The most accurate clock in the world … The “age of the universe” must be delayed by one second

The wall clock, invented by a Chinese-American and his Japanese colleague, in one of the laboratories of the “University of Colorado”, is distinguished by the fact that it is offset by one second from the real time, which takes 15 billion years, which is roughly equivalent to the age of the universe.

Thanks to this invention, Chinese-American scientist Jun Yi will share with Japanese Hidetoshi Katori, $ 3 million, as part of the 2022 Breakthrough Prize, in the fundamental physics category.

Working independently, the two have developed technologies that use lasers to trap and cool atoms, then harness their vibrations to power what are called “optical retina” clocks, the most accurate of all.

By comparison, the current generation of atomic clocks lose one second every 100 million years.

But what is the need for all this precision? “It really is a tool for exploring time in the universe,” Jun Ye told AFP.

In their laboratory, the two researchers showed that time passes more slowly for a clock placed a few centimeters lower, which is consistent with Einstein’s theory of relativity. These clocks could help improve the accuracy of the Global Positioning System (GPS) a thousandfold, or help spacecraft land on Mars with much greater accuracy.

A brief history of watches

Improving the accuracy of time measurement has been a challenge since sundials and hydraulic clocks in the days of the ancient Egyptians. The major breakthrough was the invention in 1656 of pendulum clocks, which use an oscillating mass to measure time. A few decades later, the stopwatches were accurate enough to locate a ship at sea.

The use of time to determine trends is very common. For example, if a person walks for thirty minutes to a park, and knows the speed at which they are moving, that gives them an idea of ​​how far the park is.

The early 20th century saw the emergence of quartz watches, a mineral that vibrates at a specific frequency when electrically stimulated. Frequency refers to the number of vibrations in a given period of time: by knowing the frequency of a substance, the time that elapses can be measured by counting the number of vibrations.

Watches that use this technology are everywhere, but they are subject to change, due to the design process or external conditions, such as temperature.

A further step was to master the vibrations of atoms in order to develop atomic clocks. When exposed to a high frequency, particles called electrons, which orbit the nucleus of a certain type of atom, change to a higher energy level. The atom in this case is called the excited atom.

Atomic clocks use a crystal oscillator which generates a frequency, bringing the electrons to this higher energy level. Counting the number of these excited atoms returns a signal to the oscillator, whose frequency is then very precise, and this is then used to run the clock.

Explore the universe

Jun Ye and Hidetoshi Katori found a way to improve atomic clocks. Instead of a crystal oscillator, the researchers used lasers, with a frequency hundreds of thousands of times faster than that used in conventional atomic clocks.

In order to continue counting atoms, they had to find a way to hold them in place. For this, the two innovators used a very cold temperature, and deliberately created an “optical network”, and by pointing two lasers at each other, types of waves are formed and in its cavity atoms of strontium are trapped.

Jun Yi is excited about the possible applications of his system. For example, synchronizing the time of the best observatories in the world with these clocks could allow astronomers to better observe black holes. Better clocks can also provide a plethora of answers about geological processes on Earth.

In fact, relativity teaches us that time slows down as a large mass approaches, so a sufficiently accurate clock can distinguish solid rock from volcanic rock below the surface and help predict eruptions. It can measure the level of the oceans or the water flowing under the desert.

The next challenge, according to Jun Yi, is to make the technology smaller so that it can be moved outside the lab. The scientist acknowledges that discussing the subject with the public is complex, “but when people hear about the watch, they feel that it is something tangible, and they can feel a connection with it, which is very useful” .

(France Brosse)