The "suppressed" growth of galactic clusters suggests the possibility of new physics.

For the last few decades, astrophysicists have relied on what is known as the standard cosmological model. This theoretical framework, crafted by scientists, depicts the structure and evolution of the universe, and until recently, there was no better alternative. Overall, it presents a picture where approximately 70 percent of the universe's mass-energy is attributed to dark energy, around 20-25 percent to dark matter, while all ordinary matter, including galaxies, stars, planets, and so forth, constitutes a mere four percent.

To recall, dark energy is a hypothetical, unknown force that causes the empty space of the universe to expand at an accelerating rate. Dark matter is thought to be an entity that interacts with ordinary matter solely through gravity: it attracts with its immense mass but does not exhibit any other effects. Thus, there are two opposing forces at play: gravity, which gathers matter into clusters, and something akin to anti-gravity that expands the spacetime between these clusters.

The standard model describes how all of this evolves and changes over time. It posits that under the influence of dark matter, ordinary matter first formed stars and galaxies, which then began to coalesce into increasingly larger structures, ultimately creating unimaginable filaments of the cosmic "web." Scientists explain that this is how cold dark matter is supposed to function: as hypothetical particles moving slowly.

Many years ago, this theory was countered by the concept of "hot" dark matter, which suggested that the evolution of matter in the universe occurred in the opposite manner: superclusters formed first, and then gradually fragmented into smaller entities. However, this version has long been dismissed, and efforts are now focused on searching for particles of cold dark matter.

Meanwhile, the expansion of the universe continues to puzzle scientists, particularly the action of dark energy. The issue is that the rate (or rather, the acceleration) of this expansion has been measured in two different ways, yielding two different results. From the light of bright variable stars known as Cepheids and supernova explosions, it was calculated that at a distance of 3.26 million light-years (one megaparsec), they move away from each other at a speed of 73 kilometers per second; when the distance doubles, this speed also doubles, and so on.

The same measurement was conducted using ancient, so-called cosmic microwave background radiation. This faint electromagnetic "echo" of the Big Bang suggested a speed of only 68 kilometers per second for each megaparsec of distance, not 73. One might think that at the very beginning of the universe's history, it expanded differently than it does now. This discrepancy has been termed the Hubble tension. It has been suggested that this could be explained by the idea that dark energy changes its properties over time, possibly due to interactions with dark matter. Thus, the hypothesis of dynamic dark energy emerged.

Recently, astrophysicists from the United States decided to test all of this by examining large galactic structures located relatively close to us. They shared their findings in an article for Physical Review Letters (available on the Cornell University preprint server). The researchers were able to determine how the selected numerous galaxies move not only in relation to us but also in relation to each other, that is, how their clusters grow and develop.

According to the researchers, they observe a "suppressed" growth of large galactic structures: it is progressing too slowly to be considered influenced by dynamic dark energy. This means that Hubble tension, in this case, has not found an explanation, at least not with changing dark energy, and the dilemma within the standard cosmological model remains. Astrophysicists suspect that resolving this cosmic puzzle may require a fundamentally different theory.