In astrophysics and physical cosmology, dark matter is considered a type of matter which corresponds to 27% of the energy-matter of the universe, which is not dark energy, ordinary matter, nor neutrinos.

Some observations have indicated the existence of dark matter in the universe, such as the speed at which galaxies rotate, the gravitational lenses of background objects, or how the hot gas temperature is distributed by galaxies. The current theory is that all galaxies exist within a large cluster of dark matter. Its existence can be deduced from its gravitational effects on visible matter, such as stars or galaxies, as well as on the anisotropies of the cosmic microwave background present in the universe. However, its composition remains as a mystery to this day.

It’s called so because it does not emit any type of electromagnetic radiation (such as light). In fact, it does not interact in any way with electromagnetic radiation, being completely transparent throughout the electromagnetic spectrum.

An experiment confirms that it has been detected dark matter in the proximities of our planet, however; some scientists think that this is wrong. What is clear is that for the moment dark matter cannot be seen even with the largest telescope in the world, and will remain as an interrogative for years. 

Why could be important the dark matter?

If there is not enough dark matter to gravitationally bind to the Universe (i.e. if the Omega value is less than 1), it could continue to expand infinitely. On the other hand, if there is enough mass (that is, if the Omega value is greater than 1), the Universe could finally slow its expansion, stop it and start contracting, eventually collapse.

Note that "Omega" is a term that cosmologists use to refer to the full mass of the Universe.

Since the totality of visible matter is only a small fraction of the total mass of the Universe, knowing the exact amount of dark matter with some accuracy could help us to determine its evolutionary future. 

Thanks to important technological advances, both in the astronomical instruments available and in the power of the computers dedicated to astrophysical research, the coincidence of the observational results with the theoretical investigations has become not only possible, but crucial for the progress in the resolution of the mystery of the dark matter, one of the keys to discover the origin, the evolution and the destiny of our Universe.

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