#31: He Is Placed on Unpaid Medical Leave at the University of Arizona in 2023
In 2023, following serious health issues, he was placed on unpaid medical leave from his position at the University of Arizona. The decision reflected the impact of his declining health on his ability to continue regular academic duties.

The announcement made clear that his public appearances would be limited. For decades, he had maintained a steady pace of interviews and lectures. The leave marked a visible shift from active participation toward a more private period focused on recovery.
