On Wednesday, scientists announced that a massive particle detector known as the Alpha Magnetic Spectrometer-2, mounted on the International Space Station, may have detected evidence of dark matter.<\/p>\n
Dark matter<\/a> is considered to be the elusive, hidden substance that \u201cholds\u201d the universe together.\u00a0 Although dark matter has thus far been undetected by instruments, it is thought to be nearly six times as prevalent in the universe as ordinary matter, which makes up approximately four percent of our universe.\u00a0 In contrast to ordinary matter, which can be seen easily, dark matter does not emit or interact with light and cannot be detected by telescopes.\u00a0 Scientists know dark matter exists because \u201csomething\u201d in the universe is exerting great forces on the things we can see\u2014dark matter\u2019s presence is detected through its gravitational pull on normal matter.<\/p>\n According to Space.com<\/a>, \u201cPhysicists have suggested that dark matter is made of WIMPs<\/a>, or w<\/span>eakly i<\/span>nteracting m<\/span>assive p<\/span>articles, which almost never interact with normal matter particles. WIMPs are thought to be their own antimatter partner particles, so when two WIMPs meet, they would annihilate each other, as matter and antimatter partners destroy each other on contact.\u201d<\/p>\n The discovery recorded by the Alpha Magnetic Spectrometer-2 (AMS-2) consisted of about 400,000 positrons, which are the antimatter partner particles of electrons.\u00a0 Based on physicists\u2019 speculation of what happens when there is a collision between WIMPs, \u201cthe energies of these positrons suggest they might have been created when particles of dark matter collided and destroyed each other\u201d according to Space.com.<\/p>\n So are these positrons evidence of dark matter?\u00a0 According to Space.com, \u201cthe characteristics of the positrons detected by AMS-2 match predictions for the products of dark-matter collisions\u2026Furthermore, the positrons appear to come from all directions in space, and not a single source in the sky. This finding is also what researchers expected from the products of dark matter, which is thought to permeate the universe.\u201d<\/p>\n Although the positron signal detected could be evidence of dark matter, it could also have come from another source, such as pulsars in our Milky Way Galaxy.\u00a0 Pulsars<\/a> are highly-magnetized pulsating stars which emit a beam of electromagnetic radiation.<\/p>\n It is hoped that as AMS-2 continues to collect more data, scientists will be able to determine the actual source of the signal.\u00a0 In the meantime, scientists will attempt to detect WIMPs using \u201cunderground experiments on Earth such as the Cryogenic Dark Matter Search and XENON Dark Matter Projects\u201d according to Space.com.<\/p>\n The Cryogenic Dark Matter Search (CDMS<\/a>) \u201cis a series of experiments designed directly to detect particle dark matter in the form of WIMPs.\u00a0 Using an array of semiconductor detectors at millikelvin<\/a> temperatures, CDMS has set the most sensitive limits to date on the interactions of WIMP dark matter with terrestrial materials.\u201d\u00a0 The original experiment took place in a tunnel under the campus of Stanford University.\u00a0 The current experiment is \u201clocated deep underground in the Soudan Mine<\/a> in northern Minnesota.\u201d<\/p>\n The XENON Dark Matter Project<\/a> is attempting to detect WIMPs \u201cthrough their elastic scattering,\u201d and is located underground at LNGS, Italy.\u00a0 At the time of its inception in 2007, Xenon was considered \u201cto be one of the most important experiments in the world by Discover Magazine.<\/em>\u201d<\/p>\n So what does this discovery mean and why is dark matter important?\u00a0 Because matter and antimatter annihilate one another on contact, one of the big questions in astrophysics has been \u201cwhere is all the antimatter?\u201d\u00a0 The discovery by AMS-2 may help scientists finally move from inference to actual evidence of the existence of dark matter.<\/p>\n Understanding dark matter is important because dark matter not only gives our universe its structure, it may also determine our universe\u2019s fate.\u00a0 We know our universe is expanding, and that \u201cgravity will ultimately determine the fate of the expansion.\u201d <\/a> Because gravity is dependent upon the mass of the universe<\/a>, measurements regarding mass need to include both light and dark matter.\u00a0 Thus, it is important to know just how much dark matter there is in our universe to know our universe\u2019s ultimate fate.<\/p>\n