“RAYS” Awareness. The Discovery Museums. 177 Main Street. Acton. 11:00 a.m. Why should you wear sunscreen? Learn about ultraviolet light and do simple experiments to see how sunscreen protects you by blocking harmful rays. Make your own UV detector bracelet to take home. Outdoor program, weather permitting. Free with admission. 978-264-4200. www.discoverymuseums.org