On March 9, 2018, special "Longitude Clues" are given which allow students to calculate the approximate longitude of each Mystery Class.

Before this, the weekly sunrise/sunset data revealed infomation about the LATITUDE of the Mystery Classes, but nothing about their LONGITUDE. With longitude uncovered, their global search for the location of the secret sites will narrow.

The special Longitude Clues coincide with the spring equinox, and help students estimate the longitude of the sites based on the time of sunrise there. These clues only work on the equinox! By knowing the amount of hours and minutes between sunrise at a Mystery Class and sunrise at the Prime Meridian on the equinox, students can actually estimate that Mystery Class's approximate longitude.

Students will be given a Longitude Clues Worksheet, a World Map and a Equinox Sunrise Table. For an example of how this amazing calculation works, take a look below at some sample materials from a prior Mystery Class season:

Sunrise on the Equinox
View animation as you work on the Longitude Clues.

Challenge students to explain why the longitude clues only work on the equinox. For details about the science and math behind the longitude clues:

• Teacher's Practice Packet #2: Longitude Clues (see pages 2-4)