Sean Carroll

Talk about quantum fluctuations can be vague. There are really 3 different types of fluctuations: Boltzmann, Vacuum, & Measurement. #qf

Boltzmann Fluctuations are basically classical: random motions of things lead to unlikely events, even in equilibrium. #qf

The *macro*state of a system can be static (equilibrium), but stuff is churning beneath the surface. That allows Boltzmann fluctuations. #qf

Vacuum Fluctuations are the differences b/w quantum and classical states. Classically-definite observables can have a quantum variance. #qf

Zero-point energy, virtual particles, the Lamb shift -- all due to vacuum fluctuations. But notice something important... #qf

Nothing actually "fluctuates" in vacuum fluctuations! The system can be perfectly static. Just that quantum states are more spread out. #qf

Measurement Fluctuations are the bridge b/w Boltzmann and Vacuum fluctuations. They occur when you repeatedly observe a quantum system. #qf

@seanmcarroll this might not be a good question bc of my lack of understanding. But do any of these fluctuations end by observing?