Search for the Missing Universe 420
Chris Gondek writes "The Sydney Morning Herald has reported that one of the greatest discoveries of our time could be made under the Yorkshire moors. Deep in a Yorkshire mine, scientists are toiling to solve a cosmic puzzle that has baffled astronomers for 70 years: about 90 per cent of the universe is missing. Analyse the movements of stars and you can work out how much matter is making them swirl round in galactic islands and how much makes galaxies cluster together as they do - in other words, you can work out how much mass makes the universe look the way it does. But measurements suggest that the universe is not what it appears."
Bush Administration cites Missing Universe Theory (Score:4, Funny)
Re:Bush Administration cites Missing Universe Theo (Score:5, Funny)
Clearly, 90% of the universe needs to be destroyed. Facing clear evidence of peril, we cannot wait for the final proof -- the smoking gun -- that could come in the form of a mushroom cloud.
Correction... (Score:5, Funny)
I think you meant "liberated".
In other news.. (Score:3, Funny)
For starters (Score:4, Funny)
I'd look in Windows.
Just another WIMP-seeking experiment (Score:4, Informative)
To show that neutrinos have mass, it suffices to observe solar neutrinos and look for changes in neutrino flavour. Last I heard, although large regions in which the neutrino masses could have lain had been ruled out, the evidence was mounting in favour of flavour changes and neutrinos having mass.
However, with all I've heard about neutrino studies over the last few years in a Nuclear Physics department, this article doesn't give enough information to let me work out if I already know of the experiment or not (though I probably have attended seminars by associated researchers; these projects are not exactly three-person exercises capable of being missed!) They don't even give the experiment's *name* - NOMAD, CHORUS, SNO, etc (many listed on this page [in2p3.fr])
The article *might* be referring to the UK Dark Matter Collaboration [rl.ac.uk] who apparently look for neutralinos instead (neutralinos appear to crop up deep inside what we Nuclear Physicists call 'Particle Physics', which is full of leptons and mesons and other fun particles, fine, and some of the most brain-bending mathematics it has been my priviledge to not understand.)
Rachel
Re:Just another WIMP-seeking experiment (Score:5, Informative)
The discussion has pretty much moved toward conclusion, and the conclusion is that neutrinos DO have mass, and that the limits placed upon their mass, while greater than zero, do not yield enough total mass to account for the remainder of missing mass. These results might shift slightly with corrections of experimental error, but a drastic change is unlikely.
You really have no clue... (Score:4, Funny)
Did you look in your shoes? (Score:5, Funny)
Whenever I lose something, sometimes it turns up in my shoes.
</obligsimpsons>
Re:Did you look in your shoes? (Score:5, Funny)
Hey, go ahead and laugh, but it's at least as good a guess as anyone else has managed to make. It just has much less funding.
Re:Did you look in your shoes? (Score:2, Funny)
Yeah okay okay I did find a $20 and a $5 in there so only $20 in real coins
You might be a lot more funded then you think you are
Re:Did you look in your shoes? (Score:5, Informative)
Go to a decent grocery store that sells USDA Prime beef. Find yourself some fillet steaks, also known as fillet mignon. You want two steaks as close to the same weight and thickness as possible. They should be between 6 and 8 ounces.
Heat your oven to 500. If your oven won't go to 500, set it for as high as it will go. Then sit down to watch The Simpsons or something, because getting a home oven to that temperature takes a while. Be patient here.
Dry your steaks thoroughly with paper towels. You want the surface to be completely dry, both on the top and bottom and on the sides. Why? Because liquid turns to steam, and we don't want steamed steaks. Your goal is perfect dryness here, so do a good job.
Once your oven is hot, put a heavy, all-metal, oven-safe skillet on top of the stove. Cast iron works, but I have a stainless-steel-clad, aluminum-core skillet with a riveted metal handle that I use for this. Turn the burner or element to high, and leave it there for at least five minutes. You're looking for something really incredibly hot here. Don't be afraid to let your pan get hot. It'll be fine.
Season your steaks liberally with salt. You want something with a coarse grain, because it makes a great texture when it cooks in. I like kosher salt for this (Morton's) but sea salt is good too. Fleur de sel is the best, but at $10 for a couple of ounces, it's a little pricey for most folks. But if you're blowing $25-$30 on raw meat, you might as well go all the way.
