Dark Matter Is Even More of a Mystery Than Expected 236
schwit1 writes: Using the Hubble and Chandra space telescopes astronomers have discovered that dark matter is not only invisible to direct observation, it is invisible to itself! Quoting: "As two galactic clusters collide, the stars, gas and dark matter interact in different ways. The clouds of gas suffer drag, slow down and often stop, whereas the stars zip past one another, unless they collide — which is rare. On studying what happens to dark matter during these collisions, the researchers realized that, like stars, the colliding clouds of dark matter have little effect on one another. Thought to be spread evenly throughout each cluster, it seems logical to assume that the clouds of dark matter would have a strong interaction — much like the colliding clouds of gas as the colliding dark matter particles should come into very close proximity. But rather than creating drag, the dark matter clouds slide through one another seamlessly." The data here is on the very edge of reality, built on too many assumptions. We know that something undetected as yet is influencing the motions of galaxies, but what exactly it is remains completely unknown. These results only make the mystery more mysterious.
WIMPs (Score:5, Interesting)
Isn't this what one would expect if dark matter is WIMPs?
Re:WIMPs (Score:5, Insightful)
Isn't this what one would expect if dark matter is WIMPs?
Indeed. I don't think that any of this is new. The reason dark matter was hypothesized in the first place was because of the behavior of colliding galaxies, such as the Bullet Cluster [wikipedia.org]. The missing mass couldn't be stars, because it didn't emit light, it couldn't be gas or dust, because it didn't experience drag, so it must be either WIMPS or MACHOs [wikipedia.org]. Further observations ruled out the MACHOs. So what is new about this observation?
Re:WIMPs (Score:5, Interesting)
That the thing about dark matter... it has a perfectly reasonable explanation (WIMPs). It's not that weird of a "thing".
Dark energy on the other hand, that's just WEIRD ;) It doesn't act like any "energy" as we know it, even though everything is clearly moving into a higher energy state. A question I've had for a while... if space itself is being inflated (or any sort of mathematically equivalent scenario) - everything inflating in all directions at all scales - wouldn't there be some sort of weak radiation signal from electrons expanding into a higher energy state due to dark energy and then collapsing back down? But I have trouble picturing how to reconcile an absolute, varying distance at the atomic scale with quantization of energy states, positions, etc...
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From what I understand, currently dark energy is too weak to have local effects, with local being as large as our local cluster of galaxies.
Some do postulate that it will (continue to) increase to the point it will overcome all forces ripping even atoms apart.
Re:WIMPs (Score:4, Interesting)
Dark energy is just the latest name for the Cosmological Constant - I guess it's a better name if it's not actually constant, but the cosmologists I've seen talking about it don't like the new name either (not that anyone has a better suggestion, really). The key thing about it is that the energy density of it is insanely low - I suspect that on the quantum scale it actually "rounds to 0" the way things can in QM, where no measurement is possible at that scale. I think even at the scale of our galaxy it's a very tiny effect. It's a testament to how sparse matter really is in the universe that dark matter is the dominant effect overall.
Re:WIMPs (Score:4, Insightful)
Dark energy is just the latest name for the Cosmological Constant
You know, I'm as happy as anyone else that physicists have been able to do so much with their models, but what kind of navel-gazing mathurbation is this?
Dark energy is an observed physical phenomenon.
The cosmological constant is a term in an equation. It's a very good equation, mind you, but a lot of very good equations have later turned out to be wrong or good for only a special class of phenomena. Equations can predict, but they don't prove anything. It's also worth noting that the cosmological constant was supposed to predict a force that would hold the universe together. Dark energy is a force that is tearing the universe apart. Someone clever pointed out that hey, that works if you just flip the sign of the cosmological constant but I'm not sure I'd call that a win.
And regardless, I don't think it's reasonable to imply that the territory is imitating the map.
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what kind of navel-gazing mathurbation is this?
Its the kind of mathurbation that happens when someone looks at the "dark energy" in real data.. tries to match it with the equations.. and discovers that it exactly fits what Einstein's cosmological constant would have done if he hadn't rejected the idea at the start.
