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Re: POE summary--long! (but *last* from me)




I guess I'm not totally satisfied by John's last (and final)
reply. First, just because the accelerometer attached to the tree needs
to read 9.8 m/s^2 to satisfy GR doesn't necessarily mean that this
acceleration is changing the speed of the tree, it may only be changing
the DIRECTION of its velocity vector (presumably by the needed amount to
stay on the curved spacetime worldline). Second, being an old
experimentalist, I get very uncomfortable when people tell me to ignore
the readings of my instruments. If the accelerometer on the train has a
time-dependent component in addition to the steady value of 9.9 m/s^2
(normal to the surface of the earth), that makes the measurements by the
person on the train inherently different than those of the person
handcuffed to the tree.

Which frame is the better one in which to compute changes in
kinetic energy - one in which the accelerometer always has a steady
reading, or one in which the accelerometer is showing time varying values?

Dr. Mark H.. Shapiro
Physics Department
California State University, Fullerton
P.O. Box 6866
Fullerton, California 92834-6866

Phone: ++ (714) 773-3884
Fax: ++ (714) 449-5810
e-mail: mshapiro@fullerton.edu