All atoms are made up of subatomic particles. But not every particle spends its time locked into an atom. Some particles, like neutrinos, whiz around and through our oblivious bodies every day, while others are created when humans smash matter together at high speeds. To see these ultra-tiny particles, however, we have to use enormous machines called particle detectors.
Some of these detectors are cool enough to be mad scientist lairs. Some are buried deep in ice, others weigh as much as a hundred jet planes, while others are carefully calibrated to search for dark matter. Here are ten of the most amazing scientific tools you'll ever see.
1. Super-Kamiokande Experiment
Deep in the Japanese Kamioka mine, 1000 meters below the surface, a huge stainless steel cylinder sits, lined with 13,000 photomultiplier tubes and filled with 50,000 tons of purified water. Built in 1991 with experiments beginning in 1996, Super-Kamiokande has been observing neutrinos from space and those generated on Earth for longer than any other neutrino detector currently running. Those photomultiplier tubes serve as light detectors, picking up the Cherenkov radiation that is emitted in the rare event when a neutrino interacts with matter and releases a charged particle.
Why pump water into a tank when we have oceans of liquid H2O? The ANTARES experiment 2.5 kilometers beneath the Mediterranean Sea is a Cherenkov detector like the Super-Kamiokande experiment, but it looks at neutrino interactions with the water in the naturally occurring ocean, and detects the resulting Cherenkov light with arrays of photomultiplier-based optical modules. Although this is one of only two neutrino observatories now running under natural water, they won't be the last: the proposed KM3NeT project in the Mediterranean will cover several cubic kilometers of water, include thousands of sensors, and incorporate the work from other Mediterranean-Sea-based neutrino observatories, namely ANTARES and from the currently-inactive Mediterranean NEMO and NESTOR projects.
Similarly to ANTARES, the neutrino telescope in Russia's Lake Baikal also uses arrays of optical sensors to search for neutrinos. Unlike ANTARES, however, the Baikal detector has a winter camp, when it must be reached by drilling through the ice that forms over it. (This is apparently "a work for real men," as noted in a photo album that also contains the entry, "Not only neutrino one can fish in Baikal - rich in fish, the lake is a domain of fishermen.")
4. IceCube Neutrino Observatory
The IceCube Neutrino Observatory in Antarctica makes the on in Baikal look wimpy. It also relies on water-albeit in its solid phase—to ferret out neutrinos from space. But although it uses the same type of regular array employed by ANTARES and Baikal, this array cannot merely be lowered into the solid ice of the South Pole. First, researchers had to take a hot-water drill to the ice, building shafts 2.5 kilometers deep, and only then could each string of optical modules be carefully lowered into the void-for a total price tag of $271 million. Another difference is size: composed to over 5,000 optical modules that together take up a volume of about one cubic kilometer, IceCube is much larger than ANTARES or the array in Lake Baikal.
5. Soudan Underground Laboratory's CDMS II
Minnesota's Soudan Mine is the oldest mine for iron ore in Minnesota-and in addition to iron, it also houses detectors for both neutrinos and dark matter thousands of feet below the surface. The detectors were built at this level to reduce the interference of cosmic ray muons, which can cause too much noise in sensitive detectors. We know that dark matter is somehow contributing more mass to the universe than the visible matter can account for, but its true nature is unknown. Some researchers, however, have posited that very heavy particles, which neither emit nor absorb light, could be the source of that extra mass. If any of these WIMPS, or weakly interacting massive particles, reached Earth, they would disturb any matter they passed through-and the CDMS II project aims to detect that disturbance. The mine also houses the neutrino-detecting MINOS project.
6. SLAC's Fermi Gamma Ray Space Telescope
Detectors in the sea, detectors in the ice, and now, a particle detector…in space! SLAC's Fermi Gamma Ray Space Telescope was launched in June 2008 to look at high energy gamma rays. Although its function is to act as a telescope, its operation is analogous to that of a particle detector. The cubic telescope contains almost 900,000 silicon strips to detect the gamma rays that provide a different picture of the universe.
7. CERN's ATLAS detector
CERN's Large Hadron Collider can be used for a variety of experiments, and each detector focuses on looking for something different. Its most sizeable detector, ATLAS, is also the largest general-purpose particle detector in the world. At with a diameter of 25 meters and a length of 46 meters, it's tiny in comparison with a cubic-kilometer neutrino detector-but it does weight 7,000 tons and incorporate a whopping 100 million sensors to examine the LHC's proton-proton collisions.
8. CERN's CMS detector
There's too much physics going on at the Large Hadron Collider to limit ourselves to only one of their detectors. Besides, ATLAS may have a greater volume, but at 12,500 tons, the LHC's Compact Muon Solenoid, or CMS, outweighs it. Like ATLAS, CMS serves as a general-purpose detector. Together, ATLAS and CMS are home to some of the sexiest experiments in physics today, looking for evidence of the Higgs boson, dark matter particles, and even higher dimensions. Unlike ATLAS, however, CMS uses a huge solenoid magnet (a coil of cable that creates an electromagnet when current runs through it) to bend the particle beam, as opposed to ATLAS's multi-magnet system.
9. The Collider Detector at FermiLab (CDF)
In FermiLab's Tevatron collider, beams of protons and antiprotons crash into each other, CDF looks at the resulting carnage. Although the Tevatron has seen the top and bottom quarks, the W and Z bosons (which CERN had found first), and other fundamental particles, it was most frequently in the news this year for its race to beat CERN to the discovery of the Higgs Boson. 2011 was the Tevatron's last chance for new experiments-it's being retired this year.
10. Brookhaven National Lab's PHENIX and STAR detectors
At Brookhaven National Lab, the Relativistic Heavy Ion Collider (RHIC) smashes beams of relatively heavy gold ions together at relativistic speeds. Because the ions are a lot heavier than the particles that smash together at CERN or FermiLab, they also carry less energy. But RHIC isn't aiming to produce high-energy particles-instead, it focuses on making lots of lower energy particles and studying their interactions, particularly the quark-gluon plasma that occurs briefly when the energy of the collision causes particles to "melt." To get the full picture of the soup, you can use both active detectors at RHIC: the STAR detector is the all-purpose observer, looking at hadrons produced in the particle collision, while PHENIX searches for rare and electromagnetic particles. (Incidentally, CERN's ALICE detector also looks at the quark gluon soup that results from heavy-ion collisions, but while this is only one of many CERN experiments, it's the primary focus of RHIC's work.