New matter is created when space expands

The great mystery of time

The great mystery of time

Physics is making great strides - and yet there are still many unanswered questions. Why is it? At the natural limits of this science? Or because she hasn't found the right model yet?

Carlo Rovelli was an adventurer when he was young. Alone he set out on a trip around the world when he was twenty. Today, in his early sixties, he has to smile at his naivety back then. “But I still think I made the right choice, and in a way I'm still experiencing the adventure that began then,” he notes.

Today, Rovelli is Professor of Physics at the University of Marseille and author of inspiring books. You can do without a single one of the complicated formulas that characterize Rovelli's field. His latest has the provocative title: "What if there wasn't time?"

Richard A. Muller and the Limits of Physics

"Now - The Physics of Time" is what Richard A. Muller called his approach to the same subject. The 73-year-old is a professor of physics at the University of California at Berkeley, and his early experiences also shaped him. When he was in sixth grade at the Bronx High School of Science, a student gave him "The Limitations of Science" by John William Navin Sullivan, and he still has it today. "I hated this book," he recalls, "it confounded my belief that science was the only path to knowledge that saved us."

What he did not know at the time: Einstein had already worried that physics was incomplete, that it did not represent a complete description of reality. Einstein is dead, but the unanswered questions remain. What is more: the explanations that his theories of relativity have provided keep raising new questions. So that today's basic physics is "in a deplorable state", as Carlo Rovelli observes.

"It goes so far that we actually no longer know what space, time and matter actually are."

The room - from far and near

The basic problem of today's physics is that it is dominated not just by one, but by two theories that do not want to go together at all. Quantum mechanics explains the processes in the smallest detail, the theory of relativity the big picture. The explanations of the theories of relativity follow the laws of causality. Space and time merge in them, they become dependent on each other and on matter. In concrete terms: the faster someone moves, the slower the time flows.

This could be proven in experiments as well as the oddities postulated by quantum mechanics. That, for example, speed and energy are only available in small packages, or that there is an element of chance. Therefore, only probabilities can be determined for radioactive decay.

Space as a fabric of lines

Of course there are scientists who want to bring both together. Carlo Rovelli is one of them. His favorite is loop theory, which sees space as a web of lines. “Just as a T-shirt appears smooth from a distance, but you can count its threads with a magnifying glass, the space appears continuous to us, but when you zoom in, you can count the stitches. In the absence of crowds, the loops remain closed. In the vicinity of a mass, they open in the same way as the loops of an electromagnetic field open when charges act on them. "

For Carlo Rovelli there is no longer any space, only particles, fields and loops of the gravitational field. They all interact with each other. And just as space no longer exists, so time no longer exists either. “Time is not an absolute 'container' in which things develop. Rather, it is specific to every object and depends on its movements, ”writes Rovelli.

The teacup will never be whole again

This relativity of time contradicts our intuition. When the GPS was developed, the US generals did not want to believe that time was running faster up in the satellite than down on earth, and tested the system without the necessary correction. They quickly had to admit defeat.

Yet time remains a deeply puzzling thing. Or, in the words of Richard A. Muller, a puzzle in which you don't know whether the pieces are really all in the right place. For example the particle that explains the arrow of time. As we all know, time flows by incessantly, and except in science fiction films, one cannot travel back in time or into the future in it.

Arthur Eddington provided an explanation in 1928 for this irreversible phenomenon, which Einstein also failed. He made a connection to the Second Law of Thermodynamics, which says that disorder - physics speaks of entropy - increases and will continue to increase forever. Explained for everyday use: if the teacup falls off the table, it shatters. The reverse process has never been observed: that a teacup is made out of all the individual parts.

Crazy thoughts on Friday afternoon

Richard A. Muller believes Eddington's theory that time moves forward because of entropy is "deeply flawed and almost certainly wrong." It can neither be proven nor refuted - and therefore does not meet the criteria of science. Furthermore: "The history of civilization was not a story of breaking teacups, but a story of how they were made."

Muller has a different, simpler explanation. The universe has been expanding since the Big Bang - another of many unsolved problems - at an ever increasing rate. Space grows with every second - and with it time.

"Perhaps the stream of time should be imagined more precisely as such a creation of new time."

This cannot be measured - not yet. There is also no evidence for Rovelli's loop theory. Both Rovelli and Muller are aware of the speculative nature of their deliberations. His physics mentor, Nobel laureate Luis Alvarez, reserved Friday afternoons for crazy thoughts, says Muller. This is exactly what both of them did.

Books on the subject

Carlo Rovelli: And if there wasn't time ?, Rowohlt, 207 S., Fr. 20.–

Richard A. Muller: Now - The Physics of Time, S. Fischer, 475 S., Fr. 42.–