Old Black Holes Replace Dark Matter
The attractive force of dark matter really derives from hordes of small, black holes, which were produced in the Big Bang.
The universe may contain billions of black holes. According to a new theory, old - ancient, really - black holes could make up the universe’s unknown dark matter. Possibly, billions of black holes with masses ranging from 1/100 of the Sun’s to 10,000 solar masses were produced immediately after the Big Bang. The smallest black holes gathered around the galaxies, where they are orbiting in a disc. The attractive force of the holes is what we know as the effect of dark matter.
The relativity theory has even been confirmed via several astronomical observations of how the universe is behaving. So, scientists do not dismiss Einstein’s extensive work.
The first problem emerged as early as 1933. Swiss astronomer Fritz Zwicky discovered that the Coma galaxy cluster is rotating so fast that the gravity of the visible stars and gases in the galaxies could not possibly hold the cluster together by itself. Hence, he believed that invisible matter existed in the galaxy cluster, preventing the galaxies from being flung in all directions. In the 1970s, more observations showed that the same problem goes for individual stars in individual galaxies. The systems are rotating too fast to be able to maintain the outermost stars in their orbits.
So, scientists decided to introduce a comprehensive addition to cosmology, which could make theory and reality correspond. They invented dark matter.
DARK ENERGY EXPANDS RELATIVITY
With dark matter in the equation, the relativity theory applied again – until 1998, when astronomers discovered that the expansion of the universe is accelerating. Until then, scientists believed that the pace of the expansion had to be constant or decreasing, but astronomical observations showed that remote, exploding stars shone unexpectedly weakly as compared to supernovas close by. The best explanation was that the remote supernovas are further away from Earth than scientists expected, as the expansion of the universe had increased. Scientists explained the ever faster expansion with dark, repulsive energy.
Dark energy is immediately consistent with the relativity theory, as Albert Einstein introduced a type of repulsive energy in his work. When the theory was published in 1915, astronomers still believed that the universe was static and galaxies standing still.
So, Einstein introduced a theoretical, repulsive force, which could resist gravity’s attempts at attracting galaxies to each other. However, Einstein considered the invention of the repulsive force the major mistake of his career in 1929, when Edwin Hubble proved that the universe is not static, but rather expanding in all directions.
Einstein integrated the repulsive force in a wrong way – as a counterweight to gravity – but his theory has many similarities with the dark energy, which scientists later used to explain the accelerating expansion of the universe. The repulsive energy is believed to derive from the void between galaxy clusters. According to relativity theory, a void of certain dimensions always involves the same quantity of repulsive energy. As the universe expands, so does the void, and consequently, the dark energy has gained more strength. According to modern cosmology, the repulsion became so strong six billion years ago that the dark energy defeated gravity’s attempt to make the universe shrink, accelerating the expansion.
UNIVERSAL DARKNESS IS A... LIE?
The concepts of dark matter and dark energy filled the gaps of relativity theory – but major corrections of modern cosmology are required to make the calculations come out right. According to the theories, dark energy makes up 68 % of the total matter of the universe, while 27 % of the universe consists of dark matter. Only 5 % of the matter is ordinary, visible atoms such as stars, gases, Earth – and humans.
Such a far-reaching assertion requires proof, but in spite of decades of persistent attempts, neither astronomers nor physicists have managed to shed light on the dark side of the universe. So, several scientists are now rejecting 95 % of the universe as an unsupportable theory, trusting in other theories instead.
Several alternatives to dark matter and dark energy exist. The most radical one, known as MOND, originates from Israeli scientist Mordehai Milgrom, who thinks that the unknown matter of the universe does not exist.
Instead, the problem in explaining fast galaxy rotation is due to an error in Newton’s law of gravity from 1666. According to Milgrom, the strength of gravity does not decrease as much across long distances as the theory predicts.
According to Newton, the attractive force of a body depends on its mass. But the attractive force of a large body such as the concentration of stars at the centre of a galaxy on smaller, orbiting bodies like the outermost stars of a galaxy is very quickly reduced with distance.
In practice, this means that the stars at the centre of the galaxy cannot hold on to the outermost stars of the galaxy.
According to MOND, the theory applies to small systems such as the Solar System, but in large ones such as a galaxy stretching 100,000 light years, Newton’s law of gravity only applies to a certain extent, depending on the matter of the system.
From there, gravity does not decrease as much as Newton says. Hence, the gravity of the visible matter of the galaxy is still enough to hold on to the outermost stars.
Most scientists immediately rejected Milgrom’s theory. He does not explain why gravity behaves differently, and his new law of gravity does not describe the developments of the universe all the way back to the Big Bang. However, US astronomer Stacy McGaugh’s observations of 153 galaxies support MOND. The theory is perfectly consistent with the galaxies' behaviour and can explain their rotation without the need for dark matter.
According to another alternative theory, the unknown dark matter of the universe does not consist of particles, but is rather a huge quantity of dark holes, which formed in the first second following the Big Bang.
The idea is not a new one, and it has reemerged after detectors last year recorded gravitational waves from a collision between two black holes. Ordinary black holes from a supernova explosion can weigh 5-15 solar
masses, but the colliding black holes’ weigh 29 and 36 solar masses. The large black holes could have originated from collisions between smaller holes, but according to several theorists, they probably derive from the Big Bang. If so, the galaxies could be surrounded by old black holes of less than 5 solar masses, which exert the same force as dark matter.
The idea can be tested via astronomical observations. Black holes are invisible, but scientists can reveal them and their sizes, because the holes have such major masses that they function as gravitational lenses, bending and increasing the light of stars behind the holes.
If scientists can find black holes that are smaller than the smallest ones from a supernova explosion, the holes can only have originated in the Big Bang.
TIME TO FIND OUT
Other theories "kill" dark energy. According to one, the need for dark energy to drive the expansion of the universe is due to simple calculation errors. The relativity theory equations are so complex that scientists must work with simplifications, arriving at very different results. Scientists from the Eötvös Loránd University have used a new simplification, which makes the universe’s accelerating expansion apply without dark energy, and hence, they believe that it does not exist.
According to other astronomers, the accelerating expansion could be due to the repulsion between galaxies and antigalaxies. A CERN experiment is checking the theory by testing if floating antihydrogen atoms are attracted by Earth’s gravity to fall down like ordinary hydrogen atoms – or if they are repelled by Earth, falling upwards. If so, the theory of repulsive antigalaxies could be correct, killing off dark energy.
We will soon find out. In the tunnel under Gran Sasso mountain, physicists have restarted the large Xenon detector for new experiments. If the machine does not find the dark particles of the universe within five years, physicists must give up the theory of dark matter to find other explanations of the behaviour of the universe.