Astrophysicists have questioned the accelerated expansion of the universe

For more than 20 years, scientists have believed that the universe is expanding at an accelerating rate due to mysterious dark energy, an invisible form of energy that, according to modern cosmological models, makes up most of the contents of the cosmos. However, a new study has called into question some of the fundamental assumptions underlying this theory. Scientists have found signs that the expansion of the universe may not occur exactly as described by the current model, and the observed effects may be related to the more complex structure of the cosmos. Why researchers are talking about revising the main theory of the universe again and what this means for future science is in the Izvestia article.

From Einstein to Dark Energy: how scientists tried to explain the expansion of the universe

At the beginning of the 20th century, mankind's understanding of the universe changed dramatically. In 1915, Albert Einstein formulated the general theory of relativity, which explained gravity not as an ordinary force, but as the curvature of space-time under the influence of mass and energy. This theory became the basis of modern cosmology and allowed scientists to consider the universe as a single physical system that can be studied using mathematical models.

However, soon after the theory was created, observations appeared that showed that the universe is not static. In the 1920s, astronomer Edwin Hubble discovered that distant galaxies were moving away from Earth, and the farther away an object was, the faster it was moving away from us. This was the first serious proof that space is expanding.

However, decades later, the cosmological constant unexpectedly returned to science. At the end of the 20th century, scientists discovered that the expansion of the universe is not just continuing — it is accelerating. To explain this phenomenon, the researchers once again turned to the idea of energy, which acts as a kind of "antigravity" and causes space to expand faster.

This mysterious force was called dark energy. Today, it is one of the key elements of the standard model of cosmology, the ΛCDM model. According to modern calculations, about 70% of the universe is made up of dark energy, about 25% is made up of dark matter, and the ordinary matter that makes up stars, planets, and people is only a small part of the cosmos. However, scientists still do not know what exactly dark energy is. It cannot be seen directly or detected using conventional telescopes. Its existence is judged only by how it affects the movement and distribution of space objects.

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The universe may be more complex than the model suggested: what scientists have discovered

The new study is related to one of the main foundations of modern cosmology — the assumption that the universe on a large scale is homogeneous and uniform in all directions. This idea is the basis of the Friedman—Lemaitre—Robertson—Walker (FLRW) model, which is used to describe the expansion of space. According to this model, there is no "special" direction in the universe: if you observe space on a large enough scale, its properties should look approximately the same regardless of where the telescope is pointed. It is on this assumption that many calculations related to dark energy are based.

However, scientists have studied data on distant Type Ia supernovae and found signs that the picture may be more complicated. These space objects are often referred to as "standard candles": their known brightness allows astronomers to calculate distances in the universe and study its expansion rate. In 2011, Saul Perlmutter, Brian P. Schmidt, and Adam G. Riss were awarded the Nobel Prize in Physics for this work.

The analysis showed possible differences in what the acceleration of expansion looks like in different directions. This may mean that some of the observed effects, which were previously associated exclusively with dark energy, may be related to the heterogeneity of the universe itself. We are not talking about the fact that scientists have discovered the "center of the universe" or proved that the Earth occupies a special position in space. The researchers are talking about a more complex problem: perhaps some properties of the universe on a large scale differ from what the standard model assumed.

One of the important concepts in this discussion was the so—called cosmic dipole anomaly - the observed differences in the distribution of space objects in different directions. If such deviations are confirmed in future studies, scientists will have to clarify existing ideas about the structure and evolution of the universe.

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The end of dark energy: why scientists are not in a hurry to rewrite the history of the Universe yet

Despite the big headlines, the new study does not mean that dark energy has been recognized as a mistake or that the current cosmological model no longer works. In science, such conclusions need to be confirmed by independent observations and a large amount of data. Dark energy still has several important confirmations. Its existence is consistent not only with observations of supernovae, but also with the study of the cosmic microwave background — radiation left over from the early Universe, as well as with the analysis of the distribution of galaxies in space.

However, it is precisely such studies that help scientists test the boundaries of existing theories. The history of science shows that even the most successful models may require refinement: once upon a time, Einstein's ideas changed the concept of space and time, and now new observations can force researchers to take a fresh look at how the universe itself develops.

If future observations confirm the detected deviations, this may lead not to the rejection of dark energy, but to the creation of a more accurate model of the cosmos that better explains all available data. In the meantime, scientists continue to study one of the biggest mysteries of modern physics. Dark energy remains a hypothesis that helps explain the observable universe, but new research reminds us that even fundamental ideas about the cosmos are not definitive. Perhaps the next revolution in understanding the universe will begin with those deviations that seem small today.