Sean Carroll
Let's conjure some science up in here. Science is good for the soul. Today: what are "quantum fluctuations," anyway? #qf
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Talk about quantum fluctuations can be vague. There are really 3 different types of fluctuations: Boltzmann, Vacuum, & Measurement.
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Boltzmann Fluctuations are basically classical: random motions of things lead to unlikely events, even in equilibrium. #qf
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The *macro*state of a system can be static (equilibrium), but stuff is churning beneath the surface. That allows Boltzmann fluctuations.
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Vacuum Fluctuations are the differences b/w quantum and classical states. Classically-definite observables can have a quantum variance.
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Zero-point energy, virtual particles, the Lamb shift -- all due to vacuum fluctuations. But notice something important...
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Nothing actually "fluctuates" in vacuum fluctuations! The system can be perfectly static. Just that quantum states are more spread out.
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Measurement Fluctuations are the bridge b/w Boltzmann and Vacuum fluctuations. They occur when you repeatedly observe a quantum system.
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By itself, a system can be static, but observational outcomes are probabilistic. Observe over and over again, get different results.
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That makes us confuse (static) vacuum fluctuations with (dynamical) Boltzmann fluctuations. We think what we see is what really is.
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But quantum mechanics says that what really exists is very different from what we see. In an atom, electrons aren't fluctuating at all.
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@seanmcarroll Butterfly effect :) -
@seanmcarroll can we think of Boltzmann Fluctuations as probability density functions?
Güray MOLLAOĞLU
Kathleen Nicoll, PhD
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