Why is the sky blue and a sunset red? Why do stars twinkle? What is a rainbow and where does its color come from? Optics professionals who can answer these questions might consider volunteering at the fourth annual Optricks Days, to be held March 10 and 11 from 10 a.m. to 5 p.m. at the Discovery Science Center in Santa Ana, Calif. Sponsored by the Optical Society of Southern California (OISC) and the Optics Institute of Southern California, the event will feature hands-on demonstrations to school-age children, teens and adults on subjects such as making kaleidoscopes or rainbows, "eyeball optics," fun with Moiré patterns, Fresnel lenses and lasers. This year, Optricks Days will also be part of the health-care related themes in the center's "Sesame Street Presents The Body” exhibit. On Saturday, the Southern California College of Optometry’s Eye Care Center will perform free eye screenings, including visual acuity tests, eye alignment and screening for refractive error. On both days, Optricks Days volunteers will be on hand to offer demonstrations and workshops and will present more advanced optics demonstrations to older children and adults. Volunteers are still needed to assist with 3-D Laser Theater presentations, eye screenings, workshops and various tabletop displays. Parking and entrance fees will be waived for volunteers, who are required to sign up in advance. For more information, visit oisc.net or contact Donn M. Silberman, OISC director: e-mail, donn@oisc.net; phone: (949) 636-6170