In 1250 BC, the ancient Egyptians along the Nile divided day and night into 12 hours, recorded the passage of time and observed the movement of stars.
1090, it took China astronomer Su Song three years to build a hydraulic instrument platform, which became the earliest astronomical clock in the world.
/kloc-at the end of 0/5th century, with the great discovery of geography, ocean voyage required further improvement of the accuracy of time measurement, so the navigation clock came into being and human science and technology began to develop rapidly.
In A.D. 1670, Galileo discovered that the swing period of a simple pendulum remained constant with the passage of time, and physicist Huygens made the world's first mechanical clock by using the principle of simple pendulum.
For centuries, one second has been defined as 1/86400 of a day. However, due to climatic and geological effects and tidal friction, the length of a day is slightly different and the clock error is getting bigger and bigger.
1967, with the exploration of the atomic world, scientists found that the * * * vibration frequency of the same atom was certain, so one second was defined as the duration of 9 vibrations of cesium atom 192 63 1770. Atomic clocks came into being, with an accuracy of 1 second every 20 million years.
But scientists didn't stop there. 20 17, 10, 16, the gravitational wave generated by the merger of two neutron stars was directly detected by human beings for the first time; 19 April 18, humans got the first photo of a black hole. With the deepening of the exploration of the universe, time, as one of the basic attributes of the universe, needs more accurate measurement to capture the ripples of time and space.
Optical lattice clock surpasses the operation mode of traditional atomic clock and improves the timing accuracy by 1000 times. After 30 billion years of operation, the accuracy can reach less than 1 second, which is more than twice the age of the universe.
As we all know, atoms are composed of nuclear electrons and extranuclear electrons, which are in different energy layers. When electrons absorb or release energy, they will jump and release electromagnetic waves. Atomic clocks use the frequency of electromagnetic waves radiated when electrons jump as a time metronome. However, the frequency of optical transition is 654.38+ million times higher than that of microwave transition, and the higher the frequency, the higher the timing accuracy. Based on this principle, scientists have designed an optical lattice clock with high-frequency invisible waves as the timer!
When entering the high-frequency state of atoms, the first problem that scientists face is how to measure these high-frequency vibrating atoms. Scientists use the standing wave generated by laser to create an optical trap, trapping atoms in the optical trap and forming an optical lattice similar to the "crystal structure" in solid physics. Then, the atom can be excited by laser to form a constrained electronic transition, which can be detected by laser fluorescence to form a "tick" of the clock.
Most optical lattice clocks use a one-dimensional array of atoms. In order to improve the accuracy and stability of the clock, it is necessary to strengthen the number of atoms in the lattice. However, with the increase of the number of atoms constituting the clock, the interaction between atoms will be strengthened, which may lead to the frequency shift of the signal, thus reducing the overall accuracy of the clock.
In order to solve this contradiction, Jun Ye creatively expanded the geometric shape of the lattice from one dimension to three dimensions, so that the optical lattice clock in the three-dimensional state can use the properties of degenerate Fermi gas to reduce the interaction of individual atoms in the lattice. With the gradual weakening of the interaction between atoms, the atomic density in the clock can be increased, thus improving the stability of the optical lattice clock by several orders of magnitude. It is because of this contribution that Jun Ye won the Breakthrough Award in Basic Physics.
As far as practical use is concerned, the optical lattice clock can greatly improve the accuracy of global positioning system and other satellite navigation networks, guide deep space detectors more accurately, and prevent spacecraft from appearing Star Trek in space.
But this high-precision clock will help scientists to explore the nature of the universe. According to Einstein's theory of relativity, gravity bends space and time. Therefore, the clock at the top of Mount Everest is 30 millionths of a second faster than the same clock at sea level. The only way to accurately measure such a small time difference is to drive the clock measurement through the tiny vibration of the atom itself.
And in time and space, as long as there is gravitational fluctuation, it will cause tiny time changes. As long as the optical lattice clock captures these tiny time changes, it can capture the generation of gravitational waves.
Secondly, optical lattice clocks can help scientists discover dark matter. Dark matter is one of the most elusive things in the universe today. Although scientists have found that the universe is full of dark matter, they can't observe and capture it, but dark matter must have interacted with ordinary matter in some way. Therefore, scientists hope to see that ordinary matter on earth may contain the characteristics of dark matter, even if it is very weak. When dark matter passes by, the clock may slow down or accelerate, and scientists hope that the optical lattice clock can capture this change.
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The Breakthrough Award is known as the "Oscar of Science", which aims to recognize the research achievements of the world's top physics, mathematics and life scientists. A single award is as high as $3 million, far exceeding the Nobel Prize and becoming the "first prize" in the scientific community. 20 12 was founded by Russian billionaire yuri milner and his wife, and now it is initiated by famous industrialists such as Google co-founder sergey brin, Facebook co-founder mark zuckerberg, Tencent co-founders Ma Hua Teng and yuri milner.
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