The idea that the universe is expanding is quite young, and emerged less than a hundred years ago. At the beginning of the last century, many physicists, including Albert Einstein, favored the hypothesis that our universe is stationary and stable. This is precisely why the great scholar initially reacted very negatively to the work of Alexander Friedman published in 1922 that proposed the idea of non-stationary universe. Later, after checking the calculations, Einstein acknowledged that his opponent was right.
Soon, this hypothesis has received an experimental confirmation. In the 1920s, several astronomers, including Georges Lemaitre and Edwin Hubble, independently discovered the so-called red shift (a special case of the Doppler Effect). If an object moves in the direction opposite to that of the Earth, the frequency of the electromagnetic radiation will be shifted towards the red part of the spectrum (in the same way as the sound of a vehicle moving away always shifts to bass).
The astrophysicists noticed that most galaxies have this redshift, and the farther away a galaxy is, the stronger the effect. This gave impetus to the hypothesis of an expanding universe. In the second half of the twentieth century it was followed by the Big Bang theory that explained not only how the universe appeared, but also this expansion that seems strange at first glance. As it often happens, while explaining some things, this hypothesis created a number of difficulties in other areas of physics.
One of them is the so-called cosmological singularity, the state of the universe at the initial moment of the Big Bang, characterized by infinite density and temperature of the matter. This state is absurd from the point of view of classical thermodynamics, because if the density is infinite, then the entropy (a measure of randomness of the system) must tend to zero. However, it cannot coexist with infinite temperature (as this would cause an infinite increase of entropy).
This and other inconsistencies prompted the great physicist Stephen Hawking to make his famous statement that the results of our observations supported the hypothesis that the universe originated at a specific point in time. However, the moment of the beginning of creation, the singularity, is not subject to any of the known laws of physics. The statement could be expected of Hawking who has long been thinking in the universal categories. It was much more difficult for his more „mundane” colleagues to acknowledge the fact that at the heart of the universe there is a process that cannot be studied through the techniques of modern physics.
When contemplating this idea, it turns out that science was penetrated by the idea of a supernatural origin of the world, which is not scientific, but religious. This is nonsense, because science cannot go beyond its well-defined framework. That is why now many scientists are trying to deal with this unfortunate singularity and other „side effects” of the Big Bang theory. A theoretical physicist with the University of Heidelberg (Germany), Christof Wetterich created and presented to the world his cosmological model. In his model the universe is not expanding, and therefore there is no need for singularity in the Big Bang. This is the new version of the stationary model of the universe.
But how did this scientist managed to ignore such an obvious fact as the redshift of galaxies? Wetterich did not ignore it, he just offered a different interpretation of this phenomenon. He noted that the electromagnetic radiation emitted by the atoms depends on the mass of elementary particles that constitute the atoms, in particular electrons. It turns out that if the mass of the atom increases, the emitted photons carry more energy. Since higher energy corresponds to a „high-frequency” of emission and absorption, it is logical to assume that for the observer they will shift to the blue part of the spectrum. However, an inverse effect is possible, and if the particles become lighter, the frequency of the radiation undoubtedly demonstrates that same redshift.
Next, Dr. Wetterich concluded that since the speed of light is finite, when observers are looking at distant galaxies they seem to be traveling back in time, watching them as they were at the time of emission of radiation. Thus, if the mass of the universe was lower in the past and has since steadily increased, the emission of old galaxies seems to be shifted to the red part of the spectrum, and the degree of red shift is proportional to their distance from Earth. This would not mean that they will be moving away from us.
However, Christof Wetterich does not eliminate the expansion and the Big Bang. According to his model, the universe expanded rapidly over a short period of inflation (the period of accelerated expansion immediately after the Big Bang). According to the same model, this expansion was not preceded by the ill-fated moment of singularity. The scientist established that the Big Bang was stretched in the past for essentially infinite time. The modern space according to this hypothesis is quite static, or even began to slowly shrink.
So far, Wetterich’s work has not been published in any peer-reviewed journals, but none of the experts contacted by Nature journal saw any obvious errors in the preprint of the article. Moreover, some of them had very favorable reviews. An astrophysicist HongSheng Zhao with the University of St. Andrews (United Kingdom) said that Wetterich demonstrated a serious approach worthy of consideration.
However, all reviewers, as well as the author of the work, recognize one significant weak point in this research. It is unlikely that an experiment to test this hypothesis could be successful. Since mass is dimensionless, it can be measured only in one way – by comparison to a certain model whose weight is well-known (for example, the mass of objects on the Earth’s surface is measured relative to the standard kilogram stored at the International Bureau of Weights and Measures in the outskirts of Paris). This implies that if the mass of all particles in the universe grows proportionally, it is impossible to record this change in practice because there is no point of comparison.
However, some of Wetterich’s colleagues believe that this hypothesis is still useful for the world of science. „It is always good to find an alternative explanation consistent with all the known observations before we get too comfortable with the standard model,” said physicist Arjun Berera with the University of Edinburgh (UK). And then the fact that the verification of the scientist’s hypothesis is impossible now does not mean that it is impossible in principle. The theory of relativity, for example, had to wait for a decade to be tested, but it still happened.