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How to Measure the Sun's Shadow

The position of the sun's shadow at particular times of day can tell us a number of things. For one, it can be used to tell the time, which is the principle behind sun dials. The path of the shadow throughout the year also shows that the orbit of the Earth and its axis are neither perfectly straight nor perfectly round. For this reason the shadow cast by the sun at a particular time of day will be different at different times of the year.

Things You'll Need

Yard stick
Pegs
Watch

Instructions

- 1
  Press the yard stick into the ground at a location where it will get sun at noon throughout the year. Make sure the yard stick is as straight and firmly pressed into the ground as possible.
- 2
  Mark the position of the tip of the shadow cast by the yard stick at midday on the first of the month. Use a peg to do this and make sure that you do not knock the stick at any point.
- 3
  Repeat this process on the first day of every month for the whole year. Remember to account for daylight saving time and deduct or add an hour depending on when you started making your records.
- 4
  Notice the shape made by the pegs. You should, if everything has gone to plan, see a figure eight marked out by the pattern of pegs. This is caused by the elliptical shape of the Earth's orbit and the tilting of its axis in relation to the plane of its orbit.

Astronomy