Everything that is not forbidden is compulsory.

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

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.

Enthusiasm is followed by disappointment and even depression, and then by renewed enthusiasm.

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.

Sustainability is living on nature's income rather than living on its capital.

If someone says that he can think or talk about quantum physics without becoming dizzy, that shows only that he has not understood anything whatever about it.