A reader asks: This seems to be as good a place as any to ask a question about closed universes. See, in a lot of popular science books, they teach you that an "open" universe is one where space is … Continue reading
[Fixed typo in Schrodinger's equation below—AW] Previously I talked about interference, the chief weird thing about QM that makes it different from Classical Mechanics. You have to think about complex-valued "amplitudes", from which you derive (real-valued) probabilities. From this you … Continue reading
Strictly speaking, most of the other rules about QM are already implicit in what I've already said. But a few implications of this setup are worth pointing out. First note that, in QM, the "state" includes information about every single … Continue reading
A bunch of people have been asking me about the interpretation of QM. Now, every interpretation of QM predicts (or claims to predict) the same experimental results in any experiment (or at least, any realistically feasible experiment). Otherwise they wouldn't … Continue reading
Imagine if somebody said that only one height exists at once—whichever elevation you happen to be in at the moment, only things at that elevation really exist. The moles in the ground are can be asserted to be "below", but … Continue reading
