If human beings can't achieve interstellar migration, how many people can be supported by the resources on the earth for how long?

For a long time, resources have been the goal pursued by mankind. Individuals and countries want more and better resources. But after all, the earth is limited, and the total number of human beings is growing rapidly, so the debate about "depletion of earth resources" and "saving resources" has never stopped.

However, oil resources have not been used up for decades. Although water crisis happens occasionally, it is basically caused by geographical factors. When we call for saving resources and protecting the earth, we don't seem to have thought about the bearing limit of the earth, let alone whether today's 7.5 billion people really have the ability to completely drain the blue planet under their feet. In fact, even without interstellar migration, the earth is enough to feed tens or even hundreds of billions of human beings. This is not an exaggeration or a boast, but a real possibility. Judging from the hard demand, what human beings need is only water resources and food.

At present, seawater desalination technology is very mature, and the only drawback is that it costs electricity. In the future, controlled nuclear fusion will provide unlimited electricity for seawater desalination projects, and crops needed by human beings can also grow rapidly in super-large greenhouses with unlimited electricity supply. With a certain degree of genetic technology and artificial intelligence, everyone can eat and drink well. Although human beings seem to be all over the earth, in fact, human beings only occupy a small part of the whole surface area, and most of the rest areas are uninhabited or sparsely populated due to the current technical conditions.

When the scientific and technological conditions are sufficiently developed, water resources, energy and food are not problems, and housing is not a problem. In addition to the vast surface, humans can even build super-large-scale space cities and even sky cities. The so-called threat theory of resource shortage and overpopulation is only temporary and can be solved before enough technology is available.