FIRST EVER IMAGE OF BLACK HOLE AGAIN PROVED THAT THERE IS NO FLAW IN THEORY OF RELATIVITY
First ever image of a black hole
was released in April, 2019. This image was first visual confirmation of existence
of Black Holes as predicted by Einstein’s Gravitational Theory. This image also
opened the door to new discoveries regarding black hole theory.
The image taken by the Event
Horizon telescope was of a supermassive black hole at centre of M87
Galaxy, at a distance of 55 million light years from us.
A result published by the
Event Horizon Telescope (EHT) Collaboration in Physical Review Letters on
October 1, 2020, shows that the size of shadow cast by black hole on the
glowing disk of matters swirling around it is same as predicted in theory.
The size of the black
hole as obtained from the image is significant in performing second order test to
verify Einstein’s theory of general relativity.
“The second order test cannot
be done in the solar system, because the gravitational field is too weak”, says
Lia Medeiors of ETH team from the Institute of Advanced Study.
Now let us understand
what this second order test of general relativity is and what does it signify –
We can think of general
relativity as a set of corrections to the Newton’s theory of gravity. General
relativity basically supplies the corrections needed to explain the phenomena
of gravity. Now if a physical measurement of any gravitational phenomena shows
any deviations from what predicted by the theory then we can clearly say that
general relativity alone can’t explain all gravitational phenomena and more
higher order corrections are needed to explain the whole picture of
gravitational effect.
The gravitational field of
our solar system is too weak to testify any second order corrections predicted by
the general relativity. In solar system we can verify first order corrections, which
very efficiently explain phenomenon like slowing of time by the effect of
gravity, bending of light by the effect of gravitational field. General
relativity has all time successfully explained those phenomena.
The size of the black
hole was used by the researchers as the verification of the second order
correction predicted by the general relativity. Disappointing those physicists hoping to find
any flaw in the Einstein’s theory of general relativity, the size matched as
predicted by the theory.
ETH team member Dimitris
Psaltis of University of Arizona said, “The fact that general relativity still
refuses to bend is worrying for those of us who are old enough that we were
hoping to get an answer in our lifetime.”
The same kind of results were obtained from gravitational wave experiments, like one from the Advance
Laser Interferometer Gravitational-Wave Observatory. This experiment was also a
second order test of general relativity. The result of this experiment earlier
showed that the ripples in the space time, generated by merger of two black holes,
as recorded by the interferometer was in accordance with the theory. But this
current experiment has its own significance because, it’s the first second
order test involving observation of a black hole.
Paper
D. Psaltis et al. Gravitational test beyond the first post-Newtonian order with the shadow of the M87 black hole. Physical Review Letters, October 1, 2020. doi:10.1103/PhysRevLett.125.141104.
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