Slashdot Mirror
Dark Matter Discovered
sebFlyte writes "Wired is reporting that scientists have come up to a solution as to where all the matter in the universe actually is. Experiments being done with Chandra, NASA's X-ray telescope have shown up a likely candidate for the solution of the dark matter problem. There are massive quantities of Baryons in a super-heated gas cloud several hundred million light years away."
There are massive quantities of Baryons in a super-heated gas gloud several hundred million light years away."
Which, IMHO, is a damn fine place for them to be, rather than here.
The absorption pattern, as detected by Chandra, is consistent with interference caused by carbon, neon, nitrogen and oxygen ions -- in other words, baryons.
It's really a neon sign on Frogstar World B announcing the construction of a restaurant to be constructed on this location in several billion years and reservations are welcome.
"Assuming that what we see is a standard portion of the universe, we extrapolated the data and derived the volume density (of baryons in all the clouds) -- and it's consistent with 50 percent," said astronomer Fabrizio Nicastro, of the Harvard-Smithsonian Center for Astrophysics and lead author of the study.
Later a two-headed, three-armed man entered and ate a piece of fairycake and destroyed their model.
Whereas baryons account for 4 percent of the total matter and energy in the universe, dark matter is thought to make up 23 percent. The remaining 73 percent of the so-called matter-energy budget consists of what scientists call "dark energy." This energy acts like an anti-gravitational force that, in theory, is causing the universe to expand rather than contract.
And here I thought it all existed somewhere along Lucas Valley Road and explained the Jar Jar character and Episodes I-III...
A feeling of having made the same mistake before: Deja Foobar
And would this "superheated gas pocket" perchance reside in Nibbler's lower intestinal tract? ;D
In case anyone's wondering what a baryon is...
http://en.wikipedia.org/wiki/Baryon
I don't see anything??
Here's a picture.
I think the dark matter is in the mods brain.
They found some of the ordinary matter that has gone unaccounted for, not dark matter. Read the article.
CDE open sourced! https://sourceforge.net/projects/cdesktopenv/
scientists have come up to a solution as to where all the matter in the universe actually is.
In the middle somewhere?
This discovery will bring back Enterprise!
Nope can't do it. =)
Those giant gas clouds got a Baryon enima?
Never answer an anonymous letter. - Yogi Berra
"There are massive quantities of Baryons in a super-heated gas gloud"
Google wants to know if you mean "gas cloud".
Wired is reporting that scientists have come up to a solution as to where all the matter in the universe actually is.
WIRED also said that "Push is the next Big Thing."
I've always enjoyed how everything has an "on" suffix to it in physics.
What happens when someone by the last name of Mor finds exotic particles?
Morons I tells yous.
What about some science dude who goes by Hal?
Halon I tells yous.
Yes! I listen to NYC Speedcore and do math at 3AM. I suggest you try it too.
In physics we don't call it dark matter. We call it "make the theory fit the data" matter.
The summary is not correct (big surprise there) in that this is a confirmation of a long-suspected theory as to where the missing ordinary (baryonic) matter in the universe is. This does not solve the dark matter problem at all.
9
Read more at the press release from the Chandra team at Marshall: http://www.spaceref.com/news/viewpr.html?pid=1604
Dark matter is yet another topic altogether, as is the even more elusive dark energy.
They are extremely interesting for anyone fascinated with physics.
Creative Demolition
With the massive quantity of Barry Whiteon gone, cool, heavy dark matter is ruled out, I guess.
Don't disappoint your bird dog. Go to the range.
This should be "Missing Matter Discovered" not "Dark Matter Discovered"
They HAVE NOT found dark matter, they've found the 'missing matter' as the article says. They have found a clue as to the dark matter, as a result of the discovery.
Although discovering the dark matter would be much cooler, (yeah I was excited when I read the title).
[rant] Why is it the only 3 times I've 'emailed the on duty editor' before publishing, I've been ignored and the mistakes gone through?? [/rant]
Windows in 6 Bytes (IA-32) : 90 90 90 90 CD 19
I mean really now, Baryons, oh come on nasa. Try something new and exciting like, antiquantafusitrons.
Your mom's weight is the answer to Fermat's equatione e235b3f26a3a14acabf5b&PID=18&PHPSESSID=3e618ab1a0e e235b3f26a3a14acabf5b
http://yourmom.com/index.php?PHPSESSID=3e618ab1a0
all those Water discovered on Mars stories. Astronomers invented dupes. Or maybe they were trying to give someone a hint.
The message on the other side of this sig is false.
google has bought up all known dark matter.
"Baryons, along with mesons, belong to the family of particles known as hadrons, meaning they are composed of quarks. Baryons are fermions composed of three quarks, while mesons are bosons composed of a quark and an antiquark."
Wikipedia cleared that one up nicely!
-=test-sig_0.1.5(NoWhitespaceVersion)=-
This title is somewhat misleading... considering they did NOT actually find dark matter. They found baryons... baryon != dark matter.
I thought Baryons and dark matter are two different things. It was my impression that the clouds of baryons mass they discovered were suppose to be "out there" and and we know what it's comprised of. Where as with dark matter, our scientists have no idea what it is or what it's made of. All we know is it's exerting gravitational forces and is holding back the expansion of the universe. As far as I'm concerned this discovery did nothing to shed light on dark matter... Can any astrophysists out there explain more?
It was only a (dark) matter of (space) time.
Sincerely,
Pan Tarhei Hosé, PhD.
"Homo sum et cogito ergo odi profanum vulgus et libido."
Is how do these extremely difficult scientific questions get answered so quickly lately.
It was just a couple days ago that slashdot reported that dark matter was being postulated as the reason for the extra mass of galaxies:
Simulating the Universe with a zBox.
Now, in less than a week, we have proof for the existence of dark matter? Amazing!
How can scientists go from hypothesis to proof in such a short time? Are we really progressing by such leaps and bounds? Or, is this an example of media jumping to conclusions about initial research.
Hey! Stop copying my sig!!! Stop copying my sig!!! Stop copying my sig!!! Stop copying my sig!!!
the fact that this got modded "funny" is proof of that.
Its the hunters running away from the stench of Bloodnut the flatulent...
Every component of matter has an anti, correct? Light itself is a wave/matter combination, notably photons. However, what I read says that photos are their own anti. Does this mean I have no hope of making a flashlight which makes things darker? Is it possible for two photons moving in different directions to cancel eachother out (destructive interference)?
In other words, if regular stuff is about 5% of the energy density of the universe, with dark matter at about 20%, and dark energy at about 75% -- the stuff in this story comes into that 5%, ie, regular stuff and not dark matter.
Here's what I do: Bitty Browser & Andromeda
I have it on good authority that all the dark matter is in Iraq, and that's why we had to invade.
