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The Starry Sky Just Got Starrier
An anonymous reader writes "Astronomers have surveyed eight elliptical galaxies, and found that we've vastly underestimated the number of dim red dwarf stars in these giant galaxies. When they used the new number of red dwarfs in their calculations, they tripled the total number of known stars in the universe."
dark matter much?
It's full of three times the stars.
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dark matter much?
Apparently less :)
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To phrase that as a real question: What effect does this discovery have on the current estimates of the amount of dark matter in the universe?
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Good question. Assuming you are asking something along the lines of "How does this finding effect the ratio of dark to regular matter?" My guess is, not much, because I don't think the ratio ever really depended on observations of stars, per se.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
Really? I thought that they used gravity to determine the approximate mass of the galaxy, and then subtracted the amount of visible matter to yield the amount of dark matter. If that's how they did it, then increasing the amount of visible matter would have to decrease the amount of dark matter.
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Good question. Assuming you are asking something along the lines of "How does this finding effect the ratio of dark to regular matter?" My guess is, not much, because I don't think the ratio ever really depended on observations of stars, per se.
What was the need for there to be dark matter in the first place? Wasn't it invented as a concept to explain why the universe is the way it is assuming it has a specific amount of stars in it? Has anyone proven that dark matter exists or is it just a convenient kludge to make a model of the universe fit observations?
If they discovered that there are 3 times as many stars as previously believed then what purpose does the concept of dark matter serve?
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Yes, but the estimates give a ratio of dark-to-visible matter of 20 to 1 or so. Here they only triple the number of stars, and they are all on the low mass end of the scale, resulting in only a minor change in that ratio.
"I guess the moral of the story is, don't paint your airship with rocket fuel." -- Addison Bain
If they discovered that there are 3 times as many stars as previously believed then what purpose does the concept of dark matter serve?
the other ~70% of the observed mass... 3 times the stars still means a lot of dark matter.
dark matter isn't something intangible. it's matter with not enough light bouncing off it for us to see.
The Chirpsithra will be thrilled.
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Non-baryonic dark matter has to exist in order for certain observations made on the cosmic background radiation to make sense. Basically, the Big Bang couldn't have happened without it. There's a lot more to it than just missing mass.
As for evidence, there's enough to infer it exists, but its exact composition remains elusive, so far as I know with my layman's understanding of this stuff.
Minor corrections:
- Not only the visual spectrum, but the entire electromagnetic spectrum.
- Black holes are also added to the baryonic matter count, and their masses are estimated based on their effect on observable matter. For faraway objects, one can assume that the number and sizes of black holes compared to visible matter is lower than the ratio in our neighbourhood, simply because faraway galaxies are much younger, giving black holes less time to appear and grow.
Anyhow, I see this as good news for our descendants. Red and brown dwarves are likely better targets for extrasolar exploration than bigger stars are.
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( http://en.wikipedia.org/wiki/Starry_night )
I only had two . . .
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True, Dark Matter, like Dark Energy, is just a placeholder name for something that we know is there. What we're seeing is patches of gravity where none should exist. Even with all those red dwarfs being added it still doesn't come close to making up for all the extra gravity. I heard Neil deGrasse Tyson say at a lecture (which certainly could be outdated) that observable mass accounts for about %5 of of all the stuff out there.
They don't determine the mass of a galaxy by counting stars.
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It won't boost as much as you think. It increases the number of stars, but red dwarfs are small and not very massive. They are usually stars that went nova but were too small to collapse and form a black hole.
A handful of super-massive black holes could probably cover this tripling of the stars.
Even if the amount of matter tripled, however, it still would not eliminate dark matter. Currently, visible matter accounts for 4.6% of the matter in the observable universe. Dark matter accounts for 23% (the rest is dark energy). Tripling the visible matter would bump it up to 13.8% of matter in the universe, and would bring dark matter down to 13.8%, or roughly equal.
That's still a hell of a lot of dark matter that is currently invisible, and is still plenty to screw up astronomical observations.
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You are correct, but the amount of dark matter figured in this way was roughly four times the amount of visible matter. A full tripling of visible matter (which is not what happened - these are teeny tiny stars, which is why they were missed before) would only set dark and visible matter roughly equal to each other.
Security is mostly a superstition... Avoiding danger is no safer in the long run than outright exposure. - Helen Keller
...since these estimates came from Astronomers who previously worked at Goldman Sachs. Sub Prime real estate as it were.
Or rather, humans just got less ignorant about the universe in which we reside? To say the sky got 'starrier' would imply that more stars are there than before...
IANOP, but this galaxy is 90% dark matter is just another way of saying that the amount of matter visible to us as stars and interstellar gas is dreadfully insufficient to account for how this galaxy rotates, even if we generously account for very dim collapsed stars and stellar black holes, for as many of them as we think have appeared since the Big Bang. Either General Relativity is wrong on a galactic scale, or there is a crap-ton of matter hanging out there that does not produce, block, or reflect any light. The "visible" matter is mainly just stars and interstellar gas, and is composed of familiar protons, neutrons, and electrons. Dark matter, whatever it is, is probably radically different from anything we've encountered so far, although alternative laws of gravity and halos of massive dark objects such as black holes are not totally ruled out.
it's more full of stars!
> True, Dark Matter, like Dark Energy, is just a placeholder name for something that we _think_ is there.
FTFY.
Probably will get modded down, but if you "knew" it, then you would be able to prove it exists. Since no one has seen it, touched it, tasted it, smelt it, or felt it, therefore it is a mathematical kludge, aka, the aether of the 1900s. (Yes, I'm aware of http://www.nasa.gov/home/hqnews/2006/aug/HQ_06297_CHANDRA_Dark_Matter.html )
Ergo, while said more politely, "it falls out of the math", which will allthough appear quite reasonable at first, given the current limitations of understanding gravity / light / mass & energy, it is still one a big hack-job based on one assumption after another, namely:
a) that there is only one type of gravity and
b) gravity is universal (which is a little preposterous / pretentious to base how the WHOLE universe works based on one tiny little planet.)
c) redshift is accurate (ARP has interesting evidence that calls into question this assumption)
This prof. provides a half-decent summary though:
http://zebu.uoregon.edu/1999/ph123/lec08.html
{peers upward}
It looks the same to me.
http://alternatives.rzero.com/
I believe this is one piece of very strong evidence for some sort of pervasive weakly interacting massive stuff. Two galaxies collide. The normal matter interacts with other normal matter and slows down, The "other stuff" does not interact, and keeps moving. We know it is there because it creates a gravitational lens. If the lensing were caused by any sort of matter that interacted with other matter, these lenses would not be located where they are.
So the theory of Dark Matter is more than just "there is more stuff than we can see." We can see specific phenomenon that normal matter just can not produce.
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Actually, last I heard it was 5 to 1. So those tiny stars and any rocks orbiting them could have a bigger impact on those numbers than you think.
The best evidence is that, by observing galaxy rotations, it seemed like the galaxies needed to be about 80% dark matter for the rotations to make sense (there were several competing theories at that point). Then the CMBR observations pegged the composition of the universe at that early time at about 80% dark matter. The unrealted theories agreed to a couple of significant digits, which pretty much settled the matter (as much as anything in cosmology can ever be known).
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Since they can make predictions with it, and have tons a data supporting there is an effect going on, you're wrong.
"Since no one has seen it, touched it, tasted it, smelt it, or felt it."
the same can be said for gravity.
Now if you added 'measured it' then it couldn't be said for gravity. Of course then it couldn't be said for dark energy and dark matter.
a) There is no evidence of any other kind. Should some good evidence actually come in, then great.
b) Every measurement we have made using our understanding of gravity seems consistent. Again, if there is actual evidence of something else, then thing will change.
c) interesting evidences doesn't matter, strong* evidence does.
Your post shows a large amount of ignorance on this matter, and ignorance on the scientific process.
*no pun intended.
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No, it's out there. Things like the bullet cluster pretty much prove that there must be large amounts of some sort of weakly interacting matter. Basically, two galaxies collide. Normal matter in one galaxy interacts with normal mater in the other, slowing it down. But something massive wasn't slowed down and kept right on trucking along the same path at the same speed as before. We only know it is there because of the gravitational lensing it produces. So, we have direct evidence of matter that we can not see, and that does not interact with other stuff except through gravity. Call it whatever you like, it's out there. And that is just one piece of evidence. Galaxy rotation and the CMB are others.
