Headache around the universe

Man looks in wonder and curiosity into the cosmos. (Image: solarseven / iStock)

Dark energy, the big bang, the expansion of the universe … Cosmologists are gaining more and more insight into the mysteries of the universe – but with the answers, new questions always arise and inconsistencies become apparent. In the April issue, bild der Wissenschaft takes a look at current developments in cosmology. The focus is on the controversy about the expansion of space: the Hubble constant causes headaches. Does the standard model of cosmology need to be revised?

People have been looking at the sky in wonder and question since time immemorial. Religious ideas were gradually replaced by science. But what can the so-called precision cosmology actually clarify? In the first article of the three-part title topic “Cosmology in Crisis”, the bdw astronomy expert Rüdiger Vaas takes a look at the research into the basic questions of cosmology. A historical comparison shows how great the progress in knowledge has been in recent decades.

From this review, he then developed an estimate of which of the current main problems of basic cosmological research could be solved in the future. Among other things, it is about the Big Bang, quantum gravity and dark energy. As part of his “Front Visit to the Limits of Science”, Vaas, together with the American physicist Lee Smolin, explains the particularly persistent puzzles and how the cosmologists continually raise new questions in the search for answers.

Controversy over the Hubble constant shakes cosmology

In the second part of the cover story, the focus is on the currently particularly explosive topic in cosmology: the expansion of the universe after the Big Bang. It is considered one of the most important findings in cosmology. In the article “The Ladder to Heaven”, Vaas first describes the literally gradual recording of the distances and the escape speed of the objects in space. They are determined using cosmic background radiation and using supernovae and variable stars. The dynamics of space are described by the Hubble constant. This is a value with far-reaching significance: the structure, the age and even the future of the universe depend on the Hubble constant. It is also the basis of the standard model of cosmology that scientists have developed over the past two decades.

But this meticulously arranged description of the universe is beginning to falter because its foundation is breaking away – the Hubble constant. It is becoming increasingly clear: the data on the expansion rate of space today and shortly after the Big Bang do not seem to match. This finding puts the cosmologists in considerable need of explanation. Vaas talked about this topic in the context of the sub-article “The measured constant” with the astrophysicist Adam Riess, whose team recently showed that the results are not just slips. As the article makes clear, the controversy surrounding the Hubble constant is indeed groundbreaking. The question arises: Does the world view of physics need to be drastically expanded?

Find out more in the April issue of bild der Wissenschaft, which will be available in stores from March 17th.

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