DO NOT PUT PEPPER ON YOUR STEAK. I don't care if you like it that way. Pepper burns at the temperatures we're planning on using. If you want pepper, crack a little over your steak once it's on the table.
Once your pan is hot enough to brand a steer--which is basically what we're planning to do here--plop in the steaks. No oil, no nothing. Just drop 'em into the dry, rocket-hot pan: szzzzzzz. There will be some smoke, so crack a couple of windows for ventilation.
Do not touch the steaks for two solid minutes. Seriously. Don't touch them. Don't move them, don't poke them, don't prod them. Don't talk to them. Don't ask them questions. Just let them sit there.
"But the meat will stick to that hot pan!" you cry. And you're absolutely right: it will. That's exactly what we want. What we're doing is called "searing." Searing is cooking in a dry pan over incredibly high heat. Searing isn't frying; frying involves lubricating the pan with fat or oil, and we don't want that. Instead, we just want dry, raw meat to hit blisteringly hot metal and to sit there for two minutes.
What's happening is called the Malliard reaction. (That's pronounced "my-yard.") It's complicated, but the short version is that proteins in the surface of the meat are denaturing and chemically changing into a brown, crusty substance that tastes really, really good. You don't get that with any cooking method other than searing.
After two minutes, turn the steaks over with tongs. Not with a fork, not with a spatula. Tongs. Grab the steaks gently around the middle and lift straight up. They'll lift right off of the pan, no sticking. If they do stick, just wait a few seconds. They'll let go by themselves because of the heat of the pan and that Malliard thing I talked about. Turn the steaks over and leave them for one minute.
During that minute, look at the seared surface of the meat. It should be brown and crusty, almost like it was battered and deep-fried, but darker than that. If there are tiny black specks here and there, that's okay. If there are big black specks, you left it on too long, but it's still edible. If the whole thing is solid black... well, the dog's in for a treat tonight.
After one minute, move the entire pan--use an oven mitt for god's sake, that pan is a branding iron by now--to the oven. We've seared the surfaces of the steak, and now we're going to cook the interior.
There
Re:Did you look in your shoes? (Score:2)
That really is a good idea, except that you missed a really important detail.
Your piece of meat needs to weigh about twelve ounces, and be at least an inch thick.
Oh, and it should be accompanied by a bottle of reasonable wine, like maybe a Gigondas, or a Chateauneuf du Pape. Something with enough body to carry the flavour of the meat.
My own pereference, however, would be to just sear the meat for about 90 seconds per side, so the inside is still bleeding raw.
Re: Did you look in your shoes? (Score:3, Funny)
> I guarantee you, if you follow these directions to the letter and use halfway decent ingredients and equipment, these will be the BEST steaks you've ever eaten. Period.
I'd rather just swing by Krusty's for a ribwich.
One Quibble (Score:3, Informative)
Most people are afraid to get their oven and cooking utensels hella hot, and that's a shame because that's the only way to really cook your food well. For the longest time, I shared my mom's fear of taking the oven over 375 (Fairenheit) and my cooking suffe
Perhaps it's not lost. (Score:5, Funny)
Not 42? (Score:4, Funny)
Re:Not 42? (Score:4, Funny)
Re:Not 42? (Score:2)
Jason
ProfQuotes [profquotes.com]
Re:The question bad then too?! (Score:3, Funny)
That's twice. (Score:2)
It never was. Try "What do you get when you multiply six by nine?" And the answer is 42 iff you do the arithmetic in base 13 and read out the answer in base 10:
As I understand it, Douglas didn't plan it that way. The universe is always odder then it seems.
Re:That's twice. (Score:2)
Not really saying much... (Score:5, Interesting)
Also, I'm confused by the article's representation of MACHOs as being "failed underweight stars". My understanding had been that MACHOs are actually massively compact and hard-to-observe objects, such as (relatively) low-mass black holes which were created by events other than the traditional supernovae collapse. I think they might be refering to brown dwarves, which may be hard to see but aren't, by definition, very massive (again, all of that relatively).
Someone correct me if I'm wrong.
Re:Not really saying much... (Score:2, Flamebait)
These guys are describing typical heavy water tanks in mines that have been traditionally used to detect neutrinos.
I have no idea what the point of the article is either.
