# What is beyond space-time matter

## How fast is the universe clock ticking?

Physicists have been arguing for decades whether time is continuous or whether there are even the smallest units of time - a kind of universal basic ticking. Researchers have now calculated how long one of these ticks will last. Accordingly, this universal basic clock of quantum time should not be longer than 10-33 Take seconds. This is far beyond what can be measured with atomic clocks - yet there could be a way to prove the existence of this universal clock.

Since Albert Einstein it has been clear: time is a continuous quantity that can pass slower and faster depending on gravity and acceleration - this is dictated by the general theory of relativity and it can also be measured with the help of atomic clocks. But other rules apply in quantum mechanics. It requires time to be universal and to tick ahead with a steady rhythm.

### Is the time quantized?

But how can this contradiction be reconciled? One solution would be to start from a "quantized" spacetime, as is done, among other things, by quantum gravity. According to this, space-time is not a continuous matrix, but is divided into the smallest units. These “space-time pixels” would then have to have the Planck length of 10-35 Meters - they are much too small to be detectable.

But what does that mean for time, which according to Einstein is inextricably linked with space? The quantization of spacetime requires that time also run in discrete “packages”. Accordingly, there should be a kind of universe clock whose ticking marks the smallest possible unit of time in the cosmos. Such a universal timer, like the Higgs field, would permeate the entire universe and interact with matter.

### A tick takes less than 10 to the power of -33 seconds

But how fast does this universe clock then tick? This is what Martin Bojowald and his team from Pennsylvania State University have tried to determine theoretically. In their model, the universe clock is a quantum oscillator, a system that regularly switches between two states. In order to determine the clock rate of this oscillator, they coupled it with a second, much slower oscillator, similar to an atomic clock. The coupling required that the net energy of the two together always remain the same.

The highlight here: This condition leads to the two oscillators becoming desynchronized over time. On the basis of this divergence of the two model clocks, Bojowald and his colleagues have determined that the universal oscillator must not tick any slower than 10-33 Seconds. One tick of the universal clock is therefore a billiard times shorter than the ticking of today's best atomic clocks.

### Desynchronization as an indicator?

But that's not all: the new model also reveals how one could perhaps prove the existence of such a universal watch. Because the physically prescribed desynchronization would make it almost impossible for any normal atomic clock to keep its clock constant in the long term. No matter how precise it is, its synchronous mode is disturbed by the interaction with the universe clock, as Bojowald and his colleagues explain.

This means that there is an absolute limit to precision for such watches. Even with all imaginable technical improvements, it is not possible to construct clocks that keep their pace precisely for all eternity. If one were to construct two atomic clocks that run almost exactly at the precision limit, their deviation could reveal whether the universal clock exists or not.

"This behavior could allow researchers to confirm that time has a fundamental period," says Bojowald. However, even the most modern atomic clocks are still too far removed from this precision limit. Nevertheless, the physicists' model at least gives hope that the riddle of time may one day be solved. (Physical Review Letters, 2020; doi: 10.1103 / PhysRevLett.124.241301)

Source: American Physical Society APS

June 25, 2020