While I understand the angle that the brain drain creates inequality among regions, perhaps it could be argued that it is thanks to those people congregating in few places, and hence there being many of them in the same place, that there have been scientific advances. In other words, had those people stayed in their home countries it's not a given that we would have had more, if any, moon missions.

> Now smart scientists, if they want to work in person with the widest supply of good colleagues, will go to other wealthy countries.

Right. I would say they will go to the countries where other smart people are, which turn out to be wealthy countries.