the science story about the watch

According to the relativist theory of the great scientist Albert Einstein: A clock (A) placed on the floor runs relatively slower than a clock (B) placed on the stool because the clock (A) is lower and therefore it is more subject to gravity. Note: clock (A) and clock (B) are identical.

Relativity and the story of the watch

Today, physicists have demonstrated this by using two clocks that are super accurate and lifting the watch several centimeters higher than the other. So up to this point, scientists have been able to use watches that prove that over time your nose is faster than your navel. 'It is interesting to prove that gravity changes with altitude by lifting a watch to a height of 0.3048 m. '

According to Daniel Kleppner, a physicist at the Massachusetts Institute of Technology in Cambridge, Massachusetts, USA. He added, however, that this experiment " does not change people's perception of relativity. "

The great scientist Albert Einstein found that time passes at different speeds depending on different circumstances . For example, suppose he was standing on the platform of a train station with a genuine Rolex watch on his wrist at the same time his friend wore a genuine Rolex watch of the same type but was on an express train. Certainly your watch will run slower than your watch, the reason is that your friend is moving relative to you. Einstein gave this special prediction in his theory of relativity.

And according to the theory of relativity, Einstein identified the gravitational force associated with a giant object such as Earth, which would contract according to the structure of space and time. As a result, the watch is placed at a lower altitude so, affected by lower gravity, should be slower (at a rate of about 3 / 1000,000 seconds / 1 year / 1km to height) a bronze identical lakes are located at higher altitudes.

Such predictions seem to be absurd, but actually prove the opposite by measuring the time between super-accurate atomic clocks placed on the ground and the clocks of the same type. the jet. This finding is applied to calculations in the global positioning system of satellites.

Today, Chin-wen Chou, Till Rosenband, and colleagues at the Institute of Standards and Technology (NIST) in Boulder, Colorado, United States use a new sample atomic clock called an optical watch discovered. changes in timeline that are caused by the effect of moving the object below 10 m / s and due to the change in height of the object under 1m.

Atomic clock.Illustration

Atomic clocks take advantage of the state occupied by atomic electrons emitting or absorbing electromagnetic waves with a set frequency. The researchers tracked the waves emitted on atoms, and repeated the feedback and adjusted the frequency of these waves so that the atom kept jumping back and forth this process repeatedly 4 times. . The oscillating wave then marks the time only when the pendulum oscillates faster and steadily. Today, atomic clocks set a standard time for microwave ovens using a standard frequency of about 9.2 billion cycles per second to make vibrating atoms simultaneously emit equal energy levels.

In contrast, researchers at the Institute of Standards and Technology (NIST) use a clock that uses laser light with a frequency of 1,120,000 billion cycles per second to achieve a higher leap energy state. called optical transition in a single aluminum ion obtained in an experimental trap. The accuracy of aluminum ion series reaches the ratio of 3/10 million. Therefore, the new aluminum clock is 40 times more accurate than the atomic clock and therefore will help prove the feasibility of predictions based on Albert Einstein's relativity theory on a larger scale.

The researchers made two aluminum clocks and to test the effect of speed, they made the aluminum ion movement move back and forth at a speed of 4m / s in the trap of the experiment. The result is a motion slower than 2/10 million billion caused by the clock by the motion of aluminum ions. To test the effect of gravity, physicists placed clock 2 at a distance of 17cm below the clock 1, then they raised the watch 1 to a height of 33 cm. Note that these two clocks are identical. Results They found that the clock's operating frequency soared to 4/100 million. This result confirms that the predictions of general relativity are correct. Researchers have published the results in Science on September 24.

Yu Nan, a quantum physicist at the NASA Jet Propulsion Laboratory in Pasadena, California, said: ' The accuracy of optical clocks really surprised me because it was the dream we pursued throughout 10 or 20 years ago. Today, it is the advancement in laser technology that makes that dream a reality. 'Yu predicts that in the next few years, a series of microwave technology applications will use more advanced optical clocks. Christophe Salomon, a physicist in Supérieure École Normale in Paris agrees with the statement, but he also notes that optical clocks are still in the testing phase for new technologies. " Optical clocks are advancing scientific progress, but they don't run continuously ," Salomon said. that is the problem that the NIST researcher has been looking for.

Ho Duy Binh
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