Does dark matter really exist 2

Does dark matter exist?

Return of an outsider
  1. Astronomers have deduced a new type of particle from the inexplicable movement of stars in galaxies. These are likely to interact with classical matter almost exclusively through gravity.

  2. But there is still no direct evidence of "dark matter". In addition, some recent observations cannot be reconciled with it.

  3. Using alternative models, physicists are investigating whether instead gravity works differently on different scales. Such ideas have only played a minor role so far - perhaps wrongly.

The greatest secret of the stars today is no longer why they shine, but why they move the way they do. The problem first appeared almost a century ago: in the 1930s, the Swiss astronomer Fritz Zwicky observed in a cluster of galaxies that some of the 1,000 or so galaxies contained therein orbit the common center of gravity surprisingly quickly. Even generous estimates of the individual masses did not provide enough gravity to explain the behavior. Zwicky suspected that an invisible dark matter must influence the system.

In the 1970s, the US astronomer Vera Rubin discovered the same phenomenon within individual galaxies. The speeds of the stars far outside the center remained about as great as those further inward. Astronomers had expected that more distant stars would slow down because of the lower gravitational pull. Here, too, the visible mass was insufficient to explain the observations. Rubin came to the conclusion that the mysterious dark matter must also exist in galaxies.

This article is featured in Spectrum of Science September 2019

Since then, more evidence has accumulated that astronomers are missing something. The evidence includes firstly the pattern of the tiny temperature fluctuations in the so-called cosmic background radiation, secondly the deflection of light from distant sources by galaxies and galaxy clusters, and thirdly the way in which structures have formed in the course of the development of the cosmos. The phenomena cannot be explained on the basis of the known laws of nature with normal matter alone ...