Dear Fellow Shadow Watchers,
Imagine a man sitting on the sun, (Yes! rather hot), watching
the light of the sun fall on the Earth. As light takes 8 minutes to
reach Earth, then it should be possible to see a small dark edge due to
Earth's rotation. This will represent 8 minutes of rotation,
equivalent to around 2 degrees rotation of the Earth's circumference -
probably hardly discernible.
I am no astronomer, but I would imagine that this sort of effect
can be seen from Earth on other heavenly bodies, such as perhaps
Jupiter, where the dark band would probably be wider than this?
I can also imagine a hypothetical planet that could be invisible
if its day length was exactly twice the time that sunlight takes to
reach it.
We must forget where the sun really is and just use its delayed
light for our shadowy purposes.
ANOTHER TOPIC
I am shortly to renovate a vertical dial that I made in 1986,
the year of Haley's Comet. By now much of the original paint has peeled
from its surface, although it is still quite legible in most parts. The
base board is marine ply.
I want to find some better type of paint that will last a bit
longer. Is 25 years asking too much for a dial that is alternately
frozen then roasted in the sun? I originally used several coats of
exterior grade undercoat, then painted the lines etc. with standard
lacquer paints, and then covered the whole with yacht varnish. The
varnish peeled off very quickly!
Would it help to leave each coat to weather before applying the
next coat? or will it stick better to a still tacky surface? Maybe the
dial could be baked in an oven, (big oven), to harden the paint before
exposing it to the elements?
Any advice will be most welcome.
Regards,
Mike Cowham.
Cambridge, UK.