Tachyons are in fact hypothesized faster-than-light-particles, appearing for instance in certain string theory scenarios.
:-)
But baryons are by no means the counterpart to tachyons. All known elementary particles in the universe are either fermions (particles with spin in integer multiples of 1/2) or bosons (particles with integer spin). Bosons include the photon, the gluon and many others. The fermions are further subdivided into leptons and quarks. Leptons include the electron and the electron neutrino among others. Baryons are particles made up of three quarks, and are fermions and include among others, the proton and neutron, which are the most commonly found baryons in nature, since all heavier baryons normally decay.
Two quarks (fermions) can combine to form mesons, which are in fact bosonic in nature (since two quarks with spin half combine to form a particle with integer spin).
Hope that confused the issue a little
A bit more on-topic: Finding baryons in this amount is a big deal, since baryon has previously been suspected to primarily exist in galaxies, and only in small amounts outside galaxies. While it by no means doesn't solve all problems of cosmology, it is a big help.
I thought baryonswas under my bed, now I dunno what is that stranger things.....
http://www.michel.eti.br
So they say they've found the missing matter, but nowhere in the article do they actually tell us where all the missing socks went. Sure sounds like a scam to me!
Yet another place we'll soon see another Starbucks.
- Just my $0.02, take with a grain of salt, your mileage may vary.
Now, on to the puzzling challenge of explaining the reasoning behind female group behavior in restroom explorations...
Puzzling? You should hang out with more females. They're just talking about someone who's still sitting at the table. They usually know what each other is thinking about a person so when one says "I'm going to the bathroom" it's like announcing "If you're thinking what I'm thinking, come with me to discuss it." When the other says "Ok I'll come with you" they're acknowledging that they're thinking alike and they will come and gossip. There really isn't much mystery to females, but I've been fortunate enough to have a sister close to my age so we hang out a lot (usually with her girl friends) so I get to pick up a lot of info.
Anyway this is way off topic...
> > In case anyone's wondering what a baryon is...
> > http://en.wikipedia.org/wiki/Baryon
> In case anyone's wondering what slashdot is...
> http://www.slashdot.org/
In case anyone's wondering why the hell am I wasting my time so pointlessly.... I have no life.
Is this a case of a reporter being out of his depth?
I'm sure it's already in layman's terms as your average reader of Wired probably still has their eyes glaze over when you bring up the Life of Small Black Holes (an actual talk at our Astronomy Club, which still has me scratching my head.)
Or maybe it's me, a Slashdot poster?
<Bugs Bunny Voice>Nnnnnyyy could be!</Bugs Bunny Voice>
Place your bets! :-)
I'd go with the less general term 'baryons' over 'general purpose matter' as it give it some mystique, which always helps when going for funding.
A feeling of having made the same mistake before: Deja Foobar
As I understand it dark matter is a broad term for matter that equations tell us exists, we just can't see it. These Baryons, apparently very heavy, solve some of the problem, maybe all, because it's more mass that we didn't know was there before. It came out of the dark. Nobody knows if there is another class of matter but clouds of baryon fill the gap.
-- Checking emails and kicking cheats `till the day I die.
They reversed the anti-proton to tachyon ratio in the main deflector array after flooding it with a plasma burst diverted from the warp core and then polarising it by reinforcing the nucleon field.
Drill baby drill - on Mars
Wasn't Google looking to buy up all the Dark Matter, not too long ago? Sware I read it here...
"Who are in control, they are not in control of anything - they don't even control themselves!" - Glen Beck
I thought one of the sure indicators that showed the presence of unseen matter was that most galaxies behaved as though they were more massive. That the rotational energy of many/most/some galaxies should be ripping it apart, yet clearly there was some extra amount undetected mass in a galaxy that held it together.
These clouds are great for a macro-framework missing mass solution but unless they are found to exist in a somewhat smooth (or central) distribution in a galaxy how would massive clouds several hundred million light years away provide a solution for cases like this?
Huntred
Assuming that what we see is a standard portion of the universe
An astrophysicist, a physicist, and a mathematician are attending a conference in Scotland. During a break, they take a walk through some of the countryside, and come upon a black sheep.
"Aha," exclaims the astrophysicist. "I had no idea that all sheep in Scotland are black."
The physicist looks at her colleague in disbelief. "All sheep in Scotland are black? Are you nuts? We've only seen one sheep!"
The mathematician interrupts. "And only one side of that sheep."
Which is what they're constantly doing. I heard the theories in my astronomy class. There's plenty of them, such as brown dwarves just drifting around out there. How do you explain them? Well some star has a vector or some light appears bent (lens effect) and it's figured there's some large enough object out there not emitting light which is doing it. And who's to say it isn't large amounts effectively of bits the size of pea gravel drifting around?
In other words, if regular stuff is about 5% of the energy density of the universe, with dark matter at about 20%, and dark energy at about 75% -- the stuff in this story comes into that 5%, ie, regular stuff and not dark matter.
Dark matter is, as I understood, matter which isn't emitting some radiation, i.e. visible light or gamma rays. It's predicted, because without something being somewhere a number would be +0.0000150 instead of +0.0000146 and we can pretty much drop the old Intel Pentium jokes.
A feeling of having made the same mistake before: Deja Foobar
but then again, some crazy girl with a bird hit me over the head with a rock, so I'm not thinking very clearly...
"Empathise with stupidity, and you're halfway to thinking like an idiot." - Iain M. Banks
Am I thinking of a different term, or aren't "baryons" just the counterpart to "tachyons?"
You're thinking of "bradyons". Tacyons travel faster than light. Photons travel at light speed. While bradyons travel slower than light. Baryons are bradyons along with all other matter we've seen so far.
I can see the project now: "Gloud: The GNU open source cloud."
Mythos : Logos
Not exactly... They think the regular stuff they CAN see is being held together by stuff they can't... Like when you glue your hand to a phonebook, you can't see the glue, but you know there has to ba a reason the phonebook isn't falling to gather all the "normal matter" in the Earth.
Watch for Penguins, they eat Apples and throw rocks at Windows.
I found it 10 years ago! Oh, real dark matter...nevermind.
You can hold down the "B" button for continuous firing.
+/- 3 orders of magnitude is considered precise.
"Reality is that which, when you stop believing in it, it doesn't go away." - Philip K. Dick
Turns out it was behind the sofa cushions all along.
"Win treats sysadmins better than users. Mac treats users better than sysadmins. Linux treats everyone like sysadmins."
Obviously that's where the bulk of all the Univere's matter is. Each pound of the stuff weighs 10,000 pounds.
between those ears is another anomoly!
