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Menelaus of Alexandria (c. 70–140 CE) was a Greek mathematician and
astronomer, the first
to recognize geodesics on a curved surface as natural
analogs of straight lines.
Although very little is known about Menelaus's life, it is
supposed that he lived in Rome,
where he probably moved after having spent his youth in Alexandria. He was called
Menelaus of Alexandria by both Pappus of
Alexandria and Proclus,
and a conversation of his with Lucius, held in Rome, is recorded by
century CE) also
mentions, in his work Almagest (VII.3), two astronomical
observations made by Menelaus in Rome in January of the year 98.
These were occultations of the stars Spica and Beta Scorpii by the moon, a few nights
apart. Ptolemy used these observations to confirm precession of the equinoxes, a phenomenon that
had been discovered
by Hipparchus in the
2nd century BCE.
Sphaerica is the only book that has survived, in an Arabic
translation. Composed of three books, it deals with the geometry of
the sphere and its application in astronomical measurements and
calculations. The book introduces the concept of spherical triangle (figures formed of three
great circle arcs, which he named "trilaterals") and proves Menelaus'
theorem (an extension to spherical triangles of a previously
known result). It was later translated by the sixteenth century
astronomer and mathematician Francesco Maurolico.
The lunar crater Menelaus is named after him.
The titles of a few books by Menelaus have been preserved:
- On the calculation of the chords in a circle, composed
of six books
- Elements of geometry, composed of three books, later
edited by Thabit ibn Qurra
- On the knowledge of the weights and distributions of
- He may also have written a star catalogue.
Britannica "Greek mathematician and astronomer who first
conceived and defined a spherical triangle (a triangle formed by
three arcs of great circles on the surface of a sphere)."
Bulmer-Thomas. "Menelaus of Alexandria." Dictionary of
Scientific Biography 9:296-302.