starting at around 11:00 Carroll explains quantum physics:
Science don't really understand quantum mechanics, but is using its findings comprehensively. It's like we use smartphones. We don't know how it function but we install apps, make photos or make phone-calls with it. Large majority of scientists and institutions are not interested or sometimes are actively against trying to pursue explanation of foundations of quantum mechanics.
Quantum Physics has two set of rules. One for the world where we don't observe particles and second for the world when we do. Which is explained in Double Slit Experiment
Carroll Talks about the Many Worlds hypothesis. Electron can spin either clockwise or counterclockwise. When it goes through some gate that measures its spin it's not that it has a defined position and you can measure it. When you measure it the decision collapses and the reality splits into two.