Accessibility links

Distant Pulsar Lends New Support for Einstein’s Relativity Theory

  • Rick Pantaleo

A recent study is providing new support for a theory that many scientists consider to be one of the two major pillars of modern physics - Albert Einstein’s General Theory of Relativity.

It seems there are always members of the scientific community who are eager for the chance to knock the air out of Albert Einstein's nearly 100 year-old General Theory of Relativity. This milestone work describes how the elemental force of gravity helps to shape the geometry of space and time. And some of its predictions - involving phenomena like the dilation of time, the motion of bodies in free fall and the gravitational bending of light - are mind-bendingly different than those of classical physics.

But, despite decades of assaults, Einstein’s famous hypothesis keeps coming out on top, passing every test it’s subjected to, including a recent examination that some scientists called one of its most stringent tests ever.

The test was conducted by a group of astronomers and physicists using a unique cosmic laboratory, created by the discovery of a rare celestial circumstance - a rotating neutron star, or pulsar, tightly orbiting a white dwarf star nearly 7,000 light-years from Earth.

Scientists say that the pulsar, weighing twice as much as our Sun, is the most massive neutron star ever identified, with a gravitational field more than 300 billion times stronger than that on Earth.

"They’re [pulsars] very, very close to being black holes. And that’s actually one of the very special things about this system is that this pulsar, this neutron star, is one of the most massive neutron stars we’ve ever seen, which means that it has incredibly strong gravity. It’s in orbit around a white dwarf which is much less massive,” said Dr. Scott Ransom, who is with the National Radio Astronomy Observatory, which first spotted the pulsar system.

The massive pulsar and its white dwarf companion were discovered with the Observatory’s Green Bank Radio Telescope in West Virginia.

Researchers from Germany’s Max Planck Institute for Radio Astronomy led the study, which combined data gathered by other radio and optical telescopes around the world.
Some of the researchers initially believed that their observations would prove Einstein's theory wrong.

But guess what? Ransom says their research found new evidence in the pulsar system’s massive gravitational field to support Einstein's predictions.

“Einstein’s Theory of Relativity and most of the related classes of gravity theories as well, suggest that those systems that are orbiting very, very compactly like that will give off what’s known as gravitational radiation. Basically, they cause ripples in space-time and those ripples in space-time, those waves take away some energy from the orbit; so the orbit should be shrinking with time and getting smaller,” Ransom said.

And evidently those orbits are getting smaller. Paulo Freire, a scientist at the Max Planck Institute for Radio Astronomy and a member of the study’s research team, said that their radio observations of this odd binary system were so precise that they were able to measure a change in the system’s orbital period of 8 millionths of a second per year, which is exactly what Einstein predicts in his theory.

As Albert Einstein’s Theory of General Relativity approaches its centennial year, new challenges abound. Relativity is often at odds with the second pillar of modern physics - quantum mechanics - which focuses on atomic and sub-atomic particles. Does Dr. Ransom think there are many scientists who are still eager to prove the famous theoretical physicist wrong?

“In a way, yes, because we know that general relativity doesn’t mesh with quantum mechanics. They don’t work together. But every test that we’ve thrown at general relativity, it seems to have passed with flying colors. So, if anyone does figure out where it eventually breaks down and how to mesh it with quantum mechanics, they’ll certainly be getting the Nobel Prize, because it’ll be a revolutionary discovery,” Ransom said.

Many scientists believe that Einstein's model of gravity and space-time will sooner or later be proved invalid under extreme conditions. And physicists are hoping that they will someday find an alternative description of gravity that can mesh both relativity and quantum physics and finally explain what now seem to be incompatibilities.

Ransom and his colleagues reported the results of their study in a recent edition of the journal Science.