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From Popular Science you can read:
" 'Within these galaxies, a good chunk of the mass that had been ascribed to dark matter is probably stars,' said Pieter van Dokkum, the lead researcher on the project."
So I bet "a good chunk of the mass" is a bit more than "a minor change".
But we will probably soon get an exact new ratio after the smart guys have made new calculations, other than any of the above.
Five to one or twenty to one, you still have a significant amount of mass.
Then, as you mention, you have to add all the hard to detect planets for another small fraction. (If weren't seeing the star you can bet they weren't measuring its wobble). Admittedly its probably a small addition relative to the stars themselves.
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gravity is universal (which is a little preposterous / pretentious to base how the WHOLE universe works based on one tiny little planet.)
It would be, except that our observations of the effects of gravity cover countless measurements over the entire observable universe.
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I explained the need for Dark Matter previously here on /. and folks seemed to like the explanation so I am reposting:
It is something more along the lines of this: We have a good number of formulas and calculations that work properly with the things we can measure - planets, the sun, cars, planes, kitchen scales. One of these might be:
y + 3 = 5
Nice and simple for this example. Lets say that the "y" here represents gravity and the formula has been proven in every experiment we have done.
We therefore assume that this calculation is correct and true. BUT when we try to use this calculation when looking at things like galaxies, we seem to find the wrong answer:
y + 3 = 7.2
This is clearly not correct, but as we don't want to throw out all the formulas and understanding we have about how things work, we add another variable to the formula like so:
y + 3 + x = 5
The "y" still represents gravity, but now we add the "x" which represents something we don't understand and we don't know where it came from. We call it Dark Matter because we can't see it, don't seem to be able to interact with it and have no real idea of what it is - but with this new addition to the formula, the answer once again comes out at what we know (think) to be true. We just now need to find what this x variable is.
THAT is why finding/understanding Dark Matter (and on that note, Dark Energy) is so important. We know (think we know) the right answers, but our formulas just don't seem to fit so well when applied to certain really, really, really big things (like clusters, superclusters etc). When we find this "x" in the formula, it will once again work perfectly for all our calculations.
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Teeny tiny is a relative term.
Up to 40% of the mass of the our sun is the usually quoted cut off for red dwarfs. That is still a pretty sizable object.
Two or three of these add up to our sun.
An interesting visual of relative solar system masses is here
http://en.wikipedia.org/wiki/List_of_Solar_System_objects_by_size
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In addition to what others have said about large stars probably mattering more than small ones and about how much dark matter out-masses luminous matter, there's another thing to consider. Namely, most luminous matter in a galaxy is in the form of gas and dust and not stars. So increasing the number of red dwarfs does far less than triple the contribution of luminous matter to the universe's total mass.
Nice, more stars.
can't wait to take my telescope out and look at them.
wait, what?
Be seeing you...
Bah.
Postulating Dark {Matter, Energy} is the height of hubris, since it implies that Astronomy Has Seen All There Is To See from our tiny little glasses on our tiny little rock in a backwater arm of the Galaxy.
Thank The FSM that there are still a few rational scientists out there actually *looking* for stuff.
"I don't know, therefore Aliens" Wafflebox1
That's incorrect. Red dwarfs do not have enough mass to go nova. They just slowly burn up their nuclear fuel until they cool off. And it takes a supernova to create a neutron star or black hole. A nova is a less energetic phenomenon where one star steals gas from a companion star, until the density/temperature becomes critical and the star's surface layer is blast away in a fusion reaction. In many cases this can be repeated several times, since most of the star survives.
Your incorrectly summarize your own cite.
Two galaxies collide. The stars are slowed by gravity but mostly go on their way, the gasses collide and slow down while emitting X-rays, some other stuff does not interact and keeps moving.We know it is there because it creates a gravitational lens. That lens is detected in the same place as the visible stars but has no observable light.
Further from your cite
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By that standard virtually all of science is based upon hubris as we haven't actually discovered everything there is to discover before coming up with hypothesis to test. By that measure it was arrogant of people to come up with the second without realizing that relativity is involved and that time doesn't exist at 0 kelvin.
Now, if you want legitimate arrogance, just look at those guys with their "string theory." It's been decades and they still haven't managed tho have a single testable hypothesis coincide with their ideas. A lot of things look good on paper as theory and then completely disintegrate when applied to the real world.
nice link icebike! is it just me, or is there a irresistible urge to put "your mom" in "Examples of objects between 20 km and 1 km in radius" list and see if anyone notices?
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You're ignoring something important. The laws of conservation of matter and energy.
These are stars that went supernova, but for which the remaining gravitationally bound matter did not turn into a black hole. It takes a lot of matter for a star to nova, and it doesn't just disappear.
In short, they tripled the number of stars that were at one time on the order of 10 times more massive than average.
After all, I am strangely colored.
Wrong. The canonical number used in galaxy modelling is 20-to-1. That number is inferred from the rotation curves of spiral galaxies, not ellipticals, but that's the ballpark. And then there' this:
"But there’s still plenty of dark matter, too, according to van Dokkum. In fact, the new stars probably won’t change the accounting of dark matter very much."
But hey, look at me being lazy and just quoting the article you cited.
"I guess the moral of the story is, don't paint your airship with rocket fuel." -- Addison Bain
Nevermind, I'm wrong about red dwarves.
After all, I am strangely colored.
It's just the opposite, Dark Matter is something we know we haven't seen, yet. It is a way to measure the "unexplored".
It's like saying that I know that of 20 persons in this room I can see 5 (and I can describe them).
If I have some way of knowing (gravity for example) that it must be equal to 20 persons, I can call the missing persons Dark People. They might be 15 normal people, its just that they are behind stuff (my self for example) so I cant see them straight on. I might catch a glimpse in a reflective surface and so on. But I might also have a number of persons and the rest are dogs, just because I haven't seen a dog doesn't mean there aren't any.
So Dark Matter might be known stuff (new stars like this) or unknown stuff (like the dogs).
I'm afraid your referential opacity places you squarely in the realm of dim matter.
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Call it whatever you like
How about "really dim baryonic matter". After all, we're Really, Really Far Away.
"I don't know, therefore Aliens" Wafflebox1
In a word, no. Supernovas that don't turn into black holes end up as neutron stars, not red dwarfs. Red dwarfs are the remains of stars too small to go supernova, which is why they're so small.
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Sorry, got the bit wrong about the stars. But how could cold gas clouds not smash into each other? And why does this observation match up with so many others that also show the existence of dark matter? Critics like to take each piece of evidence separately, and cast doubt on each one, but they rarely seem to want to take on the whole package of evidence at once.
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Mass questions aside, how do we know the age of these stars? The cores of rock planets in this solar system, especially Earth and Mars, resemble red dwarfs, and at a young age they were probably very similar. What about the planets of origins that are not so similar as ours, like Jupiter? There is some evidence that Jupiter, at an early stage of our solar system, was very similar to the Sun. By chance or what have you, two massive gas balls had a gravity fight, and the Sun won. The gas giants are more similar to the sun than they are to the interior planets and the outlying planetoids (as we apparently are now refering to neptune and pluto). If the collusion of gas and heavier element clouds create stars, and the collision of condensed gas and heavier element clouds create planets, and the gravitational eccentrices decide which cloud becomes a star and dominates its system, where the heavier, rockier objects collude, how do we know what designs a solar system? The point is, are these red dwarfs actually stars, or are they planetary objects orbiting in a still undefined system? Will one of them become a star like the sun, or will they collide and disperse into the galaxy as a mix of chemical elements? Is anything orbiting them, if so, is anything orbiting one of them at a more rapid rate than its partner? If Jupiter could have been a star, how do we not know that these phenomena are the birth of solar systems? I guess this news is not new to me, it just opens a lot of unanswered questions, and the proposition that Jupiter, at one point, may have been the center of the solar system, but remains a outlying planet of fusion reaction of gas and is not a star, begs more questions. Like are these dwarfs nebulous accumulations of gas that are in the process of forming solar systems? Will one of these red dwarfs become a sun and contain a system like ours? Or will many of them collide and become a blue giant and blast off there accumulative accretion disk, maybe become a gravitational phenomena? Will one red dwarf become a Jupiter while the other red dwarf is bombarded with outliers until it becomes a Sun and develops rocky planets like ours?