The reason there are two different names is because it came from two different sources (one data, one math). A bit of a "holy shit even Einstein didn't realize how smart Einstein was" moment. The second paragraph of the Wikipedia article [wikipedia.org] (so
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My gut still says that if the constant was predicted to be a negative value and turned out to be a specific positive value, that is in no way a slam-dunk. I've also heard some talk about it not remaining cons
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still no confirmation of gravitational waves
This is a peculiar one. While we have not directly detected gravitational waves, when watching a binary neutron star, the orbits degrade exactly as predicted if gravitational waves exist. No other known theory would give this exact effect.
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Yeah, but that is widely considered not to be good enough.
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Equations can predict, but they don't prove anything.
You've got that backwards, I'm afraid. Science isn't in the business of proof; proof is the realm of mathematics and formal logic. One can prove that one equation, or other statement in a formal language, is equivalent to another under some axioms. Once cannot prove anything about the universe we inhabit.
Science is in the business of useful, predictive models. Dark matter and energy are both "dark" in the sense that we don't have one of those yet. We can characterize them, and there's been some real pro
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You've got that backwards, I'm afraid. Science isn't in the business of proof; proof is the realm of mathematics and formal logic.
Except there are a vast number of physics equations describing universes that do not exist--Higgs-less models, for example, can probably be tossed in the trash at this point. They are mathematically sound. There is no formal logical flaw with them. But they do not match reality.
Math proofs are meaningless without physical observations to back them up.
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Math proofs are meaningless without physical observations to back them up.
Fully agree. And, as it happens, General Relativity has a massive amount of physical observation backing it up, and no physical observations contradicting* it.
* If you believe in MOND / TeVeS, then the dark matter observations contradict GR. Let's just say that there is not yet consensus around that view.
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Dark energy is just the latest name for the Cosmological Constant
You know, I'm as happy as anyone else that physicists have been able to do so much with their models, but what kind of navel-gazing mathurbation is this?
Dark energy is an observed physical phenomenon.
The cosmological constant is a term in an equation. It's a very good equation, mind you, but a lot of very good equations have later turned out to be wrong or good for only a special class of phenomena. Equations can predict, but they don't prove anything. It's also worth noting that the cosmological constant was supposed to predict a force that would hold the universe together. Dark energy is a force that is tearing the universe apart. Someone clever pointed out that hey, that works if you just flip the sign of the cosmological constant but I'm not sure I'd call that a win.
This is physics. Everything is a term in an equation.
The cosmological constant is the only free parameter in Einstein's equations. The. Only. One. And, it fits exactly all of the available data. Unless and until that changes, there is no good reason to believe to believe that we do not live in a de Sitter space.
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I dunno. Usually when a theory requires more and more unseen entities over time it's a sign that it's time to replace the theory. We know General Relativity is incomplete, both because it doesn't take into account quantum effects and because it has internal contradictions - specifically, it assumes a continuous spacetime geometry but predicts non-continuous points (black hole singularitie
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Could you elaborate on what you mean by "alter orbital structure and energy levels"? Are you saying that the energy level of, say, ground state would increase with time? If so that sounds... weird. And sounds like *that* should have detectable consequences too, if so.
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One thing that dark energy can't be is *all* fundamental constants, plus position, velocity, etc scaling up evenly. Because if such was the case then there would be no perceptible change.
If youe saying that for example what is ground state would change too then it seems like you're arguing that things at the quantum level *aren't* moving into higher energy states. But things at the macroscopic level absolutely are moving into a higher energy state. So are you arguing that dark energy doesn't act on the quan
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I dunno. Usually when a theory requires more and more unseen entities over time it's a sign that it's time to replace the theory. We know General Relativity is incomplete, both because it doesn't take into account quantum effects and because it has internal contradictions - specifically, it assumes a continuous spacetime geometry but predicts non-continuous points (black hole singularities).
That is not thought to be an internal contradiction of General Relativity, as, even though GR does have singularities, thanks to event horizons and cosmological censorship, there are no known cases where you can use these singularities to derive multiple different estimates of the same observational quantity (which is what having an inconsistent physical model means). I don't believe that there are any mathematical proofs of this, but I suspect you would have to come up with a counter-example if you wanted
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That the thing about dark matter... it has a perfectly reasonable explanation (WIMPs). It's not that weird of a "thing".
Having one solution does not suffice, you need to prove it. WIMPs have been proposed, but they require Supersymmetry (which is not proven), and also WIMPs have never been detected in particle accelerators. Dark matter is a weird thing, because one way or another, you need new physics which does not interact using the strong force or electromagnetism, is present already in the very early Universe (380000 years after the Big Bang).
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That's exactly backwards.
