How Does That Work? Calculating the Circumference of the World
Grades: 3 - 8

Video Description: New May 2022! Learn how Eratosthenes, way back in ancient times, successfully calculated an accurate measurement of Earth’s circumference.

Type of Video: Topical*
Unique Video ID: HDTW-4**

Quick Ideas for Using the Video:

  • Before viewing the video, check for student understanding about the word “circumference” and how that word applies to the Earth.
  • As students view the video, have them create a list of the “educated guesses” that Eratosthenes made and how he sought to validate what he believed to be true. Discuss the examples after viewing the video.
  • Have students look at the still thumbnail image on the video and ask them what they think it’s an image of. Based on that image, what do they think they are going to learn about in the video?


*Topical videos are filmed on location in the classroom/workspace/laboratory, in studio, or a combination of both to explain and/or demonstrate specific concepts, events, topics, or processes.

**The unique Video ID can be used to quickly locate a single video in the ET collection. This search function is designed to let teachers assign students to watch a specific video and have only that video appear as a search result. Just click on Search and choose “By Video ID.” Then type in the Video ID as it appears above. Be sure to include the dash.