Dark matter is one of those enigmatic entities in the universe—for which there is no physical evidence, but scientists and astronomers know exists. It does not emit any heat or light; it is disarmingly inconspicuous—and yet members of the scientific community have concluded that it occupies a gargantuan portion of the universe. Dark matter cannot be directly observed, given that it neither absorbs nor emits light—it can only be detected and studied based on its effects on its surrounding environment. Perhaps it is this quality that lends it such a mysterious, exciting air; indeed, dark matter is one of the most intriguing objects present in the universe.
So how have astronomers come to the conclusion that dark matter even exists? In the 20th century, it was theorized that galaxies were spinning at such monumental speeds that they should have torn themselves apart; so, this led scientists to the conclusion that there must be some extra source of gravity that prevented the galaxies from collapsing. Moreover, stars were found to have been revolving much faster than was possible, give their mass. In other words, the mass of these bodies was not sufficient to form such complex structures. So, dark matter has been attributed to this mismatch—it essentially acts as additional force that holds the stars and galaxies together. In fact, an enormous 27% of our universe is composed of dark matter, and only 5% is visible matter! This means that the beings on earth, the planets, and the stars occupy an incredibly minuscule portion of the entire universe! This is not only an amazing revelation, but is also quite humbling—we are just a little speck of life against the vast backdrop of the universe. As said by the site Hetdex, “everything that we can see is like the tip of the cosmic iceberg”.
Astronomers have come up with other methods of detecting dark matter as well; one way is by examining the effect dark matter has on the path of light. Due to the gravitational forces caused by the dark matter, light passing by deviates from its predetermined path; so, by perusing the magnitude and direction of the distortions in the light’s path, astronomers can actually pinpoint the regions of the universe wherein dark matter exists, in addition to the quantity of dark matter present! Moreover, as reported by National Geographic, “dark matter could also explain certain optical illusions that astronomers see in the deep universe”. These illusions and distortions can be explained by the phenomenon known as gravitational lensing.
Calculation and scientific observations have shown that there is a halo or disk of dark matter surrounding the Milky Way Galaxy. It has also been theorized that there is a different, special particle that is behind the very phenomenon of dark matter—which reacts and interacts with light in unexpected way; the Hadron Collider—the most complex research machine ever built—is trying to uncover these elusive particles. As published by CERN, dark matter is hypothesized to be composed of “supersymmetric” particles. Furthermore, one of the leading theories for the types of particles behind dark matter is the WIMP—weakly interacting massive particles. If scientists can actually discern what dark matter is composed of and how it works, it could be an enormous breakthrough in the field of astrophysics and astronomy. Because even though dark matter is not visible to the human eye, it is still the reason we even exist—even though we may believe that it plays no immediate role in our lives, it is in fact the matter that holds the Milky Way Galaxy, and ultimately the entire universe, together.