PERFECT VACUUM!
e
First, I had to look up "tachyon". You are right, tachyons are apparently particles that travel faster than the speed of light. I've only heard the term from Star Trek, and for the time being that's where these particles are from - the realm of (science) fiction. I've certainly never had them mentioned in class!
Baryons are not the counterpart to tachyons. Baryons are simply particles that are made up of quarks. The two best known examples are neutrons and protons, which make up virtually all of the stuff you own. Yes, baryonic matter is pretty much everything we interact with.
Two examples of particles that are very common and all around us are electrons and neutrinos. You're familiar with electrons (which are not baryons!), and the nuclear reactions in the Sun are constantly producing a mind-boggling number of neutrinos. Generated in the centre, they travel at nearly the speed of light which means that the ones passing through your body right now are about 8 minutes old. By comparison, the light from the Sun (photons, also not baryons) bounces off all the photons there, so by the time it actually reaches you it's about a million years old.
Finally, and most importantly, dark matter has not been discovered. You are also right in that the reporter is very much out of his depth. The article states that there is evidence for baryons to be found in places where we have not seen them before. What's one theory as to how they got there? Dark matter.
In other words, baryons in those clouds are the *EVIDENCE* of dark matter, but not the dark matter itself.
Just to add my two cents (I do cosmology research) to the chorus of complaints about this post, this research is NOT about discovering a new form of dark matter. This is about solving the "missing baryon" problem, which is a whole different kettle of fish. It's well known how many baryons (normal stuff) there should be according to big bang theory. However, if you look out at the universe and count observed gas and stars, you just don't see as much as you should. So people have assumed there are some hidden regions, where the gas is too cool to emit significant radiation for example, that contain enough baryons to make up the missing baryon budget.
Also, this seems pretty provisional stuff. I doubt this is the final word on the missing baryon problem. It certainly has nothing to say about the nature of dark matter or dark energy. But I guess some gushing "dark matter discovered" hype is just too tempting.
The world is everything that is the case
At least there were, several hundred million years ago.
slashdot broke my sig
There is a problem of assumptions here. The reason all these simulations say that there is missing matter is that they share one faulty assumption -- the Big Bang. If you stop to consider for a second that maybe the Big Bang theory is just a theory, those simulations don't say anything except what MIGHT happen if the Big Bang theory were true. Since they show that lots of additional matter must exist, then either the theory is flawed or there must be more matter somewhere.
As more experiments and opbservations come in, we consistently see that any additional matter we find is not nearly enough to satisfy the simulations of the Big Bang. They've been trying to find this missing matter to "save the theory" for a long time now, and this is another pebble, but they haven't found it yet. I personally am convinced that the Big Bang is a defunct theory. You don't have to be convinced yet, but I am.
If you want something to chew on, read "The Big Bang Never Happened" by Eric J. Lerner. It has details and citations aplenty.
To those of you for whom this idea is new, remember this post. In ten years when everyone "knows" that the Big Bang is a dead theory, you can say that you knew that way back in 2005.
--Sandy
The problem with the galactic rotation curve is not that "the rim [...] spin[s] at the same rate of the hub", but that the curve levels off into a plateau. No mention of cosmology yet.
As to all of this plasma in the Universe, what is the heating mechanism that keeps all of this matter super-hot? The Universe is a very cold place.
How does this plasma theory explain galaxy lensing? The path of light is bent by matter, not electromagnetism. Plasma is matter, so the temperature shouldn't matter in this case.
Finally, where are the links to peer-reviewed papers? Didn't think so. :)
I've never taken any astronomy, or astrophysics courses so I really don't know what I'm talking about, but it always seemed to me like the whole dark matter thing was a big fudge to make our observations fit with current theory. So I have a few questions:
1. Is the "error" in galaxy mass consistent among different galaxies, big ones small ones, distant and close ones?
2. How do they even estimate the mass of a galaxy in the first place?
3. Are there any other observations that don't fit with current theory that would be explained by the existence by dark matter other than the unexpected rotational velocities of galaxies?
3. Shouldn't outer rim stars in a galaxy orbit slower than inner rim stars? Or do they and is that why they form spirals? (this is sort of an unrelated question but I'm pondering about galaxies right now)
What I wonder is how Baryons are estimated, as the article says, at only 4% of the universe's matter. It dark matter thought to be in greater numbers because of the level of influence its gravity has, even affecting galaxies, or is there some other train of thought that leads to that conclusion?
:)
Anyway (and prolly getting ever so slightly off topic here...)
So if I get it right, in these two clouds is supposed to be exactly the missing half of all ordinary matter in the universe. I find it odd, and perhaps very interesting, that after the big bang whose results have shaped our fascinating universe, would also result in half of its ejected matter just sitting in a big cloud in the middle of nowhere.
I guess in my mind, it doesn't solve many problems as I don't lose sleep over where all those Baryons wound up, but thinking about it this way seems to illuminate a couple of fallacies in my view of the universe -
(1) That everything expelled into the universe naturally ordered itself as per the galaxies and such.
(2) That our universe is ordered at all. So all the matter is floating in a cloud, so what? Is that any less remarkable than our matter existing as fleshy metabolism factories on a huge hunk of rock?
Then again, maybe I'm just struggling to rationalize the idea that big black clouds could be the most important masses of matter in the universe, this is the one social situation where not being an astrophysicist makes you feel like a boring person
Yup...
The expected proportions of 'normal matter' and 'dark matter' have been known for a while now, and there has been an ongoing problem because the amount of observable NORMAL MATTER was smaller than the expected quantity. This finding provides a possible explanation for the missing NORMAL MATTER.
Now, they ARE claiming that the gravitational force required to produce these balls of NORMAL MATTER is strong enough that they must also be associated with a source of dark matter, but they certainly are NOT claiming to have 'discovered' any dark matter, nor have any theory on its origin.
If we are right, each single one of these filaments is connected to a cloud of dark matter," said Nicastro. "If there wasn't dark matter there, or something with strong gravity that pulled on the matter in these filaments, we wouldn't have galaxies or filaments."
The operative phrase is "connected to", not to be mistaken for "is" !
So _that's_ where it went. I've been looking for this stuff for weeks. At first I thought I lost it in the woods when I went camping, but then I thought that perhaps I left it in the shed, or maybe the Dryer Gnomes absconded with it. All of this time, it was in a super-heated gas cloud millions of light years away? Who knew?
Regards,
John
Falling You - beautiful
Since you do cosmology research, I'm directing this question to you.
Do you believe that there "must" be more matter out there -- enough to satisfy the simulations that say there must be more? Do you believe that Dark Matter must exist to make the equations work out? Do you believe that the simulations (based on the Big Bang) are more likely to be right than our observations to date?
I certainly hope that someone in your position is aware of the researchers trying to disprove and move past the Big Bang theory. If you discount their findings and hang tight to the Big Bang theory, what do you find to be the most compelling pieces of data to support your position?
