Is there life on Naknar Three?

This is a lecture I give each year to my undergraduate astrobiology students at the end of their course. It’s a lecture by an alien about a distant world, Naknar3, which turns out to be a familiar place.... In the lecture, the alien explains why it can’t possibly be a location for complex life, let alone intelligence. It invites my students to think about our assumptions on habitability and life and whether these assumptions are right. The lecture is designed to give the impression that our views of life are narrow. However, can sulfate reduction really power an intelligence? Would an alien really conclude that low UV radiation would be bad for life? Perhaps, after all, we are not so wrong in the way in which we assess the habitability of other planets. What do you think? In the process of giving this lecture, my students also get a chance to laugh at their professor, which at the end of the course, they should have the chance to do... This lecture was recorded for the 2020 course as it could not be delivered in person (or ’in alien’ or whatever the english phrase is for an absentee alien).