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Now, if you want legitimate arrogance, just look at those guys with their "string theory." It's been decades and they still haven't managed tho have a single testable hypothesis coincide with their ideas. A lot of things look good on paper as theory and then completely disintegrate when applied to the real world.
String theory is the mathematical/logical synthesis of theories. As such, it can only predict what the logical closure of its sub-theories predict.
String theory cannot make any new testable hypotheses, because any testable hypotheses will be a testable hypothesis of the old sub-theory. String theory is still falsifiable: it is as falsifiable as General Relativity, Quantum theory, and the rest. Because it is them, taken together, and expressed in a unified mathematical framework.
After all, I am strangely colored.
Really dim baryonic matter would only explain some of the many different lines of evidence.
I don't really have a horse in this race, I mean, I could care less which theory turns out to be correct. It just seems like the preponderance of evidence points to a non-baryonic source of mass at this point.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
That reminds me. There's a few wags at my institution who like to send examples to a certain mailing list of kookie religious people being kookie. Someone posted a discussion on a Christian web site of some fundamentalist "physicists" talking about how the reason regular physicists had to invent dark matter is because they weren't taking into account the mass of Heaven and Hell.
I am not making this up. When I get time I'll try to find the link and I'll post it to a journal here. Some of you godless heathens might get a kick out of it.
You are welcome on my lawn.
The obvious question (at least to me) is that other than creating a gravitational lens, how did the dark matter gravitational interact with the normal matter? Shouldn't there be some deviation in the path of the normal matter due to the gravitational effect of the dark matter? Did it simply slow the normal matter down more than would be expected in a normal matter to normal matter collision? The article you link to mentions that this example does not shed any light on the galaxy rotation problem that gave birth to the idea (not theory!) of dark matter. In any case, this is a just a data point. For this to be a useful data point, we need examples (at the same scale) of pure normal matter interactions. Or a whole new idea.
Depends on what we call "a good chunk", "a minor change", "not very much".
A change to 19 to 1 from 20 to 1 might be any of the above (not that I'm saying that the change will be that or even close).
For us mortals the change might be minor, but for a scientist it might be a huge change.
Important to you, maybe...
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Just because you can't see the other 15 people, doesn't mean that you wouldn't see them if you had an IR camera.
Before Van Dokkum wrote his paper, the DM/DE proponents thought they'd found all the matter there is to find. Suddenly there's 3x more. Which is a slight reduction in the need for DM.
Who's to say that in 1-20 years other heretics find 10x more baryonic matter, thus reducing even more the necessity for DM.
"I don't know, therefore Aliens" Wafflebox1
He doesn't say that they do. He's saying they determine the mass of a galaxy some way, and count the starts to see if it matches up with what they determined, adding dark matter to account for the rest.
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Darn it, modded you down, meant to mod you up, and the mod thang disappears after modding, so it can no longer be fixed. So, posting to undo the mod. Bloody broken slash-code.
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Not quite. It's just matter we haven't seen and so can't account for, if we have the mass estimates for the universe right, which is in itself doubtful. For instance, a small galaxy directly behind a large one in a position that doesn't allow us to see it -- that's "dark" from the dark matter point of view, even though it's glowing like crazy. Some of it might not be radiating, or radiating too dimly; but on the other hand, our math may just be entirely wrong.
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Sorry, but the Ptolemaic system was, back in ancient times, a very accurate representation of planetary movements. From your first line, then, Galileo would be wrong.
There always needs to be a sufficient amount of skepticism to everything we devise. Dark matter really is aether. We don't know what it is, we can't observe it so far, the only thing we know is the effects it does. However, interesting theories (such as Hoava–Lifshitz gravity) have sprung up that try to explain the effects we see without requiring the intervention of an exotic matter/energy mix. In many ways, the situation is similar to the birth of relativity.
What does this mean for the mass of the Universe? Has the estimated quantity of dark matter been overestimated?
The game.
Postulating Dark {Matter, Energy} is the height of hubris, since it implies that Astronomy Has Seen All There Is To See from our tiny little glasses on our tiny little rock in a backwater arm of the Galaxy.
Thank The FSM that there are still a few rational scientists out there actually *looking* for stuff.
There are observations that have been made which cannot be explained by any quantity of unseen "regular" aka Baryonic matter. This is the result of people actually looking for stuff, and not in their hubris assuming that we have Seen All There Is To See. Indeed it is very much a case of realizing that we have not seen it all.
Hubris is dismissing (the non-Baryonic subset of) Dark Matter because it's not the same as the "regular" matter we are familiar with in a much more extreme case of assuming we have Seen All There Is To See. Red dwarfs are nothing new; and you're strongly implying you think such examples of normal objects will explain away the need for Dark Matter, as in we won't find anything new. We Have Seen It All.
Even though what astronomers have seen strongly suggests that is not true, and there is stuff out there completely different than what you are comfortable with.
It is kinda funny how often people give "arrogance" as the reason why scientists put forward certain hypothesis when they are completely unaware of the actual scientific reasoning behind the hypothesis. By attributing arrogance to others as a consequence of their own ignorance, they demonstrate tremendous hubris.
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Zing! Your excessive use of big words along with a obligatory astronomy reference clearly shows that your sense of humour is fundamentally superior.
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Well, considering that nothing in our physics confirms that the big bang even COULD have happened, I'm pretty comfortable with not assuming invisible things exist to back up an hypothesis that isn't possible under normal physics anyway. The big bang is just hand-waving at this point in time.
Ascribing it the status of certainty is the result of not consuming the available objective facts, in particular that the states described for the important part of it aren't possible under any configuration of reality we understand.
So it's either wrong (quite possible) or else there's a good bit of science to come before we can confirm it's right.
As for the rotation rates of certain galaxies, that is integral to the mass, and it's not at all clear that we've got mass estimates right as yet, either. Every example we have is in our galaxy, and in our local stellar neighborhood. Those values may hold elsewhere, or they may not. There may be other forces (see the Pioneer anomaly, for one) or there may not. Just too soon to be sure on several fronts. Considering that at least two major forces are only visible to us by their effects (gravity, magnetism), it may be optimistic to presume that there aren't others, especially when the scales change from our local experience to one the size of a galaxy, or spanning many galaxies. Look at the strong atomic force; on a small scale, it's a ripper; across ten feet... means absolutely nothing. We may simply not be able to measure something that is going on because of scale.
And it isn't that I have anything against the idea of matter we can't see. On the contrary, I'm sure there's plenty of that. It's just this assumption of already-settled-truth WRT the big bang that irks me. If it's settled in your mind, then I assure you, you don't understand it. Ask a cosmologist -- they'll be the first to tell you the same thing.
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The galaxy rotation problem is basically this: Stars towards the edge of galaxies (mainly spiral galaxies) rotate much faster than they should based on Newtonian gravitation using only the visible material (the Einstein corrections are negligible at the speeds and distances being talked about, so they can't account for the differences). To explain this, you have basically two options: MOND, MOdified Newtonian Dynamics (ie., changing the laws of the universe at large distance scales like kiloparsecs), or dark matter (which can include baryonic dark matter as well, but generally refers to non-baryonic things), which corrects for it by assuming that there's a vast halo of objects that outweighs everything else in the galaxy and thus speeds up the rotation of objects far away from the galactic core.
The evidence at the moment seems to be in favor of dark matter, and in any event I have some doubt that we will ever see "examples at the same scale of pure baryonic matter interactions" as you put it; it may be that the phenomena in question are simply things that appear on the very large scale and aren't observable on the small scale, just the same way that relativity only becomes important under certain conditions and Newtonian dynamics works perfectly well in our "normal" world. (But I'm not an astrophysicist, just aiming to be one!)
Or things like the Bullet Cluster prove that we don't understand gravity nearly as well as we think we do.
