Albert Einstein’s theory of general relativity has undergone the most rigorous test to date and has passed it successfully. An international research team led by the Anton Pannekoek Institute of Astronomy at the University of Amsterdam, in the Netherlands, has shown that the equivalence principle, which holds that all bodies in the same gravitational field are equally accelerated, is correct. The astronomers observed that Einstein’s theory of general relativity is correct after examining triple star system made of one pulsar and two white dwarfs.
This new test on the equivalence principle has used the exotic triple star system ASR J0337+1715, located at 4,200 light years from Earth. At its center, there is a pulsar, a type of neutron star, that emits a beam of radio waves as it rotates. But if the pulsar moves, due to the gravitational influence of other stars, the regularity at which it emits radio waves is altered. Astronomers can measure the movement of the pulsar and the bodies that rotate along with it through these irregularities.
Equivalence principle of the Einstein’s theory of general relativity proven correct in a triple star system
What makes this system ideal for the test is that the pulsar is so dense that it exerts a gravitational influence even on itself. According to alternative theories of gravity, this class of objects does not comply with the equivalence principle. On the other hand, according to Einstein’s theory of general relativity, pulsar’s behavior under an external gravitational field should not be different from that of any other body within that field, be it a feather or a star.
Astronomers determined the acceleration of the pulsar and that of its white dwarf companions. They noted that the pulsar and one of the white dwarf stars are within the gravitational field of the second dwarf star. According to the Einstein’s theory of general relativity, both the pulsar and its first white dwarf companion should be equally accelerated since they are in the gravitational field of the external white dwarf.
In line with the general theory of relativity with its equivalence principle, the examination of the triple star system has not detected differences in the accelerations of both space objects found in the same gravitational field of the third one.
Thus, Einstein’s theory of general relativity has passed the most rigorous test to date, while other alternative approaches, such as some versions of string theory, have been virtually ruled out.