Some people will say that space is not very big. There are countless planets there. When the resources of the earth are exhausted, we don't have them.

The continuous growth of population on the earth, the gradual shortage of resources, the deterioration of ecological environment caused by human activities on the earth, and accidental events from outside the earth, such as the impact of small celestial bodies, abnormal solar activity, supernova explosion, etc. Will lead to the fact that the earth is no longer suitable for human habitation. Hawking once warned that in 1000 years at the most, human beings on the earth would be extinct.

To take a step back, even if human beings avoid the above risks perfectly, after 5 billion years, the sun will devour the earth while dying. The destruction of the earth is only a matter of time. For the continuation of civilization, human beings must escape from the earth before it is destroyed. So in what way will mankind leave the earth in the near future?

It is a good idea to emigrate to other planets in the solar system, which can be barely realized with the existing technology and time. According to relevant data, Mars, Europa, Enceladus and Titan all have conditions suitable for supporting the existence of life in the solar system. Only by improving their environment can human beings build permanent settlements on them, thus alleviating the population pressure on the earth and diluting the risks brought by occasional disasters to the continuation of human civilization. But this is only a stopgap measure, and better methods are needed to realize the long-term development of human civilization.

The realization of controlled nuclear fusion should only be a matter of time. When controlled nuclear fusion's technology is mature, mankind can build some self-sufficient space stations, use nuclear energy to obtain all the energy needed, and build a complete ecosystem in space, no longer relying on the earth and the sun. The resources in space are enormous. With the corresponding technology, these space stations can make full use of various resources in the universe for self-repair and self-renewal.

These space stations can accommodate thousands to tens of thousands of people and have their own government, hospitals, industry, agriculture and military facilities. When the technology is mature, they can leave the solar system and become the seeds of human civilization wandering in space. Although the speed of the space station is not high and it takes a long time to travel through space, the human beings in the space station thrive in it. One day, they will meet the right planet, and then the seeds of human civilization will take root and sprout on it.

The progress of science and technology will make these space stations more and more advanced, and humans on earth will take these space stations in batches and then go further and further in the universe. At that time, the scene of the indigenous people of other planets in Avatar being demolished may be truly presented. Of course, if you accidentally touch the hard core, human beings will be unlucky, so the principle of these space stations is that "eggs are not packed in one basket."

Superluminal flight, space jump, warp drive and wormhole can all be realized casually, and human beings can easily achieve the goal of interstellar migration. But these things are too far away from us, and whether they can be realized is a huge question mark. We won't discuss it in detail today.