"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

In our solar system, there are 2 planets in the habitable zone of the solar system, one of which is our home planet Earth, and the other is Mars

The modern Earth's atmosphere is so rich in oxygen that the vast majority of this hydrogen will be re-oxidized to water without escaping from the Earth's top atmosphere

Titan is the largest moon of Saturn and the second largest in our solar system, even a little larger than Mercury, one of the eight planets. Due to tidal locking, Titan's rotation period and revolution period are the same, similar to our Moon

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

For humans, the universe is too dimensional for us to see the details of its depths for the time being

This satellite is the communications satellite LES-1. In the 1960s and 1970s, the United States launched several such communications satellites, from LES-1 to LES-9, which were relatively small, weighing only about 32 kg, each with a horn antenna and an x-band transponder, as well as a 237 MHz signal transmitter, which were powered mainly by solar panels

There is a view that the reason why the Earth looks round is because of the role of the Earth's oceans, which simply means that a large amount of seawater has "filled in" the undulations of the Earth's surface.

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