Put simply: two things interact, but don't conform to our expectations of how they should interact. Therefore:
1. Our expectations must be wrong.
or
2. There must be something we're not seeing about the interaction.
Dark Matter is basically saying "2, because our expectations seem to pan out for other interactions"
But then...Dark Energy...
Put simply: two things interact at very long distances, but don't conform to our expectations of how they should interact. Therefore:
1. Our expectations must be wrong.
or
2. There must be something we're not seeing about the interaction.
So, non-intuitively, we say "2 again, despite the thing we're not seeing being completely different/opposite to the thing we didn't see with Dark Matter"
Of course, redoing the assumptions about gravity at galactic scales will be hard, and there won't be any megabuck research grants and facilities to do it, so I don't really blame people for not wanting to go down that path...
Business/App ideas are like arseholes: everyone's got one, they're mostly shit, but very rarely they contain a diamond
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...the astronomer wasn't just hit on the head with a cartoonishly large wooden mallet?
.
Prisencolinensinainciusol. Ol Rait!
I don't really have a horse in this race, I mean, I could care less which theory turns out to be correct.
Me neither. But it really seems odd that so many Slashdotters are so rabidly against the idea of dark matter.
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The extra mass could simply be a much larger black hole in the incoming galaxy that had previously consumed most of it's surrounding matter. There's just too much that isn't known here to draw firm conclusions about anything.
I've fallen off your lawn, and I can't get up.
Rocks that orbit the stars are irrelevant for the purposes of mass calculation. All the mass in our solar system that isn't the Sun or Jupiter is less than Jupiter. Jupiter's mass is less than 1/1000th of the Sun's. Granted, our solar system may not be representative of other star systems, I bet it would be. Due to the process of stellar formation, there's always a shit-ton more Hydrogen and Helium than anything else.
Learn something new.
hang on, that's exactly what Khenke is saying...
astronomers/astrophysicists don't ascribe everything they don't know to "dark matter" in the sense that supernaturalists would say "God did it". dark matter is just a cool sounding name for stuff we can't see but we know it's there - ie the people or dogs or both in the room.
Dark matter and dark energy are two totally different things. They're placeholders for vastly different phenomena. Dark matter explains why galaxies rotate at the speeds they do, even though their visible mass is much, MUCH, lower than the spinning speed shows it should be. Dark energy is the pressure that's causing the universe to accelerate outward. The universe isn't just expanding, the rate of the expansion is increasing, not decreasing as you would expect. Some force is being exerted on the fabric of the universe that's causing it to expand at a faster rate every second.
So, to recap:
Dark matter = mass that's causing galaxies to spin faster than they should be
Dark energy = force that's pushing the universe apart
Learn something new.
Before Van Dokkum wrote his paper, the DM/DE proponents thought they'd found all the matter there is to find.
No astronomer thought they had found all the normal matter there is to find. In fact the search for dim red dwarfs in specific was part of trying to answer the Dark Matter mystery -- which originally only meant matter we had not seen yet, and only came to mostly refer to non-Baryonic Dark Matter when observations suggested that most of it was.
In fact, would you believe that when "DM Proporents" estimated the amount of non-Baryonic matter and added it to the known visible matter in galaxies, they still saw a discrepancy in observed gravity in elliptical galaxies? And that finding more normal matter was one prediction to explain it, and in fact this new observation may end up explaining the difference, solidifying our calculations of dark matter.
Suddenly there's 3x more. Which is a slight reduction in the need for DM.
3x the stars is not 3x the mass (particularly when the discovered stars are red dwarfs), but regardless...
Who's to say that in 1-20 years other heretics find 10x more baryonic matter, thus reducing even more the necessity for DM.
Indeed, who's to say? But as long as there are observations that cannot be explained by baryonic matter, it will be necessary.
I really like the characterization of this researcher as a "heretic", btw. I like it because this "heretic" was given access to the Keck Interferometer -- the combination of two of the largest telescopes in the world and thus a highly sought-after instrument -- in order to conduct his research. And then said research was published in Nature.
Because that's how we do things in science: we invite the "heretics" to make observations and disprove our current theories and hypothesis so we can create even better ones. They are not shunned, they are not shut out from access to the tools they would need to prove themselves,. Quite the opposite. Indeed, quite the opposite of a "Church" and "heretic" relationship. Which is why it's funny.
The enemies of Democracy are
Because it is them, taken together, and expressed in a unified mathematical framework.
Don't you mean it's most of them, with small but important bits missing?
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
And finally, matter == energy, for anyone who wasn't confused already
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
The big bang is just hand-waving at this point in time.
Hand-waving, one of the most successfully predictive theories of the last century, these are both the same. I'll make them seem like they're both the same by... wait for it... waving my hands.
The enemies of Democracy are
Me neither. But it really seems odd that so many Slashdotters are so rabidly against the idea of dark matter.
The story of humanity is full of whole chapters which basically boil down to a bright spark being smothered by a bunch of ignorant fuckwads attached to their idea of how the world works. Every once in a great while the spark lands in a pile of tinder not in the furnace-equipped basement of a firetrap and something wonderful is born, but mostly people shun what they don't understand and it's their children or their children's children who are willing to incorporate it into their lives as an escape from the previous generation who doesn't "get it". This is why the technological singularity is the religion most appealing to the technological elite...
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
b) Every measurement we have made using our understanding of gravity seems consistent. Again, if there is actual evidence of something else, then thing will change.
Except for all of the measurements that led to coming up with the concept of "dark matter." We'll have to see if the dark matter concept actually hangs together consistently.
"Since no one has seen it, touched it, tasted it, smelt it, or felt it."
the same can be said for gravity.
Really? Where do you live? I feel gravity constantly.
Space game using normal deck of cards: http://BattleCards.org
It probably depends on what you're talking about really, from WP:
dark matter accounts for 23% of the mass-energy density of the observable universe, while the ordinary matter accounts for only 4.6% (the remainder is attributed to dark energy).[2] From these figures, dark matter constitutes 80% of the matter in the universe, while ordinary matter makes up only 20%.
So ordinary matter accounts for 4.6% (1/20th) of all mass+energy in the universe - this I suppose has to do with Einstein's E=mc2 that allows for mass to be converted to energy and the other way around. And looking at actual mass, not taking the energy into account, this would end up at 1/5th. So both numbers are in a way correct, depending on context. I thought actually it was about 90% dark matter, so let's call that number the average. Then at least I'm not wrong myself.
Now I don't really know what they mean with the "dark energy" part or how that's measured, the "dark matter" I understand somewhat as it has to do with gravity.
Anyway this whole "dark matter" thing sounds to me like the hypothetical "aether" - we don't know what it is so make up something to make the formulas work. So now we found that there is 3-4 times as much "visible" matter in our universe than we thought before. Oh well that's quite some "dark matter" that has come to light. I'm quite sure the rest will follow sooner or later.
So why was it wrong for Einstein to add Cosmological Fudge Factor X to the equation, but not for us? How do we know, or what makes us think, that the missing matter is non-baryonic in nature?
So this "other stuff" is there, does not interact with itself, but does interact with OTHER matter (light in this case) to create a gravity lens?
I may miss something but to me it seems to contradict. How can its gravity interact with light, but not with itself or the non-dark matter in those colliding galaxies? If it produces that much gravity to create a gravitational lens, why doesn't it pull the rest of the galaxy with it?
Dark matter interacts or it doesn't. It holds galaxies together, creates gravitational lenses, but doesn't interact with itself nor with other galaxies.
you mean like the diffuse hydrogen forming the intergalactic medium? that's seen in shockwaves? Check out the articles about the bullet cluster and keep an open mind. the worst that could happen is you might learn something.
It's full of stars!
is getting tantalizingly close. Ok, half way to go, but maybe there are more eliptical galaxies.
The pot heads would be insufferable.
There is an interestuing theory being postulated by Astrophysicists at Manchester University, namely Kinky Vortons.
The theory is that these are planes (or bubbles in 3D space) of enormous amounts of dark energy, these planes are thought to encapsulate whole galaxies or more, consituting a domain wall. A rediculous amount of energy to cross a domain wall because any particle that wants to make the transfer from one side of the Kinky Vortons to the other has to have as much energy as the Kinky Vorton - a sort of activation energy, if you will.
