“Are we alone in the universe? That’s the core question we’re trying to answer here,” Meenakshi Wadhwa, a planetary scientist with ties to NASA, tells her spellbound class. As she explains that to answer this “we need to go back to Mars to collect rocks”, one student scribbles notes while another holds up an iPhone to take a snap of the slides. In many ways this lecture hall at Arizona State University (ASU) is like any other. A group of keen women sit attentively in the front row; the men are spread out in the back. But the hearing aids hint at how unusual this class is.

Mirabella, a 20-storey “university retirement community” on ASU’s campus, is home to over 300 pensioners. When it opened its doors in 2020, the senior-living facility was nearly fully subscribed, despite the pandemic. Most residents are having a ball. They get a university pass, which allows them to attend the same classes and cultural events as students, but with the distinct benefit of not having to take exams. Golf buggies can drive them around the sprawling campus, though many are still fit enough to mountain bike.