In short, I have been convinced that the Big Bang theory is not accurate. (Plasma cosmology is more compelling, but there are holes in that too. More work needs to be done regardless.) What would you say to try to talk me into believing in the Big Bang?
Thanks,
Sandy
<disclaimer> I am a physics postgrad involved in one of the searches for dark matter.</disclaimer>
Whoa. Wait a minute, as this gives you more credibility than 99% of Slashdot, I'd say that's the opposite of a disclaimer.
I've only heard the term from Star Trek [...] I've certainly never had [tachyons] mentioned in class!
Yeah, I wasn't sure, but I doubted that any evidence for tachyons has yet cropped up. The counterpart that I was thinking of (as another poster has mentioned) was "tardyons." I don't think I've ever heard of these "bradyons." Sounds kinda hokey, even for physicists. ;-)
Thanks for your reply.
Accountability on the heads of the powerful.
Power in the hands of the accountable.
Astrophysics is math, talking about math. "But look! We can see that there is consistancy in the application and the result!"
It tells you more about mathemematics as an instrument, than it does about the nature of the universe.
Bloody materialists! Worse than Libertarians! :-)
"Flyin' in just a sweet place,
Never been known to fail..."
"Dark" matter is regular stuff. Forget all the hyperbole about "exotic" new forms of unpredictable Star Trek technobabble with physics-defying properties. It's called "dark" matter because it's not "bright" matter, like stars, conveniently radiating bazillions of units of energy for us to easily spot them.
It seems perfectly reasonable that there exists matter that's not formed into glowing plasma balls and is thus harder to spot.
But that presentation is kind of prosaic, and wouldn't sell lots of issues of the World Weekly News.
I've got a friend over at NASA who gave me a preview of some of the pictures.
Pretty fascinating if you ask me.
http://www.masturbateforpeace.com/
in a universe that is supposedly uniform, these sorts of things only happen hundreds of millions of light years away?
You can tell a great deal about the character of a man by observing those who hate him.
The tactic of citing the lack of peer review is rather amsuing considering most of the Astronomical community is enthralled with the conventional gravitation dominated Universe and refuse to recognize alternatives or dismiss them without explanation. On to the Dark Matter issue (taken from http://www.bigbangneverhappened.org/):
,Astrophys. J., vol. 529, p.911; B.R. Oppenheimer et al Science, 292, p. 698]. While these observations have been sharply criticized, they have been confirmed by new observations [R. A. Mendez ,arXiv:astrop-ph/0207569].
The existence of "dark matter"
Dark matter, or "non-baryonic" matter is a hypothetical form of matter different from any observed on Earth but which is nonetheless required by the Big Bang. Current versions of the (ever-changing) theory require that total gravitating matter density be equal to 0.3 of the critical density but that of ordinary, baryon matter be only 0.05 of the critical density. This means that 0.25 of the critical density has to be in the form of some undiscovered, non-baryonic matter, generally described as Wimps, weakly interacting massive particles.
This "cold dark matter" or CDM, was hypothesized as essential for the Big Bang theory back in 1980--23 years ago. Since then physicists have searched diligently with dozens of experiments for any evidence of the existence of these dark matter particle here on Earth. Oddly enough every one of the experiments has had negative results. In fields of research other than cosmology this would have long ago led to the conclusion that CDM does not exist. But Big Bang cosmology does not taken "NO" for an answer. So the failure to find the CDM after so many experiments does not in any way shake the faith of Big Bangers in such CDM. This is evidence that what we are dealing with here is a religious faith, not a scientific theory that can be refuted by experiment or observation.
The idea that neutrinos might form a bath of Hot Dark Matter has also been undermined by experiments that indicate that while neutrons do probably have some mass, it is of the order of 0.1 eV (energy equivalent), which means that total neutrino mass in the universe is likely to be around one tenth of the mass of ordinary matter.
Wright argues that the existence of dark matter if proved by the difference between the total gravitating mass inferred for galaxies and cluster of galaxies and the mass in observable stars. But this is an absurd non-sequitor. Observations have demonstrated that stars constitute only a small fraction of the total mass of ordinary matter that can be observed. In clusters of galaxies we can observe by X-ray emissions huge clouds of hot plasma, which have masses far greater than that of bright stars.
There is extensive observational evidence for ordinary matter in two other forms that are relatively dim, One is white dwarfs in the halos of spiral galaxies. Recent observations of high proper motion stars have shown that halo white dwarfs constitute a mass of about 1011 solar masses, comparable to about half the total estimated mass of the Galaxy [R.A. Mendez and D. Minnitti
Observations of ultraviolet and soft x-ray absorption has revealed the existence of "warm plasma' with a temperature of only about 0.2keV, which amounts to a mass comparable to that of the entire Local group of galaxies.(Nature 421, 719). If we adds up the warm plasma, which is sufficiently dim to be observable only as it absorbs radiation from more dint objects, the hot plasma, and the white dwarfs, we have enough matter to equal that which is inferred by the gravitational mass of cluster of galaxies. So there is no need for non-baryonic matter and there is no room for it either.
Conclusion: the evidence against the existence of non-baryonic"dark" matter is stronger than ever. Ordinary matter is only the only type of matter that exists.
For further evidence (taken from http://www.skepticalinvestigations.org/controversi es/bigbang.htm):
An idea I had recently.. ZPE has heaps of energy, energy and mass are interchangable, would the mass distribution of ZPE be effected by gravity in the same way it is effected by and influences electromagnetic fields? could this explain the pioneer anomaly and account for the extra gravity and mass normally associated with dark matter?
09F91102 no, 455FE104 nope, F190A1E8 uh-uh, 7A5F8A09 that's not it, C87294CE no. Ah! 452F6E403CDF10714E41DFAA257D313F.
I've always been a bit confused - how exactly can one logically consider "dark energy", whatever it is that has these antigravitational properties, as counting toward the positive mass of the universe? Wouldn't having antigravitational properties give it a NEGATIVE mass? Thus, if the "stuff" of the universe is 25% (matter + dark matter) and 75% dark energy, you wind up with a net negative mass for the universe, which thus does not collapse but acceleratingly expands, exactly as it seems to be.
Like with electricity, we say that something with a lot of electrons compared to protons has "a lot" of charge, but specifically, a lot of negative charge; while something with the opposite ratio still has "a lot" of charge, but this time, positive charge. Between the two the net charge is negated. So dark energy may be "a lot" of the mass in the universe but if it it antigravitic then it must be a lot of NEGATIVE mass, and it seems wrong to count it along with all the regular (incl. dark matter) mass of the universe. Say we've got 100% of the regular mass of the universe in regular + dark matter, and 300% as much negative mass in dark energy.
