Einstein passes the rigorous test of a cosmic laboratory

An international team has used telescopes around the world to complete the most challenging tests yet to demonstrate the validity of Einstein’s theory of relativity.

The observation of any deviation from general relativity, enunciated more than 100 years ago, would constitute an important discovery that would open a window to the new physics beyond our current theoretical understanding of the Universe.

Research team leader Michael Kramer of the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany, says in a statement: “We studied a compact star system that is an unrivaled laboratory for testing theories of gravity in the presence of very strong gravitational fields. To our delight, we were able to test a cornerstone of Einstein’s theory, the energy carried by gravitational waves, with an accuracy that is 25 times better than with the Nobel Prize winning Hulse-Taylor pulsar, and 1,000 times better than what is currently possible with gravitational wave detectors. ” He explains that the observations not only agree with the theory, “but we were also able to see effects that could not be studied before.”

Ingrid Stairs of the University of British Columbia in Vancouver gives an example: “We follow the propagation of radio photons emitted by a cosmic beacon, a pulsar, and trace their motion in the strong gravitational field of a fellow pulsar.

We see for the first time how the light is not only delayed due to a strong curvature of space-time around the companion, but also that the light is deflected by a small angle of 0.04 degrees that we can detect. Never before has such an experiment been performed with such a high space-time curvature. “

This cosmic laboratory known as the “Double Pulsar” was discovered by team members in 2003. It consists of two radio pulsars that orbit each other in just 147 minutes with speeds of approximately 1 million km / h. A pulsar spins very fast, about 44 times per second. The partner is young and has a rotation period of 2.8 seconds. It is their movement around each other that can be used as a near-perfect gravity laboratory.

Dick Manchester of Australia’s national scientific agency CSIRO illustrates: “The fast orbital motion of compact objects like these, about 30% more massive than the Sun but only about 15 miles wide, allows us to test many predictions. different from general relativity – seven in all! In addition to gravitational waves, our precision allows us to probe the effects of light propagation, such as the so-called “Shapiro delay” and bending of light. We also measure the effect from “time dilation” that makes clocks tick more slowly in gravitational fields.

We must even take into account Einstein’s famous equation E = mc2 when considering the effect of the electromagnetic radiation emitted by the fast-spinning pulsar on orbital motion. This radiation corresponds to a loss of mass of 8 million tons per second! While this sounds like a lot, it is only a tiny fraction – 3 parts in a billion trillion trillion! – of the pulsar’s mass per second “.

The researchers also measured, with a precision of 1 part in a million, that the orbit changes orientation, a relativistic effect also known from the orbit of Mercury, but here 140,000 times stronger. They realized that at this level of precision they must also consider the impact of the pulsar’s rotation on the surrounding spacetime, which is “pulled” with the rotating pulsar.

Norbert Wex of the MPIfR, another lead author of the study, explains: “Physicists call this the Lense-Thirring effect or frame-dragging. In our experiment, it means that we must consider the internal structure of a pulsar as a neutron star. Thus, our measurements allow us for the first time to use precision tracking of neutron star rotations, a technique we call pulsar synchronization to provide constraints on the extent of a neutron star. “

The pulsar synchronization technique was combined with careful interferometric measurements of the system to determine its distance with high-resolution images, resulting in a value of 2,400 light-years with only an 8% margin of error.

Team member Adam fDeller, from the University of Swinburne in Australia and responsible for this part of the experiment, highlights: “It is the combination of different complementary observational techniques that adds to the extreme value of the experiment. In the past, similar studies they were often hampered by the limited knowledge of the distance of such systems. This is not the case here, where in addition to pulsar synchronization and interferometry, information obtained from the effects due to the interstellar medium was also carefully taken into account ” .

We would love to give thanks to the author of this article for this incredible content

Einstein passes the rigorous test of a cosmic laboratory