Aliens are the floorboard of life beyond the earth imagined by human beings.
There have been daydreams about aliens in ancient and modern times, but today, human beings can't actually detect whether there are aliens. Although many people have claimed to have witnessed aliens visiting the earth and even contacted themselves, most scholars and experts believe that the so-called different degrees of contact between humans and aliens is actually a psychological effect. The chances of humans finding "aliens" are very small, and even if aliens are found, it is almost impossible to have any contact with them.
In the search of the past 50 years, astronomers have not found any conclusive clues about aliens. But in theory, it is almost inevitable that there are other intelligent creatures in the universe.
As of 20 15, the scientific community generally believes that "life will only appear on planets around stars that can emit light and heat, but not all stars necessarily have planets". According to nebula theory, stars are formed by the contraction of rotating primitive nebulae.
During contraction, due to the conservation of angular momentum, the rotation is accelerated, and the nebula is gradually flattened due to centrifugal force. When the central temperature reaches 7 million degrees, a thermonuclear reaction from hydrogen to helium occurs and stars are born. In this process, the outside of the disk will condense into several small celestial bodies-planets.