Re:Not really saying much... (Score:4, Informative)
All Michaelson and Moreley were doing in 1887 was actually measuring the directional velocity of the ether, relative to the earth. They were surprised by their failure to measure anything but zero at all hours of the day and all months of the year. But in retrospect it turned out that their experiment was an extremely effective demonstration that the speed of light is constant in all reference frames.
Often we go through the bother of performing experiments even though we expect a certain result in advance. Science wouldn't progress as fast as it does if we decided these experiments were a waste of time.
Re:Not really saying much... (Score:3, Insightful)
You either have to read the original papers, or read the dumbed down garbage that got through the intellect of a "science reporter". Any concept too subtle to make it into a Bruce Willis movie won't get covered by the popular press.
Re:Not really saying much... (Score:2, Informative)
Hope this he
Re:Not really saying much... (Score:2)
Re:Not really saying much... (Score:2)
What about (Score:2, Interesting)
Re:What about [planets] ? (Score:5, Insightful)
Mass of our Sol: 1.9e30 kg
Mass of Pluto: 1.31e22 kg
Mass of Jupiter: 1.9e27
So even if all planets were as big as Jupiter there would need to be a thousand of them around every star to even double the % mass contributed to the universe. And remember that Jupiter is over 50 times more massive than Saturn, the next largest.
Reference: http://seds.lpl.arizona.edu/nineplanets/nineplane
Re:What about [planets] ? (Score:3, Interesting)
Planet Mass
Jupiter 1.90e27 (19.0e26)
Saturn 5.69e26
That just didn't sound right to me. You're right about your main point though. I don't think we have room for 1000 Jupiters.
Typical Monday (Score:5, Funny)
An infinite number of universes, and I wind up with a defective one.
*fills out RMA request*
Re:Typical Monday (Score:5, Funny)
From: $DEITY
Re: RMA request
I'm terribly sorry that The Universe as you ordered it isn't exactly what you expected. However, I can assure you that things are exactly as they should be. Please read paragraph 1a of the Existing Universe License Agreement that came with your copy, to which you agreed before installing The Universe.
1a. I, $DEITY, am perfect, therefore The Universe is perfect. By definition, something that's perfect cannot be defective.
As you have agreed that The Universe is perfect, I cannot grant your RMA request. Sorry.
BTW, I see that you haven't fully paid up on your purchase of The Universe. My colleague, $EVIL_ENITY, will be around to collect on your past due account. Sorry, no returns are allowed on The Universe - again, please read the EULA.
Kindest Regards,
$DIETY
Re:Typical Monday (Score:2)
{#
if ($every_minute) { return $sucker_born=1; }
}
Soko
HAHA! (Score:2, Funny)
$DEITY=NULL;
I imagine vatican is going to have some scope issues with this...
Geeky scientists never give up (Score:4, Funny)
These acronyms need modernising.
eeky scientists never should give up (Score:2, Funny)
Ohh... wait... Nerdy chicks are not discovered yet! Keep on searching in those salt mines :S
Duh, which way to mars? (Score:2, Interesting)
froggie
Thought... (Score:4, Interesting)
I'd welcome any thoughts on this one... Anyhow, it's late and this is way out of my area of expertise, so forgive my spitballing.
Re:Thought... (Score:2)
Re:Thought... (Score:2)
Re:Thought... (Score:5, Interesting)
The answer is a bit involved.
But basically, the weighing of the matter (as quoted in the article) does not depend on just mass, but a quantity called "mass-energy". It is true that a particle moving at very high speeds seemed to gain "mass". But depending on observers travelling at different velocities relative to this particle, each will see a different mass. However this particle, irregardless of its velocity, will have a consistent "mass-energy" to all observers. In other words, everybody in the unvierse can agree on the amount of "mass-energy" each particle have. So there is a consistent picture of weighing the amount of mass of the universe.
That is the beauty of Einstein's Special Relativity, which is to unify mass and energy into a (jargon warning) relativistically consistent picture of mass-energy.
Re:Thought... (Score:5, Interesting)
The problem is that while there is no direct tests of gravity at very large scales, there are a lot of "consistency" checks of the various cosmological observations (say of the cosmic microwave background anisotropies) that you have to satisfy.
In other words, there is no proof that such theories of modified gravity do not exist. But to find one is really hard.