The WIMP miracle is over; unless the LHC finds success with its Hail Mary pass, interest in WMPs will inevitably decline, and people will look (are looking) at other explanations for Dark Matter.
Dark Energy, on the other hand, is just a cosmological constant. Nothing mysterious (from a General Relativistic standpoint) about it at all.
Re:WIMPs (Score:4, Informative)
You didn't like the Wikipedia article for WIMPs. But since you put the other two as Wikipedia articles, I assume you consider it a valid source.
The answer isn't just "WIMPs", but a special kind of WIMP, or not one at all.
What's new?
I don't have the article in the mail yet, but I'm guessing that's new. At the very least, Weakly Interacting is now Really Weakly Interacting.
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I don't have the article in the mail yet, but I'm guessing that's new. At the very least, Weakly Interacting is now Really Weakly Interacting.
Here you go [spacetelescope.org].
From my perspective, it hardly changes a thing (it lowers the cross section / mass constraint a little, but not even an order of magnitude). But, then, I'm not a WIMP guy.
Re:WIMPs (Score:4, Informative)
Yes.
There are actually many proposed extensions to the standard model that predict dark matter particles that would be classified as WIMPs, and there are some others where the interaction is not through the weak force but through a "hidden sector" force. Some of the possible parameter space of some those hidden sector models predict a cross-section that they would have been able to detect in this experiment. So this is indeed a useful result -- it does rule out some possibilities. But they're not necessarily the possibilities that most people would be betting on anyway, so the headline is overhyped.
[TMB]
More than that: it is a requirement! (Score:4, Interesting)
Thought to be spread evenly throughout each cluster, it seems logical to assume that the clouds of dark matter would have a strong interaction
It would actually be completely illogical to assume that precisely BECAUSE Dark Matter is spread evenly through each cluster. If it had a strong self interaction then, just like matter, it would bump into itself and coalesce into clumps just like that other strongly, self interacting stuff we call matter. The fact that Dark Matter has a completely different mass distribution than ordinary matter is clear evidence that it does not have a large self interaction cross-section...and we have had direct evidence of this since the Bullet Cluster [wikipedia.org] was discovered.
It's always nice to have more confirmation but since another recent story on the same site was talking about the "new" possibility of invisible Higgs decays to Dark Matter particles (something we looked for 15+ years ago at the Tevatron as well as the previous Run 1 of the LHC) I have to wonder if the writers of the site have suffered extreme time dilation for the past decade or two.
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Isn't this what one would expect if dark matter is WIMPs?
No... you're thinking of Dork Matter.
Just kidding. But that was a great "straight line".
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Rei's right. That's exactly what one would expect if dark matter is WIMPs.
I know. You got the "that was just a joke" part, yes?
Yeah, it's bit of a letdown. (Score:2)
1. The gravity of dark matter affects luminous matter (we knew this.)
2. The gravity of dark matter doesn't affect other dark matter (...wtf?)
That would have been... interesting.
But I made the mistake of clicking the article and it looks like they're just talking about kinetic interactions (no observed slowdown due to "friction" between separately moving clouds.) I guess it's news, but given that we're already pretty sure it doesn't interact with baryonic matter (ex
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No. This really applies _to_ WIMPs. It doesn't apply to condensed dark matter, or to axions.
News At 11 (Score:5, Funny)
Dateline: Millions of light years (even faster parsecs than the Kessel run)
Lede: Scientists in the Dark; Does it Matter?
Today scientists announced that they can't see anything happening with stuff they can't see, but think is there, because otherwise the math is no good. After receiving directions to his laboratory on the phone, I went to see an authority on dark matter. During the interview, Dr. Seemore Lichspittle told this Any Paper, Any Time reporter that the thing about dark matter that one has to understand is that "it goes to eleven." When confronted with the observation that the sensing instruments only had scales from 0-10, he responded "Yes, yes, that's exactly it. The numbers... the numbers only work out in the dark. When the instruments are off. Matter of fact, it's all dark, really." At that point the interview was cut short as two lab assistants in white coats hustled Dr. Lichspittle into his own custom white lab jacket. Late for an important meeting, no doubt. As he left, nodding, he called back "it's really quite dark." Food for thought! Leaving Arkham, I was struck by the picturesque beauty of the stonework, and very appreciative of the tight security. We can rest easy, knowing that national treasures like Dr. Lichspittle work in such a safe enviroment.
