Modern Physics

the dark matter

Faced with the immensity of the universe, we can observe infinite celestial bodies, there are galaxies and more galaxies and each one composed of billions of stars. There is a lot of matter in the universe, although it is becoming increasingly clear that this matter is not so evenly distributed. And this even agrees with the Big Bang theory, which assumes an inflation of the universe in t ~ 10 -34 seconds.

Before the Big Bang there was nothing, not even time, it was the beginning of space-time. From then on matter began to be formed, protons and neutrons formed from quarks. Estimates say that this event took place about fifteen billion years ago. Currently, scientists from various parts of the world, including the American space agency (NASA), are still trying to discover how this matter is distributed in the universe. The first investigations made them believe that matter would be evenly distributed, but, as mentioned above, data obtained later, more precisely in 1992 by NASA’s Cosmic Backgroud Explorer (COBE) satellite, reveal that matter is not distributed. evenly, on the contrary, in the universe there are regions with a lot of concentration of galaxies while others are practically empty. In addition, studies carried out by Doctor Vera Rubin and her collaborator Kent Ford also show that in the universe there is some type of matter that cannot be observed, this matter apparently does not interact with radiation, that is, it does not emit, reflect or absorb radiation. , so it is not yet possible to observe it.

Then you must be wondering how we know it exists then! Well, this suspicion began after years of observation by Dr. Vera Rubin and her collaborator Kent Ford, in the laboratory of the Kitt Peak National Observatory, in the State of Arizona, United States. They made measurements of the rotation of remote galaxies and were surprised to analyze the data, as they showed that stars located in regions farther from the center of the galaxy had the same speed as more central stars. This fact was in disagreement with what was expected, as it was believed that the stars closer to the center would have higher speeds. The result was also contrary to classical mechanics, unless there was some kind of matter that could not be seen. The search for more evidence of the existence of this “invisible” matter began.

This “invisible” matter has been called dark matter by scientists. It is estimated that approximately ninety percent of the entire universe is composed of this dark matter. Normal matter, which can be observed, is called baryonic matter, as it is formed by baryons, which are the particles of the nucleus of the atom, protons and neutrons. More recent studies show that dark matter contains a small part of baryonic matter. What then would this mysterious, virtually undetectable matter be formed from?

Apparently, it is formed in part by neutrinos, although the mass of the neutrino is very small, it is believed that the amount of neutrinos existing in a galaxy is large enough to explain part of the dark matter. As I said, the presence of the neutrino in dark matter does not fully explain its occurrence, because even this gigantic amount of neutrinos present in galaxies is not enough to justify all the mass of the universe. The search for answers continues, but so far it has not been possible to fully determine the composition of this mysterious matter.

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