‘ Einstein’s gravity theory passes extreme test’

Washington, July 5: Albert Einstein's insights into gravity hold true even in one of the most extreme scenarios the universe can offer, according to a study.

Einstein's understanding of gravity, as outlined in his general theory of relativity, predicts that all objects fall at the same rate, regardless of their mass or composition.

This theory has passed test after test here on Earth, but scientists have wondered whether it still holds true for some of the most massive and dense objects in the known universe, an aspect of nature known as the Strong Equivalence Principle.

The new findings, published in the journal Nature, show that Einstein's insights into gravity still hold sway, even in one of the most extreme scenario.

To date, Einstein's equations have passed all tests, from careful laboratory studies to observations of planets in our solar system.

However, alternatives to Einstein's general theory of relativity predict that compact objects with extremely strong gravity, like neutron stars, fall a little differently than objects of lesser mass.

That difference, these alternate theories predict, would be due to a compact object's socalled gravitational binding energy — the gravitational energy that holds it together.

In 2011, the National Science Foundation's ( NSF) Green Bank Telescope ( GBT) discovered a natural laboratory to test this theory in extreme conditions: a triple star system called PSR J0337+ 1715, located about 4,200 light- years from Earth.

This system contains a neutron star in a 1.6- day orbit with a white dwarf star, and the pair in a 327- day orbit with another white dwarf.

“This is a unique star system,” said Ryan Lynch of the Green Bank Observatory in the US.

“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,” he said.

Since its discovery, the triple system has been observed regularly by the GBT, the Westerbork Synthesis Radio Telescope.