*WHOOP!* *WHOOP!* PC Police Takedown! (Score:4, Funny)
Supersymmetry ? (Score:2)
Re:Supersymmetry ? (Score:4, Informative)
If there is a vacuum in space, would their need to be a corresponding antivacuum?
No. Because of Heisenberg's uncertainty principle, there can never be a complete vacuum. Even if there was, you couldn't measure it without destroying it.
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If there is a vacuum in space, would their need to be a corresponding antivacuum?
There is an antivacuum in the universe . . . more specifically, in my apartment.
At least that is what my cleaning girl claims . . . when she tries to vacuum here . . .
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If there is a vacuum in space, would their need to be a corresponding antivacuum?
There is an antivacuum in the universe . . . more specifically, in my apartment.
At least that is what my cleaning girl claims . . . when she tries to vacuum here . . .
An antivacuum is usually called 'gas'.
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More likely "plasma" which is much more common then "gas"
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Right, but plasmas are a bit thin on the ground where humans live and humans are the ones who call things things. There may be aliens who call plasmas and gasses things, but they probably have different words for them. "No Fnakquar, an antivacuum is called a 'congressman' " or some such.
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Leaf blower... ...in space!
Heh, maybe it is superfluid? (Score:2)
Just partially kidding...
Paul B.
is it real? (Score:4, Insightful)
isn't there a good chance that the dark matter theory is incorrect, and was created to account for an error in certain physics equations? Mb dark matter is so invisible because it doesn't actually exist?
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Of course there's a chance, but it doesn't look like a 'good' chance. If the dark matter hypothesis is wrong, it's likely wrong yet highly insightful in the same way that Newtonian gravity is wrong.
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For my next exam, if I get x==3 as a result and I know it should be x==100, I'll just define dark_x = 97.
Done!
Certainty in Science (Score:5, Insightful)
It really bothers me to see quotes like this one: "There is more dark matter in the Universe than visible matter, but it is extremely elusive."
That's so matter of fact, and leaves no room for the possibility that the theory of dark matter is wrong. I feel that the certainty level around our understanding of this topic is low enough that it isn't fair to competing theories to say things like that as if they are observed fact. In fact, we've never detected dark matter. We infer its existence from a number of things that don't add up gravitationally without it, indicating we're missing something. Dark matter that interacts gravitationally allows us to model a universe that adds up, if only this invisible stuff were distributed just so.
This article shows yet another data point indicating that dark matter may not exist, because of how it continues to not react with stuff, just as it would if it weren't there at all. I don't mean to say that it's 100% wrong, but I think it's unfair to say with 100% certainty that it's true either. Shouldn't we as scientists be more careful with our words, and say that dark matter is BELIEVED to make up more of the universe than does visible matter, based on our current leading theories? I think being careful with what we know and how well we know it is important to maintaining trust with the public and with each-other.
--Jaborandy
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Indeed. I've always wondered why there's an automatic assumption that matter of some sort must be causing these excess gravitational effects that are popularly associated with dark matter. I believe there's just as much merit to the idea that our understanding of gravity is simply wrong, and that it can exist absent of matter. I would think of it as space time curvature that is inherent to the universe. Matter would naturally "fall in" to these wrinkles of the fabric in space time, and perhaps that is w
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There isn't any such assumption. Go look up MOND. Dark matter is just the best match we've come up with so far that fits the data.
So anyone who isn't actively researching exactly that topic may as well go with the prevailing best match. It might turn out to be wrong, but its at least less wrong than the next best match. And certainly less wrong than just ignoring the data because you don't happen to like the term that was coined to describe it.
belief and faith (Score:2)
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Dark matter is stuff that behaves like matter but isn't visible. Dark energy is stuff that behaves like energy, but isn't visible. When you know that, it makes sense.
"Dark Matter" is a placeholder for "whatever the hell is causing this".
There is more "whatever the hell is causing this" than visible matter.
That is so matter of fact, and it leaves no room for... wait, it leaves a lot of room for a description of "whatever the hell is causing this".
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Man2: Ever think that our understanding of the chemistry is wrong, and the gasoline is losing energy in a way you never expected?
Man1: I'm going to go with the gas station added an ethanol mix which reduced the energy density
Man2: But what if our current understanding of chemistry wildly wrong, and you're car is special and shows our flawed understanding?
