"earth"

A rigorous discussion of the unknown is not possible, so it is necessary to narrow down the universe we are discussing to only the universe we can see

The earth has been spinning since its inception and has been doing so for 4.5 billion years now, so why has it not stopped yet?

The universe is so big, but man's range is so small that the furthest man has been so far is the moon, which is only 380,000 km away from earth on average. Of course, humans have also launched all kinds of probes, and if you include them, the range of human activities is much larger.

According to our knowledge of known life, liquid water is essential for life. In other words, if there is liquid water on a planet, there is a possibility of life, and it is for this reason that scientists always consider liquid water as the first requirement when assessing the possibility of life on a planet.

The earth was born more than 4 billion years ago, when it was very different from the earth of today, one of which is that the environment of cosmic space is more different.

Earth is the only home we have in the universe and the only planet we know of so far that has life on it, and because of this, we usually think of it as a perfect planet.

The 500 trillion ton comet was discovered in 2010 by astronomers Pedro Bernardinelli and Gary Bernstein

Nowadays, Mars is obviously unsuitable for direct human habitation, because the environment of Mars is very different from that of Earth, such as Mars is unusually arid, desolate and without a trace of life. Despite this, scientists are still keen to explore Mars

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

The legendary prehistoric civilization is not the only one "Atlantis", then this mysterious "yellow brick road" could be the remains of some other prehistoric civilization left behind?