Mystery Class Update: March 14, 2014
Please Report
Your Daylength!
Report Your Sightings
Time Clues are here! Use sunrise times on the equinox to estimate the longitude of Mystery sites.
Video of the Week
Music video
Looking for Clues?
Photoperiod Clues: Week #7
Local Photoperiod Data

Mystery Classes Photoperiod Data

Report Photoperiod
Photoperiod Map
Time Clues: Estimating Longitude
Make one copy for locating each Mystery Class site.
Sunrise on the Equinox Table Longitude Clues Worksheet Map
Time Clues
Sunrise on the Equinox

Step-by-step guide
Plot east/west location

Sunrise on the Equinox

View animation as you work. You can estimate the longitude of each mystery site with the Time Clues and these key facts:

  • The Earth turns to the east as it rotates.
  • It spins 1 degree longitude every 4 minutes.
  • The time between sunrise at the Prime Meridian and sunrise at a mystery site on the equinox reveals approximate longitude.
Sample Worksheets for Practice
Longitude Clues Worksheet Longitude Clues Worksheet Longitude Clues Worksheet
Sample A
West of Greenwich
Sample B
East of Greenwich
Sample C
Farther east of Greenwich
Next Update March 21, 2014