"universe"

Everything we can see in the universe has an internal structure and they are all made up of smaller matter, so what is the smallest matter in the universe?

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

It has long been discovered in practice that the phenomenon of "gravitational time dilation" does exist

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

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

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

If someone asks the question, are humans alone in the universe? I believe that most people would answer in the negative. In fact, the scientific community also generally agrees that there are a large number of intelligent civilisations in the vast universe, some of which may even be far ahead of our civilisation, and in order to better describe the technological level of intelligent civilisations in the universe, scientists have also proposed the concept of "Cosmic civilisation levels".

Further research shows that this mysterious force accounts for 68.3% of the total mass energy of the universe, and it is because of this that it is able to overcome gravity and become the dominant force controlling the operation of the universe

Between the Earth and the Moon there exists a much more empty space than imagined, so what can be put down in this space?