I think a lot of this may be confusion on the part of laymen authors, not the scientists themselves. I've known so many people (including jr college physics teachers) who thought there was some paradox involved between the distribution of mass causing gravity but gravity causing the distribution of mass, when if you read Einstein's original work on it (he even wrote laymens' versions of his theories), he makes it clear that the mass of something and it's gravitational effects are one and the same. So if dark energy has anti-gravity, then it must have 'anti-mass', or more aptly put 'negative mass'.
-Forrest Cameranesi, Geek of all Trades
"I am Sam. Sam I am. I do not like trolls, flames, or spam."
Further research has shown the clouds to be rife with "nemories": events that never happened, that you can't remember. Much of the 73% of the dark "matter" estimated to be "energy" is actually the "dark info" of nemory. Chandra can't distinguish enthalpic joules from entropic joules, but if the volume of spacetime it's imaging is typical, it's mostly nemory, just like here on Earth.
--
make install -not war
You can detect hydrogen in X-ray telescopes. You're correct, there are no transitions and therefore no lines. However, X-rays ionise hydrogen and are absorbed, reducing the flux at low X-ray energies (below ~500 eV). It makes spectra kind of curve off towards zero at low energies.
Our view of distant galaxies is affected by this, you always have to take account of a) the ~known amount of hydrogen in our galaxy and b) any other hydrogen between us and the source - this will give a redshifted absorption since it's at cosmological differences. It's pretty tricky with the quality of data you get with current telescopes to work out the redshift of any hydrogen that's out there (i.e. to figure out if it's associated with the source or an absorber on the line of sight like the one they discovered), because it's a smooth curve and not a line. That's probably why there are no numbers given. I'll have to read the paper though...
Slashdot - Mutual Assured Discussion
it's punishment for subscribing.
-pyrrho
Dark matter might yet prove to be baryonic, but since about 70% of the universe is the even weirder dark energy, why is it so impossible to believe that 25% could be a new type of matter that interacts gravitationally, but not in other expected ways?
Here's what I do: Bitty Browser & Andromeda
Confusion sometimes arises because there are expected to be several different kinds of dark matter, and several different dark matter problems. The current best picture of the makeup of the universe is that it's about 4% baryons (i.e. atoms), 23% non-baryonic dark matter (exotic particles), and 73% dark energy. This comes from the WMAP satellite's measurements of the cosmic microwave background radiation, combined with (and checked by) independent results from galaxy surveys, supernova distributions, big bang nucleosynthesis, etc.
But most of the 4% baryonic matter is not stars, or easily visible gas and dust. It's made of normal stuff, but also dark - baryonic dark matter. That's what's under discussion here.
Even if this points the way to all of the baryonic dark matter, the 23% non-baryonic dark matter and the 73% dark energy still need accounting for. So you don't have to find _all_ the kinds of dark matter to have discovered some of the dark matter, and there's nothing wrong with the headline.
(Missing mass and dark matter, by the way, are pretty much synonyms.)
Why not try all 3?
That paper you linked did not sway me, in part because it was clearly written without an open mind. It uses phrases like "the only way to do X if you rule out Y is to theorize something clearly unreasonable" to make its points. If observations disprove one theory, it does not prove the only known alternative. It simply means that you should question some more of your assumptions to figure out what you missed.
Clearly not all matter is in stars, so if that is your definition, then some dark matter must exist. My BS subject refered to the theories that dark matter must be something undiscovered, because we can't seem to find enough to fit the Big Bang theory's predictions. I remain convinced that the percentage of dark matter necessary to make Omega equal to 1 does not fit with observation.
I don't pretend to know what the correct theory is, but I am convinced that the Big Bang is not accurate, and that there are forces/processes at work in the cosmos that are being thrown out prematurely because they contradict the Big Bang, thus preventing the most accurate theory from surfacing. Ned Wright's defenses and criticisms are not the open-minded evaluation that I was looking for.
--Sandy
At the bottom of the Wired story, there is a Google ad, "Buy Dark Matter on eBay".
I just wonder if they throw in free shipping.
Pete Carr Owner Chatmag.com
According to Wikipedia one form of dark matter is something called MACHOs (Massive Compact Halo Objects)
I simply refer to it as the "Xbox"
Matt
Hi --
Distinguishing between baryonic matter -- stuff that bears any resemblance to everything around you, whether it is visible or not -- and other "dark" matter that does not fall into that category, is actually pretty commonplace in astrophysics. This seems like semantics, but turns out to be an important distinction.
The point is that the fraction of baryonic matter in the universe is, we think, reasonably well constrained (by both observations of light element abundances in conjunction with Big Bang nucleosynthesis models, and by measurements of fluctuations in the cosmic microwave background) to be only about 5% of the total mass/energy density. Yet there's an additional matter component (accounting for about 25% of the total density) that we know little about -- this is what most astronomers mean when they say "dark matter" these days.
This article says nothing at all about that 25%. It does, however, provide some clues towards a more complete accounting of the 5% that is "normal" (i.e. baryonic) matter. This is a very significant result, but the slashdot writeup and most of the comments to this article are completely distorting it.
The puzzle regarding the "normal" 5% was this: in the local universe (redshifts less than 2), only 10% or so of it is luminous matter, stars and galaxies and the like. More (40% or so) has been accounted for by studies of cool clouds of gas residing between stars, but this still left 50% in an unknown reservoir of baryons. Theory/simulation had suggested that one such reservoir might be the "warm/hot intergalactic medium" -- gas that is heated to millions of K.
The problem is that detecting low-density gas at that temperature is quite difficult, partly since most bound electrons have been lost. Only the more massive elements retain any electrons, and so can be visible in absorption in the FUV or X-rays.
What the paper discussed here (published today in Nature) does is to describe a plausible-looking detection of such filaments of "warm-hot" gas, through X-ray absorption. They use this detection to extrapolate a matter density of this WHIM component, and find that it could account for 30-50% of the baryonic mass, and so constitute the "missing" baryonic matter.
Note that this says nothing at all new about the 25% of truly "dark" non-baryonic matter.
One fairly large quibble is that the 30-50% number represents an extrapolation from just two absorbers, over a comparatively short distance, to infer the WHIM density in the whole universe. That's sort of a big jump, in case that part wasn't obvious. But you can't do this sort of analysis for very many sightlines -- you need a really bright emitting object on the other side of the WHIM clouds if you're going to see them, and such objects are few and far between -- so for right now that's what you get.
If you happen to be somewhere that has a subscription to Nature (most universities do), you can check out the two articles related to this in today's edition:
There's a "news and views" article by Mike Shull that's a nice summary of the issues involved. And there's the full research article by Nicastro et al.
