For decades, scientists have been puzzling over the fact that our universe is expanding. From a logical point of view, gravity should attract galaxies to each other, but observations of the 1990s showed that the Universe is not just expanding, it is expanding with an accelerating trend, and the so-called dark energy is to blame.
Dark energy (not to be confused with dark matter) is a hypothetical force that accounts for up to 68.3 percent of all energy in the observable universe. And scientists believe that this energy pushes galaxies away from each other. Nevertheless, despite many indirect evidence of its existence, no one has yet been able to directly determine the presence of dark energy, or at least adequately explain where it came from.
However, according to the new hypothesis, the answer to this question lay literally before our noses. According to this hypothesis, dark energy is absolutely commonplace when viewed from the point of view of one of the fundamental laws of the universe, which we often forget when we consider this issue. This fundamental law is the law of conservation of energy. They talk about him back in high school. In simple words, he says the following: energy cannot just be created or destroyed, it cannot just disappear. The only thing it can do is to flow from one state to another or move from one body to another. Most of our fundamental physics is based on this law.
A new study by a team of physicists from different institutions suggests that if even a subtle loss of energy occurred during the earliest days of the universe, this could explain the nature of dark energy that many scientists are talking about today. The authors of the study add that, it is quite possible that this leak, although it violated a fundamental law, violated it so insignificantly that in the end no one would have noticed it.
The hypothesis is quite daring, it should be noted. But here it is interesting to understand what exactly led the researchers to such a hypothesis. In order to understand the issue of dark energy and try to explain it, you need to go back to 1917, the year when Einstein was trying to understand why the universe is static and does not tend to shrink or expand. At that time, this theory was very popular.
To explain the absence of a gravitational tie, Einstein suggested that there must be something in the Universe that could create resistance to gravity on a universal scale. This is how the cosmological constant appeared. However, he abandoned this idea in 1929 when astronomer Edwin Hubble first saw the signs of an expanding universe, which he noted in his calculations. In the early 90s of the last century, scientists proved that the Universe is expanding with acceleration, and Einstein's constant became relevant again. Astrophysicists have come to believe that this constant, which Einstein spoke about in his works several decades ago, in fact, has always been the thing that we call dark energy today.
So what is this, dark energy? In a general sense, it is considered as a cosmological constant, unchanging energy density that arises and uniformly fills the space of the Universe. We know from quantum mechanics that in fact, empty space is never empty - it is filled with quantum particles and the energy that appears under the influence of the appearance and disappearance of these particles. And some of these particles may have repulsive power - that very dark energy.
Perhaps the single most controversial point is that the predicted amount of emerging dark energy within the framework of this process should be greater than the indicator currently put forward taking into account the observation of the expansion of the Universe - up to 120 orders of magnitude more, to be more precise. This may indicate that we either measure this volume incorrectly, or we do not at all understand where exactly dark energy originates.
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New research suggests that the latter is the most likely scenario, and a new hypothesis is put forward on this occasion. What if, early in its appearance, the universe experienced some energy leakage, and this loss set the pace for the emergence of dark energy?
“In our model, dark energy is represented by something that can indicate the amount of energy and momentum that has been lost in the entire history of the universe,” says one of the researchers, Alejandro Perez.
Central to this new hypothesis is an alternative model of general relativity, which Einstein arrived at in the 1910s. It is called the unimodular gravity model. According to her, energy does not have to be conserved at all. At the same time, the researchers say that when applying the model of unimodular gravity in calculations, the value of the cosmological constant is ideally correlated with those observations according to which our universe is expanding with acceleration.
It is also important to note that this model does not necessarily strongly contradict our current understanding of the universe. Although the disappearance of energy in the early Universe will affect the change in the values of the volumes of dark energy, it will not affect anything else, or at least it will not be noticeable in our modern experiments.
“The energy of the substance that makes up matter can be transferred to the gravitational field, and this 'energy loss' will act as a cosmological constant - it will not dilute later with the expansion of the universe,” says Thibault Josse, another member of the research team.
“With this in mind, the loss or creation of energy in the distant past could have serious consequences today and at a completely different level and on a larger scale.”
Here, however, the question arises: if the disappearance of energy does not have any effects on the Universe, other than changing the value of the darkest energy itself, then how can the correctness or incorrectness of this hypothesis be verified? This is the main problem.
“Our proposal is very general, and any change in the law of conservation of energy is likely to contribute to the efficiency of the cosmological constant. For example, it could place new constraints on phenomenological models outside of quantum mechanics,”says Josse.
“On the other hand, direct evidence that dark energy is powered by ordinary energy that changes its state seems beyond reality, since we already have the value of the lambda term (it is also a cosmological constant), and, in addition, we are limited only the last time of her (dark energy) evolution”.
In general, this hypothesis seems to be what it is so far, a hypothesis that has not yet been tested. However, physicists say they want to investigate it in more detail for probabilities in the future.
“There is no question of any certainty. But this new idea seems to be at least interesting and therefore deserves attention,”says Lee Smolin, a theoretical physicist at the Canadian Institute for Theoretical Physics in Waterloo, who was not involved in the study.
NIKOLAY KHIZHNYAK
