Monday, August 19, 2019
Dark Energy: The Mystery of This Millennium :: Biology Essays Research Papers
Dark Energy: The Mystery of This Millennium Billions of years ago, the universe was nothing but an infinitesimally small particle. Then, in less time than the blink of an eye, the universe expanded and increased in size by a factor of 1050. Expansion eventually began to slow down, allowing galaxies, star clusters, and so on, to form. Theoretically, expansion should still be slowing down; but to the contrary, expansion is in fact accelerating (10). Some scientists theorize that an unknown force, called Dark Energy, may be the cause of this accelerated expansion, while others disagree. For some time, exploding stars, or supernovas, were used as a "cosmic measuring stick" (4). That is, scientists used these supernovas to calculate the age of the universe. In 1998, two groups of astronomers surveyed supernovas in very distant galaxies. These supernovas were much dimmer than expected to be, and calculations proved that the stars were over ten billion light years away, much farther away than they should be had the universe been expanding at a slowing rate, or even a constant rate, as previously theorized (5). This discovery proved that the cosmos are not expanding at a slowing or a constant rate, but instead they are expanding at an accelerated rate (4). Since this discovery, scientists have been trying to uncover what it is that accounts for this accelerated expansion. Scientists have calculated the density of the cosmos, and they have also calculated the total mass of all visible galaxies. However, the galaxies make up less than one-third of the density needed to satisfy the current calculations of the early universe (2). Simple logic tells us that there must be something else in the universe, with some kind of mass, which accounts for over two-thirds of the density of the cosmos. The new theory incorporates a different force called Dark Energy. At first, scientists did not know how Dark Energy works or what it is physically made up of. Some proposed ideas of Dark Energy are: a cosmic field associated with inflation, a low-energy field called "quintessence," and the cosmological constant, or a negative pressure, as suggested by Albert Einstein (7). In July of 2003, scientists confirmed that Dark Energy exists, but they still cannot truly explain it (6). They do know that Dark Energy is different from every other kind of energy found. Some say it is a negative gravity (1), while others say that it does not necessarily act opposite to gravity, but, instead, it acts more like a negative pressure (5).