"earth"

In general, when a spacecraft, probe or rocket wreckage re-enters the atmosphere, they are fast, reaching several kilometers per second or even faster

Earthquakes are a common natural phenomenon. On average, millions of earthquakes occur on Earth every year, except that most of them are so mild that they are largely imperceptible to humans.

In this 5.5 million-year-old cave, not only is there no sunlight, but the environment is also very harsh

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?

Prehistoric civilization have always been the talk of the town, and it's no wonder - after all, humans have been around for so short a time in the history of the planet that if we were to compress the history of the planet into a single day, then humans would probably only appear in the last two minutes of that day. In the past, there have been frequent claims of the discovery of suspected prehistoric civilization, the most notable of which would be a two-billion-year-old nuclear reactor.

At the time of the "family photo" of the solar system, the Voyager 1 probe has reached a distance of 6.4 billion kilometers from Earth, very distant, so in the view of the Voyager 1 probe, the solar system, the major celestial bodies are very small

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