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"Dark Matter" Observed
An anonymous submitter writes: "The space news site Space Flight Now has an article about the first direct "observation" of so called dark matter. Galaxies appear to have more gravitation (mass) than we can currently observe. The theory of dark matter tries to explain this missing mass by the existence of massive bodies too faint to detect. These bodies include everything from dim stars to exotic particles called WIMPs. The previously dark matter, a dwarf star, was detected when it passed in front of a brighter blue star, creating a gravitational lens. It is thought that there are many more like it out there creating all that extra gravity, we just can't see them." Wired has another story; or see the European Space Agency's original article.
How long until Dark Matter is banned as a circumvention device for light waves?
The universe is held together with duct tape and karma. What goes around, comes around, and gets stuck to your forehead.
The fate of the universe is held by dark matter. Without dark matter, there is insufficient gravity to bind all matter together forever. If there is enough dark matter, with its attendant gravity, then eventually the universe will collapse back onto itself. Probably the end result of that would be another Big Bang.
What a pair of choices.
So long and thanks for all the fish . . . !!!
The result greatly strengthens the argument that a large fraction of the 'normal' Dark Matter in and around our Galaxy exists in the form of MACHOs and that this Dark Matter is not as dark as previously believed!
Does anyone else have the feeling we are just playing peek-a-boo.
"Hey, its dark in here. Where did everyone go?"
"Ummm, move your hands!?"
"Oh, there they are. That was really weird!"
You've just got to love cosmology...
Dark matter is increasing, the universe is going to expand until we are so far apart that we all freeze to death.
The universe will not collapse, that theory was proven false a long time ago. Since its proven that we are moving apart, Its safe to assume that we will move apart forever.
Also for big bangs, Big bangs happen all the time, in fact Big bangs are happening right now.
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The observed object is a dwarf star. It is luminous. This article should have been titled "Confirmation that one of the MACHO objects is not Dark Matter".
Liberal (adj.): Free from bigotry; open to progress; tolerant of others.
Correct me if I'm wrong, but the article said MACHOS were just really large clumps of normal mass that don't emit any light, so when they say they've found MACHOS, they mean they've just found stuff. You know, really big rocks and such. It's impressive that they's partially proven a theory that would explain where all the dark matter is, but it really sounds like they're trying to sound impressive when they call what they've found MACHOS. Why not just "rocks", or "stuff"?
Mr. Spey
Cover your butt. Bernard is watching.
Is the theory which says, at any given moment the universe can simply destroy itself, and while the chances are 1 in a billion or something really high and unlikely, the possibility is there for ALL matter in the universe to cease to exsist.
Time wont end, just our lives. Even if matter no longer there in this form, its energy will still be there
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We are already pretty sure that most of the missing matter must be non-baryonic (i.e., it must be made of something other than protons, neutrons and electrons).
Liberal (adj.): Free from bigotry; open to progress; tolerant of others.
...it's that stuff in the back of my refrigerator!
:)
which means its time to move
Recursive: Adj. See Recursive.
It was indeed Bohdan Paczynski who wrote the first paper about that specific phenomenon, if I recall correctly, the paper was titled "Microlensing on small optical depths". And indeed, he was the one who invented the term "microlensing".
However, I'm more concerned with "extragalactic" microlensing. The funny thing is that stars in remote galaxy can cause microlensing of even more remote quasars. This was first discussed by Chang and Refsdal in an article in Nature, December 6 1979.
The great thing about this is that in galactic microlensing, there are very few MACHOs between us and the stars, so you would have to watch a lot of stars (millions), whereas in extragalactic microlensing, there will be lots of stars, so microlensing events happen all the time. You only need to separate it from the intrinsic variations of quasar...
Now, galactic microlensing has been a so much bigger field of study than extragalctic microlensing, we haven't really got that much attention. In part, it can be becuase galactic microlensing gives so much more solid results, but then, it is just addressing what's going on in our backyard, while the extragalactic microlensing really deals with the universe... :-)
Employee of Inrupt, Project Release Manager and Community Manager for Solid
I, too, used to think that 'dark matter' was some powerful, mystic thing that sucked in light like a black hole.
:)
My current understanding is that dark matter is just normal matter that doesn't emit light. For reference, all matter does 'suck in' light (meaning the energy is absorbed, usually given off as heat).
