When the interstellar object named Oumaumua hurtled through our solar system, scientists were simultaneously excited and confused. It was the first object discovered in our neighborhood which definitively originated somewhere else in the galaxy. But it also acted strangely, exhibiting a bit of acceleration which couldn’t be accounted for by the sun’s gravity.

That led Avi Loeb, chairman of Harvard University’s astronomy department, to write one of the most controversial articles in the scientific community last year. He gently suggested that we couldn’t rule out the possibility that the object wasn’t just a chunk of rock, but possibly some type of alien ship or probe. In a recent interview, he’s not backing down and insists that we should keep our minds open to all the possibilities.

However, the biggest surprise came last June, when new data from the Hubble Space Telescope showed that the mysterious object had accelerated during its visit to the inner solar system in 2017 – an acceleration that is not explained by the sun’s force of gravity.

Acceleration of that sort can be explained by the rocket effect of comets: The comet approaches the sun, the sun warms the ice of the comet and the ice escapes into space in the form of gas, an emission that makes the comet accelerate like a rocket. But the observations did not reveal a comet tail behind Oumuamua. Moreover, gas emission would have brought about a rapid change in the rate of the object’s spin, a change which was also not observed in practice, and it also might have torn the object apart.

If it wasn’t comet outgassing, what force caused Oumuamua to accelerate? It is precisely here where Loeb enters the picture. According to his calculations, Oumuamua’s acceleration was caused by a push.

To be clear, Loeb isn’t saying that Oumuamua definitely was a spaceship or autonomous alien probe. He offers other possible explanations which fall into the more mundane range of astrophysics, none of which I’m qualified to translate into English for you. But the object’s strange behavior was more than enough to at least open the door to the possibility that it might not be a natural formation.

And is that really so unlikely? I’ve long held that nobody can say with any amount of certainty whether life arose anywhere else in our galaxy and eventually reached levels of intelligence and technological capability that match or even vastly exceed our own. If this object really did come from the vicinity of Vega, as scientists currently believe, it would have been traveling for more than 600,000 years to reach Earth. How much dust, rock, and space debris might have accumulated on it during that long journey? Enough to coat it and make it look like a cigar-shaped asteroid perhaps.

Think about our own Voyager missions, currently heading out into the interstellar void. They’re not going nearly as fast as Oumuamua, but they’re still traveling at a fairly good clip. Eventually, they might cruise through the planetary system of another star. What will they look like in a million years? Would they be recognizable as “technology” by then or would aliens on some planet out there simply mistake them for random frozen rocks zooming through their neighborhood?

We managed to launch those vehicles out into the void barely fifty years after we first achieved powered flight. How much better might a probe be if it was built by beings that had thousands of years more to advance their technology? Sadly, this remains yet another thought experiment because the object is gone and we only had a brief window to observe it from afar. What I really regret is that we didn’t have enough advance notice to get a mission together to go out and intercept it. If it turned out to be a piece of technology, our entire view of the universe would have changed overnight.