Explanation:
In 1655, three hundred fifty years ago on this date,
Dutch astronomer
Christiaan Huygens
discovered Luna Saturni - now known as
Saturn's moon Titan.
To celebrate,
consider
this intriguing picture of his
telescope lens, all that remains of the
instrument
he used, designed and constructed in collaboration with his brother,
Constantijn Huygens.
The lens itself measures 57 millimeters (just over 2 inches) in
diameter and is inscribed along the border "X 3 FEBR.
MDCLV":
its focal length (10 Rhineland feet) and
the date of its final polishing, 3 February 1655.
It also bears a verse from the Roman poet
Ovid,
"Admovere Oculis Distantia Sidera Nostris"(They brought the distant stars closer to our eyes).
Huygens used the verse as part of an anagram announcing
his discovery.
The use of
an
anagram, a practice common in his time,
established a date for his discovery but kept its details
secret until he wished to reveal them.
Decoded and translated, his anagram reads "A moon revolves around
Saturn in 16 days and 4 hours.", a good agreement with
the modern value for
Titan's
orbital period.
