"universe"

The universe is so unimaginably large that even if humans were able to travel at infinitely close to the speed of light, they would not be able to penetrate its mysteries. Fortunately, the speed of light is not the speed limit of the universe, so it is entirely conceivable that in the distant future, humans may somehow be able to escape the shackles of the speed of light.

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

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

The mass of a star cannot grow indefinitely, it can only reach the "Eddington limit" at most, so beyond this threshold, it will soon "eject" the extra material

Although the Earth is just a "grain of dust suspended in the sun" in the universe, for us humans, this "grain of dust" is irreplaceable.

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

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

Since gravity is actually a manifestation of gravity, and the magnitude of gravity is proportional to mass, for those objects with smaller masses, their own gravity is smaller

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.

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