What problems have space immigrants encountered?

Now, human beings have mastered relatively mature space technology, and traveling or even living in the universe is no longer a dream. Faced with the population pressure of the earth, scientists put forward the idea of emigrating to other planets in the universe. But this idea can't be realized for the time being, because it involves extremely complicated scientific problems in all aspects. First of all, human beings and animals have gradually adapted to the physical and chemical living environment on the earth after a long evolution. Once you go to live in space, the living environment there is completely different from the earth. Even if the design is similar to the earth's environment, it is difficult to maintain for a long time. Once the environment changes, the consequences are unimaginable. Secondly, once human beings live in space, they will escape in the air when they are attacked by meteors. Without air to maintain human survival, humans and animals can't survive. Third, it is not only expensive to build human living quarters in space, but also difficult to achieve with the current level of science and technology. Therefore, the idea of human beings moving into space is still difficult to realize.