So, I'm gonna go soon, and eat my dark-matter lunch
Moderation: Put your hand inside the puppet head!
My biggest problem with modern science (physics and astrophysics in particular) is this truly inane method of making "conjectural" observations...that is, assuming that and unobservable activity has been proven simply because something observable has occurred. It's an antiquated way of doing things, and it seems totally backwards. This is a good example...all this time, physicists have assumed that "dark matter" - the matter that provides a great deal of the gravitational force that holds the universe together - is "invisible" or "unobservable" or in some extreme cases "existing in a separate yet intertwined reality". Doesn't it make a LOT more sense to think that dark matter is just the stuff floating around that doesn't have any light bouncing off of it? What, just because we can't see it with our super-expensive orbiting telescopes means that it's invisible? I can COMPLETELY believe the idea that dark matter is just regular matter that isn't being illuminated or is not emitting enough radiation for us to detect! But it seems that this, the most obvious explanation, is the last one that physicists want to believe.
I really think it's past time for these researchers to change the way they think about the universe. Stop making it so difficult on yourselves. There really CAN be very simple explanations to difficult problems. And sometimes - sorry to tell you this - you're not going to be able to determine EVERYTHING that you want to figure out. That's the way the universe works. Give it time - a LOT of time. Don't come up with unprovable theories to explain irrational phenomena. LET THEM REMAIN UNEXPLAINED UNTIL WE ARE BETTER ABLE TO OBSERVE THEM.
as a matter of fact, it's all dark.
The funny part is, within 90%-95%, this is really true of the entire universe.
The living have better things to do than to continue hating the dead.
Wonderful bit of observation.
/unit space. That will let us get at least a rough estimate of how much of the universe's dark matter is bound up in these MACHO's.
But the teams are going to need to be funded so that they can do a complete survey of a larger area of the sky, and begin to get a bound on the number of MACHOs/galaxy or
Anyone know what the longer term funding situation is here? Is it NSF funded?
In illa quae ultra sunt
Also, every object currently moving outward from the center of the universe is being slowed but the sum total of all of the gravition of the objects behind it.
There's no such thing as the centre of the Universe. If there was we'd be able to tell whereabouts we were because everything would be rushing away from the centre. Instead the Universe is isotropic and homogenous - ie. it looks the same in all directions and from all positions. Wherever you are in the Universe you'll see the rest of the Universe spreading away from your position.
And anyway, whether gravity can slow down the expansion of the Universe enough depends on the amount of matter within it, which is a conserved quantity. Of course, as gravity follows an inverse square law the forces slowing down spacetime expansion get weaker over time, and we just don't know whether there's enough matter so that gravity is strong enough.
Probably not, but who knows?
Learn about a dark light here.
"Coffee should be black as hell, strong as death, and sweet as love." -Turkish Proverb
Well.. neither am I. But that's what science is about. Observation, hypothesis, experimentation, etc.
It's not BACKWARDS. It's a big universe.. so we need to have a good idea of what to look for.
I think it was perhaps thought that, if this 'normal matter' accounted for what we saw, we would SEE MORE OF IT, because it's not hidden.
Oh. BTW. We observe electrons, quarks, and the rest of the subatomic particles only through your so-called 'conjectural' observations. Same with some of the 'properties' of these particles.. they exist purely in a mathematical model that works for a certain set of cases; it's not complete.
The point is that they think it's likely that, given the amount of 'missing' matter from what we have observed to date, there may be some 'exotic' reason we can't see it.
Seriously, even if no central point can be defined from a distance perspective (which I am perfectly willing to accept), there must still be a gravitational center - a location where the amount of matter, and the average of that matter's distance works out to be roughly equal in all directions.
That's the whole point of it being isotropic and homogenous - there is no single preferred point at which you can say "this is the centre". At any point you choose there is a (approximately) uniform distribution of matter in every direction. Sure there are local irregularities (galactic superclusters for instance), but on a large enough scale this uniformity seems to hold.
Of course, this is speculative, and as much as I'd like to see a unified theory of everything someday, I don't know that we'll ever get there. The thing I like about the cyclic Big Bang/Big Crunch idea is that it puts us on a timer! We don't have forever to solve all of the riddles of the universe... It's more like (Forever - 1).
