Astronomers have announced they have discovered what many consider the holy grail of their field: ripples in the fabric of space-time that are echoes of the massive expansion of the universe that took place just after the Big Bang.
Predicted by Albert Einstein nearly a century ago, the discovery of gravitational waves would be the final piece in one of the greatest achievements of the human intellect: an understanding of how the universe began.
Gravitational waves are feeble, primordial undulations that propagate across the cosmos at the speed of light. Astronomers have sought them for decades because they are the missing evidence for two theories.
One is Einstein's general theory of relativity, published in 1915, which launched the modern era of research into the origins and evolution of the cosmos. The general theory explains gravity as the deformation of space by massive bodies. Einstein posited that space is like a flimsy blanket, with embedded stars and planets causing it to curve rather than remain flat.
Those curvatures of space are not stationary, Einstein said. Instead, the gravitational waves propagate like water in a lake or seismic waves in earth's crust.
The other theory that predicted gravitational waves is called cosmic inflation. Developed in the 1980s, it posited that in less time than the blink of an eye after the Big Bang, the infant cosmos expanded exponentially, inflating in size by 100 trillion trillion times.
The Big Bang is the explosion of space-time that began the universe 13.8 billion years ago.
In addition to making the cosmos remarkably uniform across vast expanses of space, inflation caused everything it touched to balloon exponentially. That included tiny fluctuations in gravity that, when inflated, became gravitational waves.
Although the theory of cosmic inflation received a great deal of experimental support, the failure to find the gravitational waves it predicted caused many cosmologists to hold off their endorsement of it.
That may change after the announcement on Monday.
"These results are not only a smoking gun for inflation, they also tell us when inflation took place and how powerful the process was," said Harvard University physicist Avi Loeb.
"This has been like looking for a needle in a haystack, but instead we found a crowbar," team co-leader Clem Pryke, with the University of Minnesota, said.