How Accurate is Using a Sundial Compared to an Atomic Clock?

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Author: Sofia PC

Grade Level: 5th - 6th; Type: Physical Science


In this experiment, students will discover whether a sundial is as accurate as an atomic clock when telling time. We are only going to test hours, since sundials are designed only to show hourly changes in a day. It is obvious that an atomic clock is more precise.

Research Questions:

  • How exactly does an atomic clock work?
  • Are there any other forms of time-telling that were used in the earlier years? What about currently?

Time is intangible, but it affects our daily lives dramatically.

Sundials are an early form of time-telling. It relies on the position of the sun in the sky to tell time. It is done by casting a shadow on its style, which is a thin rod or edge. Where the shadow hits on the marked (numbered) surface, is the time.

An atomic clock uses microwaves that are part of the electromagnetic spectrum and is much more complicated in structure than a sundial or even your regular wall clock.


  • Atomic clock
  • Sundial
  • An open mind

Experimental Procedure:

  1. Obtain a sundial, place it on a surface outside, and make sure it is facing the “true north” on the earth. You should have researched on this.
  2. Take your atomic clock and check the time on it, record this time.
  3. Take a look at your sundial and see where the “shadow” is cast. Which number? Does this match your atomic clock? Record this.
  4. Repeat steps 2-3 a few more times during the day.
  5. Evaluate your results.

Terms/Concepts: Atomic Clock; microwaves; sundial; sun position;  true north


May, William Edward, A History of Marine Navigation, G. T. Foulis & Co. Ltd., Henley-on-Thames, Oxfordshire, 1973, ISBN 0 85429 143 1

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