The Oumuamua Spacecraft Hypothesis –Harvard’s Avi Loeb Responds to the World’s Media

“Only a fraction of the interstellar objects might be technological debris of alien civilizations. But we should examine anything that enters the Solar System from interstellar space in order to infer the true nature of `Oumuamua or other objects of its mysterious population.”

Avi Loeb, chairman of Harvard’s Astronomy Department  and Frank B. Baird, Jr., Professor of Science, replied by email today to our question about the media frenzy that followed his paper on Oumuamua, along with additional comments below.

Here is our question: “We’re doing a follow up to our recent post on We’d like to include a quote (of any length) from you on your thoughts about human implications of the Oumuamua “spacecraft” debate. In short, it seems that we are rooting beyond the science for validation of the spacecraft hypothesis. In the rancorous, tribal environment we’re living through, it appears the human species is yearning for validation of intelligent life beyond our fragile Blue Dot.”
Avi Loeb’s response follows:

I was very surprised about the reaction of the media to our paper. We did not have a press release. The paper was submitted for publication ten days ago and posted on the online arXiv at the same time. It was reviewed and accepted for publication within a record time of only a few days. I received positive reactions from distinguished astronomers, such as the Astronomer Royal in the UK, Lord Martin Rees.I am glad to see the excitement about the paper, but it was not written for that purpose. We just followed the standard practice of scientific research.

I prefer not to assign probabilities to the nature of `Oumuamua. e just need to be practical and collect more data on it or other members of its population. The interpretation of existing and future data is my plan for the future.

Attached is a PDF file with some general notes , along with some additional comments below. [View PDF file of article “Harvard Researchers Suggest Interstellar Object Might have been from Alien Civilization”]

It is exciting to live at a time when we have the scientific technology to search for evidence of alien civilizations. The evidence about `Oumuamua is not conclusive but interesting. I will be truly excited once we have conclusive evidence.

`Oumuamua deviates from a trajectory that is solely dictated by the Sun’s gravity. This could have been the result of cometary outgassing, but there is no evidence for a cometary tail around it. Moreover, comets change the period of their spin and no such change was detected for `Oumuamua. The excess acceleration of `Oumuamua was detected at mutiple times, ruling out an impulsive kick due to a break up of the object. The only other explanation that comes to mind is the extra force exerted on `Oumuamua by sunlight. In order for it to be effective, `Oumuamua needs to be less than a millimeter in thickness, like a sail. This led us to suggest that it may be a light-sail produced by an alien civilization.

I welcome other proposals, but I cannot think of another explanation for the peculiar acceleration of `Oumuamua.

The response to my paper with my postdoctoral fellow, Shmuel Bialy, has been truly remarkable. We submitted it for publication only a week ago. It was accepted for publication in The Astrophysical Journal Letters merely three business days later. The attention was created by blogs on Centauri Dreams and Universe Today. But by now, Twitter is humming continuously about it.

Our own civilization is currently engaged in developing the light-sail technology. The solar-sail principle was already demonstrated by the Japanese IKAROS projectand is being developed towards the goal of reaching high speeds by the Starshot project of the Breakthrough Prize Foundation, for which I chair the advisory board. It is conceivable that more advanced civilization are using this technology routinely, and this resulted in space debris of the type of `Oumuamua.
Looking ahead, we should search for other interstellar objects in the sky. Such a search would resemble my favorite activity with my daughters when we vacation on a beach, namely examining shells swept ashore from the ocean. Not all shells are the same, and similarly only a fraction of the interstellar objects might be technological debris of alien civilizations. But we should examine anything that enters the Solar System from interstellar space in order to infer the true nature of `Oumuamua or other objects of its mysterious population.
We also asked the same question via email to Seth Shostak, Senior Astronomer at
Here is his reply:

It’s true that the Harvard paper suggesting that this object might be engineered, rather than simply the ten millionth rock from the Sun, has certainly provoked a lot of interest by the public. But one should keep in mind that the idea of alien company has perennially been interesting to the public. Personally, I think that’s because we’re hard-wired to be curious about potential competitors or – if you’re into the abduction mind set – mates. We all like the idea of aliens, and that’s not just because they’re frequent bit players on TV and in the movies (indeed, they get these roles because we ARE interested in extraterrestrials, not the other way ‘round.)

This has been true for as long as I’ve been paying attention: Any claim of alien activity has stirred interest. Much of this is kind of non-scientific – the UFO phenomenon, for example, relies a lot on witness testimony or ambiguous photographic evidence, but never fails to make the news. One-third of the public seems to think that we really are being visited by extraterrestrial tourists. That’s been true for many decades, and I think that the Oumuamua story is in some sense similar. We wish to believe that Homo sapiens is interesting and significant enough to warrant visitors from some other world. Obviously, that’s kind of self-centered (I wonder if dinosaurs made reports of alien craft come to Earth to abduct them!) But while the anthropocentrism is certainly mildly amusing, it’s also thoroughly understandable. As the self-proclaimed “crown of creation,” humans naturally would like to think that the rest of the cosmos is keen to know more about us – that we’re still, in some sense, at the center of the universe, despite Copernicus’ best efforts. It’s obviously far less interesting to suggest that Oumuamua might be no more than an insensible, random hunk of ice.

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