To date, scientists have not been able to unequivocally prove the existence of "dark matter", which supposedly consists of most of our universe.
The "dark matter" that surrounds galaxies throughout the universe is invisible because it does not reflect light. Its presence can only be noticed by the gravitational effect it has on planets and stars.
Despite a $ 2 billion experiment carried out on the International Space Station and showing signs of the existence of "dark matter", it has never been directly observed.
Holes in the sky
The first indication that something was wrong with calculating the mass of the Universe appeared in the mid-30s of the XX century. The Swiss astronomer Fritz Zwicky measured the speed at which galaxies in the Coma Cluster (and this is one of the largest clusters known to us, it includes thousands of galaxies) orbiting a common center.
The result was discouraging: the speeds of the galaxies turned out to be much higher than one would expect based on the observed total mass of the cluster. This meant that the true mass of the Coma Cluster was much larger than the visible mass. But the main amount of matter present in this region of the Universe, for some reason, remains invisible and inaccessible for direct observation, manifesting itself only gravitationally, that is, only as mass.
40 years after Zwicky's work, in the 70s, the American astronomer Vera Rubin studied the speed of rotation around the galactic center of matter located at the periphery of galaxies. Measurements have shown that for many galaxies this speed remains almost constant at a very significant distance from the center.
Promotional video:
These results can be interpreted in only one way: the density of matter in such galaxies does not decrease when moving from the center, but remains almost unchanged. Since the density of visible matter (contained in stars and interstellar gas) rapidly falls towards the periphery of the galaxy, the missing density must be provided by something that we, for some reason, cannot see.
Galactic paradox
For a quantitative explanation of the observed dependences of the rotation rate on the distance to the center of galaxies, it is required that this invisible "something" be about 10 times greater than the usual visible matter. This "something" was called "dark matter" and still remains the most intriguing mystery in astrophysics.
Another important evidence of the presence of "dark matter" in our world comes from calculations simulating the formation of galaxies, which began about 300 thousand years after the start of the Big Bang. Matter simply should not have collected in galaxies, which we, however, observe in the modern era. This problem was called the galactic paradox, and for a long time it was considered a serious argument against the Big Bang theory.
However, if we assume that the particles of ordinary matter in the early Universe were mixed with particles of invisible "dark matter", then in the calculations everything falls into place.
It turns out that the familiar and seemingly studied to the details of the visible world, which we quite recently considered almost understood, is only a small addition to something that the Universe actually consists of.
Mirror world
In 1995, the Hubble Telescope noticed that one of the stars of the Large Magellanic Cloud flared brighter. This glow lasted more than three months, but then the star returned to its natural state. And six years later, a barely luminous object appeared next to the star. It was a cold dwarf that, passing 600 light-years from the star, created a gravitational lens that amplifies light. Calculations have shown that the mass of this dwarf is only 5-10% of the mass of the Sun.
Finally, the general theory of relativity unambiguously links the rate of expansion of the Universe with the average density of the matter contained in it. If in reality the density of the Universe is exactly equal to the critical one, this cannot be an accidental coincidence, but is a consequence of some fundamental property of our world, which has yet to be understood and comprehended.
However, the new theory states that "dark matter" may contain a "mirror world" that can change our understanding of the universe.
The Planck Telescope collected data on the times that followed the Big Bang 13.8 billion years ago, showing that some mysterious matter makes up 26.8 percent of the matter in the universe - more than previously thought.
Ordinary matter - galaxies and planets, which we can directly observe, is only about 4.9 percent. And everything else is even more mysterious "dark energy", which, according to scientists, is responsible for the expansion of the Universe.
A new phenomenon
This year, an international team of researchers announced that a cosmic ray detector aboard the ISS has detected the first sign of the existence of "dark matter."
These results came when the Alpha Magnetic Spectrometer (AMS), launched into space two years ago, discovered signs of a new physical phenomenon that could be strange and unknown matter to date.
The scientists' conclusions are based on the observed excess of positrons - positively charged subatomic particles. The detected burst of positrons could be created by dying "dark matter" - a substance so central to our universe that it determines the arrangement of stars and planets.
The ultimate solution to the mystery of the appearance of mysterious matter can open up completely new areas of study for us, including the possibility of the existence of multiple universes and other dimensions.