A Purdue professor just met with Pope Francis to discuss hydrogen energy. Here’s how it went.

Pope Francis is known for having strong opinions and leading one of the most progressive papacies of all time — and, as a Purdue University professor recently found out, he also laughs at his own jokes. It’s the kind of quality one can really only find out about if they’re lucky enough to wrangle a private meeting with him. Which, years after initial efforts to make it happen, engineering technology professor John Sheffield just did.