Terminal velocity =: energy lost to drag = energy gained from gravity and change in height.
Or drag force = gravity.
If the drag is low and dense enough then terminal velocity can exceed the speed of sound (a compression wave in the medium).
Note that aerodynamic drag grow as the square of...
For the observable universe select the frame of reference that give the minimum summed momentum vector and angular momentum.
I suspect that this will approximate the rest frame of the big bang.
Observationally the Cosmic Microwave Background should give the minimum total momentum...
As I understand this situation
Measurement is an interaction with the wave function of the electron - proton combination that selects an eigenvalue of the measured quantum number (i.e. orbit number).
When you measure the orbital quantum number a photon interacts with the electron...