Dear Rolf,
I would be interested in the mathematical formulae behind your result as copied
below.
Could you please share them with us?
Best regards,
Wojtek
From: Rolf Wieland
Sent: Tuesday, January 23, 2018 10:31 AM
To: Frank King
Cc: sundial@uni-koeln.de
Subject: Hail to the Chief
Dear
Dear Rolf,
Many thanks for that diagram. It makes
everything very clear.
Where I live, at 52N, there is very little
change in the width of the shadow of a rod
gnomon over the course of the day. Almost
no one notices it.
In the tropics, the change is much more
obvious.
You can see why I chose
Dear Frank,
Yes, the width of the shadow of a round rod polos with 0.5" in diameter is not always the same. I realized this not before 2009 when I was already engaged in sundials for at least 25 years!
The figure shows the width w without penumbra on a horizontal dial as function of the
al Message-
From: Frank King
Sent: Thursday, January 18, 2018 10:03 PM
To: john.pick...@bigpond.com
Cc: sundial@uni-koeln.de ; Frank King
Subject: Re: Hail to the Chief
Dear John,
A moot point...
... why should any sane normal
person want to help Trump...
Ah. I was thinking in terms of
&qu
Dear Geoff and John,
> Surely Geoff Thurston is right?
Yes. He is!
You don't even need to think in three
dimensions. The edges of the shadow
must run to the base of the gnomon
and must touch tangentially.
The base is indeed an ellipse. The
contact points are always opposite
one another (by
in the December Bulletin, p 38), the result is clear from the positions of
the lines for 6am and 6pm.
Best wishes,
John
-Original Message-
From: Frank King
Sent: Wednesday, January 17, 2018 6:04 PM
To: sundial@uni-koeln.de
Subject: Hail to the Chief
Dear All,
I gather from the UK media
Dear John,
A moot point...
> ... why should any sane normal
> person want to help Trump...
Ah. I was thinking in terms of
"displacement therapy".
Thinking about sundials must be
better for one's mental health
than drinking copious quantities
of Diet Coke?
Just trying to be helpful :-)
Frank
Very quickly.
The reason is the diameter of the Sun and the different distances between a
point of the rod and its shadow at noon and at sunset.
At summer solstice, for example, if 10 is the distance of a point P from
the center of the sundial, the distances between P and its shadows are (if
I'm
Dear Frank,
Can I help the POTUS? No.
Can I answer your question? Maybe but I am not used to working in imperial
units.
Consider a horizontal cross section of the gnomon at any height above the
dial plate. The shape of the section would be an ellipse with minor axis
equal to 0.5" aligned
@uni-koeln.de
Subject: Hail to the Chief
Dear All,
I gather from the UK media that
the recent medical check-up
undertaken by the U.S. President
involved some "cognitive tests"
and he scored 30 out of 30.
One of these tests requires the
subject to mark in the hands of
a clock at a spec
Dear All,
I gather from the UK media that
the recent medical check-up
undertaken by the U.S. President
involved some "cognitive tests"
and he scored 30 out of 30.
One of these tests requires the
subject to mark in the hands of
a clock at a specified time.
It is, of course, reassuring to
know
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