Hope that clears at least a few things up. If I have time later tonight, I'll try to come back and respond to some of your other points.
cheers.
That's because intergalactic baryons not only fill a gap in scientists' understanding of the universe, but they may also lead to a better understanding of "dark matter," a mysterious and unseen form of matter that has so far only been detected by the gravitational pull it exerts on other bodies in the universe. "If we are right, each single one of these filaments is connected to a cloud of dark matter," said Nicastro. "If there wasn't dark matter there, or something with strong gravity that pulled on the matter in these filaments, we wouldn't have galaxies or filaments." Rather, the baryons would be pulled into galaxies and the galaxies into each other.
Basically speaking it could be that the reason this big cloud of baryons hasn't collapsed into stars is because of dark matter.
"Physics is to math as sex is to masturbation." -R. Feynman
First, this result only applies to BARYONIC dark matter, which is only a fraction of all the dark matter out there. Second, we already knew that a lot of it at the epochs in question was in the form of hot intercluster gas.
The current work is an improvement over previous studies, and is good work. But the headline rather sucks. I thought we'd detected axions or something, even though I'd already read about this result.
I teach techniques to estimate cluster masses based on X-ray emission, and have used the Chandra X-ray Observatory myself. A headline about such work shouldn't trick me.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
If you just think astrophysics is math, you'd flunk the heck out of my astronomy exams no matter your mathematical sophistication. Probably every level of astronomy, from non-major to graduate level. At least the way I teach it.
Math is a very useful tool in astrophysics, but there's a reason that math is a separate department from any physical science.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
Actually, it is well established that the dark matter is NOT baryonic.
The story is a bit about dark matter, because there is a dark matter presence implied by the newly discovered gas clouds. But that's no surprise - the observed structure of ordinary galaxies already implies that they as well are permeated with dark matter.
Photon's can bounce off photons? I know you studied this in school, but are you sure?
Neil is that you? Yeah yeah, it's me... Neil...
Cosmologists, primarily based on data from the Wilkinson Microwave Anisotropy Probe, are now willing to put pretty hard numbers on the ratios of baryonic and non-baryonic matter (about 1:7 or so). ALL of the non-baryonic matter is dark. A good fraction of the baryonic matter is dark, in the sense that it doesn't emit much light (e.g., very cool stars, non-accreting black holes, planets, etc.).
There sure is dark matter out there that we don't understand well at all, and probably more than one kind. Neutrinos are one form, since recent experiments indicate they do have some mass. Neutrinos are pretty exotic compared to normal baryonic matter. There may well be weirder stuff.
Agree with you though, that Star Trek overdoes it.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
Because none of it exists within our own solar system. Else it would have played merry games with our orbital calculations, and we would know where to look for it -- up close and personal.
Seriously: We can model the solar system quite well using only the derived* masses of planets to within a few percentage points per thousand years... Yet supposedly the universe has some random form of gravitational energy which accounts for over 80% of the 'mass'. Get real.
Non-baryonic matter is the luminiferous aether of today.
If I'm wrong, great. But the whole theory stinks of hand-waving. Just becuase you don't have a clue doesn't mean you invent some wild theory -- not when there are dozesn of equally (or more) likely, simple explinations.
Every few years somebody finds another few percent of the 'missing' matter. I'm just waiting.... For some good evidence to satisfy my cynacal nature, or for them to get up to about 90% so that I can openly mock the concept.
For now I do admit that, in general, I don't know more about physicsthan the average masters holder therein; I do, however, know a LOT about gravity -- enough to make me question everything about non-baryonic matter anyway.
*It would be incredibly unlikely that we could 'accidentally' account for any matter/mass from the observational methods by which we derived the present, assumed masses for the planets.
hmmm let me guess which DM search you're with.....CDMS 2? BTW what do you think of the latest DAMA/NaI(Tl) "result"?
- "Hear that?! The percolations are imminent! Cease your ingress!"
I think he meant bouncing off of electrons... in the "radiative zone" doncha know...
- "Hear that?! The percolations are imminent! Cease your ingress!"
Wouldn't the neutrinos actually be younger than 8 minutes by the time they pass through your body because of time dilation? If their speed was 99.9% the speed of light they would only be about .358 minutes = 21.5 seconds old by the time they reached earth in the neutrino frame. However, I don't recall the typical speed of a neutrino so this value will be off.
OK, lets be honest: I haven't read the article. Still, with the mention of 'dark matter,' I thought I'd ask the opinion of my fellow /.'rs.
From what I understand, the theory of 'dark matter' is the way we explain the existence of forces that seem to have no originating matter. We see the effects, but don't see the matter that is causing it. So we say that there is 'dark matter.'
Fast forward a few decades. We have this new thing called string theory. One part of string theory is that our force of gravity is not, as it seems, a force inferior to our other forces, but that gravity 'strings' do not have endpoints on our own plane, but in stead loop back upon themselves. This allows for the idea of gravity 'leaking' from our plane into parallel dimensions.
Here is my idea: if gravity can leak from our plane to parallel dimensions, isn't it plausable that forces might leak from parallel dimensions into our plane? Wouldn't that explain the apparently massless forces that we observe?
You wouldn't happen to have your course materials posted on a website somewhere, would you? It'd be interesting to read.
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"Dark Matter": code words for "we don't know WHAT the fuck is out there or why our math doesn't add up, so we'll make up something from a bad Star Trek episode to keep the grant money flowing...hope no one calls us on it".
Sorry, but the very idea that we can calculate the mass and size of the entire universe accurately from earth-based observations alone is sheer nonsense. And when I say earth based, I include various satellites and spacecraft as well (chandra, hubble, etc).
This doesn't mean that we should EVER stop looking, but we should realize the inherent limitations of our situation here. We have neither the mathematics, technology, or data needed to determine such things until we can travel longer distances from this rock, and, to put it simply, have a wider view, probably much wider than we can get within our own solar system. Until, it's all conjecture based on what limited data we can get.
Life is hard, and the world is cruel
Yeah, at least part of them. You can go to my website above, hit "Astronomy Work" link on the left, and be taken to http:physics.uwyo.edu/~mbrother where you'll find links to three recent courses I've taught. The intro astronomy course (1050) is currently in session and so the slides for that one are incomplete. These are slides, meant to accompany lecture, so they aren't enough on their own, but you might enjoy looking anyway.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
Shouldnt it be
'There were massive quantities of Baryons in a super-heated gas cloud several hundred million light years away'
What is the chance that it is still there?
Hey !! Someone on the 'inside' told me that dark matter is what the aliens use to create Starbucks.
They did not find "the" dark matter that was missing, they found dark ordinary matter that accounted for ordinary matter they expected to be there but that they couldn't find before.
STFU, at least they're not in particles, like me. Think I actually made a wrong career move back there somewhere.
