How big is the earth?
The equatorial radius is 6378. 137km.
The radius of the pole is 6356.752 km.
The average radius is 637 1.0 12km.
Flatness 1/298.257
The equatorial circumference is 40075.7 kilometers.
The meridian circumference is 40008.08km.
The surface area is 5.101×108km2.
Volume 10832× 108 cubic kilometers
In fact, the real shape of the earth is slightly different from the flat sphere mentioned above. Its southern hemisphere is slightly thick and short, and its south pole is sunken inward about 30 m; The northern hemisphere is slightly thinner and longer, and the north pole protrudes upward by about 10m. So it is exaggerated to say that the real shape of the earth is slightly pear-shaped.
According to Introduction to Earth Science
1663, Scottish astronomer James Gregory first proposed that transit of venus can be used to measure the precise distance between the sun and the earth. Edmund halley, a famous astronomer, observed the transit of Mercury in 1677, and found that it is indeed possible to measure the distance from the sun through the observation results of planetary transits in more than two places, and then use Kepler's third servant? The cubic X of mulberry box logging is proportional to the square of period of revolution around the sun, and the absolute distance of planets of the solar system is calculated. Moreover, because Venus is closer to the earth than Mercury, the measurement accuracy is higher, so the result will be better than the transit of Mercury. 17 16 published official papers, actively promoted the observation activities of mercury and transit of venus, 176 1 and 1769 organized international joint observation activities; 1720, the French astronomer Jean-Nicolas Delisle suggested that it is only necessary to observe the first loss (T 1), the food loss (T2), the light production (T3) and the last contact (T4) in time, and it is not necessary to observe the transit of venus in the whole process. Therefore, transit of venus on June 6th, 176 1 and June 3rd, 1769 was an important milestone in the international cooperative observation of astronomy and amateurs.
During the transit of 176 1 year, more than 30 observation teams from all over the world went to Siberia, South Africa and other places to observe. At that time, the world was in a turbulent era, and many places suitable for observation were either bad weather or war, and many observation results were not good. But Harley's wish finally came true, and the distance between the sun and the earth was calculated by using the observation results of transit of venus. However, the distance between the sun and the earth is not accurate because of the inaccurate measurement of the "first loss" time of the contact between the planet and the edge of the sun, and the influence of halo effect and black drop effect. This value has been used by astronomers in the19th century for nearly a hundred years. The halo effect is not all bad. At least in the transit of venus incident of 176 1, Mikhail lomonosov, an astronomer in St. Petersburg, Russia, suggested that this should be the symbol of Venus' atmosphere, and his idea was really right!
1769, when the war ended, there were 15 1 observers scattered in 77 different locations around the world. One of the most famous is Captain james cook's observation in Tahiti. Captain Cook, an Englishman, happened to meet the transit of venus incident on his way to explore the world and watched it in Tahiti. The crew built a simple observatory at the highest point in Tahiti, named Venus Observatory, which was specially built for transit of venus. However, the equipment of this observatory was later stolen and no longer exists. Of all the observations, the most accurate record came from a French team led by Jean-Baptiste Chap de Auteroche. They failed to observe in Siberia on 176 1, and made a comeback on 1769, and came to California for observation. These scientists finally got the information they dreamed of, but the three members of D 'returned to Paris across the ocean, two of them died on the way, and the last one finally brought the observation data back to Paris alive in 1770. Their hard journey is only known to the world.
1824, the famous German astronomer johann franz encke used the observation results of 176 1 and 1769 to calculate the distance between the sun and the earth as153.34 million kilometers, with an error of 660,000 kilometers.
1874 transit of venus inspired astronomers all over the world, led by the scientific circles of Britain and China, with the active participation of Brazil, Portugal, the Soviet Union and other countries. The United States even spent 177000 dollars to observe this astronomical event (1874 is sky-high! ), not only training and simulating how to accurately grasp the contact time of transit of venus began about 10 years before the incident, but also invented many new instruments. At that time, it was just the time when astronomers began to apply photo technology to astronomical observation. Other rapid photography techniques and spectral observation, such as taking 20 photos a second, were invented at that time, so the observation results obtained were naturally more accurate than18th century. Unfortunately, the "wet negative" technology at that time was not good, and most of the photos were not preserved.
In the 1874 transit of venus incident, the visible areas included Chinese mainland, Japan and Singapore, and French astronomers specially organized teams to observe transit of venus in Beijing. At that time, the visible events in Chinese mainland took place around noon. The author found two records in the book China Ancient Astronomical Records edited by Beijing Observatory:
In the 13th year of Tongzhi of Mu Zong in Qing Dynasty, Zhejiang, volume 1 1 Page 22: "There are sunspots in Japan and China".
