"Human"

How exactly did such a complex life emerge on Earth? This is a great mystery to modern humans, but we are almost certain that the "birth of life" is a process that has a very small probability of occurring.

Of all the known rocky planets in the solar system, the one with the most similar natural environment to Earth is Mars, and exploration data show that Mars also has an atmosphere, four seasons of the year, and even a rotation period similar to that of Earth.

Compared to radio messages sent by humans, this method seems to be more suitable for intelligent civilizations to announce their presence in the universe, because this method belongs to the "broadcast" in space, and intelligent civilizations in all directions can be observed

The energy released by the sun's nuclear fusion reaction, in addition to making the sun shine and heat, there is an important role, that is, to resist its own gravity

In theory, when a civilization develops into a civilization that can cross the stars, there is basically no risk of extinction

The solar system is a system of celestial bodies kept in motion by the sun's gravity, which means that all bodies within the effective range of the sun's gravity are part of the solar system, so by this definition, how large is the solar system?

In fact, the earth's crust itself is a natural source of minerals, many soil and rocks contain a certain amount of salt, careful observation of cattle and sheep should know, cattle and sheep in the grass, but also often "eat soil" or lick the stone, they do so, in fact, the purpose is to obtain the salt

It is proposed that birds originated from dinosaurs, and that "ancestor birds" are a transitional species between birds and dinosaurs.

Intelligent life is rare in the universe, or perhaps it is just wishful thinking on our part. As mentioned earlier, just in the galaxy, there are hundreds of millions of planets that have the natural conditions to nurture life, so a reasonable speculation is that life has evolved on many planets, and even a number of planets have evolved intelligent life.