Excuse my cynicism, but I find it hard to believe that you don't know as much physics as a masters student (and no good schools accept masters students), but you know a LOT about gravity. Gravity is one of the most difficult fundamental subjects in physics. Most physicists never learn GR.
And btw we don't observe the Hubble constant within our own solar system as well. There are many things that we do not and cannot observe in our backyard.
Tachyons were byproducts of a broken theory--they were predicted by early forms of quantum gravity. Refinements to those theories eliminated them (as a particle with imaginary mass is simply preposterous), but Star Trek still enjoys using them...
I thought Tachyons were just gluons which weren't quite dry yet...
Most of science is speculation, and therefore, shouldn't be taken seriously.
You're obviously not a scientist then.
"Speculation" is what drives science (ie. I observe something then I speculate as to what a possible explanation could be). But it doesn't stop there. That's where experimentation comes in, to throw out my hypothesis, or not. Science is actually the whole process, not just the initial attempt at explaining an observation.
Speculation would be "Diet Coke is fattening, because most fat people drink diet coke".
This is not science. You have to PROVE your statment. And not only that, but you have to publish HOW you derived the proof, so that everyone can see it and has a chance to spot errors in your technique. AND everyone has to be able to obtain the same results as you got. Then it becomes science. That's about as far away from speculation as you can possibly get.
Now if you want to know about doppler shift and how interstellar/intergalactic distances are measured and all the "theory" and "speculation" behind it, you can pick up any physics textbook.
If you flip a light switch and the light fails to come on there are only two possibilities: There is an interruption in the circuit (ie the lightbulb burned out, most commonly) or there is no power to the circuit. There is no speculation as to the results (ie maybe I was bad and God didn't want the light to come on as punishment).
Seven puppies were harmed during the making of this post.
Without going into any detail, the biggest thing that dark matter experiments are looking for is a change in the rate of WIMP detection throughout the year. We expect the most in July and the least in December. Unfortunately, using current technology this variation is only a few percent over the background.
Several years ago, the DAMA group announced finding such a variation, and thus having discovered dark matter. However... this failed to convince the dark matter community at large. It could not be unambiguously shown that the variation was due to something outside Earth. For example, detailed temperatures were not taken - what if the seasonal temperatures affected the detection rate?
Part of the dark matter search is like looking for a needle in a field. Each experiment can only cover part of the field. So even negative results are useful - it crosses off that part of the field. Problem is, another experiment had already crossed off the part that DAMA claimed to find dark matter in. So who's right?
On top of this, the collaboration has not released their raw data, which is not something scientists like. It makes verification, well, impossible.
DAMA's results are interesting, but the hunt continues!
I've believed this for some time. How many light particles are in mid-transport at any one time?
b er of photons]
For example, take a typical cube metre in space. How much electromagnetic energy would that contain (i.e. how many photons:
E=hv=mc^2
m=hv/c^2
m=(h/c^2).Sum(v_i)[i=1,num
Work out that mass, multiply it by the volume of the universe. What is this figure?
Repeat for other forces (gravity, weak, strong forces) for completeness.
Does it account for all the dark matter?
David Bond MSci
If dark matter has a gravitational signature wouldnt there be some sort of gravitational lensing effect?
The best education consists in immunizing people against systematic attempts at education. - Paul Feyerabend
We understand nothing of gravitational dynamics on the galactic scale. For example, there was a paper in Nature on an ultra compact dwarf galaxy that predicted a dm/m ratio of 100/1, and when they did the measurement, instead of finding 100 dark matter masses for ever normal mass, they found ZERO!
ZERO is what MOND [MOdified Newtonian Dynamics] predicts because if the compact nature of the galaxy in question, it is still in the Newtonian regime.
It's time to reconsider Newton on large scales.
Scientists have come up to a solution as to where all the missing matter in the universe actually is.
Apparently, it's something called "pocket lint".
Hey I have found the cure for all ilnesses in the world... it's just around that corner I'm guessing.
Now, *that* is a good pun! I'm still grinning.
I think at least half of the missing mass of the universe is piled on our bathroom counter.
If Quantum ZPE exists, then space must have mass.
--Scott 8-}
Particle Man? Doing the things a particle can?
All I can think is - Katamari Damacy
When a true genius appears, you can know him by this sign: that all the dunces are in a confederacy against him.
Yeah, that is funny in the context of this discussion, isn't it?!
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
"Yes, baryonic matter is pretty much everything we interact with."
You must be floating in the dark.
I constantly interact with photons and gravitons as well as baryons.
For a constant subtended angle, area varies with the inverse square of distance. For something that is not attenuated (or enhanced) with distance, inverse square becomes the default assumption.
Contribute to civilization: ari.aynrand.org/donate
Quantum theory also started as a simple equation
to fit the data provided by Hot body radiations.
It was upto Einstein to give it the credibility
it required. The equation was correct the theory
was not defined.
Now we have another equation that fits a lot of
data. But the theory is missing. We will
need another Einstein to find the missing theory.
I believe this equation will have a profound
impact on science as we know it. When that
theory is found.
Really? And how does anyone know that it is that far away?
You seem to be requiring some education on that topic, so let's try to answer in simple terms all the questions you have:And how does anyone know that it is that far away?
Most of the time, the way to measure distances to far away objects is to use the "doppler effect" (the effect that makes the police siren change tone when they move toward you), which depends on the speed of the object from you as well as its distance. By looking at the spectrogram of some object, you can find out what it is made of. Knowing that, you can measure how the spectrogram has been affected by the Doppler effect, hence compute its speed compared to us. Knowing the speed and knowing the rough "size" (I simplify here, universe doesn't really have a "size" like you would have) and how the universe expands, you can compute the distance to this object.Do they shoot out a signal and wait for the signal to return and then calculate the distance?
No, in this particular instance, it is X-ray bursts coming FROM the star. It shoots its energy in all directions, so that includes shooting it toward us. X-rays are just like visible light, but carrying much more energy. Such events generally light up the whole sky and are easy to detect when you already look in the direction of the event. Wouldn't that signal take several hundred million years just to reach the target even at the speed of light? Indeed! And it did! We receive the result billions of years after, but it doesn't matter. You have a snapshot of the universe at a given time. And knowing HOW it evolves (astronomers now know a lot about this), you can deduct what it is you are looking at. In the particular case of dark matter, dark matter interacts with usual matter so that is the interaction and the long-term result that we see. And the whole thing about dark matter is that we could see that *something* is interacting with normal matter, but WHAT?. With the Chandra observatory, they have found WHAT.I doubt that anyone had the technology several hundred million years ago to shoot such a signal.