The reason why I'm replying is that who is to say that the laws of physics - i.e. gravity - are the same on the other side of a Kinky Vorton? It's a very small world based assumption. Maybe particles conform to the laws of physics of the particular domain they inhabit.
http://www.jodcast.net/archive/201009/ Read under interview section
Dark Matter and Dark Energy are two entirely distinct concepts. Dark Matter is "Why does that galaxy have not nearly as much matter as it should?" Dark Energy is "Why is the rate of expansion not only constant or slowing down, but instead speeding up and changing its acceleration over the life of the universe?"
if the "thing" interacts only via gravity, why wasn't it slowed down by the collision as well? actual billiards doesn't occur with colliding galaxies, essentially the entire "collision" is one great mess of gravitic interactions.
so why claim that dark matter only interacts via gravity and then observe that it apparently doesn't?
I'm aware of the nature of the galaxy rotation problem. I was simply throwing that into the pot. The bigger issue with the Dark Matter/MOND debate is that we need more and better data to probe the universe at large scales. What would be extremely useful is to get a better understanding of how "rigid" spacetime is at galactic scales and how massive collections of matter (i.e. - galxies) distort spacetime. Gravitational lensing could yield this information provided we could collect enough data points (density and scale compared against the amount of lensing distortion compared against the distance of the object whose light is being lensed). I'm not an astrophysicist, but I don't think this type of study has been done on a large scale (no pun intended).
That's the sound of a million physicists and astronomers being humble.
Really? 3 Times the number of stars in the Universe? Who was it that said we were fairly close to some Unifying Theory? Someone needs to get they Phd revoked, or at least addend the HELL out of it.
It wasn't wrong for Einstein to add it to the math - it just ended up unneeded. It is simply a way to make what we know work, when we are clearly missing something. You can do a lot with an equation that works even if you can't understand all of the details in it - just ask most math students during an exam. They might know how to get the right answer, but not be able to explain why it is the right answer. Same thing here really.
The reason we think think it is non-baryonic is because we simply haven't found it yet. The masses of the suns and planets are easy enough to calculate, but all the mass we can account for doesn't equate with the spin rate of galaxies that we find. They are simply moving much too fast. If they were moving at the speed they are moving with only the matter we can account for, they would stop orbiting their respective centers and fly out of their orbits. You can read all about it here on Wikipedia.
Moved to http://soylentnews.org/. You are invited to join us too!
'There are observations that have been made which cannot be explained by any quantity of unseen "regular" aka Baryonic matter. This is the result of people actually looking for stuff, and not in their hubris assuming that we have Seen All There Is To See. Indeed it is very much a case of realizing that we have not seen it all.'
-cannot be explained from our vantage point with our current understanding of the universe.
BUT, educated guesses usually and typically lead to almost certainty given enough time, enough observers, and enough thinkers.
scientific community, please keep guessing and getting it wrong, one day you will get it right im sure of it.
> Since they can make predictions with it, and have tons a data supporting there is an effect going on, you're wrong.
Um, no.
http://www.newscientist.com/article/dn13280
From what I've read, a large central mass (e.g. black hole) cannot account for the observed rotation. The mass needs to be spread throughout and even beyond the observable galaxy. I appreciate your question everything attitude, but I'm not impressed with what you know about the field to take you seriously.
XML causes global warming.
FTFA:
Elliptical galaxies posed a problem: The motions of the stars they contained implied that they had more mass than one would get by adding the mass of the normal matter astronomers observed to the expected amount of dark matter in the neighborhood. Some suggested that the ellipticals somehow had extra dark matter associated with them. Instead, the newly detected red dwarfs could account for the difference, van Dokkum says.
So this doesn't really decrease the amount of dark matter in the universe. It simply shores up the anomalous hypothesized excess of dark matter observed for elliptical galaxies in comparison with spirals.
now that, sir, was definitely really interesting, thank you
beware he who denies you access to information for in his mind, he already deems himself to be your master (SMAC-ish)
The story of humanity is full of whole chapters which basically boil down to a bright spark being smothered by a bunch of ignorant fuckwads attached to their idea of how the world works. Every once in a great while the spark lands in a pile of tinder not in the furnace-equipped basement of a firetrap and something wonderful is born, but mostly people shun what they don't understand
+5 Insightful.
Excuse me, wtf r u doin?
OMG, it's full of N I G G E R S!!!
You feel the acceleration caused by gravity. You can the same effect in a different direction by accelerating in a car.
This riddle has been solved a long time ago. It was shown that this "dark matter" is actually just ordinary "doesnot matter". Can we go back to real science like smashing things and burning stuff pretty please?
On second thought, let's not go to Camelot. It is a silly place.
Sorry man, but your "it's all baryonic matter" hypothesis doesn't explain the Bullet Cluster. Feel free to try again when you can explain it using only baryonic matter, though - that should be interesting!
It seems to me that this discovery yielded a change in the calculated number of stars in the universe, while doing next to nothing about "the total number of known stars in the universe".
The story of humanity is full of whole chapters which basically boil down to a bright spark being smothered by a bunch of ignorant fuckwads attached to their idea of how the world works. Every once in a great while the spark lands in a pile of tinder not in the furnace-equipped basement of a firetrap and something wonderful is born, but mostly people shun what they don't understand and it's their children or their children's children who are willing to incorporate it into their lives as an escape from the previous generation who doesn't "get it". This is why the technological singularity is the religion most appealing to the technological elite...
But perhaps just as much due to the ratio of crackpots to revolutionary scientific insight as the fuckwads. Ok, the world has sometimes been in a "burn them at the stake" mode but most of the time it's just lack of sufficiently compelling evidence. Extraordinary claims require extraordinary evidence, it's often reasonable to assume that you've simply done something wrong or ignored some parts that didn't make sense but still punt your pet theory anyway.
Live today, because you never know what tomorrow brings
The human mind just can't really cope with large numbers. The universe is just so shockingly enormous, on the order of 10^80 atoms.
However, this is a tiny number in comparison with others. The number of possible chess games is on the order of 10^123. You'd have to encode 100000000000000000000000000000000000000 games of chess into a single atom to store every possible game.
Of course, you'd need 10^183,800 monkeys to write Hamlet on the first go.
These number all seem the same to me though, on the same order of 10^50 (number of atoms on the earth)
So, does this mean we get more grains of sand on our beaches, too?
http://Communityville.com - A free place for new and old neighborhood webmasters to hang out.
You're way off.
Aesther theories were never "place-holders". Sure, the name was conjured up to describe some unobserved material, but it was very much meant to be a viable explanation of the world, on-par with Newtonian physics.
Secondly, dark matter is not some made up theory, it is very literally a place-holder that exists to indicate that there is an unknown disparity. It's not just the formulas that don't work... scientists observe behaviors that should be impossible. Dark matter literally means that everything indicates there is matter there, but we don't know what it is. It has never been a folk theory. It's only the uninformed who think that there's literally "dark matter". After all, our knowledge of matter and energy is very extensive, and there's very few question marks remaining in fundamental physical forces. If there was a literal form of "dark matter", CERN and Fermilab would have been trying to create or otherwise observe it, instead of always the Higgs Boson.
Slashdot gets worse every day... Pipedot: News for nerds, without the corporate slant
"How does this finding effect the ratio of dark to regular matter?"
Or its existence altogether...
All of this refers back to the big bang theory, of a limited universe being correct and the theory of an infinite universe being incorrect.
The basic problem is that just about all the theories and explanation rests on data collected at the ourter edge of our engineering capabilities or in short we have no real idea of how valid the data that seperate the few dusin different solid state and big bang theories apart is.
The actual data we have of events outside of the milky way is about as precise then the data newton had on internal workings of atoms.
[rollseyes] Oh, please. Horizon problem? Doppler problem? CMBR problem (well, two of them, really)? Anti-matter problem? Dark matter / energy fudge factor / problems? Large scale void problem? Speaking of fudge, inflation? Really? Distant young galaxy problem? And the really big one, the singularity: BB theory doesn't actually oblige us by conforming to what we know about physics. It's just a math model, and it looks a good deal more like dividing by zero than it does 2+2 at this point in time.
