1. comet collision theory: this theory holds that a comet entered the sun a long time ago and laid down several planets different from the sun, including the earth (1749).
2. Meteorite theory: This theory holds that limited stars accumulate to form the sun and planets (Kant proposed it in 1755's Introduction to the History of the Universe).
3. Cosmic Nebula Theory: 17% year, put forward by French Laplace in Cosmic System Theory. He believes that the accumulation of nebulae (dust) produces the sun, and the sun emits gaseous substances to form planets.
4. Binary star theory: This theory holds that there was once a second star besides the sun, and all the planets were produced by this bright star.
Planetary plane theory: this theory holds that all planets revolve around the sun on a plane, so that the solar system can be produced by the coiling of primitive nebulae.
6. Satellite theory: This theory holds that the satellites of Neptune, Earth and Saturn are equal in size. There may also be hundreds of days as big as the moon, which constitutes the solar system. As we know, satellites are "unused" materials left behind.
Among the above theories, Kant's meteorite hypothesis and Laplace's cosmic nebula theory, although the specific terms are different, both believe that the solar system originated from the diffuse matter "nebula". Therefore, this hypothesis was later collectively called Kant-Laplace hypothesis, and was recognized by quite a few scientists.
However, with the development of powder science, it is found that the "nebula hypothesis" also reveals many new problems that cannot be justified, such as retrograde satellites and abnormal angular momentum distribution. According to the facts observed by astronomers, in the solar system, the mass of the sun itself accounts for 99.87% of the total mass of the solar system, and angular motion only accounts for 0.73%. The mass of the other nine planets and all satellites, comets and meteors only accounts for 0. 13% of the total mass of the solar system, but their angular momentum accounts for 99.27%. This strange phenomenon is called solar angular motion in astronomy, and its distribution is abnormal. For the reason of this abnormal distribution, the nebula expresses "helplessness".
In addition, modern space science has found that more and more large celestial bodies are in contact with each other. 1On August 30th, 979, an American satellite P78- 1 captured a rare phenomenon: a comet rushed into the flame of the sun at a speed of 560 kilometers per second. The photo clearly records the scene of the comet rushing to the sun and being swallowed up. After 12, J%, the comet disappeared without a trace.
1887 also had a "space accident". It is observed that when the comet passes the perihelion, its head is swallowed up by the sun. 1945, a comet also "disappeared" at perihelion. Former Soviet astronomer Schaefer Lonov also realized that.