The broad definition of the universe is the general name of all things, and it is the unity of time and space. The narrow definition of the universe is the space and matter outside the earth's atmosphere. The definition of "universe" of "space navigation" is a narrow definition of "universe", which refers to space navigation outside the atmosphere.
Some objects in the universe observed by human beings are composed of about 4.9% ordinary substances (substances that make up stars, planets, gases and dust) or baryons, 26.8% dark matter and 68.3% dark energy. Baryon matter forms a "spider web" between galaxies.
Extended data:
The creation of the universe:
At the initial stage of explosion, matter can only exist in the form of elementary particles such as neutrons, protons, electrons, photons and neutrinos. The continuous expansion after the explosion of the universe caused the temperature and density to drop rapidly.
With the decrease and cooling of temperature, atoms, nuclei and molecules are gradually formed and combined into common gases. Gas gradually condensed into nebulae, which further formed various stars and galaxies, and finally formed the universe we see today.
Baidu Encyclopedia-Universe