Expand their world! Scientists in Grades 4-6 track day length to see first hand how Earth's Cycles operate. Our students need to know these concepts!As days get longer through the spring, students collect sunrise and sunset data from the Internet and graph photoperiod, or day length, to locate the longitude and latitude of a given town, their town, and an unknown location. Use world maps, graphs, authentic data, and simple calculations to see cyclical relationships between sun, earth, and moo