I really don't think "successful" in this context means what you think it means. When a theory is riddled with errors and wrong predictions and fails to match the available evidence, "success" isn't exactly the word of choice, even if it's been fudged (and that is the correct word) to match some, though certainly not all, of the observations.
I guess since you can't refute the physics (specifically the fact that our physics don't allow for any of the early stages of what the big bang hypothesis describes), I'll just have to watch your hand-waving. But someone should really sit you down with a cosmologist someday and explain all this to you. It's pretty simple, really; you can only fit so much in a particular amount of space. BB theory doesn't actually work because of that slight inconvenience. So, no matter what it predicts, and no matter what it gets right, something else is wrong: Either it's the theory, or its the physics. But again, you need to hear this from a cosmologist. Or perhaps read up on it a bit.
You'll note I don't refute BB theory. I just point out that it is far from settled. Hilarious that you were knocked so off kilter by that, and even funnier that some slashdot moderator came in here and pulled a "moderator disagrees." Sometimes this place is just a circus of the incompetent. Other than that moment of fine humor, though, how have you been, Chris?
I've fallen off your lawn, and I can't get up.
So the total amount of stars in the Universe is infinite + 300?
I agree with UnknownSoldier on this one. The evidence I've seen for Dark Matter is unconvincing. I'm sure it's useful to assume in certain calculations but I find no reason to elevate it to some kind of 'truism' about the Universe. Had they simply named it 'Unexplained Discrepancy' we probably would not be having this discussion.
Maybe science should just stop coming up with interesting names for things because I've seen this same problem come up with String Theory and the Heisenberg Uncertainty Principle. Relatively benign observations or approaches to solve a physics (calculation) problem somehow get repeated and hyped to a somehow become a deep Matrix-like truism about reality.
One more item. I remember why I stopped coming by here it's because of comments like these:
"Your post shows a large amount of ignorance on this matter, and ignorance on the scientific process."
"The story of humanity is full of whole chapters...................."
Not so much that they were made... rather that they were moded up.
I miss being around smart people and slashdot is full of smart people. However every time I come by I'm reminded that smart people are often pretty unpleasant to be around.
Sorry, I didn't realize anything significant depended on "impressing" you. Someone forgot to pass me the memo. Let me see, am I impressed by your post? No, looks like you didn't even understand what I said, so I guess... no worries. You just go right on with your unimpressed self, there. Isn't life fun?
I've fallen off your lawn, and I can't get up.
Dark energy is some form of "stuff" that is pushing the universe apart, somehow. Saw that in the same show, and I don't know much more about it. And yes, dark energy is about 3/4 of the mass of the known universe, and dark matter is about 80% of the remaining 25%.
By the way, they've built a sensor for dark matter, as it does pass through objects, but not without affecting them with gravity. Which causes the molecules of objects they pass through to vibrate. Heat. And they use that to measure it. ...
They've had some results, but not enough to prove they've found something.
Dark stuff is confusing, and the universe has a damn lot of it.
Of course working on the assumption that Dark Matter even exists. Unless I am mistaken there is no actual direct evidence to its existence and it is used mostly to explain phenomena not fully understood. It may be the modern equivalent of luminiferous ether and disproved in the future.
Of course working on the assumption that Dark Matter even exists. Unless I am mistaken there is no actual direct evidence to its existence and it is used mostly to explain phenomena not fully understood. It may be the modern equivalent of luminiferous ether and disproved in the future.
Well, there's the classic Bullet Cluster. There's something that bends light but is otherwise completely invisible. It's not necessarily dark matter, but other explanations sound even more far-fetched.
But perhaps just as much due to the ratio of crackpots to revolutionary scientific insight as the fuckwads.
Just to be clear, I don't have an opinion on the existence of dark matter because I don't know enough about physics, largely due to an inability (so far) to understand the math involved. If I only I'd had better math teachers :(
It's the people who are saying "there can not be any such thing as dark matter" and especially the people saying "dark matter doesn't exist because we've never seen any" who are the lames.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
Someone mod this +5 goddamn funny, please...
8 of 13 people found this answer helpful. Did you?
But it really seems odd that so many Slashdotters are so rabidly against the idea of dark matter.
I don't think they're many, they're just vocal... Applies to anybody who has a strong opinion, especially when evidence doesn't really support that opinion.
I mean, there's evidence for dark matter, and no good alternative explanations (ie. the alternatives have much bigger gaps in them). No need to get vocal about it, let the evidence speak for itself. But if you oppose dark matter, evidence is quiet, so you must take care of making noise :-)
So this "other stuff" is there, does not interact with itself, but does interact with OTHER matter (light in this case) to create a gravity lens?
I may miss something but to me it seems to contradict. How can its gravity interact with light, but not with itself or the non-dark matter in those colliding galaxies? If it produces that much gravity to create a gravitational lens, why doesn't it pull the rest of the galaxy with it?
Dark matter interacts only through gravity, both with itself and with normal matter. It does not collide with itself or normal matter, nor does it absorb radiation (well, we don't know for sure of course, but it doesn't seem to do that, at least).
In bullet cluster, colliding normal matter (clouds of gas and dust basically) slows down, while dark matter just passes through itself and normal matter. Once past each others, two clouds of dark matter will start to slow down due to gravity of course, but normal matter slows down more because of collisions, radiation pressure and such.
Yep, dark energy is something that pulls things apart. It is a very weak pull, and is visible mainly in the huge spaces that exist betwwen galaxy clusters. Also, it fits some equations about mass creation after the Big-Bang to give us the observed distribution of background radiation.
What you have it wrong is that there is no sensor to detect dark matter. It would be quite a hard sensor to construct, since dark matter affects what is around it only by gravity, and gravity being a very weak force, don't make any visible difference in any medium as it passes.
Rethinking email
Yeah, let's forget that one of the stated goals of the LCH is to observe dark matter.
Rethinking email
> They don't determine the mass of a galaxy by counting stars.
Nope, counting stars comes after a lively round of fisticuffs!
(I was going to go with good geek dating, but any good geek would know to use sampling techniques.)
-- IANAL, this isn't legal advice, and definitely isn't legal advice for you. Also, Squee!
> When they used the new number of red dwarfs in their calculations, they tripled the total number of known stars in the universe.
No, they've tripled the number of estimated starts in the universe.
PS - I like your T-shirts.
XML causes global warming.
You know that's what's great about the universe. Just when you think you know something to some degree of accuracy, and then make up other stuff on those assumptions, we see that we are out by not 0.1% or 1%, or even 10% but 300%.
Science: "Whoopsie my bad!"
My hope is that all that missing 'Dark Matter' turns out to be all those neutrinos zipping around out there. Up until recently they were considered massless, but detection of neutrino flavor oscillations means they apparently must have some rest mass.
Tiller's Rule: Never use a word in written form that you've only heard and never read. You will end up looking foolish.
Planets make up less than 1% the mass of the solar system. We expect about the same ratio of other systems. Also brown dwarfs are tiny compared to a "real" star. So 3x the number of *stars* is not the same as 3 times the mass. In fact the mass estimates won't change much at all. Its not like we haven't though of this before you know.
If information wants to be free, why does my internet connection cost so much?
Postulating Dark {Matter, Energy} is the height of hubris, since it implies that Astronomy Has Seen All There Is To See from our tiny little glasses on our tiny little rock in a backwater arm of the Galaxy.
:)
Postulating that it doesn't exist also counts as the height of hubris, since it implies that Particle Physics Has Seen All There Is To See from their tiny little accelerators on our tiny little rock in a backwater arm of the Galaxy.
That would have slowed down with the *rest* of the baryonic matter that we did observe, because its affected by the other forces. The massive amount of mass that we can literally see its gravitational influence was not slowed down and hence is at best only very weakly interacting as far as all other forces are concerned (most importantly the electromagnetic). aka "dark".
Dark matter is not "dark" in the sense that's its hard to see. But dark in the sense that it pretty much only interacts with other matter via gravity. And we have "Seen" it. Many people including myself had to just admit that dark matter is the best theory to explain the observations after the bullet cluster discovery. I (and many others) where not such big fans of the theory before this.
