Those who are not shocked when they first come across quantum theory cannot possibly have understood it.

The very nature of the quantum theory ... forces us to regard the space-time coordination and the claim of causality, the union of which characterizes the classical theories, as complementary but exclusive features of the description, symbolizing the idealization of observation and description, respectively.

Not only is the Universe stranger than we think, it is stranger than we can think.

If anybody says he can think about quantum physics without getting giddy, that only shows he has not understood the first thing about them.

If quantum mechanics hasn't profoundly shocked you, you haven't understood it yet.

If quantum mechanics hasn't profoundly shocked you, you haven't understood it yet.