"Human"

Theoretically, life can take many different forms, such as silicon-based life, sulphur-based life, carbon-based life, amino-life, hydrogen-based life, etc. However, so far we only know that life exists on earth, and all known life, including us humans, is carbon-based.

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

The existence of reproductive isolation, so that these situations can not occur, even if there are some individuals of different species sometimes complete the mating, but they generally can not produce offspring, or produce offspring can not continue to reproduce

How long can humans survive on earth? This is a question that many of us want to know, and i believe that we do not want to wake up to a "Purgatory" Like venus, and hope that the earth can remain alive forever, so that we humans can continue and our generations can survive on earth forever. If the earth's environment were to change drastically and become an extremely hot planet like venus or mercury, then naturally everything in the world, including humans, would not be able to exist.

The reason we don't see time travelers is actually because they are not in our timeline

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

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?

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

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

In orbit for longer and longer periods of time, we need to solve not only inorganic resupply problems such as food, water, oxygen and propellant, but also the various problems faced by astronauts flying in orbit for long periods of time