The Suffolk County Vanderbilt Museum’s Reichert Planetarium, 180 Little Neck Road, Centerport presents One World, One Sky: Big Bird’s Adventure on Nov. 21 and 22 at 11 a.m. Elmo and Big Bird live in the United States and Hu Hu Zhu lives far away in China, but they discovered that they see the same stars at night. For ages 2 to 8. Tickets, which include admission to the museum and access to the grounds, are $13 for children, $16 adults, $15 seniors. To order, visit www.vanderbiltmuseum.org.