Stars don't exist for human beings. Before man invented the telescope, there were about 6000 stars visible to the naked eye in the northern and southern hemispheres; Since man invented the telescope, we found that there are countless stars in the sky.

Take the Milky way for example. There are more than 200 billion stars. In the observable universe, there are more than 100 billion galaxies like the Milky way; If the number of stars in the whole universe is counted, it almost exceeds the number of sand grains on earth.

The emergence of general relativity and quantum mechanics has injected new life into astronomy. Modern astronomical theory can quantitatively describe the evolution and development process of a star or even a galaxy. It also gave birth to the big bang theory. For the first time, human beings can use scientific theory to study the origin of the universe.

All these astronomical studies are hidden in the stars in the night sky, which keep a lot of information about the evolution of the universe; Every star and even every galaxy in the night sky accurately contains their distance from the earth and the parameters of the celestial body itself.

For example, by studying the spectrum of celestial bodies, we can judge the composition of celestial bodies. By measuring the brightness and redshift of celestial bodies, we can know the distance between celestial bodies and the earth, and then by comparing the stellar Hertzsprung–Russell diagram, we can know the age and size of stars, which is very unbelievable.

If we can't see these stars in the night sky, we will know nothing about the universe and think that the solar system is the whole of the universe. Maybe this is why stars exist!