In late 2017, scientists at a Hawaiian observatory glimpsed a strange object soaring through our inner solar system. Astrophysicist Avi Loeb conclusively showed it was not an asteroid; it was moving too fast along a strange orbit and leaving no trail of gas or debris in its wake. There was only one conceivable explanation: the object was a piece of advanced technology created by a distant alien civilization. Professor Avi Loeb wrote about his encounter with this object, ‘Oumuamua, in his 2021 book Extraterrestrial. In this interview, I speak to Avi Loeb about how we would detect the existence of intelligent civilisations beyond Earth, the implications of such discoveries for science, culture, and our planet and why space archaeology could be our species’ most important project.