AIUI, we "hear" that motion. It's not that it takes billions+ of atoms in order to effect a motion at all, it's that the amount of motion here, _of the sensor_

AIUI, we "hear" that motion. It's not that it takes billions+ of atoms in order to effect a motion at all, it's that the amount of motion here, _of the sensor_, is just an atomic diameter. If it takes billions of atoms to move the sensor, the sensor itself is comprised of trillions+ (I'd guess, decillions+) of atoms. That we can "hear" the movement of just a single atomic diameter in distance of such a relatively massive structure doesn't seem amazing? I'm even more amazed that with such sensitivity, we aren't inundated with the noise from that, and can still hear normal volume sounds, whose movement must be absolutely massive compared to a single atomic diameter. I guess that effect is similar to the eye's. We cannot see a single photon in the presence of daylight. That only works in a darkened (pitch black in this case) room.