You do not require technology for this. Remember, it is the UNIVERSE. Forces at stake are nothing comparable to any technology you have on earth. We happen to live next to a relatively small star, and there is already a lot of energy coming out from it (you feel it each time you sunbath). Objects that blow up in supernovaes are billion times more energetic than our sun and what happens when they explode (and we receive the x-ray from it long afterward) is like a thermonuclear explosion, but million times more powerful than ANYTHING you'll ever see.If that distance is correct, wouldn't we be seeing what that object looked like several hundred million years ago?
Yes, but again that doesn't matter. It still clues scientist to what filters it before it reaches us. And it is the filter part that is important.That object may have ceased to exist millions of years ago.
For once you are probably right. Stars live millions to billions of years. Ones tha t transform in supernovaes are very unstable and blow off in only a few days/months! And it is incredible luck and very exciting when you can actually catch such an event with a telescope. That is part of what is so exciting about those bursts: they are FAR away, hence VERY OLD, they happen very rarely but they are so energetic that we can use them for collecting ALOT of information on the universe.So, why are we wasting our resources on it?
I won't discuss the importance of science, but I can kinda illustrate why: If we would not, you would never have had a micro-wave to heat your chicken, no way to forcast weather for your week of holidays in Cuba, no cell phones, etc.If people did not spend time understanding where we live, we would still be at the stone age. I'm sure you would not like it!
Most of science is speculation, and therefore, shouldn't be taken seriously.
That is utterly stupid and troll of you to say this. If you really believe it, I am sorry to say that you're out of your mnid. If you don't you are trolling around and I'm happy to try educating a troll.Remember that quantum physics + cosmology combine to give the biggest error in the history of physics: predictions of vacuum energy more than 10^100 times bigger than the observed value.
;) It's too soon to say there is an observed value, and really if there's no lower energy state for vacuum energy to flow to, it's pretty meaningless form a thermodynamics point of view anyway.
Well, it would be more fair to say that predictions of vacuum energy vary by 100 orders of magnitude, which is a big error bar even by cosmology standards.
Vacuum energy may join the cosmological constant in being an invention to fudge the numbers when the theory does't work any more.
Dark matter, OTOH, is an observed phenomenon not predicted by theory, which makes it much more exciting.
Socialism: a lie told by totalitarians and believed by fools.
Cosmologists, primarily based on data from the Wilkinson Microwave Anisotropy Probe, are now willing to put pretty hard numbers on the ratios of baryonic and non-baryonic matter (about 1:7 or so).
I find that claim pretty far fetched. We have little enough experience with (uncharged, massive) naturally occuring non-baryonic matter to begin with, and this group can "put pretty hard numbers on the ratio" for the whole universe? That would be cool, but color me skeptical. Any links available for that research yet?
Socialism: a lie told by totalitarians and believed by fools.
Wayne Hu at the university of Chicago has a great set of webpages that explain these results. If you don't have much of a background, start with the lowest level and work up. To get to the hard numbers (two significant figures), check out the "experiments and data" link. They're based on the relative amplitudes of the acoustic peaks in the microwave background.
The page can be found here.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
neutrinos do not clump in galaxies. Majority of the dark matter must be slow-moving stuff.
I doubt that we will ever figure out - and I suspect that even if we did figure out we couldn't do much about it
Mind you, it's an astrophyisics textbook so it ain't cheap.
"Why can't everyone just be straight with me?"
"Because we live in a bendy world, dear."
Thanks for the link. I hadn't seen any analysis of the MAP data, so this is very cool. I don't see anything in the "MAP Year 1" summary about the mass ratio you mentioned, however, so maybe I'm missing something.
The early results around the inflation theory are also quite interesting - that's another one I'm skeptical of, but the early data seems good.
The really curious thing to me about dark matter is the distribution of the "missing mass" in our own galaxy (based on observerd rotation speed). From what I've seen, the missing mass is only in the disk, not the bulge, and very linear with total enclosed dark matter vs distance from galactic center. This would mean a density of dark matter that doesn't have any obvious relation to the density of visible matter (with the total mass of dark matter at a given distance constant, but none in the bulge).
To me that suggests a cloud of baryons with a very believeable density curve (and once density was high enough, it all became "light" matter), not somthing produced by stellar activity like neutrinos.
But perhaps intergalactic dark matter is totally different from galactic dark matter?
Socialism: a lie told by totalitarians and believed by fools.
It's more like 10 times as much non-baryonic matter. The numbers to compare are Omega_matter = 0.28 (total matter) versus the Omega_baryon (0.024). The Omega parameter is proportional to density, so you can work out the relative ratios of the two types.
We're still working out just how dark matter is distributed, and on what scales. Some are easy. Some are hard.
Neutrinos, by the way, are present in large numbers from the early universe just like the background radiation (and neither comes from stellar activity). There's also a "neutrino background" we can someday, in the very far future, hope to study.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
Without knowing it ahead of time.
Socialism: a lie told by totalitarians and believed by fools.
Part one:
I like cynical people, in general. They tend to question assumptions such as above. My answer:
My degree (and interests) = Orbital Mechanics related.
Part two:
True. Then there is the tedius point that I was lazy and didn't write 'unknown forms of matter that only interact gravitationally and not in any other way' etc and instead wrote 'Non-baryonic matter'. Which I think we both know is horribly, horribly wrong.
I'm too tired to explain why, and this is slashdot, so nobody cares anyway.
That's hilarious :D and does have *some* truth to it... can't get much past teaching grade school science anymore without a good math grounding, at least linear alg and above, afaik
:) I might be able to help with that if I can ekk out some time.
As a beside, that page isn't very friendly to the Konqueror web browser:
This presentation contains content that your browser may not be able to show properly. This presentation was optimized for more recent versions of Microsoft Internet Explorer.
If you would like to proceed anyway, click here.
and it comes out messy. I assume you haven't had time to convert it to proper html yet
Cheers and how are you?
SB
It's old. The more humans I meet, the more I like my cats. At least they are honest.
Hi Andy -- been too busy as usual, and down with the flu this week. I just use the powerpoint web default, even though I have similar problems looking at the slides from my linux box without explorer (mozilla there). No student complaints yet! Microsoft has conquered the college campus at least.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
Sorry guys, forgot to carry the one!
Universal mass problem solved.
Move along now, no dark matter to see here...
Science advances one funeral at a time- Max Planck
"dark matter" is just matter that's not yet oberved. Could be baryonic or not; we don't know because it's not yet observed! (Well, perhaps until now.) That's all the "dark" in the term means.
Try not to be misled by that extremely stupid "dark matter" X-Files episode where they make out it's necessarily a weird "other" form of matter with tacky blue-lightning special effects:-)
Cameron Simpson, DoD#743 cs@cskk.id.au http://www.cskk.ezoshosting.com/cs/