If information wants to be free, why does my internet connection cost so much?
Historically it was a theory that got a lot of heat within the community as well. The bullet cluster data was the turning point for a lot of people.
If information wants to be free, why does my internet connection cost so much?
originally yes, the math said that galaxies needed to be more massive than they apeared to be in order to behave the way we observe them behaving. At that point one such theory was "maybe there's a whole bunch of non-luminous matter out there we can't see" that's where the term came from.
However, as more observations were made it became apparent that there was "something" out there that doesn't interact directly with light, but does have a gravitational effect. These observations can't be explained by more stars, planets, nebuli, black holes, etc. There has to be something else. That something else has inherited the term "dark matter".
Imagine for a moment observing a gravitational lensing effect and trying to identify the object that created it. You start bay calculating it's mass, and ruling out all know objects that aren't stable at that mass. Then you look for other teltale signs of the remaining objects (emited light from a star, the ecretion disc from a black hole, etc.), but you don't find them. So what is it? well it's dark matter. It's something new and poorly understood because it's really hard to observe. But there have been observations made, and they indicate some very unisual properties that aren't true of "normal" matter.
Every alternative theory to dark matter explains *less* of the observations than dark matter does (typically only one thing ie galactic rotation, but not CMB or large scale structure). Like or love it, its the best theory that fits the data that we have. And despite the fact that its wasn't well like for a long time, a better theory just have not been put forward.
If information wants to be free, why does my internet connection cost so much?
Dark Energy:
The universe seems to be expanding much more rapidly than it "should" be, based on our understanding of the big bang and the contrary pull of gravity. Based on what we currently know, gravity should have slowed the expansion of the universe down by a lot more than it seems to have done.
"Dark Energy" is physics shorthand for "whatever it is that's allowing the universe to keep expanding so damn quickly".
So the contrast is kind of interesting: Dark Matter is to explain why in some cases there seems to be *more* effect from gravity than their "should" be, while Dark Energy is to explain why in other cases there seems to be *less* effect from gravity than there "should" be.
We can "see" darkness. There is no light there in any wavelength... even the CMB. So the "dust blocking light" doesn't work. Lumpiness does not affect galactic rotation and still doesn't really work for large scale structure. Mass estimates wrong? Well then binary stars etc would orbit with different periods to what is observed and galaxies would be either much brighter or dimmer than they are.
The rest of your theory's are "worse" in the sense you are adding not a particle but a force, or changing forces themselves than a dark matter theory and don't explain the observation of the bullet cluster.
Your final speculation is close to just claiming that the FSM did it. Practical useful theory's are preferable(aka dark matter) to "we can't understand".
If information wants to be free, why does my internet connection cost so much?
and we can get rid of ether. I mean, black matter.
^[:wq!
-cannot be explained from our vantage point with our current understanding of the universe.
Heh, very true. And our understanding is certainly limited, and what we do understand could be wrong. And it would have to be in order for these explanations to be explained with Baryonic matter. It'd have to be very wrong. Like, gravity isn't just off by some small factor only noticeable at galactic scales, but somehow pointing in directions that have nothing to do with the mass. Possible, but I'm not holding my breath.
So I guess my point is that it's very unlikely that non-Baryonic Dark Matter will be discarded as an explanation based solely on further observations of normal matter.
Though I'm not sure why that is so important to some people. We already know that non-Baryonic matter exists. Dark Matter could be explained by the discovery of something that is essentially a Neutrino, only more massive.
BUT, educated guesses usually and typically lead to almost certainty given enough time, enough observers, and enough thinkers.
scientific community, please keep guessing and getting it wrong, one day you will get it right im sure of it.
Pretty much. And since they know they're making educated guesses, and know they are probably getting it wrong, I'm going to go with their current best theories as being more plausible than someone who just dismisses all the evidence as "hubris". :)
The enemies of Democracy are
effect does this discovery have on the current estimates of the amount of dark matter in the universe?
The what?
The term "dark matter" on its own, unless you an scientist using it in a specific context, is not meaningful. When a layperson uses it as you have it is meaningless.
You have to specify which dark matter you mean. There is "missing matter" at all distance scales above some relatively modest threshold, but there are quite different constraints on what it might be depending on the scale you're observing.
When anti-scientific nutjobs on /. bitch out the purported arrogance of scientists who postulate "dark matter" they never mention which "dark matter" they are talking about, which does nothing but demonstrate their profound ignorance of the issue.
Galactic dark matter, which is what is relevant to this discovery, is potentially entirely baryonic. That means it could be made of the same stuff we are.
But the H/He ratio in the early universe, and other primoridal isotope ratios that we can estimate quite well based on numerous observations and very solid theory, puts a strong limit on the amount of baryonic matter the universe can contain.
Ergo, at larger scales there is evidence for non-baryonic dark matter, which is a quite different animal, and warrants more skepticism.
There is also "dark energy" on the largest scales, which acts as a cosmological constant and which personally I'm a good deal more skeptical about.
People who are dismissive of all dark matter hypotheses but who do not understand the different roles that different types of dark matter and dark energy play in different theories at different scales are simply enemies of scientific inquiry.
--
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Does this reduce the need for the dark matter fudge ?
Having said that, I just had to point out that even in the article you linked includes other quite plausible reasons:
However, while the Bullet Cluster phenomenon may provide direct evidence for dark matter on large cluster scales, it offers no specific insight into the original galaxy rotation problem. In fact, the observed ratio of visible matter to dark matter in a typical rich galaxy cluster is much lower than predicted.[12] This may indicate that the prevailing cosmological model is insufficient to describe the mass discrepancy on galaxy scales, or that its predictions about the shape of the universe are incorrect.
[edit] Alternative Interpretations
Critics of dark matter have cautioned that astronomers expect sizable quantities of non-luminous baryonic matter to reside in large galactic clusters, positing that the Bullet Cluster phenomenon can be explained without requiring non-baryonic dark matter.[13] However, this explanation requires that baryonic dark matter is of the same amount as the luminous baryonic matter in the Bullet Cluster. This means that ~6 times the visible galactic mass exists at the gravitational centroids, possibly in the galaxies as MACHOs, brown dwarves, or cold gas clouds.
Also note that one additional dim stars are the most likely non-dark matter reason for such an occurrence. We just added 3 times the visible mass to the galaxy at large, calculations only require 6 times the visible matter in that cluster for the same effect without dark matter.
Except all bets are off when comparing earth's solar system to the system around a red dwarf.
Sig Battery depleted. Reverting to safe mode.
Go get laid.
You'll note I don't refute BB theory. I just point out that it is far from settled. Hilarious that you were knocked so off kilter by that,
There is a huge gulf between "not settled" and "just hand-waving", and you of course failed to note that it was the latter I was taking issue with. Of course it isn't settled, nothing in physics is, and yet it is in fact the case that the Big Bang Theory is one of the most successfully predictive theories of the last century. You're completely off base thinking cosmologists would agree with your "hand waving" characterization more than my "very successful" characterization.
I really don't think "successful" in this context means what you think it means.
I am certain you don't know what "successful" means in this context, or why the Big Bang Theory is considered extremely successful by cosmologists. You have no idea why it is the favored cosmology, and why it will take a great deal of evidence to knock it down.
For example you bring up CMBR problems without noting the phenomenal success that was the CMBR prediction in the first place -- did you recognize the graph in that XKCD comic? Or how even in the last decade observations of the polarization of the CMBR have matched predictions of the theory precisely?
You bring up Dark Matter as if it's a problem, rather than a prediction of Big Bang Theory (assuming you meant the non-Baryonic matter which is theorized to make up a greater portion of the universes mass-energy than 'normal' matter), which our other observations of Dark Matter have supported.
The BB has had tremendous success and it is utterly foolish and ignorant to pretend otherwise. It also has significant problems and unresolved issues (like all of our most advanced theories), but when weighed against the correct predictions, then yes, that's called "successful".
I guess since you can't refute the physics (specifically the fact that our physics don't allow for any of the early stages of what the big bang hypothesis describes), I'll just have to watch your hand-waving.
You can't refute the BB's tremendous success, not least because you appear to be completely unaware.
