DARK PHYSICS IS STUCK
Is it time to admit that cosmology is ensnared by dimly understood forces? MICHAEL BROOKS investigates.
IN 2006, I VENTURED to the Carnegie Institution in Washington DC. There, I had a long conversation with the astronomer Vera Rubin. Thirty-six years earlier, she was one of the first modern cosmologists to suggest that a huge part of the universe was missing. At the time, she had suggested it might take a decade to find this missing stuff, now best known as “dark matter”.
BY 1990, TWO DECADES later, when dark matter was still missing, the English Astronomer Royal Martin Rees said it would turn up within a decade. In 1999 dark matter hadn’t made an appearance, but Rees was unbowed: he declared himself “optimistic” that, in five years’ time, he would be able to report what dark matter is.
But by the time Rubin and I met in Washington, astronomers were all still empty-handed. What’s more, things had gotten worse: in 1997 astronomers had discovered “dark energy”, another missing component of the cosmos. Now a full 96% of the universe involved a form of matter and energy unknown to science.
Has there been progress since then? Not really. In 2018, more than 20 years after we had to acknowledge our ignorance of the vast majority of the universe, we still haven’t identified what dark matter or dark energy might be. “I’m certainly ready for the great leap forward,” says Rocky Kolb, an astronomer based at the University of Chicago.
And there is not much hope of making such a leap either. In fact, some researchers are proposing that we might be living through our generation’s “ether moment”. For centuries, mainstream science believed that light propagated through a space filled with a mysterious stuff – the ether. But by the turn of the 20th century, the ether’s existence had been refuted. Could both dark matter and dark energy be similarly seductive illusions?
THE FIRST HINT OF a dark side to the universe came in 1933, when the Swiss astronomer Fritz Zwicky noticed that the Coma galaxy cluster was spinning so fast that it should be falling apart due to centripetal forces. Zwicky suggested that they might be holding together because of the gravitational action of embedded massive particles that didn’t betray their presence by reflecting light. He called this hypothetical stuff “Dunkle
Materie”: dark matter. The search didn’t really get off the ground though until the 1970s. It was the heyday