The Steward Observatory Public Evening Lecture presents "How long since the Big Bang?" by Jeremy Mould at 7:30 p.m. in the Steward Observatory, Room N210.

Main Library unveils a new special collection titled "Paper, Paint and Ink: Selections from the Archives of Western Writers." The exhibit runs through Oct. 29 in the Main Library's Special Collections.

Guillermo Garcia speaks on "Strategies for Protecting the Bi-National Watershed in Ambos Nogales" at noon in the Shantz building, Room 440.