Who teaches, that is, a "Great Course" on the Mystery of Time as elucidated by the latest developments in physics.
The man is a phenomenon. Every sentence dense with information. Every sentence tied tightly to the next. And never a stumble; does he use a teleprompter?
In this series, one 31 minute lecture is devoted to quantum mechanics. How can anyone explain this exotic and completely counterintuitive subject to an educated but non-technical audience in 31 minutes?
Just two insights on this subject that he shares with us.
The first, that people often say that Newtonian mechanics describes our everyday world perfectly, and quantum mechanics describes the sub-microscopic world perfectly, and the biggest problem in physics is that the two appear to be irreconcilable. Carroll points out that quantum mechanics describes everything. It's just that there is an overlap because, at the scale in which we live, both systems describe things accurately.
The second more subtle and utterly like mind-blowing man! Within quantum mechanics, the "uncertainty principle" says that subatomic particles have no fixed location. The probability of being in a certain location may be determined, based on a "wave function," but the actual location is not fixed until an observer observes the particle!
Carroll asks whether it would suffice for a robot to observe, in order that the location be fixed. Or maybe an orangutan I might add? Now we are getting very much into the philosophy of science and also into epistemology -- the study of what can be known.
On what I would call philosophical grounds, Carroll rejects the idea that the universe is so anthropocentric that a simple human glance can eliminate all other possibilities and fix the location of a thing in space. What he says instead is that the observer him or herself is embedded in a wave function, and that (s)he exists in a multiverse such that (s)he might fix the location of the particle in one of any number of locations; which location can be predicted only probabilistically.
At which point I want to ask, "Yeah but what if this piece of pepperoni that we forgot to eat in our dorm at 2AM were like a whole universe unto itself??!!!"
(No Nobel Prize for that unfortunately.)