248
global audience of 500 million
tuned in to watch Neil Armstrong
land the Lunar Module and step
out onto the surface of the moon,
closely followed by Buzz Aldrin.
It was the culmination of nearly a
decade of collaborative effort and
effectively ended the Space Race.
There were six more missions
to the moon following Apollo 11,
including the near-disaster of
Apollo 13, whose lunar landing in
1970 was aborted after an oxygen
tank exploded on board. The crew
was returned safely to Earth on
the crippled spacecraft in a real-life
drama that played out in front
of a worldwide television audience.
Learning about the moon
Before Apollo, much of what was
known about the physical nature
of Earth’s only natural satellite was
speculation but, with the political
goals achieved, here was an
opportunity to find out about an
alien world firsthand. Each of the
six landing missions carried a kit
of scientific tools—the Apollo Lunar
Surface Experiments Package
(ASLEP). Apollo’s instruments
tested the internal structure of the
moon, detecting seismic vibrations
that would indicate a “moonquake.”
Other experiments measured the
moon’s gravitational and magnetic
fields, heat flow from its surface,
and the composition and pressure
of the lunar atmosphere.
Thanks to Apollo, scientists
have compelling evidence from
analysis of moon rock that the
moon was once a part of Earth
(pp.186–87). Like Earth, the moon
also has internal layers and was
most likely molten at some point
in its early history. Unlike Earth,
however, the moon has no liquid
water. Since it has no moving
geological plates, its surface isTHE SPACE RACE
not continually repaved, and so the
youngest moon rocks are the same
age as Earth’s oldest. The moon is
not entirely geologically inactive,
however, and occasionally has
moonquakes that last for hours.
One Apollo 11 experiment
remains active and has been
returning data since 1969.
Reflectors planted on the lunar
surface bounce back laser beams
fired from Earth, enabling scientists
to calculate the distance to the
moon to within an accuracy of
a couple of millimeters. This gives
precise measurements of the
moon’s orbit, and the rate at which
it is drifting away from Earth
(about 1½ in [3.8 cm] per year).Apollo’s legacy
On December 19, 1972, the sonic
boom over the South Pacific, as
the Apollo 17 capsule thumped
into Earth’s atmosphere, sounded
the end of the Apollo program.
In total, 12 men had walked on
the moon. At the time, it was
widely assumed that routine flights
to Mars would soon be a reality,
but in the intervening 40 years,Houston. Tranquility Base
here. The Eagle has landed.
Neil ArmstrongNeil Armstrong took this famous
photograph of Buzz Aldrin on the
surface of the moon. Armstrong’s
reflection, standing next to the lunar
module, can be seen in Aldrin’s visor.