Big Bang waves: Was Einstein wrong?

Big Bang waves: The recent detection of gravitational waves suggests that, an instant after the Big Bang, the universe expanded faster than the speed of light. Does this contradict Einstein's special theory of relativity?

Keith Vanderlinde/National Science Foundation/Reuters
The 10-meter South Pole Telescope and the BICEP (Background Imaging of Cosmic Extragalactic Polarization) Telescope at Amundsen-Scott South Pole Station, which detected evidence of gravitational waves, is seen against the night sky with the Milky Way in this National Science Foundation picture taken in August 2008.

If corroborated, it will be one of the biggest findings in cosmology in recent decades, a discovery that helps explain how our universe came to be.

The detection of gravitational waves, or "ripples in space-time," that were imprinted on the thermal radiation left over from the Big Bang some 14 billion years ago is being called a "smoking gun" for the inflation theory of the universe, which postulates that, an instant after the Big Bang, the universe ballooned rapidly before settling down to its current rate of expansion.

"Gravitational waves carry not only energy, but also information about how they were produced. For instance, the short burst produced in a supernova explosion differs greatly from the wave pulse produced during the merger of two black holes," notes an explainer from the Max Planck Institute for Gravitational Physics.

The discovery takes us back billions of years ago, when the universe was trillionth of a trillionth of a trillionth of a second old. In that split second, according to the theory, the universe expanded faster than the speed of light.

At first glance, it seems as though the inflationary model violates the cosmic speed limit. Albert Einstein's special theory of relativity, first published in 1905 and subsequently supported by countless experiments, states that nothing that has mass can be accelerated faster than the speed of light. That's because, according to Einstein's theory, as an object approaches the speed of light its energy and momentum approach infinity. 

But now scientists think that the universe expanded at faster-than-light speeds. If this is true, was Einstein wrong?

Absolutely not, say the researchers who announced their findings Monday.

"Einstein's relativity forbids anything with mass to travel faster than the speed of light," says Chao-Lin Kuo, Assistant Professor at Stanford University and one of the researchers. "It also forbids information to be sent faster than the speed of light. Inflation involves expansion of space itself. So there is no violation of relativity here."

John Kovac, a radio astronomer at the Harvard-Smithsonian Center for Astrophysics and the lead discoverer concurs. "This research is perfectly consistent with Einstein's theory of relativity," Kovac says. "Einstein said that nothing in the Universe can travel with a speed faster than the speed of light but in this case the space itself was growing."

In fact, this discovery helps support another one of Einstein's theories. Published in 1916, the general theory of relativity explains gravitation as a geometric property of space and time. Under this theory, massive objects "curve" spacetime. In addition to predicting black holes, general relativity predicts gravitational waves of the sort discovered by Kovac's team.

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