Explore the upcoming solar eclipse with fun, hands-on experiments

Step 1: Make your own camera obscura
Take a piece of cardboard and make a very small hole in it. Hold the cardboard in front of a sheet of white paper. When sunlight passes through the hole, it will project an image of the partially eclipsed Sun onto the paper. You can also use a colander or a slotted spoon instead of cardboard. Each hole will project a small image of the eclipsed Sun.

WARNING: Never look directly at the Sun through the hole.

Step 2: Record your observations
Draw the shape and size of the projected image of the Sun and record the time of each observation. Tip: Secure the cardboard and the sheet of paper so that they stay in place. You can then trace the projected image directly onto the paper.

Step 3: Can you answer these questions?
a. When could you first tell that the eclipse had begun? Could you also determine when it was completely over?
b. At what time was the eclipse at its maximum? Estimate the magnitude of the eclipse at that moment. The magnitude indicates what fraction of the Sun’s diameter is covered by the Moon. In Utrecht, the maximum magnitude should be about 0.901, meaning that approximately 90.1 percent of the Sun’s diameter is covered. How does this compare with your observation?
c. Did the position of the projected image change during the eclipse? If so, why do you think this happened?

Step 1: Test your thermometer
For this experiment, you’ll need a thermometer that responds reasonably quickly to changes in temperature. Test it beforehand, for example, by warming the thermometer with your hand or comparing readings indoors and outdoors. If it detects temperature differences within a reasonable amount of time, it should be suitable for this experiment.

Before the eclipse, observe how much the temperature changes under normal conditions. This will give you an idea of the natural fluctuations you might expect. For example, what happens when the wind picks up or when the thermometer moves into the shade? Try to keep the thermometer in the same place throughout the experiment and avoid changing its surroundings.

Step 2: Measure the temperature
During the eclipse, place the thermometer in a consistent location where it is exposed to sunlight. Record the temperature at regular intervals and note the exact time of each measurement. If you have access to a digital thermometer or weather station that records measurements automatically, you can use it to collect data continuously.

Step 3: Can you answer these questions?
a. How did the temperature change during the eclipse? Plot your measurements on a graph, with time on the horizontal axis and temperature on the vertical axis.
b. Did the eclipse have a measurable effect on the temperature? How large was the change compared with the normal fluctuations you observed before the eclipse?
c. Why does a solar eclipse affect the temperature? Can you explain the changes you observed?

Step 1: Set up your smartphone
For this experiment, you can use the light sensor built into your smartphone. Install the Phyphox app to access and record data from your phone’s sensors. Unfortunately, Phyphox does not currently support the light sensor on iPhones. If you are using an iPhone, other apps are available that can access the light sensor. Always check that an app is trustworthy and safe to use before installing it.

Find a well-lit location where you can keep your smartphone in the same position throughout the experiment. Think carefully about the orientation of the light sensor. Should you point it toward the Sun, or should you point it away from the Sun? Which setup will give you the most meaningful and reliable measurement of changes in ambient light?

Step 2: Measure the light intensity
During the eclipse, record the light intensity at regular intervals and note the exact time of each measurement. If your app allows it, you can also record the measurements automatically and continuously. Try to keep your smartphone in exactly the same position throughout the experiment.

Step 3: Can you answer these questions?
a. How did the light intensity change during the eclipse? Plot your measurements on a graph, with time on the horizontal axis and light intensity on the vertical axis.
b. Did the eclipse have a measurable effect on the light intensity? How large was the change?

Shadows cast by sunlight always have blurry edges. This is because the sun is not a point light source. During a partial solar eclipse, something unusual happens. Because part of the sun is covered by the moon, the sun appears smaller as a light source. This causes the shadows to become sharper in the narrow direction.

Step 1: Cut a Y-shape out of a piece of cardboard. Make sure the upper legs of the Y are exactly 90 degrees apart. Hold the cardboard by the lower leg and let the shadow fall onto a sheet of white paper. You can test this experiment with an elongated light source, such as a fluorescent tube or LED strip. The effect will be much stronger than during the solar eclipse, however, because the Sun is much farther away.

Step 2: Document your observations during the solar eclipse. Observe the shadow of the Y around the time the partial solar eclipse reaches its peak, which is around 8:11 p.m. Rotate the Y so that you clearly see one sharp leg and one blurry leg. At what time and at what angle is the difference between the two legs most obvious?

Step 3: Can you answer these questions?
a. Based on the direction of the sharp and blurry shadows, can you determine which part of the Sun was visible (top, left, right, or at an angle)?
b. How did the angle you had to use for sharp and blurry shadows change?

Take a look at the data from the day of the solar eclipse. You should see a slight dip in output around the time of the solar eclipse.