An international team of researchers have shown that Einstein’s insights into gravity hold true, even in extreme scenarios.

Albert Einstein came up with a theory in 1905 which said that the laws of Physics are exactly the same for the observers who are either at rest or moving with uniform velocity. Similarly, the speed of light in a vacuum is completely independent of the movement of the observers. Einstein changed the human understanding of time and space. He claimed that there is a lot of inherent flexibility among them and introduced a new concept called ‘Space time’. He worked for 10 years before publishing the theory of General Relativity as he strived to incorporate acceleration into it. He found that massive bodies tend to cause a distortion in the space time and behave a little differently due to the presence of a thing called ‘Gravity’.

Every scientific theory needs to have a set of testable predictions to verify the results. Probably the most important prediction in case of general relativity is the Equivalence Principal. It refers to the notion that all objects fall in a similar fashion irrespective of their size and composition. Despite all the events including an experiment on Moon by David Scott, a handful of scientists were curious to know what will happen, if the falling object is too big. They believed that alternative theories about gravity are much stronger than the Einstein’s one but a recent announcement has dealt a huge blow to their ideology.

It all started in 2011, when the Green Bank Telescope (GBT) of the National Science Foundation (NSF) discovered a triple star system which could act as a natural laboratory for testing the general relativity theory in extreme conditions. This star system is known as PSR J0337+1715 and is located at a distance of 4,200 light years from the Earth. It is composed of two ‘White Dwarfs’ which are actually superdense stellar corpses and an even denser neutron star. This system is quite strange because the neutron star and one of the dwarf star circles a central mass in a 1.6 Earth days orbit. They join the outer white dwarf in a 327-day orbit which is much farther away. The Co-author of the paper, Ryan Lynch, referred to its complexity by saying,

“This is a unique star system. We don’t know of any others quite like it. That makes it a one-of-a-kind laboratory for putting Einstein’s theories to the test.”

The triple system has been under continuous monitoring since its discovery. In addition to the GBT, Arecibo Observatory in Puerto Rico and the Westerbork Synthesis Radio Telescope in the Netherlands are also keeping an eye on it. According to a report, GBT has spent 400 hours in its surveillance as they tracked data and measured the movement of each object with respect to the others. The fact that the neutron star under observation is a pulsar helped the cause of the scientists. These pulsars rotate so swiftly that some of the most precise atomic clocks on the Earth fail to pick them up. However, GBT has the ability to match this pulsar as Lynch said,

“As one of the most sensitive radio telescopes in the world, the GBT is primed to pick up these faint pulses of radio waves to study extreme physics.”

The gravitational pull of the neutron star is so strong that it packs 1.4 times the sun’s mass in a sphere of the size of Amsterdam. On the other hand, the interior white dwarf is about the size of the Earth and accounts for only 0.2 solar masses. This is where the test for general relativity begins as the outer white dwarf should pull both of these different bodies in a similar way in order to justify the equivalence principle. The researchers used the pulses of the neutron star to test the gravity of the system.

After all the observations and calculations, they concluded that there is hardly any difference in the acceleration of the neutron star and the inner white dwarf. The margin for all the other alternatives have decreased even further after this finding and Nina Gusinskaia, a Doctoral Student at the University of Amsterdam who is also a Co-author of the study, mentioned that in the following words:

“If there is a difference, it is no more than 3 parts in a million. Now, anyone with an alternative theory of gravity has an even narrower range of possibilities that their theory has to fit into in order to match what we have seen.”