A detector in Italy could have cracked the mystery of dark matter ̵
1; if only other scientists could reproduce the results
In the history of physics, there are occasional metaphorical cries from the Void, which are observed once and never again. The wow! Signal, one of the best candidates for a radio communique from a foreign civilization, was discovered only once in 1977; repeated attempts to hear in the region in which they had originated were fruitless. While it has long been believed that single-pole magnets are physically possible, the experimental demonstration of a magnetic monopole on Valentine's Day in 1982, though never again seen, was an experiment in progress in Italy involving dark matter particles Discover, the gravitationally attractive substance that makes up much of the universe, continues to produce tantalizing and positive results. The reservation? Other dark matter detectors around the world do not see the same thing.
For 20 years, the DAMA / LIBRA project (short for "DArk Mater / Large Sodium Iodine Bulk for RAre processes") has been attempting to directly observe dark matter. Indirect detection is easy; In fact, only by observing the orbital pattern of stars in our galaxy can we see that they are guided by an invisible gravitational hand that occupies much more mass than is apparent. Most dark matter detectors, including DAMA, operate on the principle that dark matter is likely to be a weakly interacting particle, meaning that their gravitational force is observable on a massive (galaxy-wide) scale but seldom interacts with "normal" matter other way. That's why we call it "dark": it can bounce off of itself and have its own pressure, but it flows through unnoticed and between us, like tears in the rain.
There are many dark matter experiments in the world, and most of them work on a similar principle: if dark matter is indeed a particle, it should be very, very, very, very, very occasionally "normal" Matter, which would create a very weak spark of light or a jiggle of light atom that we could recognize. This is essentially the mechanism by which humans discover neutrinos, another slippery particle: by placing photomultiplier tubes in a field of dark, still water (or water ice), the tubes discover the occasional rebound of a neutrino on an atom of normal matter.
The detection of dark matter is similar, although the threshold at which dark particles can occasionally trigger baryonic (normal) matter is much lower. When neutrinos are like a gentle knock on the shoulder, dark matter is more like a dust particle – barely perceptible. The dark matter discovery experiments use different materials, but similar principles: create a very calm environment and then listen to the traces of the particles.
Many of these dark matter experiments are underground, where there is less background noise and fictional in their glory: XENON1T, another Italian experiment, lies deep in a mountain and uses liquid xenon (an inert inert gas) in huge water tanks. 8,000 feet underground in an abandoned South Dakota mine, the LUX experiment also uses xenon to listen to the dark matter's dark spot. DAMA / LIBRA, under the mountain Gran Sasso in L'Aquila, uses crystals of sodium iodide and thallium; Ideally, the crystal lattice should vibrate continuously when touched by a particle of dark matter.
And DAMA / LIBRA and its precursor DAMA / NaI (NaI, which means chemically "sodium iodide") had intended some scintillation (pun)) Results: Exactly as expected, during the half of the year, there were more discoveries that the Earth moved against the tide of dark matter relative to the galaxy and less during the time it moved with the tide. As with any experiment, there were small margins of error, but the results were promising. "During seven independent experiments of one year each, [DAMA/NaI] pointed out the existence of a modulation that satisfies the many peculiarities of an effect induced [weakly interacting massive particle]which leads to significant evidence," write the scientists in a paper from 2003. [19659011EinigeVorbehaltehiernatürlich:KeineanderenExperimentezurErkennungdunklerMateriekonntendieErgebnissevonDAMA/LIBRAoderDAMA/NaIreproduzieren-nochnichtVorallemaberkonnteniemandbeweisendassDAMA/LibraetwasfalschesgetanhatwasihreErgebnissehätteverzerrenkönnen”DasMysterium[r] is why their result is incompatible with almost any other result in the field, "said Juan Collar, physicist at the University of Chicago, told Nature.
Now, after the DAMA / Libra experiment in 2010 The scientists want to publish their new results, you can see a preview of them by browsing through this abstruse PowerPoint (inexplicably written in Comic Sans) from the beginning of this week, but basically the so-called modulation – the pattern of rising and falling falling signals, which may be dark matter particles that strike the detectors ffen – exist.