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T
he launch in 1957 by the
Soviet Union of the first
artificial Earth satellite,
Sputnik 1, was a turning point
in history, both politically and
scientifically. Politically, it provoked
the “space race”—a battle for
supremacy in space between
the Soviet Union and the United
States. Scientifically, it opened
up new possibilities for astronomy.
Telescopes could be put into orbit,
giving them a view unhindered
by Earth’s atmosphere. Robotic
explorers could be sent into the solar
system to study planets and other
bodies from close quarters. NASA’s
Mariner 2, the first successful
mission to another planet, was
launched toward Venus in 1962.
Meanwhile, ambitious projects
to send people into space carried
on. In 1961, Soviet cosmonaut YuriGagarin became the first man to
orbit Earth. Just eight years later,
the Americans succeeded in
putting men on the moon. They
would bring pieces of our satellite
back with them, which would
shed new light on the formation
of the early solar system.Seeing from space
Until the mid-20th century,
astronomers peered through
the narrowest of atmospheric
“windows,” looking only at visible
light. Earth’s atmosphere is
transparent to only two parts of
the electromagnetic spectrum: the
narrow waveband we call visible
light (with a little ultraviolet and
infrared on either side) and the
radio band. Astronomers had no
means of knowing about the
intense output of ultraviolet, X-,and gamma rays from hot, high-
energy cosmic sources, which are
absorbed by Earth’s atmosphere.
Cool and concealed constituents of
the universe, such as infant stars,
were also lurking, waiting for their
infrared radiation to be detected.Radio astronomy
The main kind of “invisible
astronomy” open to ground-based
observers is radio astronomy.
After tentative beginnings in the
1930s, the field developed rapidly
in the 1950s. Scientists who had
worked in radio science during
World War II were instrumental
in founding astronomy research
groups, such as those at Cambridge
and Manchester in the United
Kingdom. Also around that time,
astronomers at Harvard in the
United States identified radioINTRODUCTION
1950
1959
1963
1964
1961
1962
Dutch astronomer
Maarten Schmidt
demonstrates that quasars,
discovered by radio
astronomers in 1960,
are distant galaxies.Giuseppe Cocconi and
Philip Morrison propose a
place on the electromagnetic
spectrum to look for
messages from aliens.In a speech to the US
Congress, President John
F. Kennedy announces
the intention to put a man
on the moon by the
end of the decade.In his book universe,
Life, Intelligence, Soviet
astronomer Iosif Shkovsky
speculates about
extraterrestrial life.Dutch astronomer
Jan Oort argues that
a cloud of comets is
to be found orbiting
the sun at the edge
of the solar system.
US astronomers
Arno Penzias and
Robert Wilson discover
cosmic microwave
background radiation,
evidence for the Big Bang.