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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."
and there's an on-going discussion as to whether or not neutrinos have mass, because if they do, there's enough of them that they might well make up the missing mass of the universe.
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.
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.
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There is a more detailed article about this at the BBC
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")