter is not very scientific. "But it works if you add in Dark Energy!" *eye roll*
Dark Matter is very different from Dark Energy:
Dark Matter is an explanation for why galaxies hold together.
Dark Energy is an explanation for why the expansion speed of the universe increases.
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Dark Matter is very different from Dark Energy:
Don't blame the OP for being confused. This is an article on Dark Matter published in a journal about Dark Energy.
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Dark Matter is very different from Dark Energy:
would be interesting if it turned out they both had the same cause.
We think of Gravity as "pulling" or "falling" towards the center of a mass. Be interesting if what is really happening is that something is pushing everything towards a mass's center. Like how Dark Energy is supposed to work.
Read an article once, pre-WWW, I think it was in OMNI magazine. Made a good argument for our current belief of how gravity works being wrong. It's why I've never bought into "Dark Mater" actually being some kind of p
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Dark Energy is an explanation for why the expansion speed of the universe increases.
Except that it doesn't increase, measuring distance and speed by red shift is accurate only at relatively close distances. It's absurd to postulate that galaxies are moving away from each other faster than the speed of light. All the scientists belly ache about nothing being able to move faster than light, but oh yeah, if it makes their model of the universe work, then its OK. Our solar system rotates around a gravitational center, which rotates around another gravitational center, and so on which rotate
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Yes, Jesus had some dark matter in his head.
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You do understand how parentheses can be used?
Your lack of scientific rigor is on display. You state that dark matter composes about 25% of the know universe. This is incorrect (or technically unproven). What you actually mean to say is "If gravity acts at longer distances as it does at shorter distances, then there is currently less baryonic matter (that we can observe) than required. Therefore there is either more unobserved matter, or gravity does not act the way we currently understand."
Perhaps English
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You do understand how parentheses can be used?
Do you you know what parentheses are? It seems you lack fundamental meaning of words.
Your lack of scientific rigor is on display. You state that dark matter composes about 25% of the know universe.
I do not state this. Multiple studies have estimated that dark matter is about 27% of the known universe [nasa.gov].
This is incorrect (or technically unproven).
Again you keep using the word unproven when it has no validity. It further underscores your lack of scientific understanding.
What you actually mean to say is "If gravity acts at longer distances as it does at shorter distances, then there is currently less baryonic matter (that we can observe) than required. Therefore there is either more unobserved matter, or gravity does not act the way we currently understand."
1) You do understand what you are proposing is that gravity acts differently only for the situation you want it to act differently. 2) No one yet has any evidence gravity does act differently.
Perhaps English is not your first language, so you may not be aware that your last sentence makes no sense.
Plea
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I got up to the point where you said "I do not state this" when you clearly did, then I stopped reading. Troll.
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Dark matter, or is physics wrong? [Re:Doesn't...] (Score:2)
Dark Matter is no more "proven" than modified gravity, or gravity acting differently at larger distances.
There's some good evidence for dark matter (the Bullet cluster, for example), but no, not "proven".
The laws of physics are modified for very small distances, why can't gravity act differently (less/more) at large distances?
There are observations that can't be explained by the matter that we can see. I'm not sure why some people have a lot of difficulty with the statement "possibly there is also matter that we can't see," and are so committed to the idea that we can see all matter that they say "no, that's unlikely, it must be that the laws of physics are wrong."
We see stuff that's glowing, and we see stuff that gets in the way
Re: Doesn't gravity cause halos? (modified..) (Score:1)
why can't gravity act differently (less/more) at large distances?
Nobody said it couldn't. Fortunately, it seems that you've found an elegant mathematical framework for gravity that accounts for the observed deviations from general relativity and no dark matter. Please point us to your publication so that we can stop all of this foolishness.
Epicycles (Score:2)
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I wonder how well some of these models take into account that fact that gravitational forces are not instantaneous
Dark matter is not a model, it's an observational fact. They have
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You started off fine, and then went off the rails. Yes "Dark Matter is basically the error term between the current theory and observation. ".
The rest of your comment is taking lazy journalistic comments as the scientific consensus. There's lots of work going on trying (so far, IMNSHO, unsuccessfully) pin down just what "dark matter" and "dark energy" are. Anyone who tells you "Scientists say that dark [matter|energy] is ..." should be immediately doubted. Lots of different people are exploring differen
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I have noticed throughout my career in academia and industry that engineers are prone to look at unrealted areas of human endeavor, notice that something bears a resemblance (in their possibly quite limited view) to something they learned in engineering, and then believe they understand all about it, and the experts in other fields are fools for not sharing their penetrating insight. This is apparent in just about all fields of engineering.
Not saying that only engineers do this, but the trait seems especial
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I agree. We do that all the time. Everything is just the same. There is only one thing.
Why is it called dark matter? (Score:5, Funny)
And now Astrophysics is off the hook? No way Jose!
We demand the term "dark" matter to be discontinued. Use something unwieldy like "visibility challenged" matter or something. Or "matter previously called dark"
Bunch of Light-ists (Score:2)
There is a cohort of people here who have an unreasoning prejudice in favor of the electromagnetic spectrum. Unless something emits photons they don't think it really exists. Detecting something by its gravitational field - a universal property of all matter - is somehow not real.
This curious way of thinking can't really be defended by any claims of consistency since the gravity field of dark matter does interact with photons (so if "photon evidence" is required you've got that), and the existence of black
Problem Is Probably Not Going To Be With GR (Score:2)
The failure of the dark matter to match the distribution they have been predicting is probably not due to a flaw in General Relativity. That is one possible explanation for the discrepancy, but it is not as if you can look at the equations and say "Aha! Clearly this requires gravitationally interacting only particles to distribute according to these statistics!". Deriving an expected statistical distribution of dark matter involves a lot of complex modeling. Most likely they will find ways to improve their
“where our reality exists” (Score:2)
Were these BBC guys interviewing scientists, or just some guy selling crystals in a holistic medicine shop?
Dark Matter Map vs. Cosmic Microwave Background? (Score:1)
I wonder how well (or not) these two maps align statistically. Does anyone (expert) know if that has been done or plans to be done to see if there is any correlation. If not, is there any reason to believe they should or should not correlate somehow?
Just curious.