Man2 could be correct. Hell, anyone could be correct about anything, there is no real 100%
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Scientists (with perhaps a few exceptions) leave room for the possibility that the theory of dark matter is wrong. Uninformed journalists - not so much.
Given how old this 'insight' is, I think it comes from the latter group.
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Yes.
Gravitational effects show that something is there which we cannot see.
That's the bit that's treated as a matter of fact. What that stuff actually may be is where we don't have anything that can be treated on the level of facts.
So we are certain that something is there but not certain as to what it is, apart from ruling out a lot of things that should make sense but don't fit (dust, brown dwarfs etc)
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Re:Certainty in Science (Score:5, Insightful)
The quote that bothers me somewhat is this one:
The data here is on the very edge of reality, built on too many assumptions.
Data is data. Assumptions are the stuff of models and theories. Don't mix the two.
Data is nothing if you do not have any way to interpret it. Models and theories provide the context for interpreting the data.
It is like saying "bits are bits, assumptions are the stuff of encoding and decoding". Problem is, without any assumption to decode your bits, it would be as useful as any random noise. The fact that we can have a conversation here is because I (or rather, my browser) made the assumption that the bits are encoded with a certain pattern, and so did you.
Without any assumptions, models, or theories, the signals we received from Hubble would be no different from random noise.
Without the assumption that the photons came from a distant galaxy, we cannot form the image we can see.
Without the assumption of what they saw were the result of the collision of two galaxies, it would just be a bunch of stars in a strange shape.
Without the assumption of the current model of our universe, we cannot guess what would be the most probably original form of the two galaxies.
Without the assumption of the Theory of Gravity, no one can make sense of what could have happened when two galaxies collide, and thus compare with this observation.
Without the assumption of the model of gases and stars, we cannot reach the conclusion that gases should interact and slow down, while stars would not.
The problem is, with our currently best assumptions, models and theories, those that are able to explain most of our observable universe, we found that it would require the present of some undetectable matter in all the galaxies to make everything consistent -- hence "dark matter".
Yeah, you can claim that is too many levels of assumptions. Feel free to build up your own that could consistently match all the known data even better than the one commonly used.
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Also possibly fictious (Score:2, Insightful)
Here some someone with a propeller beanie on his head will tell me that dark matter must exist because "math"... which is fine only "math" is not actually evidence of something being there absent emperical evaluation because even if the numbers add up a certain way so do orbital epicycles.... and they were bullshit.
A pitfall of the "math" argument is that if you have some very clever people come up with some very clever theories they can confuse Tolken-like world building with "reality".
The justification fo
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Yes, dark matter and dark energy are convenient constructs to make our existing models fit.
When they find data that doesn't fit the constructs, then scientists have two choices:
1) Change the constructs
2) Change the model.
They're usually going to choose #1 because Occum's Razor prefers #1. They won't go with #2 until there's a sufficient body of evidence that the constructs are completely wrong. Until then, it's just going to be more tweaking and retweaking of the constructs.
Now, when I say "they", I don't m
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If I were handing out funding grants, I'd be less interested in doing it on the dark matter energy research and more interested in throwing the money at seeing if there isn't a model that doesn't require such "constructs".
The whole thing reads like epicycles to me. Those curly cue micro orbits that they used to think our planets traveled in to explain their movement.
And that only went away when they realized the earth wasn't the center of the solar system but rather it was the sun itself.
I'm not an astrophy
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Plan 1: Come up with reasonable hypothesis. Build math that works with it. Build detectors to test it. A negative result is still a result.
Plan 2: Throw up our hands because if we can't immediately get an answer then why even try.
You seem to be preferring plan 2.
And yes, there is research into alternate theories. Plenty of it with MOND being the biggest/most well-known competitor. But so far none of them have come close to matching the accuracy of dark matter theories so there's no much point spendin
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"The justification for dark matter is unexplained gravity"
You imply that this is the *only* justification. Is this because you are unaware of the rest pf physics or because you are trying to mislead others about the rest of physics?
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Particle physics predicts certain weakly-interacting particles (http://arxiv.org/abs/hep-ex/9802007) which just so happen to have properties that coincide with the WIMPs which are one of the possible predicted particles from cosmology. There is data coming in from non-gravitational experiments (http://www.sciencemag.org/content/327/5973/1619) though not a lot so far. However, conformation of the particles' existence is not necessary to refute your claim there that there are only gravity-based predictions.
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Neither of your sources actually found dark matter.