Heh, well the latest theory to come out of superstring research is called the Big Splat, and involves four-dimensional manifolds embedded in a five-dimensional manifold, of which two collide and start the Big Bang...
Dark Matter is not as dark as previously believed!
Does this mean that the jedi knights are winning with the fifth element weapon?
Star Wars episode III: The Perfect Element, Source of Clones!
The article says that they observed the microlensing event several years back and then recently took another look at the area using Hubble. They found a faint red dwarf which probably cause the lensing of the nearby (arc second wise) main sequence star.
So, if we can observe the 'dark' matter as being a red dwarf, it's not exactly 'dark' is it? I would assume that objects like red dwarfs, if observable, would have already been counted in the total 'bright matter' column. If not, someone is just undercounting objects that are observable using normal astronomical methods, and needs to go back and make a better estimate of how many of them are out there.
-josh
If in fact dark matter is matter which exists gravitationally but will not interact w/the EM spectrum, wouldn't you be able to feel it with your hands but not see it? (Provided you have a small bit of it nearby)
:)
Then, couldn't you somehow use this "material" for stealth purposes? Body armor making you invisible, etc. etc.
I find it amusing that as humans, we can only detect the existence of something if we can collide EM particles w/it (photons, etc.) We should rephrase a familiar motto to be "I can interact w/EM particles, therefore I exist."
Praying for the end of your wide-awake nightmare.
In my kid's diaper..
In that catbox....
Oh wait.. that's not what you're talking about, is it?
Polymorphism -- It's what you make of it.
I can COMPLETELY believe the idea that dark matter is just regular matter that isn't being illuminated or is not emitting enough radiation for us to detect! But it seems that this, the most obvious explanation, is the last one that physicists want to believe.
I used to work in a research institute that had a lot of physicists in it, and I think most of them would prefer the mundane explanation. However, they would not rule out wild possibilities, and the minority that preferred the wild possibilities would not rule out mundane explanations.
I think that your problem may be with the reporting of science, which I agree sucks. One thing I have learned (rather painfully) upon my transition from research science to industry is that scientists operate and think very differently from the way journalists think. The journalist tries to translate what the scientists are saying into what he and/or she thinks is the language of most people. This causes distortion, for two reasons:
I dealt with a lot of journalists during my 13 years as a research scientist, and I cannot think of a single instance where the journalist got the story even approximately right. The worldview of the journalist is simply too different from the worldview of the scientist. Very, very few scientists are gifted enough with words to provide alternate explanations, and even when they do, they are usually ignored by people who have read a lot of journalistic reviews of science and love to tell the scientists that they're wrong.
Scientists love to toss around wild guesses and argue fiercely about them. The reason they do this is that this process stimulates imagination and the generation of hypotheses, which give hints on what to look for. The sky is just too big simply to passively look around and gather evidence that you will synthesize later. That approach might be ideal if we had an infinite number of scientists, but we don't. The next best thing is to have a diverse community of scientists, each looking for a different thing. Most may be looking for mundane explanations, but a few will be following wild hairs. This is not a bad thing, because whether the wild hairs turn out to be supported or unsupported, knowing this information reduces the number of ideas that have to be considered. Eventually, if we're lucky, a consensus eventually emerges. But, remember, this is the first observation of a class of objects, not the last.
So, some people will be looking for A, and some will be looking for B, etc. Some of them will get evidence that confirms their guesses; some will not, but all will contribute to the sum of knowledge.
It's a bit like doing detective work. You can't just put cameras everywhere and feed the output into a massive algorithm that solves all possible crimes. Instead, you have to follow leads, guesses, hunches, etc. The only difference in science is that a lot of scientists are doing it, and they tend to keep each other honest.
Now, the journalist wants to make a good story, above all. The mundane does not make a good story. Neither does the concept of a working hypothesis, a guess, or a hunch. So, the journalist (or ESA public relations department or whatever) writes a dramatic story focusing on the exciting bits.
Then, finally, when it gets to the readers, they conclude that something is an Explanation from On High, when it is really nothing of the kind. That's just what happened to it in the process of translation through the journalist.
