Hipparchus
CIRCA 190 B.C. – CIRCA 120 B.C.
When you talk about the greatest ancient scientist, there’s little
doubt that you mean Greek astronomer Hipparchus of Nicaea.
He’s best known for his discovery of precession: After measuring
the positions of several bright stars, his results didn’t agree with
the ones Greek astronomers a century earlier had recorded. He
concluded that the positions of the equinoxes were changing. We
also have him to thank for originating the magnitude system. In
his catalog of some 850 stars, he ranked them in order of bright-
ness, from 1st to 6th magnitude. PORTRAIT: WIKIMEDIA COMMONS7
NOV. 9, 1934 – DEC. 20, 1996
Nobody did more to popularize astronomy than American
astronomer Carl Edward Sagan. The landmark 1980 televi-
sion series Cosmos: A Personal Voyage, which he co-wrote
and narrated, has been viewed by more than half a billion
people. He also wrote popular science books, including
The Dragons of Eden, Pale Blue Dot, and the novel Contact,
which was turned into a motion picture.
But Sagan was no slouch scientifically. He predicted
that Venus’ temperature should be above the melting point of lead due to a runaway
greenhouse effect. He also imagined that Jupiter’s moon Europa might have an
underground ocean. PORTRAIT: PBS
6
Carl Sagan
As a member of the
imaging team for
NASA’s Voyager
probes, Carl Sagan
hatched the idea for
Voyager 1 to take
the image that
would become
known as the Pale
Blue Dot. In it, Earth
is seen from a
distance of
3.7 billion miles
(6 billion kilometers)
as “a mote of dust
suspended in a
sunbeam,” he later
wrote. NASA/JPL-CALTECH
NOT QUITE
ASTRONOMERS
Many of you might be thinking, “OK,
Einstein — where’s Einstein?” Although
his discoveries revolutionized astron-
omy, Albert Einstein was a physicist,
the most famous of all. Here’s a list of
10 physicists who had a tremendous
influence on astronomy, this time in
alphabetical order.(^) Niels Bohr
OCT. 7, 1885 – NOV. 18, 1962
(^) Christian Doppler
NOV. 29, 1803 – MARCH 17, 1853
(^) Albert Einstein
MARCH 14, 1879 – APRIL 18, 1955
(^) Carl Friedrich Gauss
APRIL 30, 1777 – FEB. 23, 1855
(^) Stephen Hawking
JAN. 8, 1942 – MARCH 14, 2018
(^) James Clerk Maxwell
JUNE 13, 1831 – NOV. 5, 1879
(^) Isaac Newton
JAN. 4, 1643 – MARCH 31, 1727
(^) Erwin Schrödinger
AUG. 12, 1887 – JAN. 4, 1961
(^) Kip Stephen Thorne
B. JUNE 1, 1940
(^) John Archibald Wheeler
JULY 9, 1911 – APRIL 13, 2008
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