And I see no point in denying that there's a big problem with current physics and describing energy densities at the level of the first instant after the Big Bang. GR predicts singularities, too, which is a problem when combined with things like the Pauli Exclusion Principle but I don't hear you calling that or QM "hand waving". It is well known that high-energy physics is an area where we need a lot more development and that our best theories don't play nice with each other in this domain.
And yet, starting nanoseconds after the unknowable and hypothetical Singularity, the Big Bang model allows us to make extremely accurate predictions about many aspects of the development of the universe. Clearly not everything, yet clearly much more than you believe.
So, no matter what it predicts, and no matter what it gets right, something else is wrong: Either it's the theory, or its the physics. But again, you need to hear this from a cosmologist. Or perhaps read up on it a bit.
Yes, of course something is wrong. We know something is wrong. We know something is wrong with GR and QM and the Standard Model. Yet no cosmologist would call those, or BB, anything but what they are: Extremely successful predictive theories. Even cosmologists who are coming with alternative theories must acknowledge that. So while BB Theory is wrong, far more wrong is your belief that cosmologists, or scientists for that matter, would agree that because it's known to be wrong, the BB Theory is "just hand waving" and not "one of the most successfully predictive theories of the last century".
Because, as any cosmologist or astrophysicist can tell you, wrong is relative. Maybe try talking to one.
The enemies of Democracy are
What if anti-matter produced anti-gravity (i.e. the "Dark Energy")? Shortly after the Big Bang occurred the matter/anti-matter annihilations, with scientists always wondering why matter prevailed. Well maybe anti-matter is having the last laugh as it is "still there" and causing the runaway expansion of the universe.
I come here for the love
We know specifically that the missing matter is non-baryonic due to the CMBR measurements. The CMBR gives us a snapshot of the universe at the time of recombination (~370k years old). By studying the patterns of density, the cosmologists can caluclate the ratio of overall mass to mass that interacts with light (that is total matter vs non-dark matter) with some real precision.
Baryonic matter is affected by light pressure (technically, the elctrons are directly affected, but they drag the nuclei along with them as the move) and gravity, while dark matter is only affected by gravity. The harmonic oscillation of more dense and less dense areas of the early universe (the music of the spheres) gives the ratio between the two, in the same way you observe the oscillation of a mass on a spring and determine the spring constant.
Socialism: a lie told by totalitarians and believed by fools.
So ordinary matter accounts for 4.6% (1/20th) of all mass+energy in the universe - this I suppose has to do with Einstein's E=mc2 that allows for mass to be converted to energy and the other way around.
More correctly, Einstein's E=mc^2 says that mass Is energy and vice versa. It's not an equation that only applies when performing certain conversions, it is an equation that always holds true. Mass and energy are equivalent. It's why a bound molecule has less mass than the constituent particles despite every particle still being present. It's not that when oxygen and hydrogen combine in an exothermic reaction to form water that mass is converted to energy. It's that the escaping energy, by the equivalence principle, has (is) mass and always did.
It's a subtle difference that it took me a while to grasp and then accept. But E=mc^2 is about much more than just the fact that if you annihilate matter with anti-matter you get a crap-load of energy released.
The enemies of Democracy are
Pressure AND gravity slow matter like interstellar gas clouds down. Only gravity slows down dark matter. We have observed gravity slowing it down. Just not as much as the gas clouds that get slowed down by pressure.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
People here think they are smart. Some of them are. Some are not. Some that think they are smart, but are not, like to try to prove their intelligence by being contrary. Basically, they take any scientific story, think about it for thirty seconds, come up with one objection based on their misunderstandings, and run that objection into the ground.
They believe this demonstrates their intelligence.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
Your point one and two are functionally equivalent, rendering your whole point rather moot.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
However, interesting theories (such as Hoava–Lifshitz gravity [wikipedia.org]) have sprung up that try to explain the effects we see without requiring the intervention of an exotic matter/energy mix.
What's so exotic about a new type of Lepton? We already know of particles with every required property for Dark Matter except for sufficient mass. We have theories that predict the existence of such particles for reasons that have nothing to do with dark matter. That means it is still theoretical and quite speculative, but I don't get why there's such a desire to avoid introducing a new particle that is a logical extension of the existing Standard Model.
And I thought most alternative gravity theory projects had given up on explaining Bullet Cluster and other observations without non-Baryonic matter, since in pretty much any gravitational theory it's still going to hold true that mass is attracted to other mass, not random locations in space. MOND already has, I know. Not that the theories aren't still interesting; there are more important consequences to alternative gravity theories than obviating the need for a heavier neutrino.
The enemies of Democracy are
Um... you seem angry.
I'm definitely not anti-science, and I don't think I'm a nutjob, but I'm not an astrophysicist; this is my first time hearing about baryonic dark matter. I think your expectations of laypeople are a little high. You have, I think, answered my question, though.
Correct me if I'm wrong, but you're saying that this doesn't affect current estimates of non-baryonic dark matter (what I was referring to as "dark matter") because that stuff is used to explain phenomena relating to structures larger than galaxies.
I explicitly release the above into the public domain.
Not to be too pedantic, but from what I remember of what little I studied of philosophy of science your statement is problematic:
It's not just the formulas that don't work... scientists observe behaviors that should be impossible.
Formulas "don't work" when observation doesn't agree with them. Observations are considered as "should be impossible" when they disagree with the interpretive/explanatory model being used (often formula-based like e=mc^2 or whatever). There's no difference between the two statements, as best I can tell. Like I said, kind of pedantic..
Is that you, Sheldon?
Bloody Hell. I will tell you all once again the invisible thing that is bending light is a large group of gravity waves and if you look behind it you can't see the dark matter (but may stub your crotch on it)
The new right fascists are bilingual. They speak English and Bullshit.
WTF? what does that have to do with *anything*. Double the mass of every red dwarf, and you change nothing.
Also see ...
Bubbles of Energy Are Found [in our] Galaxy [Center]
http://www.nytimes.com/2010/11/10/science/space/10galaxy.html?scp=5&sq=galaxy&st=cse
Looks like Science/Scienctists might discover White Holes as early as next year if this keeps up. :-)
There's a big difference, actually. The "formula" wasn't pulled out of the air, you see. It is an accepted theory because it was "proven" with observations (closer to home).
While it's always possible to formulate some (more complex) equation based on updated observations, that wouldn't help to solve the "near-far" problem, that the physical laws we observe here, doesn't match the action we observe at great distances...
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A majority of the mass in each cluster, like in most clusters, is in the form of diffuse inter-galactic gas. While it's diffuse, it's also a lot more compressible than matter which has condensed into stars. The dark matter and the stars of the galaxies in each cluster slid past each other with very little interaction (compared to the amount of mass involved) while the gas clouds interacted much more strongly, heating the diffuse atoms and molecules to the point of ionization and emission of x-rays.
Sure, some stars would have collided into one another, and dark matter may be very weakly self-interacting or may interact through the weak nuclear force with baryonic matter, but the evidence of such interaction is drowned in the noise of the emissions from very normal looking stars and interstellar dust.
So we can use gravitational lensing to see where the mass of the clusters is now. There are five main chunks of mass: a pair of invisible blobs that have a very low gravitational potential, trailing behind the centres of mass of those blobs, lots of ordinary looking galaxies (with a lower gravitational potential still), voids of relatively high gravitational potential, and in the middle a huge amount mass-energy in the form of hot, radiating gas.
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Anyway this whole "dark matter" thing sounds to me like the hypothetical "aether"
And every time I read that, it sounds to me like another arrogant, know-it-all Slashdotter who thinks he's smarter than the thousands and thousands of PhD's who've studied this topic... despite only knowing enough about DM to state that it 'has to do with gravity', while not even 'understanding 'the "dark energy" part or how that's measured'.
Aether was coined by just those PhD's or whatever they were called at the time. It is not that they were fully correct there either.
I know I'm not smarter than them; I acknowledge that there are problems with the current models, but this "dark matter" sounds simply like a something made up just to make things add up. It's not even sure whether there is indeed more matter out there, or that the theories are simply plain wrong. Or both.
Just because someone has PhD in front of his name doesn't mean they're always right, or that we should just believe them without further thought.