Huygens, Christiaan (1629–1695)
Dutch physicist and astronomer who discovered Titan,
in 1655, and determined that Saturn has rings.
He also figured in one of the great unsung moments in planetary exploration
when at 7 p.m. on November 28, 1659, he sketched a feature – a dark
triangular patch – on the surface of Mars
which he had just seen through his modest telescope. Eventually, it came
to be known as Syrtis Major, the "Great
Marsh", and for many years was presumed to be some kind of watery body.
The significance of its sighting lay in the fact that, whereas the large
bright and dark areas on the Moon had been visible for all to see from prehistoric
times and Galileo had telescopically discovered the Great
Red Spot on Jupiter (an atmospheric
feature), Syrtis Major was the first permanent marking to be glimpsed
on the surface of another planet. Huygens quickly used his discovery to
demonstrate that the martian day – the time it takes Mars to spin
once around on its axis – is similar in length to our own. With his
brother, Constantijn Huygens (1628–1697), he built tubeless telescopes
supported by cables of very long focal length to reduce the problem of aberration.
He also invented the Huygenian eyepiece
and the first pendulum clock (1657), contributed
to the wave theory of light (1678) and several other areas of physics, and
solved the tautochrone problem.
Quote by Huygens
"What a wonderful and amazing Scheme have we here of the magnificent
Vastness of the Universe! So many Suns, so many Earths... "
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Huygens was deeply involved in speculation about the existence of extraterrestrial
life, a subject that dominates his Cosmotheoros, or New Conjectures Concerning
the Planetary Worlds, Their Inhabitants and Productions, published posthumously
in 1698. Huygens employs the same five arguments in favor of pluralism
as Fontanelle had done in his hugely
popular work, but reveals (not surprisingly) a greater command of late 17th
century astronomical data. The evidence he marshals against life on the
Moon is pertinent and almost decisive (see life
on the Moon). However, he is less sure-footed when it comes to making
inferences about the planets. He notes the excessive solar heat received
by the inner planets, and the deficiency suffered by those lying beyond
the Earth's orbit, but fails to explain how the supposed inhabitants of
these worlds cope with the temperature extremes to which they are subject.
Again, he notes the spots seen telescopically on Jupiter but then rashly
assumes these are clouds of water vapor and, therefore, evidence of habitability.
Concerning the possibility of extrasolar worlds and life, he writes:
Why then shall we not ... conclude that our
Star has no better attendance than the others? So that what we allow'd
the Planets, upon the account of our enjoying it, we must likewise grant
to all those Planets that surround that prodigious number of Suns. They
must have their plants and animals, nay and their rational creatures too,
and those as great admirers, and as diligent observers of the heavens
as ourselves ...
He makes some creditable estimates of stellar distances based on a consideration
of how far away the Sun would have to be to appear as bright as Sirius,
and then uses these estimates to account for the failure to detect extrasolar
worlds.
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