Re:Thought... (Score:2)
So either e!=mc^2 or we just don't quite know everything about everything out there.. I'd guess the latter.
Re:Thought... (Score:3, Interesting)
Anybody ever stop to consider that the other 90% must have some sort of structure? There's probably dark matter stars, planets, gas clouds, etc. Perhaps some sort of dark matter inteligent life as well. Whereas we are trying to figure out where 90% of our universe is, the other side may be trying to figure out where their missing 10% is.
Most of us here belive in some sort of extraterrastrial life. I doubt many o
Re:Thought... (Score:4, Insightful)
There is no logical necessity for that. Although you can conceive of matter that exists subject to a host of strong interactions but which does not interact with us -- that there are two "classes" of matter that exist separately -- there is no evidence for that. Occam's Razor says, don't invent whole universes for the heck of it. The simplest explanation consistent with the facts is taken to be true.
Indeed, many of the "hot" dark matter theories presume exactly no structure to the dark matter
Not True (Score:5, Insightful)
Gravity is only tested to solar system scales, and in an indirect way, galactic cluster lensing effects.
At very large scales, say of the Hubble radius, we have no tests of gravity. Cosmological models are almost always based on the belief that Gravity works at the very large scales, an extrapolation of many orders of magnitude. There is no proof that this is a valid extrapolation, and there are hints that they are not. (Like they lead to an extremely highly unlike situation. Check out This Talk [uchicago.edu])
Large scale modifications of gravity may affect the smaller scales, but these effects are naturally suppressed (you can cook up theories where they are not suppressed, but then it is not "large scale" modifications anymore). So to discover these effects are hard.
We have experimental constraints of course, but they are not very strong.
Yes, there are tests... (Score:4, Informative)
From the abstract:
"A pilot experiment suitable to test Newton's law of gravity down to the regime of acceleration typical of galaxies has been carried out in Omega Centauri. Stars in the extreme periphery of this globular cluster are used as test particles immersed in such weak gravitational field. The stellar velocity dispersion is found to remain constant at large radii, rather than decrease monotonically, starting at acceleration a=10e-7 cm/s2. This is comparable to the acceleration at which the effect of dark matter becomes relevant in galaxies. Explanations for this result within Newtonian dynamics exist (e.g. cluster evaporation, tidal effects, presence of dark matter) but require fine tuning of the relevant parameters in order to make the dispersion profile flat. An interesting alternative is that this result, together with a similar one for Palomar 13 and the anomalous behavior of spacecrafts outside the solar system, suggests a breakdown of Newton's law in the weak acceleration regime."
Re:Yes, there are tests... (Score:3, Interesting)
They found that gravity "breakdown" at some small acceleration scale. The problem with "acceleration scales" breakdown is that 'acceleration', as defined in their paper, is not a (jargon!) covariant statement. In other words, they are saying acceleration with respect to the center of mass of the cluster.
Re:Not True (Score:4, Interesting)
Agree. And we make an awful lot of assumptions about the continuity of physics even at galactic scales.
The bottom line is that we start by assuming that because a theory fits some observed properties of the universe -and- we have not yet thought of a better (or at least more appealing to us) theory, the one we have is true. "If the only tool you have is a hammer, every problem looks like a nail."
This is especially true of the really grand assumptions like "the universe has no centre and no edge" and "the en-bloc redshifting of distant objects is evidence of recession caused only by the stretching of space"; the problems these assumptions cause conventional science [heretical.com] run deep, yet so well embedded in orthodox scientific dogma are they that the vast majority of scientists would rather reject the growing collection of conflicting data than the dogma. (see here [3dresearch.com] for discussion of something even weirder).
Re:Not True (Score:3, Informative)
Very accurate positional measurements by radio telescopes (using very long baseline interferometry) revealed the astounding fact that some quasars appeared to be expanding at up to ten times the speed of light. This was in complete violation of the accepted laws of Einsteinian physics
This is an argument from incredulity. IN fact, the apparent superluminal expansion is explained neatly away by the fact
Historical Analogues (Score:5, Insightful)
Back in the 19th century, astronomers had noticed that there was a minute procession in the perihelion of Mercury (in other words, the point in Mercury's orbit that is closest to the sun kept moving forward) that they couldn't account for using the Keplerian/Newtonian model of celestial dynamics. Astronomers thought that it must have reflected the influence of some massive, distant unknown planet; predictions were made about where this planet was and what its mass was, but astronomers couldn't find it. Then all of a sudden General Relativity came along, and our understanding of mechanics in gravitational fields was improved, and the procession was easily predicted (within an incredibly small margin, as I recall). So it seems just as likely that the "missing mass" is due to a theoretical deficit as it is due to an observational deficit.
