Page 28 - EngineerIT January 2022

SPACE

Einstein was right after all!

The theory of general relativity passes a range of precise tests

set by pair of extreme stars

An international team of researchers from ten countries led by Michael Kramer
from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has
conducted a 16-year long experiment to challenge Einstein’s theory of general
relativity with some of the most rigorous tests yet. Their study of a unique pair
of extreme stars, so called pulsars, involved seven radio telescopes across the
globe and revealed new relativistic effects that were expected and have now
been observed for the first time. Einstein’s theory, which was conceived when
neither these types of extreme stars nor the techniques used to study them
could be imagined, agrees with the observation at a level of at least 99.99%.

ore than 100 years after Albert Einstein presented are not only in agreement with the theory, “but we were also able to
his theory of gravity, scientists around the world see effects that could not be studied before’’.
Mcontinue their efforts to find flaws in general Prof Ingrid Stairs from the University of British Columbia at
relativity. The observation of any deviation from General Vancouver gives an example: “We follow the propagation of radio
Relativity would constitute a major discovery that would open photons emitted from a cosmic lighthouse, a pulsar, and track their
a window on new physics beyond our current theoretical motion in the strong gravitational field of a companion pulsar. We
understanding of the Universe. see for the first time how the light is not only delayed due to a
The research team’s leader, Prof Michael Kramer from the Max strong curvature of spacetime around the companion, but also that
Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany, the light is deflected by a small angle of 0.04 degrees that we can
says: “We studied a system of compact stars that is an unrivalled detect. Never before has such an experiment been conducted at
laboratory to test gravity theories in the presence of very strong such a high spacetime curvature.”
gravitational fields. To our delight we were able to test a cornerstone This cosmic laboratory known as the “Double Pulsar” was
of Einstein’s theory, the energy carried by gravitational waves, with discovered by members of the team in 2003. It consists of two
a precision that is 25 times better than with the Nobel-Prize winning radio pulsars which orbit each other in just 147 min with velocities
Hulse-Taylor pulsar, and 1000 times better than currently possible of about 1 million km/h. One pulsar is spinning very fast, about 44
with gravitational wave detectors.” He explains that the observations times a second. The companion is young and has a rotation period

Fig. 1: Artistic impression of the Double Pulsar
system, where two active pulsars orbit each other
in just 147 min. Credit: Michael Kramer/MPIfR

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