Sundials
Geometry & Trigonometry
How is the sun used to tell the time? - Explore the mathematical principles and create your own unique investigation.
Where this idea comes from
Start here — these are the sources that inspired this exploration.
Introduction
Here is an example of a simple sundial, which can be used to find East and West, and tell the time. What are the mathematical concepts at play here?
Guiding Questions
- How does the shadow of a vertical stick move during the day? Track one and record angles over time.
- Why must a sundial's gnomon point at the celestial pole, and what angle does that mean at your latitude?
- Calculate the hour-line angles for a sundial at your latitude using trigonometry.
- Build the sundial and test it. How far off is it, and what explains the difference (longitude, season)?