Re:Historical Analogues (Score:2)
Who knows if the current mess of missing matter would not go away if we have gain deeper insight into the nature of gravity?
Re:Historical Analogues (Score:2)
Strange isn't it? How a well educated group of people who admit they haven't solved for quantum gravity use gravitational effects to conclude that 90% of the universe is missing.
A history lesson or two would probably do as much as the funding.
s/procession/precession/ (Score:2)
precession [reference.com]
Not very different, those words, but don't go astrogating without the correct one. (-:
Re:Historical Analogues (Score:4, Insightful)
While this is a useful cautionary tale, you have to be a bit careful in your interpretation of it. It is quite easy to show (and it is a typical undergraduate classical mechanics homework problem) that the perturbations of Mercury's orbit CAN NOT be explained within the Newtonian model by the addition of another point source (ie, a planet), because any such explanation would cause a larger than observed perturbation to the orbits of Venus, Earth, and Mars. And this was a well known issue BEFORE Einstein started working on his GR theory. In other words, physicists knew there was something wrong with the theory long before they had a theoretical solution, because the preminent gravitational model of the time was predicting the wrong thing when confronted with the available data.
The cautionary aspect of the tale, though, is well understood by the larger physics community, and dozens of modified and new models of gravity HAVE been proposed in the literature to explain the apparent "missing mass" of the universe without invoking unobserved particles; but they all run afoul of some observation or other. The current model has been arrived at by the consensus of a large number of physicists and astronomers around the globe over a long span of time ... it isn't a flash in the pan, and while it could be wrong, the data on many length and time scales just seems to get more compelling as we add to it, rather than less.
In this case, we understand GR, its cosmological implications, and the requisite post-Newtonian approximation schemes well enough that we have developed a model that match ALL known observations with the inclusion of dark matter and dark energy components. It isn't just one or two observations of rotation curves that have pushed us in the direction of dark matter, but literally dozens of observations, from widely different length and time scales, from cosmic background radiation to rotation curves, from earthbound laboratory measurements to interstellar radiotelescope observations. It is certainly POSSIBLE that there is a theoretical description available that doesn't require dark matter/energy, AND explains all of the data, but it looks more likely to the daily practitioner that the current theory is good at the length scales it is being applied to, and the dark matter/energy is the simpler solution.
I'd like to point out one other cautionary tale to those who want to blame the theory, and points out that well tested theories are not tossed out immediately when new or contradictory data comes along: in the early part of the 20th century, observations of beta decay led many physicists to conclude that the very fundamental conservation laws of energy and momentum (and the entire theoretical framework that so neatly explains them) would have to be tossed out the window, because the observed decay products (electrons and nuclei) didn't appear to follow those conservation laws. But some very smart people, including Pauli, said "Wait, the theory has worked so well up to now that we should look for a SIMPLER explanation; we propose a to-date unobserved particle with no charge and no mass produced in association with electrons in these decays." That was scoffed at by many, but a few years later just that very particle was observed: the electron neutrino. My point is just that, while you need to keep an open mind and be willing to challenge both experiment AND theory, you have to do so with the WHOLE picture in mind, and not just a tiny corner .... that is what science and the scientific process is all about.
So thats where my dryer sends my clothes (Score:3, Funny)
Re:So thats where my dryer sends my clothes (Score:2)
Stephen Hawking's wishful thinking (Score:5, Insightful)
When I saw that, I remember thinking that's naive and contrary to the entire history of scientific research. Anyway, it reminds me that even some of the best minds say some of the stupidest things. Especially in physics.
I'm not a physicist but I'm pretty damn sure that Stephen Wolfram and Roger Penrose have had some pretty wacky theories when they venture away from straight physics, like into cellular biology, free will, philosophy, ...
