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

In the past days, scientists have been working on the study of meteorites, and as the research continues, there is more and more evidence that life should originate from outer space

The solar system is a system of celestial bodies kept in motion by the sun's gravity, which means that all bodies within the effective range of the sun's gravity are part of the solar system, so by this definition, how large is the solar system?

In the evolutionary history of human beings, the gradual increase in brain volume is an important marker

In a good night sky, we can always see a sky full of stars and it seems to us that the whole universe is in full view. In fact, the stars we see in the night sky are only a tiny part of the milky way galaxy, which is just one of the trillions of galaxies that exist in the observable universe.

The law of conservation of momentum means that the total momentum of a system remains constant when it is not subject to external forces or when the sum of the vectors of external forces is zero

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?

The Arecibo Radio Telescope in the United States used to be the largest radio telescope in the world, with a diameter of 350 meters. As the most powerful radio telescope ever built, scientists have achieved many scientific results with the radio Arecibo radio telescope in the past decades

NASA's Jet Propulsion Laboratory's Near Earth Object Research Center has such a database, which is called the "Fireball Database."

The energy released by nuclear fusion is actually an important basis for stars to be able to maintain their stability