Solar Analemma
Photograph the sun at the same clock time every day for a year and it traces a figure-eight in the sky, called an analemma. Two separate effects combine to produce this shape, and each can be modelled as a periodic function.
Where this idea comes from
Start here — these are the sources that inspired this exploration.
Introduction
If you record the sun's position at exactly the same clock time on many days across a year, it traces a figure-eight pattern in the sky, called an analemma. This happens because Earth's orbit is not perfectly circular and its axis is tilted relative to its orbital plane. Each of these two effects produces its own periodic offset in the sun's apparent position; combining them, using published sun-position data rather than a year of original photography, produces the full figure-eight curve.
Guiding Questions
- A photograph of the sun at the same clock time every week for a year traces a figure-eight in the sky. Since collecting a year of your own photographs isn't practical in an IA timeline, use published sun-position data (for example, an online solar calculator or an existing analemma photograph) instead. What two separate effects cause the figure-eight shape?
- Model each effect — Earth's tilt and its elliptical orbit — as a periodic function.
- Combine your two functions. Does the sum produce the figure-eight shape?
- Why is the analemma asymmetric, and how would it look from Mars?