Re:Stephen Hawking's wishful thinking (Score:2)
Re:Stephen Hawking's wishful thinking (Score:2)
It's perhaps not so wrong anyway, there are after all many "theories" about what this mass may be made up of, just not many can be easily proved / disproved. Hence this experiment and
Re:Stephen Hawking's wishful thinking (Score:3, Interesting)
I have a video clip (from circa 2001) where he's being asked about this very issue. His reply is "in 1980, I said I thought there was a 50-50 chance we would find a complete unified theory in the next 20 years. Well, we didn't make it. However, my estimate is still that we will find a complete unified theory in the n
Black Listed (Score:5, Funny)
Dark data.... (Score:5, Funny)
i'm currently investigating a similar matter: dark data. It seems to occupy around 90% of my hard disk.
Bye, Martin
The New Gravity (Score:5, Interesting)
MOND or Modified Newtonian Dynamics [umd.edu] proposed by Moti Milgrom [weizmann.ac.il] is I think better. If I were to bet on someone winning a future Nobel, Milgrom would be the person.
I'm driving the VLT [eso.org] as I type this...sentence was interrupted for a preset...I'm back now.
Anyway, I know a number of scientists that seriously consider the Newton's may not work at large scales. Nature recently rejected a paper from some rather prominent that seemed to confirm that gravity behaves differently at large scales. But, science is very reluctant to change its equations and publication will have to await more data.
Just remember - Dark matter may not exist. Be skeptical of those who treat it as fact.
MOND FAQ [umd.edu]
Dark-Matter Heretic [americanscientist.org] [This is a wonderful article]
Re:The New Gravity (Score:2)
Re:The New Gravity (Score:4, Informative)
I'm at the Palomar 200-inch [caltech.edu], by the way. But we're in fog for the third night straight, so I have plenty of time for posting to Slashdot.
Re:The New Gravity (Score:3, Funny)
Re:The New Gravity (Score:2)
Re:The New Gravity (Score:3, Interesting)
This is the last of my three nights and we haven't opened yet. Hasn't even been close. Tonight looked promising in the afternoon, but the fog has just completely stalled out here. Another two hours or so and it will officially be a completely useless run. Glad you're doing better... send some of that up here.
Re:The New Gravity (Score:3, Funny)
Comment removed (Score:3, Funny)
This was solved a long time ago... (Score:3, Funny)
-- Terry
This much I know.. (Score:5, Interesting)
There are two strage things happening in the universe on the large scale. The first one is the "dark matter". Basically, if we apply Newton's equations for gravity to various galaxies, we find out that they are spinning too fast. If the force holding them together is what we think it is, most of the stars in a galaxy should have been slingshoted away and left the galaxy. So there must be something making the attraction stronger than we think.
The second strangeness - the "dark energy" - concerns the expansion of the universe. Different pieces of matter in the universe attract to each other by gravity. This slows down the expansion of the universe. As far as we know, gravity is the only thing that can affect the universe on a large scale. So, the expansion of the universe should be slowing down. However, as WMAP [slashdot.org] showed, the rate of expansion of the universe is actually speeding up. So, there must be something that makes the universe speed up faster than we think.
In both cases, there are two possibilities. The first one is that the anomality is equally distributed through space. This would mean that our equations are a little bit off. For instance, we can account for the "dark energy" by adding an extra term to Einstein's equation for the expansion of the universe. If we change Newton's equation to make gravity stronger over large distances, we can eliminate dark matter.
Yet, there is a possibility that there can be more of the "strangeness" in one point in the universe than in another. For example, one galaxy may be held together tighter than another one of the same size. That would mean that there is another strange beast in the universe apart from the types of matter and energy we know. A whole new branch of physics will be needed to deal with the beast and ask questions like "Why is there more dark matter here than there is there?" and "Does dark matter interact with ordinary matter in any other way than gravity?". Dark matter will compress things on a smaller scale; dark energy will expand things on a larger scale. Obviosly, the statement that "Universe is 75% (or whatever) dark matter" will only be meaningful in this case. As far as I know, we need more precise observations to choose between the two possibilities.
I hope that someone who actually is a physicist, is not asleep, or can reach the "Reply" button will explain all the points I'm wrong on...
The answer to the riddle of the socks (Score:5, Funny)
It's in energy (Score:2)
Re:It's in energy (Score:3, Informative)
[TMB]
Earlier BBC article about this (Score:4, Informative)
Universe Lite (Score:3, Funny)
Is the basis of the mass question valid? (Score:3, Insightful)
1. Dark Matter - Look at spinning galaxies, our current theories of gravity say they spin too fast for so little mass...do some math, ok...we're short by 90% from what is visible.
