Laser Interferometer Gravitational-Wave Observatory (LIGO) co-founder Rainer Weiss, left, and...

Laser Interferometer Gravitational-Wave Observatory (LIGO) co-founder Rainer Weiss, left, and Kip Thorne, right, accompanied by LIGO Executive Director David Reitze, bottom, hug on stage during a news conference at the National Press Club in Washington, Thursday, Feb. 11, 2016, to announce that scientists have detected gravitational ripples, just as Einstein predicted a century ago. Credit: AP / Andrew Harnik

It takes a brave man to reject a scientific paper by Albert Einstein. But that’s what the physicist Howard Percy Robertson did in 1936, as editor of the journal Physical Review. Einstein was so enraged that he never published there again.

If Einstein were alive today, he might thank Robertson, who saved the great scientist from retracting the most far-reaching prediction of his theory of relativity - the existence of gravitational waves. The first direct detection of Einstein’s waves was announced this week to much fanfare and celebration. Scientists say the waves emanated from the powerful collision of two black holes.

The finding was hailed as a vindication, though Einstein was one of the biggest doubters of his own idea. He flip-flopped several times over the years, said physicist Daniel Kennefick, co-author of An Einstein Encyclopedia. The tale ended well, thanks to Einstein’s wisdom in knowing when to be sure, when to have doubts, when to ignore his doubters and when to listen to them and regroup.

The idea grew out of Einstein’s relativity theories. He published his special theory of relativity in 1905, changing the way scientists understood space and time. He published the general theory in 1915 and changed the way scientists understood gravity, redefining it as the effect of curves in space and time.

In February of 1916, Einstein predicted that if space and time could have lumps and bumps, then perhaps those bumps could move, said Kennefick. “After all, we can see moving hills and valleys on the surface of water that we call waves, so if gravity curves space-time, why couldn’t it create moving distortions?”

Einstein understood that these waves would be subtle. Only something dramatic could emit a signal strong enough to provide a chance to detect them - something like a merger of black holes. But Einstein was skeptical about the existence of black holes at all, even though others predicted them based on his theory.

These doubts didn’t mean that that Einstein was insecure. He boldly predicted that the curve of space would produce a visible bending of starlight around the sun.

That prompted the world’s best astronomers to see for themselves, waiting for a 1919 eclipse of the sun to make the behavior of faint light from background stars measurable. When asked how he’d feel if relativity was disproved by the eclipse experiment, Einstein famously replied: “Then I would feel sorry for the dear Lord. The theory is correct anyway.”

Einstein knew when to be certain, said Kennefick. He had a good physical intuition, and he also knew when he was ranging around in new territory.

So it’s perhaps understandable that he would at one point decide to quash his gravitational-wave prediction in a high profile journal article. In hindsight, one could see Robertson’s rejection as a double negative - a negation of Einstein’s doubt that added up to positive support for his original idea.

Einstein didn’t see it that way. According to historical accounts, he was furious. He submitted the paper to another journal - the more obscure journal of the Franklin Institute in Philadelphia, not that anything with Einstein’s name on it could be obscure by that point in history. But before Einstein could reject his gravitational waves in that journal, Robertson indirectly nudged him to change his mind back again.

Robertson did this by becoming acquainted with one of Einstein’s assistants, Leopold Infeld, said Kennefick. It doesn’t appear that either Infeld or Einstein knew about Robertson’s role in rejecting the paper, as it’s traditional for reviewers to be anonymous. Robertson explained to Infeld why he thought Einstein was right the first time. That led to discussions between Einstein and Infeld, and before the paper came out, Einstein made radical revisions so that it supported rather than refuted the now famous forecast.

Who knows how history would have unfolded had Robertson let Einstein publish the original anti-gravitational-wave paper. It certainly helped to have Einstein on the favored side of things when it came to the difficult task of detection. The project that eventually led to a positive signal cost $1.1 billion over a period of 40 years. Called the Laser Interferometer Gravitational-Wave Observatory, or LIGO, it qualifies as the most expensive apparatus ever funded by the National Science Foundation.

The concept for LIGO was put forward by the MIT physicist Rainer Weiss back in 1972. The experiment is in the form of twin detectors, one near Hanford, Washington and one near Livingston, Louisiana. In each one, a laser beam travels down L-shaped pipes, each arm stretching two and a half miles. In theory, a gravitational wave would move mirrors at the ends of these pipes an inconceivably small distance that could be measured by the lasers.

The apparatus went through two iterations - a preliminary version that went up in 2010 and a more advanced version that went online in September of 2015. Within a few days of starting operation, the advanced detector registered something, which the physicists say fits the description of two black holes colliding.

The physicists say they can read a lot of information into the signal. They were able to discern the masses of the black holes - 29 and 36 times the mass of the sun - and a distance to the event of 1.3 billion light years from earth.

If they detect more collisions, the project could give scientists a more refined measure of distances to faraway objects and a better handle on the scale and expansion rate of the universe. They may observe other collisions between massive objects known as neutron stars, and learn about the nature of these exotic objects. And then there’s always the hope that they will find something completely unexpected.

Faye Flam writes about science, mathematics and medicine. She has been a staff writer for Science magazine and a columnist for the Philadelphia Inquirer. She is author of “The Score: How the Quest for Sex has Shaped the Modern Man.”