Extraterrestrial

In the Milky Way, the closest stars to the Sun are 4.22 light years away

Compared to iron, those rare earth elements in the universe, which are heavier than iron, are even rarer

The moon has no people and no other living creatures, but scientists have found a lot of garbage on the surface of the moon, which is very strange, since the moon has no people, why would there be so much garbage?

The so-called gravitational equilibrium surface refers to the surface formed by the same point of gravity. On Earth, we call the gravitational equilibrium surface that coincides with the stationary ocean surface the "geodetic level", which is actually equivalent to what we often call sea level.

It has been billions of years since life appeared on earth, and although there are seven planets in our solar system in addition to earth, as well as a number of dwarf planets, moons and other relatively large bodies, so far we have not found alien life on any other planet in our solar system for the time being. Even mars, another earth-like planet in the habitable zone of our solar system, has not found a single sign of life. Could it be that life on earth is really unique and no other planet is allowed to have life?

Although the Earth is just a "grain of dust suspended in the sun" in the universe, for us humans, this "grain of dust" is irreplaceable.

This exoplanet, known as TOI 700d, is about 101.5 light years away from our Earth, which means that even if we were to travel to this exoplanet in a light-speed spacecraft, it would take at least 101.5 years of flight to reach it, so it is very far away

According to our knowledge of known life, liquid water is essential for life. In other words, if there is liquid water on a planet, there is a possibility of life, and it is for this reason that scientists always consider liquid water as the first requirement when assessing the possibility of life on a planet.