Avi Loeb has narrated this article for you to listen to.

The foundation of science is based on the humility to learn, not the arrogance of expertise. When comet experts argued that the interstellar object 3I/ATLAS must be a familiar water-rich comet as soon as it was discovered in July, they behaved like artificial intelligence systems: only able to reflect the data sets they were trained on. For decades, the data set that established comet expertise largely comprised icy rocks in the solar system. My counterpoint is simple: humanity launched technological objects into space, so we must conclude that alien life forms could do the same. This possibility must be added to the training data set of comet experts when studying interstellar objects.

To illustrate why, consider the following: on 2 January 2025, the Minor Planet Center – officiated by the International Astronomical Union to catalogue space objects – identified a ‘near-Earth asteroid’. A day later, the officials realised that this ‘asteroid’ was following the same trajectory of the Tesla Roadster launched by Elon Musk’s SpaceX in 2018. They immediately removed the object from their asteroid catalogue, realising that it was not in fact a rock but a car. Musk, statistically, is not the most accomplished space entrepreneur in the Milky Way over the past 13.8 billion years. There are about a hundred billion stars with similar properties to the sun in the Milky Way; roughly a tenth of them host a habitable Earth-size planet. If you roll the dice on billions of Earth-sun analogues, surely you would – or at least could – find other space entrepreneurs on some exoplanets? There is no reason why 3I/ATLAS is not a ship launched from one of them.

Most stars are billions of years older than the sun. Our Voyager spacecraft, with its 1970s technology, can reach the opposite side of the galaxy over the course of a billion years. This implies that there has been plenty of time for interstellar artefacts, potentially more........

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