When can humans live on other planets?

First of all, only the earth in the whole solar system has an environment suitable for human survival, and other planets (such as Mars and Titan) must be transformed to barely allow human survival. However, the plan to transform the earth is still a theory. Even if it is implemented immediately, it will not take 100 years to build a complete ecosystem.

If you want to enter the alien world in a short time, you can only seek it outside the solar system, but you need to overcome the distance problem. Today's spacecraft will take decades to fly out of the solar system at the earliest. After all, human life is limited, and it is impossible to reach other galaxies hundreds of light years away to find settlements.

Some people will say that human metabolism can be stopped by refrigeration technology and thawed after reaching the destination. This theory is beautiful, but the current technology can only preserve corpses by freezing, and living bodies cannot survive normally after freezing and thawing.

In addition to the problem of life, there is also the problem of fuel supply. The spacecraft can't take off with too much fuel, otherwise it can't afford to fly. Before flying out of the solar system, the fuel on the spacecraft has been exhausted, and the future speed can only be accelerated and supplemented by the interaction between passing planets. After leaving the solar system, no star can provide power with other galaxies. Even if we use experimental solar sails, it is out of reach, because it is too far away from energy.

There is also a hellish gravel belt around the solar system, and it is very doubtful whether the hull can advance in this space without loss.

There is also a view that the spacecraft can quickly jump to other galaxies by using the space-time folding method of black holes. However, what is a black hole is so far limited to theoretical dialectics, and even some astronomers simply deny the existence of black holes. If a black hole really exists, the existing laws of physics are invalid for it, and it takes a lot of time to understand and explore.

So up to now, our dream of stepping into interstellar space is only a dream, and even the lifetime of this generation may not be realized.