Thermal noise, a classical equation: s2 = kT/ks
s is the mean positional error (~0.02 nm)
k is Boltzmann’s constant (~1.38 x 10-23 J/K)
T is the temperature (~300 K)
ks is the stiffness (~ 10 N/m)
See page 91 of Nanosystems for a derivation and further discussion