Dark Matter
There is no more important problem in current cosmology than that of dark matter. Dark matter is composed of particles that do not absorb, reflect, or emit light, so they can not be detected by observing electromagnetic radiation. Dark matter is a material that can not be seen directly. We know that dark matter exists due to the effects it produces on objects that we can observe directly.
Scientists study dark matter by looking at the effects it produces on visible objects. Scientists believe that dark matter can account for unexplained movements of stars between galaxies. Computers play a very important role in the search for data about dark matter. They allow scientists to create models that predict the behavior of galaxies. Satellites are also used to obtain data on the dark matter. In 1997, an image from the Hubble Space Telescope reveals that light from a distant cluster of galaxies is curved by another cluster in the first plane of the image. Based on the path of light, the scientists estimated that the mass of the cluster in the foreground should be 250 times greater than that of the visible matter of the cluster. Scientists believe that dark matter in the cluster accounts for the unexplained mass of it.
Dark matter is a matter that does not emit enough electromagnetic radiation to be detected by the usual means, that is, its existence is in doubt but it is deduced by the gravitational effects it has on visible matter, such as stars or the galaxies. Still, it is believed that a quarter of the universe is formed by this invisible matter. The current theory on the detection of this matter is called "supersymmetry", which explains the fundamental interactions of the particles, demonstrating the existence of dark matter.
Origin of the Dark Matter
But let's go back to the beginning. Dark matter is a generic term to talk about 'something' (matter) that must be there (in the universe), but cannot be seen (dark). In addition, that something is necessary for the constitution of galaxies and does not interact with visible matter.
Just a moment! Why does it follow that there is that 'something' if there is no way of perceiving it? Well, because from a certain moment (or place in space) the gravitational laws that affect our galaxy and that have been reliably proven to stop working ... unless that dark matter exists.
A brief explanation: the planets of our solar system revolve around the Sun without being engulfed by it because there is a balance between the mass of the planet, its distance from the Sun and the speed at which they move in its orbit. Let's say -with the permission of physicists- that there is a formula in which by conjugating these three factors, a universal rule can be established: if the mass is 'x' and the distance is 'y', the speed must be 'z'.
Well, in 1974 the astronomer Vera Rubin observed that this did not happen in the same way as we moved away from the galactic center (mass and velocity were not related in the same way). As it came to contradict all physical laws, he concluded that there must be a hidden mass, the mass that would be necessary for these laws to remain valid throughout the universe. That would come to be the dark matter, which is not seen because it does not emit light or electromagnetic radiation, but it is inferred, it is inferred, from its effect on the gravitation of the galaxies. OK, but could not it be that the physical laws we work with are wrong or insufficient?
Perseverance paid off and in 1978 Vera Rubin and his colleague Kent Ford discovered something unexpected that would change the conception of the Cosmos. The Law of Gravity says that the stars should move at a slower speed as they move away from the center of their galaxy, just as the farther planets of the Solar System rotate at a lower velocity than the Earth around the Sun. The further away from the body that orbits, less intense is the gravitational force. However, Rubin and Ford observed something very different: The stars move at the same speed although they move away from the center of the galaxy. It seemed impossible, but there was no other explanation: the galaxies had to have much more mass than we can see. Unknowingly, they had demonstrated the existence of dark matter, one of the great challenges of current Astronomy and Physics.
Towards the unknown
The Cosmos is much more than galaxies, planets, stars and celestial bodies. All the ordinary matter that we know, the one that makes up the Earth, the Sun, all the stars and constellations and ourselves is only 5% of the Cosmos. The rest of the Universe is made up of dark matter (25%) and energy (70%). But despite the fact that the dark is 95% of the Universe and that 35 years have passed since the discovery of Rubin, Physics still cannot explain even what makes this enigmatic matter, much less what is behind the dark energy.
What is dark matter made of?
And while some look out, here on Earth others look in the subsoil. That we still do not know what dark matter is does not mean that research has not progressed. One of the places you are looking for is at the CERN in Switzerland. The hadron collider could 'make visible' dark matter as it did with the Higgs boson (an elementary particle that plays a fundamental role in the mechanism by which the visible mass originates).
There is already some consensus that dark matter would be made up of fundamental particles similar to the quarks and gluons that make up the atoms. Well, the particles that supposedly form dark matter have been called WIMP, the acronym in English for 'massive particles that interact weakly.
WIMPs are extremely difficult to detect. The only way to do it would be to capture the impact of one of them on the nucleus of an atom, and that such an impact occurs is highly unlikely. Numerous experiments have been made in underground detector installations, but it does not appear. Hence, there is some skepticism in the scientific community. Astronomer Catherine Heymans recognizes it. "If our theories about what dark matter is true, we should have already found the particle that composes it in CERN. But it has not been that way. That suggests that our models of dark matter are not enough and we need more complex theories."