Next message: Frank Reed: "Re: Green Flash and Longitude"
Bill, you wrote:
"I let go of your Chicago observations"
They're not dead yet!
Just today, I finally got around to measuring the heights of the towers in
question above lake level --the results are suprising. Damn near froze my
fingers off --I parked too far away and forgot my gloves. But it's all coming
together quite nicely. The observations on that day in late September from the
beach in Indiana are consistent with the refraction from a moderate
temperature inversion and distinctly *IN*consistent with Bowditch Table XV. I'll get
into the details as time permits.
Before I forget (again), I wanted to mention that the "lean back" of the
buildings from the curvature of the Earth, which was something you were
concerned about, should be entirely insignificant. If a flagpole is 20 nautical miles
away from me, then it is tipped away from my vertical by 20 minutes of arc
almost exactly. The difference in angular apparent height from that tilt is
going to be proportional to the cosine of 20 arcminutes which differs from
unity by about one part in 60,000, so a one degree high skyscraper 20 miles in
the distance is shorter in apparent angular height by a thousandth of a minute
of arc because of that "lean back". The standard calculations can, and do,
account for this effect (implicitly), but even if they didn't, it wouldn't
matter.
And yet another "before I forget", Lake Michigan is not sinking. The level
fluctuates a lot, and yes very recently there have been some down-trending
years, but those boaters you mentioned who are convinced that it is draining
away because the piers are inconveniently high are wrong --it's urban legend.
The harbor builders built the piers years ago well above the fluctuations
*intentionally*. When you live on a body of water with natural level fluctuations,
it's much easier to deal with harbor infrastructure that ends up too high
for convenient use than it is to deal with infrastructure that is underwater!
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
