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Search for the Missing Universe
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."
http://www.telegraph.co.uk/connected/main.jhtml?xm l=/connected/2003/04/30/ecfwimp30.xml&sSheet=/conn ected/2003/04/30/ixconn.html
"It is not how things are in the world that is mystical, but that it exists." -Ludwig Wittgenstein
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)
The article *might* be referring to the UK Dark Matter Collaboration 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
Hey, man: $45 will NOT buy you a decent steak dinner. Here's my recipe for the best steak you've ever had.
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
Yes, there are tests for gravity at large scales. See for example: A Test of Newton's Law of Gravity in the Weak Acceleration Regime
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."
I'm at the Palomar 200-inch, by the way. But we're in fog for the third night straight, so I have plenty of time for posting to Slashdot.
There is a more detailed article about this at the BBC
Nice try, but most of the mass-energy of the universe really is in mass. In the very early universe, most of it was in energy, but the density goes down faster with the expansion of the universe than the matter density does (R^-4 instead of R^-3)... the matter is (quick calculation) about 20,000x more important currently.
[TMB]
I'm feeling smug at the moment as I went to the official opening of the latest stage of this project last Monday and actually got to go down the mine!
There are a few experiments down there, the main three are Zeppelin I, Drift I and an NaI detector.
All three are looking for WIMPS - weakly interacting objects - heavy particles that provide extra gravitation to the universe but are hard to see. But there are differences between them. The NaI experiments main job is to rule out completely (or confirm) a possible discovery of WIMPs made at another such lab - Gran Sasso in Italy. The signal seen there is very strange and indiciates masses of particles we don't expect so I think most people expect it to have a problem with that experiment.
Drift I and Zeppelin I are both really R&D devices built to test technology to be used in bigger experiments (Drift II and Zeppelin II) that are being built now. Zeppelin is a conventional dark matter detector and can search for a bigger range of pssibe masses than Drift but Drift is the first WIMP "Telescope", if it sees anything it can tell which direction the WIMP came from which makes it easier to rule out background noise but will also tell us interesting things - is the dark matter in a disc like our visible galaxy or a sphere like some simulation predict it is.
The mine itself is very cool - deepest in Europe and they mine Potash and rock salt but the tunnels are rock salt so that you they feel soft to the touch, the tuneels are much bigger than I was expecting too! They drive vans around down there that have been lowered down the mine shaft nose first!
Struggling to find a day everyone can make? WhenShallWe.com
THe article you linked to is actually full of inaccuracies. Take the bit about quasars for example.
:
:), that's it, a personal attack : becareful of Arp's ideas, many (if not all) of them are plain wrong.
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 that the jet of the quasars are pointed right at us. It is a nice little problem in relativity to show this is true.
Here is another one
The orthodox view is that quasars are just abnormal (e.g. superluminous) galaxies and that they can only have a redshift caused by velocity. Arp drew attention to quasars interlinking with galaxies. But a large body of opinion now holds that galaxies can violate the redshift distance-relation. It is the most peculiar galaxies, those most like quasars, which offer the most compelling evidence for non-velocity redshift.
This is an argument from false authority. Most galaxies close to us obey the Hubble Law to a great accuracy (those further away has a distinct deviation from velocity-distance diagram, but they are exactly as predicted by general relativity with 75% dark energy). Peculiar velocity is a contribution to red-shift, that's true, but the contribution is very small. In fact, it is a known systematic that can often be removed. (THey lead to so-called fingers of god in redshift-luminosity diagrams, i.e. a small 'stretching' of otherwise homogenous distribution of galaxies.)
It is good to entertain heretical ideas, but they have to pass the same stringent tests as those which you called "scientific dogma". Science has no dogma, just tested ideas. Any of them can fall, but if you want to overturn it, you better come up with a better one, not just a different one.
I will end this with a fallacy of my own
Mode (3) smart-aleck mode. Press * to return to main menu.
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 suffered for it. Now I'll crank it up as high as it'll go and am always rewarded.
By the way, you absolutely do not want to use a teflon or other non-stick coated surface for this. I have a cast iron pan I got at K-Mart for $5 and its entire purpose in life is to cook meat like this. And also don't ignore the suggestion to use prime meat. The difference between the USDA choice and prime ratings is easily noticable even if you don't eat a lot of beef. You might use a couple of choice steaks to get used to the idea of using a pan that's freaky-hot. They'll still be tasty. But once you move up the scale to prime, you'll see a huge difference and everyone you entertain will always talk about how you make the best steaks in the world.
I'm trying to teach myself to set people on fire with my mind... Is it hot in here?
It sounds very similar to Alton Brown's Pan Seared Rib Eye recipe. Regardless, the steaks are delicious, and using pepper (as Alton's recipe calls for) doesn't seem to cause any problems. I really need to get myself a cast iron skillet.
can't believe no one brought this up yet. Recently some astronomers have been using hubble to look at the middle of galaxies and have discovered Supermassive Black Holes [thehubbletelescope.com] there. In fact, they've found a bunch of 'em, and there's a relationship between the size of the galaxy and the size of the singularity, and every galaxy seems to have one, even our own! And IIRC they figured this would account for the missing stuff.
:)
Well, as far as I understand, that's some missing mass, but not nearly enough. More importantly, it's not the right distribution to explain the velocity curves. I did some googling (you can do some more if you like) and found this page. I'm sure theres better ones out there but it appears to be pretty accurate. This is not simply a problem of having enough mass in the galaxy, but having enough mass in the right places... The velocity curves of stars in different galaxies of the same mass provided that the mass is distributed differently. The curves we get are rather consistant with a spherical halo of dark matter (yes there's other theories but this is simple to imagine) which acts much different than a point mass at the center of the galaxy. This can be seen by the fact that anything inside a spherical shell of matter feels no net gravitational pull. for instance, if the earth was a perfect hollow sphere, on top of it you'd feel plenty of force, but go inside of it, and the forces from all directions cancel out. Same with a spherical halo of dark matter, stars only "feel" a force from the dark matter in the part of the halo that has a radius smaller than their orbital radius, the rest cancels itself out. This makes a significant difference in the measured velocity curves, and these curves do not point to dark matter simply being a point source in the center of the galaxy.
So I don't really think that discovery is that relevant to this discussion. Cool? Yes. But doesn't come close to explaining the mystery that is dark matter. (Yes, I'm aware of various modifications to gravity theory that could also explain this as well)
Cheers,
Justin
Disclaimer: I am not a physicist yet (still one more year to go before my degree). I do however have published research in astrophysics, as I do research with two respected astrophysicists here at Cornell University. If I've made a mistake anywhere in my reasoning here, someone please correct me
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
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D0 Public Information Page
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The Particle Adventure: Basic explanation of particle physics
I'd particularly recommend the last site if you want to know how much we still have to understand! (click on "Unsolved Mysteries")