CONCEPTS

What is dark matter?

We explain what dark matter is and why it is so important. Also, what is antimatter and dark energy.

  1. What is dark matter?

In astrophysics, a component of the universe other than the so-called baryonic matter (ordinary matter), neutrinos and dark energy is known as dark matter . Its name comes from the fact that it does not emit or interact in any way with electromagnetic radiation , therefore being invisible in the entire spectrum of light. It should not,however,be confused with antimatter.

Dark matter makes up 80% of the total mass of the universe , and its existence is testable because the effects of its gravity are noticeable on astronomical objects around it or on the cosmic microwave background. In fact, the possibility was proposed for the first time that it existed in 1933, when Swiss astronomer and physicist Fritz Zwicky noted that a “non-visible mass” influenced the orbital velocities of galaxy clusters. Since then, many other additional observations have coincided in pointing out its probable existence.

Not much is known about dark matter. Its composition is an enigma, but it is supposed to be composed of ordinary and heavy neutrinos , and recently proposed elementary particles , such as WIMPs and axions, or other non-luminous astronomical bodies. The definitive answer about its composition is one of the main questions of modern cosmology and particle physics.

  1. Importance of dark matter

Dark Matter - universe - nebula
The verification of dark matter would shed lights on the destiny of the universe.

The existence of dark matter is important in understanding the formation model of the Big Bang universe and the mode of behavior of space bodies. Partly because scientific calculations show that there is much more matter in the universe than can be observed. For example, it is usual for the predicted behavior of galaxies to be altered for no apparent reason, except for the possibility of a non-observable amount of matter exerting a gravitational modification on visible matter .

On the other hand, although the existence or not of dark matter does not seem very relevant for life on Earth, according to specialists, its verification would shed lights on the destiny of our universe , in constant expansion (it is known by the red shift of the lights of the distant stars ). If there is no dark matter, this expansion will continue indefinitely, and can eventually cause a rupture in the fabric of space – time. If, on the other hand, it is true that dark matter exists, then its gravitational attraction will eventually slow down and possibly slow the expansion of the cosmos, until it stops. Then it would begin a phase of contraction that would culminate in crushing the entire universe at the same point, thus allowing a new Big Bang.

  1. Antimatter

Antimatter - dark matter
An anti-electron is an antimatter particle that would correspond to an electron.

We must not confuse dark matter with antimatter. The latter is a form of ordinary matter, like the one that composes us , only consisting of fundamental particles of the opposite electromagnetic sign: positive / negative.

Thus, an anti-electron is an antimatter particle that would correspond to an electron , but with a positive rather than a negative charge. However, this anti-matter is organized into atoms and observable molecules , just like ordinary matter.

  1. Dark energy

Dark Energy - Dark Matter
Dark energy accelerates its expansion through a pressure or repulsive gravitational force.

Dark energy is a form of energy present throughout the space of the universe , which tends to accelerate its expansion through a repulsive gravitational pressure or force .

It is estimated that 68% of the energy-matter of the universe is of this type, and that it is a very dense, very homogeneous form of energy, which does not interact with any other of the fundamental forces of the universe, which is why call “dark.” But it has nothing to do, in principle, with dark matter.

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