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Astronomy was largely discarded as
the foundation of navigation in the
1970s, and replaced by artificial
satellites, which created a global
positioning system.
The purpose of astronomy
The practical reasons for pursuing
astronomy and space science may
have changed, but they still exist.
For example, astronomy is needed
to assess the risks our planet faces
from space. Nothing illustrated
Earth’s apparent fragility more
powerfully than the iconic images,
such as “Earthrise” and “Blue
Marble,” taken from space by Apollo
astronauts in the 1960s. These
images reminded us that Earth is
a small planet adrift in space. As
surface inhabitants, the protection
afforded by the atmosphere and
Earth’s magnetic field may make
us feel secure, but in reality we
are at the mercy of a harsh space
environment, blasted by energetic
particles and radiation, and at risk
of colliding with rocks. The more
we know about that environment,
the better equipped we are to deal
with the potential threats it presents.A universal laboratory
There is another very important
reason for doing astronomy. The
universe is a vast laboratory in
which to explore the fundamental
nature of matter, and of time and
space. The unimaginably grand
scales of time, size, and distance,
and the extremes of density,
pressure, and temperature go far
beyond the conditions we can
readily simulate on Earth. It would
be impossible to test the predicted
properties of a black hole or watch
what happens when a star explodes
in an Earth-bound experiment.
Astronomical observations
have spectacularly confirmed the
predictions of Albert Einstein’s
general theory of relativity. As
Einstein himself pointed out, his
theory explained apparent anomalies
in Mercury’s orbit, where Newton’s
theory of gravity failed. In 1919,Arthur Eddington took advantage
of a total solar eclipse to observe
how the paths of starlight deviated
from a straight line when the light
passed through the gravitational
field of the sun, just as relativity
predicted. Then, in 1979, the first
example of a gravitational lens
was identified, when the image
of a quasar was seen to be double
due to the presence of a galaxy
along the line of sight, again as
relativity had predicted. The most
recent triumphant justification of
Einstein’s theory came in 2015 with
the first detection of gravitational
waves, which are ripples in the
fabric of spacetime, generated by
the merging of two black holes.When to observe
One of the main methods scientists
use to test ideas and search for new
phenomena is to design experiments
and carry them out in controlled
laboratory conditions. For the most
part, however, with the exception
of the solar system—which is
close enough for experiments to be
carried out by robots—astronomers
have to settle for a role as passive
collectors of the radiation and
elementary particles that happen
to arrive on Earth. The key skill
astronomers have mastered is that
of making informed choices aboutINTRODUCTION
What a wonderful and
amazing scheme have we
here of the magnificent
vastness of the universe.
Christiaan Huygens