How long is one meter?| Science Pavilion

The metering unit "rice" can be described as a very important role in life, but everything that is with the length and size is indispensable for the participation of "rice". However, "meters" is not the product of nature, nor is it the concept that generates out of thin air. Why does it reach a certain length, we call it "1 meter"? How did "rice" born?

Astronomical geography measurement

In the late 17th century, France began to measure the length of the earth. The scientific further research put forward new requirements for the length unit of the measurement experiment. The measurement of the meter academic community urgently needed to establish a unified unit standard for the world.

On November 2, 1789, the French Revolutionary Government selected 15 scientists to form a "Technical Consultation Bureau" to conduct research work formulated by new measurement units.

On April 14, 1790, the Technical Consultation Bureau finally decided to use the length of a arc of the son's meridian as a reference, so as to be the standard of the new metering unit. The meridian is one of the "meridians" we usually say. It is a large arc that people imagine and connecting the north and south poles of the earth. The "0 degree meridian" is also called the early son's meridian. It is the meridian of the Meridian Meridian Center that passes through the Greenwich Astronomical Terrace of Greenwen in London, UK, and uses this as the starting point of calculating longitude. 1 meter is equal to one -fixtrine of the meridial length. They believe that the length of the meridian of the earth will never change. The use of new standards based on it will also make eternal. At the same time, because the earth belongs to all human beings, the units formulated accordingly will also belong to people around the world.

Source: Network

In June 1792, Jean Baptiste Joseph Delambre and Pierre Franço Méchain, Pierre Fraanço Méchain, Departing from Paris, in the opposite direction of human history, a great scientific exploration in human history. Drandbul is responsible for the northern line of Paris to Dunkirk, while Mei Shang is responsible for the South Line measurement from Paris to Barcelona. They must not only measure, but also calculate the arc length of the child's meridian according to the results, thereby providing a basis for formulating new measurement units.

Rice measurement route

The measurement work has been carried out for 7 years. Finally, it is determined that the French ancient ruler 5130740 Dudos (Toise) is the standard, and one -one -millionth of this length is the new length standard "rice".

However, according to the latest satellite measurement results, the real length of the Arctic to the equator is about 9980 kilometers. That is to say, 1 meter of that year was actually a few millimeters less than one -one -millionth of the meridian. Although there are errors, the use of sub -meridian to determine the unified standards of length standards are undoubtedly an unprecedented initiative.

Measurement of physical rice ruler

In 1798, scientists made a 1 -meter -long rice ruler based on the measurement results, with a minimum scale of 0.01 mm. On June 22, 1799, the ruler was stored in the Paris Archives, called the "File ruler". In December of the same year, the National Assembly determined the legal status of the file ruler as the standard of the rice system.

But it didn't take long for the archives to discover problems. The end surface of the file ruler is easy to wear, which makes it difficult to measure. Secondly, the endpoint of the file ruler is not clear, and it is very troublesome to use.

In order to solve this problem, starting from 1880, the International Measurement Agency has set 31 rice ruler with platinum alloy. After 7 years of production, these rice ruler finally completed in 1887. Two years later, with the advancement of industrial technology, countries have common needs for unified units. Therefore, at the International Measurement Conference in 1889, a platinum -schochrome -based rice ruler numbered NO.6 was determined to be "International Rice Original". Compare with the "International Mirahe" to ensure the accuracy of the "meter" unit.

Light wave definition

But there are still shortcomings in this rice original. First of all, as a real thing, it will inevitably be affected by the environment. Secondly, the wear situation in use will also greatly reduce the accuracy and accuracy of measurement. Therefore, after the emergence of Mirahara, scientists have not stopped the pace of research, and they are still exploring rice definition methods with high accuracy.

At the end of the 19th century, Michaelson's optical interference instrument was born. It is the first time that the cadmium red spectrum radiation is used for "rice". The accuracy of the optical wave measurement method has been greatly improved compared to the actual measurement, and the superiority is also shown in terms of stability. Later, more and more scientists began to try to measure the length of the light waves. In the late 1950s, people found that a kind of 氪-86 isotocophamum sources were more stable. Therefore, in 1960, the definition of "meters" became: 1 meter is equal to the transition between the 2P10 and 5D5 energy levels of the atomic atoms of the 氪 -86 atom.

Speed ​​measurement

With the development of the times, technology is constantly improving. In the 1960s, the use of the wavelength of 0 86 to measure the distance can no longer meet the accuracy requirements of scientific research. Laser with good direction and good brightness gradually entered the horizon of scientists. In 1975, the 15th International Measurement Conference was launched to represent the resolution of rice. This is also the definition of "rice" that is currently passing: Mi is the length of the journey that travels in the time interval of 1/299792458S in vacuum. Because the speed of vacuum light is a fixed value, theoretically, it is more accurate and stable with the speed of light. Laser rangefinder

Source: Network

At the same time, the advantage of describing rice with the speed of light is that it is not a light source that fixes a wavelength. As long as the frequency of light knows, the light sources of different wavelengths can be described in different accuracy range. In this way, there is no need to change the definition of rice frequently, and the scope of applications is more extensive. At present, describing the basic unit of length with the speed of light can be said to be the most ideal definition.

Unexpectedly, the little "rice" actually experienced so much change. From scratch, from the process of giving excellence not only reflects the in -depth understanding of the world, but also the spirit of scientists' exploration of the truth of the truth. How long is 1 meter? After reading this article, have you answered?

Creative Team: New Media Team of the Chinese Science and Technology Museum

Audit expert: Liu Yuhang Beijing International Mathematics Research Center post -doctoral post doctors

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