Dark Matter

Introduction

Dark Matter, according to hypothesis, is a kind of matter that accounts for a large part of the total mass in the universe. It cannot be seen with telescopes, simply because it does not emit or absorb light or any electromagnetic radiation. Its existence is inferred from its gravitational effects on visible matter, radiation and the large-scale fabric of the universe. Dark matter is estimated to constitute more than 90% of the matter in the universe.

               

The dark matter hypothesis arises from calculations concerning the Big Bang theory. There is insufficient observed matter to account for the current stability of the universe. If the Big Bang happened as postulated, and the universe contained only observable matter, then it should by now have spread itself into complete dissociation. Therefore, astrophysicists propose that there must be much greater gravity caused by matter, which cannot be detected by any current method. This is the dark matter proposed, and Big Bang astrophysicists assume that 84% of all the matter in the universe is dark matter. Scientists know dark matter exists by its gravitational pull but, unlike regular matter and antimatter, it's so far been undetectable. Regular matter accounts for about 4 percent of the universe's mass, and dark matter makes up about 25 percent. The rest is dark energy, which is also a mystery.

Case Study

What's regarded as the world's most sensitive dark matter detector was lowered into a 70,000-gallon water tank nearly a mile (1.6 kilometers) beneath the earth's surface, shrouding it in enough insulation to isolate dark matter from the cosmic radiation that makes it impossible to detect above ground.

The search in South Dakota began in 2003 after the Homestake Gold Mine in the Black Hills' Lead, South Dakota, shuttered for good. Scientists came to know about the site, and in July, after years of fundraising and planning, the LUX detector was moved into the Sanford Underground Research Facility, 4,850 feet (1,478 meters) below the earth's surface. It took two days to ease the phone booth-sized detector down the once-filthy shaft and walkways that originally opened for mining in 1876 during the Black Hills Gold Rush. There, the device was further insulated from cosmic radiation by being submerged in water that's run through reverse osmosis filters to de-ionize and clean it.

Scientists are currently working to finish the plumbing needed to keep the xenon as clean as possible. The xenon, in both liquid and gas form, will fill the detector and be continuously circulated through a purifier that works much like a dialysis machine, pulling the substance out to remove impurities before pushing it back into the detector.

Bibliography: Dark matter detector nearing activation in US mine, Amber Hunt.