Albert Einstein’s General Theory of Relativity, published back in 1915, once again successfully passed one of the most difficult tests, which lasted almost 16 years. A scientific team from the Max Planck Institute, Germany, the National Science Service of Australia, and the CSIRO Institute used observations from radio telescopes around the globe, including the famous Parkes radio telescope, to do so.
“The general theory of relativity describes exactly how gravity works at the largest scale levels in the universe, but this theory ‘breaks down’ at the level of atoms and subatomic particles, where the laws of quantum mechanics reign supreme,” the researchers wrote, “We needed to find a way to test Einstein’s theory at some intermediate level to see the limits of its validity.”
And a suitable “space laboratory” for such a test, a system of two pulsars 2,400 light-years from Earth, was found in 2003 using the Parkes radio telescope. “Our observations of the twin pulsar over the past 16 years agree remarkably closely with Einstein’s theory of relativity,” the researchers write, “The agreement is 99.99 percent accurate.”
As the name implies, the double pulsar system consists of two pulsars, rotating at high speed compact neutron stars that emit periodic radio signals and produce very strong gravitational fields.
One of the pulsars completes 45 revolutions per second, while the other rotates somewhat more slowly, completing 2.8 revolutions per second. Around each other these neutron stars move in an orbit, the period of which is 2.5 hours. According to the general theory of relativity, the limiting forces and accelerations occurring in this system, vibrate the very basis of the space-time continuum, and the resulting gravitational waves constantly take energy from the stars and gradually slow down the system as a whole. According to calculations, the two pulsars are expected to collide in 85 million years.
Such small changes in the energy of the twin pulsar system are quite hard to detect over a short period of time. Fortunately, the pulsars themselves, or more precisely their periodic radio signals, are a great tool for tracking even the smallest changes.
Using a network of Very Long Baseline Array radio telescopes scattered around the globe, astronomers have recorded the exact parameters of about 20 billion “ticks” of a double pulsar. Such a huge amount of data was sufficient to calculate and determine the smallest position deviations of each neutron star with a discreteness of one year.
And, as mentioned above, the results matched the predictions of Albert Einstein’s General Theory of Relativity by 99.99 percent. “But in the future, when we have new and more advanced radio telescopes at our disposal, we will revisit this problem,” the researchers write, “We still hope to find some cracks in Einstein’s theory, and if this succeeds, it will lead to the development of a new theory of gravity that is more in line with the real state of affairs.”