Zhang Fubian in Shanghai in the Republic of China Volume 1 1 Page 6: In the thirteenth year of Tongzhi, "There were sunspots in Japan and China."
The time of "November New Moon in the 13th year of Tongzhi in Mu Zong in Qing Dynasty" is equivalent to 1874, 65438+February 9th, which happens to be the time of transit of venus. I wonder if the "sunspot" seen by our ancestors is the shadow of Venus on the sun?
In view of the fact that the event of 1874 has to be classified as "very successful" in the history of science, transit of venus of 1882 has attracted more attention, which should be said to be "crazy". At that time, the visible area was mainly in South America, and some parts of the United States were always visible, but the United States Naval Observatory sent eight groups of observers to observe around the world. At that time, the American media strongly criticized it as "waste", but these scientific investigations were carried out one after another. In 1882, the dry plate photography technology has begun to develop, the quality is much better than the wet plate negative, and it is easier to save. So there are more than 2000 observation photos in the world at that time, and there are countless related papers and notes. The distance between the sun and the earth calculated according to the observation results is148.3232 million kilometers, which is much more accurate than 176 1 and 1769, but the observation error is still 86,000 kilometers.
Transit of venus (once-in-a-century astronomical phenomenon, calculating the distance between the earth and the sun)
Venus, golden yellow, is the brightest star in the sky, and its brightness is equal to 15 Sirius. Venus and China were called "Taibai Venus" in ancient times, "Morning Star" in the morning and "Chang Geng Star" in the evening. Venus is the closest planet to the Earth, with an average distance of about 410.5 million kilometers. Venus has a radius of 6,073 kilometers, only 300 kilometers smaller than radius of the earth, its volume is 0.88 times that of the Earth, its mass is four fifths of that of the Earth, and its average density is slightly less than that of the Earth. Therefore, people often call Venus the sister star of the earth. It is puzzling that the rotation direction of Venus is from east to west (opposite to the rotation direction of the earth), so from Venus, the sun actually rises in the west and sets in the east. Moreover, the rotation period of Venus is as long as 243 days, which is even longer than 224.7 days in period of revolution, so one day and night on Venus is equivalent to 1 17 days on the earth. The surface temperature of Venus is as high as 447 degrees Celsius.
Because mercury and venus are "inner planets" in the orbit of the earth around the sun. Therefore, when Venus moves between the sun and the earth, we can see a small black dot passing slowly on the surface of the sun. This astronomical phenomenon is called "transit of venus". In astronomy, the two transit of venus phenomena with the shortest time interval are often grouped together. The regularity of this phenomenon is usually 8 years,1210.5 years, 8 years, 105.5 years, and so on. According to the astronomers' calculation, the time of this group of transit of venus is June 8, 2004 and June 6, 20 12, respectively. This is mainly because Venus orbits the sun 13 times, just close to the earth that orbits the sun for 8 times, between the earth and the sun, which is equivalent to 8 years on the earth.
In17th century, Harley, a famous British astronomer, suggested that the time required for Venus to pass through the surface of the sun was measured at two different places on the earth at transit of venus time, so that the parallax of the sun could be calculated and the accurate distance between the sun and the earth could be obtained. Unfortunately, Harley lived to the age of 86 and never met transit of venus. After Harley put forward his observation method, there have been four transit of venus, and each time it has attracted great attention from scientists.
They trekked thousands of miles to the best observation site and made some important discoveries. 1761On May 26th, when Venus transited, Russian astronomer lomonosov discovered the atmosphere of Venus in one fell swoop. /kloc-in the 20th century, astronomers collected a lot of data through the transit of venus, and successfully measured the distance between the sun and the earth as 654.38+496 million kilometers (called an astronomical unit). Astronomers today are much luckier than Harley, and they can use many advanced scientific means to further study Venus, the neighbor of the earth!
Distance to the moon Earth is 38440 1 km.
The moon will be farther and farther away from the earth.
The main reason: the tides on the earth twice a day (tidal energy power generation) are caused by the gravity of the earth and the moon. This huge energy is consumed every day, and the earth's ability to bind the moon is getting weaker and weaker. The center of mass of earth-moon system will be farther and farther away from the earth. At present, the center of mass of earth-moon system is still inside the earth, about 1 600 kilometers below the ground, and the center of mass (the center of mass of the earth) is 60 kilometers below the ground.
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