Importance Of Dark Matter

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Close to 80% of the mass in the universe is unaccounted for. The only hints of the missing mass’s existence are from the breadcrumbs of gravitational influence it leaves behind on the normal matter that makes up you, my dog, and every far-off galaxy. Physicists have labeled this mysterious, unknown quantity of mass “dark matter,” and it is currently one of the biggest open problems on the frontier of theoretical and experimental physics. The effort to detect dark matter draws over $100 million each year alone, and thousands of professors and graduate students from all over the world have dedicated their careers to understanding it.
The first bits of evidence indicating dark matter’s existence came from astronomical data of distant rotating galaxies. To the naked eye, or more precisely, to a telescope capable of detecting light across the entire electromagnetic spectrum, far-off galaxies are rotating faster than they “should.” For a spiral galaxy, the rotational speed at any point on the spiral is related to both the point’s distance from the center of the galaxy and the amount of mass present in the galaxy. Given both the speed of a point on the galaxy and the radius to that point, astronomers can deduce the total amount of mass present. However, astronomers can also estimate the amount of mass simply by observing the total amount of light given off by the stars that constitute the galaxy. As it turns out, there’s a large discrepancy between these two numbers. For a given galaxy to rotate as fast as it does, it would need roughly ten to twenty times more mass than physicists and astronomers observe it having.
And yet, that mass is nowhere to be found. There simply is no luminous matter, or matter that interacts with light, to cont...

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... measures as a positive WIMP annihilation event.
Thus far, dark matter has remained elusive, but physicists see little cause for concern. Experimental data has only just begun to carve out the range of masses where WIMPs can exist. Extremely sensitive detectors are only a few years away, as both the LUX and XENON teams are currently designing devices that would make use of over a ton of liquid xenon. Further, the inability of AMS to distinguish between WIMP annihilation events and pulsars is only temporary. More data of high-energy events would give physicists the capacity to pinpoint the source of cosmic rays. Indeed, within the physics community, there seems to be general optimism that the true nature of dark matter will soon come to light. As Samuel Ting, the Nobel Laureate who designed the AMS, says, “It is only a matter of time, perhaps months or a few years.”

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