perplexus.info :: Geometry : These are E-Z

These are E-Z (Posted on 2018-06-25)

Three problems with one theme:

1) Feynman, when pledging his engineering fraternity, was quizzed: why does a mirror reverse you right to left but not top to bottom?
2) Why is East found to the left on star maps?
3) Since a screw goes into a nut by turning to the right, clockwise (CW, "righty-tighty") should not a nut go into a screw turned to the left, CCW?

Submitted by Steven Lord

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Solution: (Hide)

1) While the x-y plane is maintained, a mirror reverses the z-dimension, effectively showing your facial surface as it would look inside out.
2) Same as 1. The z-axis is reversed, so the positive x-axis is now found 90 deg CCW from positive y-axis. Another way to see this is to lie on your back with your head pointed North. Imagine looking up at the stars. East is now to your left.
3) There is no z-axis reversal here. Only the perspective is changed. The screw and nut maintain their chirality, and each has the same chirality as the other to match threads.

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
re(2): More on Procedures	Steven Lord	2018-06-27 12:44:28
re: More on Procedures	Charlie	2018-06-26 20:13:56
More on Procedures	Steven Lord	2018-06-26 16:33:14
re: Procedure Question	Charlie	2018-06-26 15:25:22
Procedure Question	Steven Lord	2018-06-26 12:39:04
solution	Charlie	2018-06-25 10:54:49

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