If We Believe in Dark Matter, Why Not Extraterrestrial Life?

Avi Loeb doesn’t need to be a muckraker. As the head of the astronomy department at Harvard University, he sits in one of the most comfortable positions in academia. Nevertheless, he has repeatedly placed himself at the center of scientific controversies—most prominently with a series of articles and interviews suggesting that a peculiar space object known as ‘Oumuamua might have been a piece of alien technology.

The discovery of ‘Oumuamua in the fall of 2017 instantly made headlines: It was the first object ever observed passing through our solar system from another star system. Then, the more closely astronomers observed it, the stranger it appeared. It was extremely elongated, shaped perhaps like a cigar (although it was so small that its shape had to be inferred from its changing brightness). It didn’t look quite like a comet, but not quite like an asteroid either. Strangest of all, it accelerated slightly as it passed the sun and headed back out into interstellar space.

Never one to shy away from a puzzle, Loeb wrote a paper with his postdoctoral fellow Shmuel Bialy summarizing all of ‘Oumuamua’s unusual traits and floating the possibility that perhaps the reason it looks so unusual is that it is artificial, a spacecraft designed to sail on sunlight. News writers jumped on that juicy idea. Many of Loeb’s colleagues were critical (or worse) of his willingness to entertain speculations about alien technology. But for Loeb, this was just one more opportunity to provoke the kind of wide-open conversation that he would like to see more of in his field.

Less than two years after ‘Oumuamua, astronomers have discovered a second interstellar visitor, Comet Borisov, currently making its closest pass by the sun. There is nothing strange about this one; it looks exactly like a conventional comet. Loeb is not at all put off by that. “When you walk down the street and notice a weird person, the fact that later on you encounter many normal people does not take away the weirdness of that unusual person. In fact, it enhances it,” he says. I caught up with Loeb to hear more about his thoughts on alien life, academic culture, and the scourge of preconceptions.

You created a stir last year with your comments that the interstellar comet ‘Oumuamua could be an alien artifact. What prompted you to stake out such a controversial position?

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