In 2017, the Pan-STARRS telescope in Hawaii spotted an interstellar object passing by Earth for the first time. Shortly after, Harvard’s Prof Avi Loeb was met with a backlash from the scientific community for suggesting it could be of alien origin.

Now, several years on, he has written a book, Extraterrestrial: The First Sign of Intelligent Life Beyond Earth, outlining why we still can’t out rule the possibility, and why scientists should always keep an open mind.

We speak to Avi on this week's episode of the Science Focus Podcast. He tells us why he believes the object, 'Oumuamua, was of alien origin, and what problems this reveals about the way modern physics is conducted.

• Read an edited excerpt of this interview

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