One thing about science that usually doesn't get around is that the scientist is always in doubt. No scientist is really, deep down, 100% sure of anything. He and/or she may be close to 100% sure, but that isn't a trivial difference; it's a vast chasm in a philosophical sense. This is a very difficult thing to learn, and some scientists forget it. The best scientists, however, do remember it, and some are articulate in describing it, such as Richard Feynman. It isn't a need that most people have to deal with at all, and so explanations tend to be ignored.
For the notion of "dark matter," nobody is even close to 100% sure about anything. The whole need to look for dark matter is because, without it, the equations and predictions relating to the big bang look ugly and unbalanced. That may seem like the flimsiest of reasons, until you remember that radio and relativity were developed as a result of precisely that kind of aesthetic judgement of Maxwell's equations. It could all turn out to be totally wrong, which leads to another poorly understood aspect of science: the most effective evidence is that which is against an idea, not for it. However, the best way we know of to find evidence against an idea is to look for evidence for an idea. This is another psychological trick: if you are emotionally attached to an idea, you will try much harder to show it is correct, and a failure to do so means more than a failure of a casual effort. If you do unintentionally distort evidence to support your hypothesis (this happens all the time, far more than outright fraud), there is always somebody else who will poke holes in your ideas. This is good, not bad, but it's very hard to translate that into the language of most people, where auditors are the enemy, not friends.
if the universe were to go into a big crunch we will be moving back toward the center.....
Not at all. Using the usual analogy think of a universe with 2 spacial and 1 time dimension, where the spatial dimensions are on the surface of a "balloon." As the universe expands (as in blowing the balloon up) things get further apart, but equally so at every point on the surface of the balloon - there is no "centre". Equally so for when it is contracting - it contracts everywhere equally and there is no centre of contraction on the surface.
Extrapolating from a 3-d sphere to a 4-d hypersphere, it's easy to see there doesn't have to be a centre in this case either. It's just a lot harder to visualise :)
From the page you linked to:
In the above all-sky map, radiation in the Earth's direction of motion appears blueshifted and hence hotter, while radiation on the opposite side of the sky is redshifted and colder. The map indicates that the Local Group moves at about 600 kilometers per second relative to this primordial radiation.
The difference between the two halves of the sky is due to the relative motion of the Local Group of galaxies, not some "centre of the universe" effect.
Probably because he's a Brit. The spellings of many words in American English differ from that of The Queen's English. This is largely due to the anti-British sentiments held by Noah Webster: he intentionally revised the spellings of many words to differentiate the American language from it's ancestor. It helps to know that Noah Webster was a student at Yale during the Revolutionary War -- during most of his lifetime, England was the enemy of the U.S., not the close ally it is today.
Why is it that the proponents of "one nation under God" are so eager to get rid of "liberty and justice for all"?
Dark matter will be declared a terrorist tool. Anyone found harboring dark matter will be found guilty of aiding and abetting terrorists.
BTW, I've always wondered, is the matter that has been sucked into black holes considered is the total matter of the universe equation? It seems that everywhere they look, they find another black hole. Maybe there's alot of unaccounted matter out there.
Just word play, the Weakly Interacting Massive Particle theory (WIMP) was competing with the MAssive Compact Halo Object (MACHO) theory.
They don't need to not emit ANY light, they just need to emit so little we can't normally see them. If the interstellar dust absorbs most of the light emitted by a distant dwarf star we can't see the light from the star. So we don't know there's a star there, but we can see the effects of it's gravity.
Maybe the Hubble lens has a smudge...
Randomly clicking into the moebiac abyss...
I used to believe the universe would eventually go through a Big Crunch/Big Bang cycle again. But the recent discovery of an expansionary force acting on galaxies (ie: the universe is increasing its rate of expansion, "blowing up quicker") has been a bit of a slap in the face for that point of view. So we're back to an open universe: it is basically a big firecracker destined for heat death.
Having a bunch of dead stars hanging around galaxies would seem to indicate a sort of "fossil history" of our galaxy. I wonder how far out these relic stars go out from the center... I mean, our system is pretty far out, but we may be the equivalent of the Earth in relation to an "Oort Cloud" of dark matter in our (somewhat bigger) galaxy.
A friend of a friend, who is doing post-grad work in Physics at Clown College, has just switched majors from particle physics to cosmology, which is a pretty big switch. I think he's smart: astronomy and cosmology are going to be the next Big Science soon enough.