I'm going to have to reject your attempt to browbeat me until you can show that there is evidence of dark matter outside of the hypothetical or the gravitational observations of distant galaxies.
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http://en.wikipedia.org/wiki/Dark_matter#Observational_evidence [wikipedia.org]
That was hard.
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You say "Observational evidence", I say "Our models are wrong".
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There is gravity in the middle of empty space with no detectable baryonic matter for hundreds of millions of light-years in all directions. You explain that without an unseen new matter. That's right. There are massive voids in space, where we can see the galaxies in the background behind them perfectly cl
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Except I referenced that already. Go back and read my post again... I can't be bothered to repeat myself if you can't be bothered to read my post the first time.
Occums Razor (Score:2)
I know which head I'd put the fucking insulting "propeller beanie" on. Questioning is one thing, ridicule another.
Looks like you don't just despise climate scientists but all of them. What broken corner of society is turning out people spreading the drivel like this idiot's posting history? We need to prop it up with more jobs, better education
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I'm not demeaning people smarter than myself. I'm demeaning people more myopic and pedantic than myself.
I found nothing in your post but baseless insults... do you have even a thought worth contributing or was that all you were able to offer? Because any halfwit child could muster that much.
Do better.
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Fine... we'll play the epicycles game a bit longer. When we're both in Hell, and the mysteries of the universe crack wide... We can see which of us was right.
I think this might be a thing were they play with it for a few more generations and then realize they had made some simple core assumption that was wrong. And by inverting that assumption everything else falls into place.
But what do I know... dark matter dark energy dark mathematics with dark chocolate and dark stormy nights.
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That's fine... keep making epicycles... maybe that is just how the universe works. In all sincerity, how would I know?
Just know I'll be over here chuckling when you find dark magnetism, dark weak nuclear force, dark strong nuclear force, and turtles all the way down.
Same as zero point energy? (Score:2)
Matter and energy are convertible one into the other. Is what scientists call dark matter/dark energy the same as "zero point energy"? Zero point energy is what is left in a container that has been emptied of all matter and then cooled to absolute zero. This energy has been measured and verified to exist. It pervades all space, including the spaces between the particles of atoms. Zero point energy is what limits how much a signal can be amplified and is the reason why liquid helium cannot be made solid with
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That was what was first assumed. There's only one minor problem.
The amount of zero point energy is *120 orders of magnitude* larger than the measured magnitude of dark energy. And dark energy has about 3x the energy density of dark matter.
So, despite the fact that it looks like zero point energy, there's something else going on.
[TMB]
How sure are we... (Score:2)
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its an hypothesis and a model attempting to explain some weird stuff we're observing. Its probably wrong, but its a starting point. A bit like the early earth centric models of the solar system originally (that actually ended up giving the correct results, even though they were wrong)
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Funny thing is that epicycles weren't "wrong" (within the limits of measurement capability of the time.) They were just not the simplest way to do the computations.
To work with a sun-centric model you have to (in your imagination) translate yourself from the Earth to the center of the sun, figure out where the planets should be, then translate those planet coordinates back into Earth coordinates.
Epicycles is essentially combining those steps into a single set of equations. It'll be ugly and complex as hel
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That Mass is a real thing and not just a "theory"? Do we have any proof yet? I know there is almost no intel coming in on it, so it is easy to keep up with and/or follow.
Dark Matter (Score:2)
Dark Matter seems to me to be a placeholder item for differences between the calculated trajectories and real.
It do adjust for the effects observed but it does not explain what it really is.
4th Dimension? (Score:2)
If the dark matter's w value would become similar to ours it would suddenly appear in our 3-dimensional space. Since
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Because of relativity this long-term gravitational effect has to move linearly with the objects through space, so it would kind of wobble with the galaxies when they moving relative to each other. When the galaxies collide the past gravitational effect would keep moving linearly.
Objects of all sizes would have this effect. But since planets moves around stars and stars don't mo
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Yep. Entirely plausible. Even been considered by actual real scientists.
But since any testing of 4+ spatial dimensions is beyond our capabilities as 3 dimensional beings, those theories tend to get shelved as interesting mathematical models while we concentrate more on theories that may possibly lead to results eventually.