2. Dark Energy - Look at far off galaxies, they are moving away from us...and they're accelerating, and since our current theories say that gravity, an attractive only force, is the only significant player on those scales.
So, if we lack an understanding of what forces act on large scale distances to such a degree that
Re:Is the basis of the mass question valid? (Score:3, Interesting)
Topology of the Universe (Score:4, Interesting)
Consider any two stars of mass m and M. With distance r between them:
The Gravitational force of attraction is G*M*m/r^2.
But you'd also have a gravitional force wrapped once around the torus of G*M*m/(r+L)^2.
Then you could wrap around again and again and again....
Of course, generally the distance would be too huge to make difference, but when you consider how many stars there are and the infinite number of loops around the torus you could make, it would add up eventually.
Any thoughts on this?
Re:Topology of the Universe (Score:3, Interesting)
I recall an earlier article [slashdot.org] about the universe being topologically equivolent to a torus.
Firstly, the experiment didn't prove anything by a long shot, it merely suggested that the universe may be topologically equivilent to a torus or cylander. But let's assume it is for a moment.
Consider any two stars of mass m and M. With distance r between them: The Gravitational force of attraction is G*M*m/r^2.
Nice to see someone re
Supermassive Black Holes (Score:4, Interesting)
-Peverbian
Re:Supermassive Black Holes (Score:3, Informative)
Well, as far as I understand, that's some missing mass, but not
Socks! (Score:3, Funny)
I stole it -- sorry (Score:3, Funny)
Oh? You meant you were only looking for the extra matter in *three* dimensions?!
-psy
another experiment, another mine (Score:3, Informative)
Recursive Universe (Score:3, Interesting)
It's a side effect of the zero dimension, i.e. no length, width, depth or time, everything is connected.
You heard it here first.
Dark side of Particle Physics (Score:4, Informative)
Although these experiments are performed deep underground, like neutrino, experiments their physics is somewhat different. Dark matter experiments are aimed at finding new fundamental particles as yet unknown to physics. Neutrino experiments, on the otherhand, study the properities of neutrinos and it is these experiments (SNO, SuperKamiokande) which have produced the exciting discovery of neutrino oscillations.
The reason dark matter is such an interesting field at the moment is because of the WMAP result. This indicates that only ~5% of the universe is what we call "baryonic matter" i.e. the stuff that we are made of. A further ~20% is made up of non-baryonic matter. This includes things like neutrinos, but just neutrinos is nowhere near enough. So, if we believe the WMAP result, there is a sizeable amount of matter which we cannot account for given our current understanding of physics.
However, dark matter experiments are not the only ones out there looking for this missing mass. I'm working on a collider experiment called D0 on the Tevatron collider at Fermilab near Chicago. This is currently the highest energy collider in the world (until the LHC at CERN, Geneva starts in ~2006). As such it is an excellent place to look for new physics and one such example is something called SuperSymmetry. You can essentially think of this as a symmetery between force and matter (in technical terms its a symmetry between fermions and bosons) and it doubles the number of fundamental particles.
So how does this explain the dark matter? Well, a lot of supersymmetrical models have the lightest supersymmetric particle being stable i.e. it cannot decay. Now being neutral, stable and weakly interacting, this would be an ideal candidate for dark matter and might make up the missing mass of the universe. So instead of looking for these particles scattering off nuclei (as dark matter experiments do) we can actually look to see if we can make them in high energy interactions.
Some interesting web sites you might like to read for more information are
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UK Dark Matter Collaboration [rl.ac.uk]
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D0 Public Information Page [fnal.gov]
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The Particle Adventure: Basic explanation of particle physics [lbl.gov]
I'd particularly recommend the last site if you want to know how much we still have to understand! (click on "Unsolved Mysteries")Re:Wrong credit (Score:2)
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'preview'
preview
n 1: an advertisement consisting of short scenes from a motion
picture that will appear in the near future [syn: {prevue},
{trailer}]
2: a screening for a select audience in advance of release for
the general public
v : watch a movie or play before it is released to the general
public
Please write a 2000 page essay on this word, along with 687 sentences of 'preview' being
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