It gives astronomers and physicists a headache. But one of the most glaring problems in astronomy now also results in a beautiful book that makes even more curious about what exactly is going on.

In recent years, scientists armed with powerful (space) telescopes and aided by exciting missions to other celestial bodies have uncovered many a secret of the universe. But some secrets, despite repeated urging from researchers, the cosmos refuses to release. Dark matter is such a secret. And science journalist Govert Schilling has now written a book about it: The elephant in the universe.

Frustrating

The title refers to a phenomenon that physicists cannot ignore, but at the same time cannot properly interpret. And with that, that proverbial elephant in the universe is pretty frustrating. This becomes clear when Schilling takes us by the hand in his book and explains where and how the idea for dark matter was born. He introduces us to the scientists who played an important role in it and all died before a solution was even in sight. We are now nine decades further and the elephant still stands firm.

The riddle

There are many fundamental questions and problems for astronomers and physicists to ponder. But in the midst of that, dark matter is without a doubt headache file no. 1. “That problem feels the most uncomfortable,” physicist Ivo van Vulpen told me a few years ago. Scientias.nl. It has everything to do with the fact that we find clues to the existence of dark matter in many places in the universe. For example, the speeds of stars in the Milky Way reveal that our galaxy contains more mass than we can see. Apparently half of our galaxy consists of invisible (or dark) matter. And other galaxies have also turned out to be heavier in the past than you would expect based on their visible matter. Dark matter is therefore omnipresent. In fact, about 85 percent of all mass in the universe could be classified as dark matter. But what kind of stuff is this?

Which brings us to the proverbial elephant in the universe. Because scientists don’t know. It’s not that they haven’t looked into it; In Schilling’s book we read about numerous (thought) experiments that attempted to reveal the nature of dark matter. But there has been no breakthrough all these years.

Doubts

And then you can start doubting. Schilling sometimes does that himself, as he already confesses in the first chapter. Does dark matter actually exist? After all, we can’t see it. And we have been forced to infer its existence from what we can see. But do we understand visible matter well enough to infer the existence of invisible matter? Or might it be possible that our theories with which we have been able to describe the universe nicely until now have gone awry and contained a mistaken assumption, forcing us to create dark matter, even though that is not at all? Schilling is in good company with his doubts. Because there are also plenty of scientists who do not take the existence of dark matter for granted. The Dutch researcher Erik Verlinde is a fairly well-known example of this. “He doesn’t believe there is an elephant at all,” Schilling says in his book. “According to his theory of emergent gravity, dark matter does not exist. Instead, what we perceive as the gravitational effect of mysterious dark stuff is in reality the interaction between normal matter and the ubiquitous dark energy (another rather mysterious and hypothetical form of energy that would be responsible for the accelerated expansion of the universe, ed.).” However, not everyone is convinced; Verlinde’s theory still has some loose ends. And so the question ‘what does the material universe consist of’ remains unanswered for the time being.

To persevere

The fact that we still cannot change such a fundamental question in 2021 is palpably gnawing at the many researchers whom Schilling gives the floor in his book. But at the same time, they are not deterred. The elephant takes up too much space for that. “Dark matter rules our universe,” says Schilling. “Without her, we probably wouldn’t be here to marvel at the nature of the cosmos.”

Whether in the future this wonder will give way to a complete understanding of the material universe remains to be seen. Many scientists are working on it and aspiring to it. Unraveling the nature of dark matter would be a breakthrough. Worthy of a Nobel Prize. But what Schilling shows very nicely in his book is that not only breakthroughs are fantastic; the road to it – with ideas, experiments, necessarily revised hypotheses and theories, trial and error – is just as fascinating.

‘The elephant in the universe‘ is published by Fontaine Publishers. The book was written by science journalist Govert Schilling and provided with a foreword by Vincent Icke, professor of theoretical astronomy at Leiden University and professor by special appointment of cosmology at the University of Amsterdam. The book costs 25 euros (paperback) or 12.99 (ebook) and is here available.