www.lesswrong.com/posts/7HMSBiEiCfLKzd2gc/quantum-mechanics-and-personal-identit...
1 correction found
we can't observe absolute speeds, absolute positions, absolute accelerations, or absolute rotations
This bundles together several different cases, but acceleration and rotation are not like absolute position or constant velocity: they are locally measurable. Accelerometers detect proper acceleration, and gyroscopes detect rotation/angular rate.
Full reasoning
The claim is too broad and is false because acceleration and rotation are observable even without external position references.
- NIST describes accelerometers as devices for sensing acceleration and explains that when the device experiences acceleration, its internal proof mass shifts in a measurable way.
- NASA explains that gyroscopes provide rotation information by measuring changes as a spacecraft turns, i.e. they detect angular rate/rotation.
So while physics treats absolute position and uniform straight-line speed differently from acceleration and rotation, it is incorrect to say that we "can't observe absolute accelerations, or absolute rotations." Those two are precisely the kinds of motion inertial instruments are built to measure.
2 sources
- A Better Way to Measure Acceleration | NIST
Accelerometers, including the new NIST device, record changes in velocity by tracking the position of a freely moving mass... The distance between the proof mass and the reference point only changes if the accelerometer slows down, speeds up or switches direction.
- Operating Hubble with Only One Gyroscope | NASA Science
Gyros provide rotation information as Hubble turns from target to target... The spacecraft uses this information to determine the velocity and direction it is turning.