Three Long-Term Projects മൂന്ന് ദീർഘകാല പ്രോജക്ടുകൾ

These projects take weeks or months. They are the kind of observations ancient astronomers made to build the calendar systems you learned in Week 2. By doing them, you will physically understand how the Sun moves through the sky across the year.

Project 1 - Build a Paper Sundial

What you need: Flat cardboard (A4), a straight stick or pencil, tape, sunny day.

Tape the paper to a flat outdoor surface. Push a 10-15 cm stick vertically through the centre (this is your gnomon - the shadow-caster). Every hour, mark the tip of the shadow and write the time. You'll see the shadow sweep from one side to the other in a curve. Connect the marks - you have a sundial.

The shortest shadow occurs at local solar noon (not always 12:00 - depends on your longitude within your time zone). The shadow points roughly North at noon (from India). If you repeat a month later, the curve shifts - because the Sun's height has changed. This is Uttarayana/Dakshinayana, observable with paper and a stick.

Project 2 - The Sunrise Photo Series

What you need: Phone camera, a fixed spot with a clear eastern horizon view.

Find a spot where you can see the horizon at sunrise. Mark your standing position. Once a month, photograph the sunrise from this exact spot - same position, same framing. After 6 months, compare the photos side by side. The Sun's position on the horizon will have shifted dramatically - from its southernmost point (winter solstice, ~December 22) to its northernmost (summer solstice, ~June 21). This northward journey IS Uttarayana. The southward return IS Dakshinayana.

Bonus: Check Orbit's Planet Tracker for the Sun's rise azimuth (compass bearing) for each date. The numbers will match your visual shift exactly. You're doing what Jantar Mantar was built for - measuring the Sun's annual drift.

Project 3 - The Shadow Pole Experiment

What you need: A vertical pole fixed permanently in a sunny spot (broom handle in a bucket of cement works), measuring tape.

Measure the pole's height. Once a week at local solar noon, measure the shadow length. Record date, time, length. Do this for 3-6 months (ideally a full year).

What you'll see: Around the summer solstice (June 21), the noon shadow is shortest - Sun at its highest. Around the winter solstice (December 22), the shadow is longest - Sun at its lowest. The change is slow near solstices and fast near equinoxes (because the Sun's motion follows a sine curve). If you plot shadow length vs. date, you get a smooth curve showing the entire Uttarayana-Dakshinayana cycle.

The deeper insight: With pole height and shadow length, you can calculate the Sun's altitude: altitude = arctan(pole height / shadow length). Do this at each solstice and equinox, and you can compute Earth's axial tilt (~23.4°). Ancient Indian astronomers did exactly this - and got it right to within a fraction of a degree.