Track the Sun

So you want to track the Sun?

Sunrise at Stonhenge - the ancient people who built this monument knew how to track the sun.
Sunrise at Stonehenge. Image credit: Pixabay.com

You don’t need to build your own Stonehenge. You can track the Sun’s position in the sky and learn how to do astronomy during the day!

Let’s get started with the basics of sun tracking. Here is everything you need to know to begin:

  • The Sun does not move; the Earth moves – it carries us under the Sun – it just looks like the Sun is moving.
  • The Earth moves every second of every day so the position of the Sun changes every second of every day.
  • Night is not the “Sun going away”, it is the Earth blocking the Sun.

One Day of Observation: the Sun rises and the Sun sets

Let’s start with a few easy observations about daytime. These are things you can notice just by waking up early one day before the Sun brightens the night.

The Sun starts the day for us on one side of the sky and ends the day on another side. At both of these times (sunrise and sunset), the Sun appears near to the ground – at the horizon.

During the middle of the day, the Sun appears to move “up” and across the sky and then back “down” again. In the middle of the day – at noon time – the Sun is high up in the sky, away from the ground.

Shadows change during the day

In the morning the Sun makes long shadows. At noon the Sun makes short shadows. At the end of the day, the Sun makes long shadows again. 

With a few simple tools you can measure the Sun’s position and shadows.

The Sun moves east to west

Over the course of one day, the Sun appears to move across the sky from east to west, rising to the highest point at noon. The Sun’s light shines on the Earth and makes shadows that move and change position and size. As the Sun “moves” through the sky, the shadows move on the ground.

Build a simple sundial, track the Sun

Sundial in Krk, Croatia showing the gnomon (stick) casting a shadow onto the marker at XII 12 o'clock noon. The shadow is shortest at 12 noon and allows people to track the sun.
Sundial – Krk, Croatia. The gnomon (stick) casts shadow on marker at XII 12 o’clock noon. Image credit: Pixabay.com

A sundial tracks the shadow of the Sun with an object that casts a shadow and time markings. For the simple sundial you can use a stick. The shadow of the stick (the stick on a sundial is called a gnomon) moves across the sundial. The shadow of the stick points to the time markings.

The simplest sundial is just a stick stuck in the ground with time markers nearby. The location of the stick’s shadow moves across the time markers throughout the day.

A stick, the Sun, another stick marks shadow. As simple as it gets. Image: Jim Champion

Mark the shadow’s position with any object (chalk drawing, a rock or another stick is a good choice). In the morning, the Sun appears low in the east and the shadow is long. The morning shadow points toward the west. At midday (noon) the Sun is at the highest point so the shadow falls in the middle and becomes short. At sunset, the shadow becomes long again – pointing to the east.

Paper Plate Sundial

A paper plate and a pencil make a simple sundial to track the Sun.
Push a pencil through a paper plate to make a sundial. Image Credit: Daniel Cummings

A paper plate with a pencil stuck through the middle makes a great moveable sundial! (Remember, when you move a paper plate sundial, you have to be careful to place it in perfect north-south alignment.)

Take this outside on a sunny day, then make a mark on the paper plate at the top of each hour. The shadow will move slightly each hour. The mark should go at the middle of the pencil shadow.

When you have completed this during one sunny day, you have made a sundial that can tell the time – roughly speaking!

An indoor sundial – the Sun Tracker

Most people think of sundials as something that you place outside. But, the Sun shines inside through windows. You can track the Sun through a window.

The Sun Tracker helps you track the Sun. It works as an indoor sundial that lets you decode the secrets of the motions of the Sun and Earth. It can track the Earth's rotation and orbit around the Sun.

An indoor sundial can help you track the Sun from the comfort of your own home! Do you have a sunny (or partly sunny) window? You can track the Sun and reveal the secrets of the Earth’s motion.

The Sun Tracker is an easy-to-use indoor sundial. Place the glistening window cling on any sunny window and then mark the position of the window cling’s shadow using one of the included stickers.

Repeat the next day or the next week at the same time of day. You will see a pattern emerging: the shadow cast by the Sun moves quite a bit each day.

If you are extra precise with recording the shadow at the same time of day, and you are able to do it for an entire year… you will see the Analemma.

The Sun Tracker is like a little bit of Stonehenge for your window.

Summary

Track the Sun with simple tools and you will reveal the motion of the Earth. There are two main motions of Earth, daily rotation and yearly orbit. Earth spins under the Sun each day and around the Sun in an orbit each year.

It is these two motions that make the Sun seem to move in the sky. Remember that the next time you are looking for the Sun – it’s where it always is… the Earth is what moves.

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