Sometimes the probabilities are very close to certainties, but they're never really certainties.

Planets are too dim to be detected with existing equipment, far away, except in these very special circumstances where they're seen by their gravitational effect.

So the old Copenhagen interpretation needs to be generalized, needs to be replaced by something that can be used for the whole universe, and can be used also in cases where there is plenty of individuality and history.

You know, there was a time, just before I started to study physical science, when astronomers thought that systems such as we have here in the solar system required a rare triple collision of stars.

Today the network of relationships linking the human race to itself and to the rest of the biosphere is so complex that all aspects affect all others to an extraordinary degree. Someone should be studying the whole system, however crudely that has to be done, because no gluing together of partial studies of a complex nonlinear system can give a good idea of the behavior of the whole.

Hugh Everett's work has been described by many people in terms of many worlds, the idea being that every one of the various alternative histories, branching histories, is assigned some sort of reality.