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The direct observation of gravitational waves with
ground-based detectors
requires a detector sensitivity higher than anything that has ever been
constructed before. The basic idea is quite straightforward: accurately
measure
relative distance variations between the end points of at least two arms of
a
triangle. Although ambitious projects like KAGRA seem well on their way to
achieve the required sensitivity, other natural phenomena exist in nature
that
let us do the exact same thing. Accurately recording the arrival times of
pulses
from rapidly rotating neutron stars also allows us to accurately observe
relative
distance variations. Observations of these so-called pulsars can be used to
construct the Galactic-scale equivalent of KAGRA, and we 'only' need to use
existing radio telescopes to acquire the observations. Projects aimed to
detect
gravitational waves by doing this are called 'Pulsar Timing Arrays' (PTAs),
and
they are currently making good progress to detect gravitational waves. I
will
explain the basic ideas, the current achievements, and the science that can
be
done with PTAs. This is an exciting era for PTA research, as the
International
PTA community is starting to produce astrophysically significant results,
with
prospects for a detecting this decade. |