Fred and Tex:
After reading the exchange on here today, I went back and re-read Fred's
Compendium article, looking closer at the development of the gnomon shape
as a cycloid. Sketching the path of a point on a circle, rolling on a
line, I see the gnomon's shape (convex away from the line) as th
Dear Tex,
I also enjoyed the article on the Cycloid Polar sundial by Fred Sawyer. The
dial as designed by Thys deVries of Prinsenbeek, Netherlands and published
in Jul 1980 De Zonnewyzerkring, has a linear time scale that can be moved to
correct for the longitude and equation of time.
I used th
Hi John, Gordon, Malcolm et. al.
Gordon is basically right saying that if not for friction the rotation
would stop at infinity and the decay of rotation would be exponential. Yet
even small amount of friction dissipates energy and the longer it works the
more its effect is visible and we are talk
Tex,
I'm pleased that you enjoyed my article!
You can find a definition and description of cycloids at the following
website.
online.redwoods.cc.ca.us/instruct/darnold/CalcProj/Fall98/NateB/definition.
htm
There you'll see that a cycloid is the locus of a point attached to a
circle rolling on
Regarding the question about Earth's slowing rotation rate. My understanding
is that eventually the Earth and Moon will eventually keep the same face to
one another, but the sun would become a red giant before this would happen.
I have to disagree with Gordan's assertion that the Earth w
Hello all.
I found Fred Sawyer's excellent article on the cycloid polar sundial
in the December issue of Compendium to be a fascinating introduction to
this rarely seen type of dial.
The math required to solve the cycloidal gnomon was challenging, but
reasonable; and the proffered templates si
John,
The earth will not stop completely, at least due to tidal friction. Ignoring
nonlinear effects, the tides cause an "exponential decay" in rotation rate, a
given fraction every year. The water in an initially-stirred jar of water
never stops either (in theory) for the same reasons.
I yiel
Dear all,
Fascinating thread, quite amazing the assembled combined knowledge.
I subscribe to several lists from astronomy;telescope-making; thro'
meteors;seismology to homebrew beer( 3 on that topic ! ) and I can say
that this time and calendar thread has been the most educational and
entertaining
Hi guys,
If the earth's rotation is slowing, due to lunar tidal drag, then in what
year will it stop completely? Will one face of the earth, presumeably the
side with the most mass, permanently be facing the sun, just as one side of
the moon permanently faces the earth? Which side of the earth
