Universal gravity constant confirmed
14 Aug 2015 by qmwwwtqmqt.d qmwwwtqmqt.d
After a decades-long study of a distant pulsar – pulsating radio star – physicists say they have confirmed that gravity is constant across the Universe.
Astronomers led by the National Radio Astronomy Observatory used the Green Bank Telescope in West Virginia and the Arecibo Observatory in Puerto Rico to measure gravity outside our Solar System and found that it is universally constant.
Research leader Professor Weiwei Zhu said: “The gravitational constant is a fundamental constant of physics, so it is important to test this basic assumption using objects at different places, times, and gravitational conditions. The fact that we see gravity perform the same in our Solar System as it does in a distant star system helps to confirm that the gravitational constant truly is universal.”
In the research, accepted for publication in Astrophysical Journal, the team observed pulsar PSR J1713+0747 – approximately 3,750 light-years from Earth – and found that it takes about 68 days to orbit its white dwarf companion.
The pulsar’s orbit was found to be uncommonly wide suggesting the effect of the gravitational radiation – the steady conversion of orbital velocity to gravitational waves – is very small and would have negligible impact. The scientists believe a more pronounced orbital change would confound the accuracy of the pulsar experiment.
Professor Zhu said: “The uncanny consistency of this stellar remnant offers intriguing evidence that the fundamental force of gravity – the big 'G' of physics – remains rock-solid throughout space. This is an observation that has important implications in cosmology and some of the fundamental forces of physics.”
Previous cosmology research suggests gravity may change over time or it may be different in different corners of the Universe. The data from this experiment, however, are consistent with an unchanging gravitational constant in a distant star system.
“These results - new and old - allow us to rule out with good confidence that there could be 'special' times or locations with different gravitational behaviour. Theories of gravity that are different from general relativity often make such predictions, and we have put new restrictions on the parameters that describe these theories,” said research associate Professor Ingrid Stairs at the University of British Columbia in Canada.
