FIRST EVER IMAGE OF BLACK HOLE AGAIN PROVED THAT THERE IS NO FLAW IN THEORY OF RELATIVITY

 

FIRST EVER IMAGE OF BLACK HOLE AGAIN PROVED THAT THERE IS NO FLAW IN THEORY OF RELATIVITY

First Ever Image of Black Hole as Obtained by Event Horizon Telescope

Image Credit: ETH Collaboration

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.