Tracking the Sun
At least 4 hours
What Will You Learn?
The length of daylight and brightness of the sky varies throughout the year. In this experiment, you’ll learn how to measure and record how the light from the sun varies over time.
Make a Pouch: Felt Version
We are going to build a phone holder to make sure all of our measurements are taken from the same location each time. You can do this a variety of ways; here’s how to do it in felt or (shown below) in cardboard.
Place your phone on a piece of felt and cut a rectangle large enough that you can fold it over the phone with a bit of material overlapping, and with the top of the phone extending over the felt.
Next, carefully glue the side and bottom edges with a hot glue gun. Make sure the inside space remains large enough to hold your phone.
Skip Past the Cardboard Version and to Attaching to a Window.
Make a Pouch: Cardboard Version
Place your phone in the center of a piece of cardboard, making sure the top of the phone sticks out above the top edge. Line a straightedge up with the bottom of your phone and draw a horizontal line the length of the cardboard.
Repeat on each side of your phone, creating two vertical lines across the width of the cardboard.
Next, measure the thickness of your phone and draw a set of lines that distance from the phone’s outline.
Remove the lower corners of your cardboard, cutting along the horizontal and vertical lines to where they intersect at the bottom corners of the outline of your phone.
Fold up along the inner lines, then out along the outer lines. This will create a box to hold your phone.
Apply tape to the bottom and corners to hold the box together.
Attach to Window
Hot-glue suction cups to your felt package and stick to window, or tape it on directly. We like to use blue painter’s tape — prolonged application of duct or other highly adhesive tape could leave sticky residue that’s difficult (or even impossible) to remove from your windows.
Choose your window well. In the northern hemisphere, it’s best to use a south-facing window that is not in a shaded area. This will help ensure that you can have the best access to daylight for your test.
Set your Schedule
The key to a good experiment is consistency. Decide how often you want to take measurements — hourly, every two hours, or more. It might be useful to set alarms on your phone to remind you when to take a measurement based on your schedule.
Take your Measurements
Take your first measurement in your chosen location. Start by creating a new experiment in the Science Journal app and then start a new test that uses the ambient light sensor. Let the test run for 30 seconds to a minute to stabilize your reading.
The sun is the fuel for our entire planet. It changes our weather. Its power fuels plants that then either directly or through another animal or two, fuel all of us. Try taking measurements at the same time every day for a few months and see how your readings change.
When taking a measurement during the brightest time of the day, you might find that the sun maxes out your phone’s sensor. Not all phones have the same range for their sensors, so experiment with yours to try to find its maximum (noon on a full-sun day should do it).
Evenings give the greatest amount of change, so try measuring every hour from 4 to 8pm to see how the light changes. As fall approaches, how do you think the light around 6pm will change from day to day? Remember weather can greatly affect your data too, so the more measurements you take, the easier it will be to create a dataset that will give you a more accurate result.