For Hal, however, this new world is too comfortable, too safe. Earth is no longer home, it is "another, alien planet". Humans themselves have changed, having undergone a procedure called "betrization", designed to neutralize all aggressive impulses. Its side effect is an extreme aversion to risk. Hal mistrusts this approach, seeing it as wrong. In particular, for an astronaut, he cannot agree with the opinion that space travel and space exploration are nothing but a youthful and dangerous adventurism. For Hal, this means that "...they have killed the man in man". He and the other returning astronauts are viewed with mistrust, seen as "resuscitated Neanderthals". They are alienated, outcasts, and subject to social pressure to undertake the "betrization". The other choice is to leave Earth again and hope that once they come back, in several centuries, Earth's society is more familiar again.