The universe consists of many celestial bodies. It is the highest celestial system in this system, including the Milky Way and other star systems. The earth is a planet in the solar system, so if the universe is the first level, then the earth should be the fourth level.

The earth is a planet in the solar system and the only planet known to have given birth to life. In the vast universe, only the earth's environment supports life at present. From the perspective of the universe, 765,438+0% of the earth's surface is covered by oceans, and the earth is also the densest celestial body in the solar system. Generally speaking, the earth has a thick atmosphere, abundant liquid water and a very unique environment.

In the physical sense, the universe is defined as all space and time (collectively space-time) and its connotation, including all forms of energy, such as electromagnetic radiation, ordinary matter, dark matter, dark energy and so on. Among them, ordinary matter includes planets, satellites, stars, galaxies, clusters of galaxies and intergalactic matter.

Physical properties of the universe:

Among the four basic interactions, gravity is dominant on the astronomical scale. The gravitational effect is cumulative. In contrast, positive and negative charges often cancel each other out, making the electromagnetic force relatively insignificant on the astronomical scale. The other two kinds of interactions, weak nuclear force and strong nuclear force, decay very rapidly with the increase of distance, and their influence is mainly limited to subatomic scale.

It seems that there are more matter in the universe than antimatter, which is an asymmetry and may be related to CP destruction. This imbalance between matter and antimatter is part of the reason why all matter exists at present, because if equal amounts of matter and antimatter are produced in the Big Bang, they will interact and completely annihilate, leaving only photons.

The universe seems to have neither net momentum nor angular momentum. If the universe is finite, it follows the accepted laws of physics. These laws are Gauss's law and non-divergent pressure, energy and momentum pseudotensors.