Of course if the alternate dimension theory is actually the right one, we may be spending a lot of time barking up the wrong tree.. but since we will never be able to tell if its the rig
A couple of crackpot ideas (Score:2)
Clinging to a hopeless theory? (Score:2)
The lack of evidence for dark matter is becoming kind of embarrassing to the theory. Anything that should provide direct evidence doesn't - dark matter is seemingly only necessary to explain large-scale gravitational behavior, but is not otherwise in evidence.
For me, as a layman, dark matter was never persuasive: "there's this stuff that only has an effect way out there where we need it, but has no local effect where it would screw up our nice models". Sure there is. There are other theories that seem to be
Dark Matter and Dark Energy are non-existant (Score:2)
Re:Non-linear gravity (Score:4, Interesting)
We're trying to explain inflation and the motions of stars orbiting galaxies not matching our naive model.... couldn't a non-linear gravity model explain all this without the dark energy/matter hocus pocus?
Sure, but that would involve even greater hocus pocus than the current theory and fails at explaining other observations. So far, trying to come up with any hypothetical explanation involving MOND has been so complex that nobody has been able to come up with one that explains even the rotation of galaxies. If you or any other person could come up with a good law of nonlinear gravity that works, even if it completely fails at any of the other observations, there's a paper in a prestigious journal and some physics cred for you.
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A change to gravity does not work because we have already measured the gravity at these ranges to be within 99.9% of the expected values. Advancements in optics and sensors has
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What objects are moving away from us faster than light and how was this determined?
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We're trying to explain inflation and the motions of stars orbiting galaxies not matching our naive model.... couldn't a non-linear gravity model explain all this without the dark energy/matter hocus pocus?
Gravity is non-linear, or maybe you didn't notice that distance is in the denominator? It's linear in mass but really very non-linear in distance. m1*m2/r^2. Not even remotely linear.
To review: double m1, you get double the force: linear in m1. Double m2, you get double the force: linear in m2. Double r and, WHOA NELLIE you get 1/4 the force: massively (pun intended) non-linear!
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Thank you for the link, AC.
I saw two errors so egregious in the first three pages that I can dismiss that paper immediately. First the authors claimed that stellar gasses need to be sufficiently ionized that magnetic field lines could be frozen in them. This represents a fundamental misunderstanding of electromagnetism. These people could not possibly give fair treatment to an electromagnetic theory with such a basic misunderstanding. Second, they claim that obviously stars are not affected by the magnet
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What I find more interesting is why stars rarely collide?
Too much empty space.
Re:Stars collision rarity (Score:5, Informative)
This.
Consider that for two stars to hit each other, they essentially have to pass within one stellar diameter of each other (absent gravity, but they're moving at over escape speed relative to each other, so gravity won't enlarge that distance a whole hell of a lot).
So, one stellar diameter is ~1.4 Gm for Sol. Nearest star is 40,000,000 Gm away. If that nearest star were headed toward us (it's not), it's course would have to be within 0.01 seconds of arc of our Sun in order to actually hit it.
And stars farther away have an even smaller course window to be in to smack us....
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You are right about that, even including all the trillions of stars the *average* density of the Milky Way is only 40 nucleons per cc (our best vacuum pumps do three hundred thousand molecules per cc!) That's a hella lot of mostly empty space
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There have been several theories built on that assumption, most prominently one called MOND (MOdified Newtonian Dynamics), but more recently one that builds on relativity rather than Newtonian gravity/dynamics.
But none of these theories (hypotheses?) have gained much acceptance from the physics community, as far as I know.
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The energy density in the universe from light is much less than the energy density from baryonic matter, which is in itself much less than the total matter energy density of the universe (which is why we infer the existence of non-baryonic, or "dark", matter).
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At the risk of feeding a troll.. what the hell are you talking about?
Set theory indicates that the integers are infinite so therefore discovering new things in the universe that aren't covered by our known science is somehow nullified by edge cases in propositional logic?
You're not even discussing the same disciplines never mind making any sort of meaningful connection between your statements.
This leads to models of these theories essentially asserting that there are countable numbers which are greater than the number of particles in the observable universe.
So what? There are also countable numbers which are greater than the number of coffee mugs currently on my desk. W
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I expect physicist to have thousands of hypotheses about dark matter.
Until you can design an experiment to distinguish between those that are bollocks and those that are true, you're not going to make any progress. That's the hard part - designing and performing such experiments. This is why beautiful and simple demonstrations like the double-slit experiments are considered the most artistic and wonderful pieces of science.
The problem with dark matter is that we have so little information about the phenom
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