Get Ready for the Eclipse With These Experiments
On Aug. 21, there will be a total eclipse of the sun, viewable in the United States for the first time in 26 years, and for the first time on the mainland since 1979. In the eclipse’s path of totality, the moon will completely block the sun, turning day into night, with the exception of the sun’s corona peeking out from behind the moon. On the West Coast, the full eclipse will be visible farther north in Oregon. In the Bay Area, we’ll experience about an 80 percent eclipse, still an exciting sight.
The science educators at UC Berkeley’s public science center, the Lawrence Hall of Science, are ready to help families prepare for this astronomical event with programming and activities designed to spark kids’ interest in science. The Hall’s new Planetarium show – The Solar Eclipse – 2017 – is currently running and will help families learn about the upcoming eclipse and how to view it safely. Staring directly at a solar eclipse can damage your eyes and even leave you blind. Eclipse sunglasses, like those sold at the museum’s Discovery Corner Store, are recommended for safe viewing. (The planetarium is open on weekends and select holidays. Tickets are $4, in addition to admission of $12 adults, $10 ages 3-18 and seniors over 62, free for children under 2, members and UC Berkeley students and staff. www.lawrencehallofscience.org/visit/exhibits/earth_and_space/planetarium.)
You can also start getting ready for the eclipse at home with these fun sun-related experiments from Lawrence Hall of Science’s DIY Sun Science app. The free app is available for iPhones and iPads, and all activities can also be viewed at lawrencehallofscience.org/do_science_now/diy_sun_science. It’s just one of several free apps from the Lawrence Hall of Science that families can use for hands-on science exploration at home, including DIY Lake Science, DIY Human Body and DIY Nano. Find more at www.lawrencehallofscience.org/do_science_now/science_apps_and_activities.
Cook With a Solar Oven (Ages 10 and up, younger with adult supervision)
Build a solar oven and use it to bake s’mores. You’ll need a bright and sunny day.
• one large pizza box
• aluminum foil
• one sheet of black construction paper
• clear plastic wrap
• graham crackers
• thermometer (optional)
Preparation: 10 minutes
Activity: 30-plus minutes baking time
Cleanup: 15 minutes
Do not look directly at the Sun! The inside of the oven can become very hot if left in sunlight for a long time. Use oven mitts or hot pads and be careful not to burn yourself when removing hot food from the solar oven.
Step 1: Line the inside of the pizza box with aluminum foil. Glue the aluminum foil to all inside surfaces except for the lid. This adds reflective surfaces to direct more of the Sun’s rays onto the food.
Step 2: On the outside of the box lid, use a marker to draw a square with edges that are 2.5 cm inside the edges of the box.
Step 3: Cut along just the front and side lines of the square, leaving the line near the hinge of the box uncut. Fold open the flap, then glue aluminum foil to the inside of the lid.
Step 4: Tape the sheet of black construction paper to the inside bottom of the box.
Step 5: Stretch plastic wrap over the hole you cut in the lid of the box. Seal any air leaks around the edges of the hole with tape.
Step 6: Assemble your s’mores on the plate, and put it inside the solar oven. Position the flap of the oven so the Sun’s rays are directed toward the s’mores. Tape a ruler along the side of the oven to keep the lid at the desired angle. Check the flap every few minutes, and adjust it so the Sun’s rays are always directed toward the food.
Tip: On a hot day, the oven can reach approximately 93° C (200° F). Check your s’mores for doneness after one hour.
Optional step: Place the thermometer inside the oven and challenge yourself to see what temperature the oven can reach! Experiment with different angles of the reflector flap, direction of the oven in relation to the Sun, tightness of the plastic wrap seal, and addition of more flaps to reflect more sunlight into the oven.
What’s Going On?
The Sun emits a lot of energy. Solar energy that reaches Earth can be absorbed by the atoms and molecules in an object. This energy absorption makes the atoms and molecules move around faster, which makes the object hotter. You can make an object hotter when it’s in sunlight – the more sunlight you reflect onto an object, the hotter it will get.
Sunlight shines on the s’mores in the solar oven, and you can get more sunlight to shine on the s’mores by reflecting the light from the lid of the pizza box onto the food.
Why Black Paper?
Objects of different colors absorb the Sun’s energy in different ways. Dark objects absorb more energy in sunlight, and get hotter than white or lighter colored objects.
You placed black construction paper in the bottom of the solar
oven so that the paper would absorb more solar energy and get hotter
Why Use Plastic Wrap?
When an object gets hot, it gives off its energy to other objects nearby, like the air around it. Instead of the hot air around the s’mores leaving the oven, we can trap it by insulating the pizza box with aluminum foil and placing the plastic wrap over the hole in the pizza box’s lid. The plastic wrap lets the Sun’s energy into the oven, but also acts like a blanket to keep the hot air from escaping.
Big Sun, Small Moon? (Ages 7 and up)
If you’ve ever seen a picture of a solar eclipse, you may have noticed that the Moon comes very close to covering the entire Sun. Use a coin and a plate to investigate why the Sun and Moon look like they’re the same size, though the Sun is much bigger.
• large coin, such as a quarter
• large round dinner plate
Any two round, stiff objects of different size will work. Instead of a plate and coin, you can create your own Sun and Moon out of construction paper. You will need a partner to help you with this activity.
Preparation: 5 minutes
Activity: 5 minutes
Cleanup: 2 minutes
Do not look directly at the Sun!
Step 1: Hold both the coin and the plate at arm’s length. The plate will look much larger than the coin.
Step 2: While you hold the coin at arm’s length, have your friend hold the plate and walk backwards away from you four steps. When your friend stops, close one of your eyes and look at both the coin and the plate as though they’re next to each other. Does the plate look smaller than before, compared to the coin?
Step 3: First, predict how far away your partner will have to walk until the coin and plate appear the same size to you. Then have your partner walk backwards away from you until the coin and plate look the same size. How far away did your partner have to walk? Was your prediction correct?
What’s Going On?
If you’ve ever seen a picture of a solar eclipse, you may have noticed that the Moon comes very close to covering the entire Sun. However, the Sun is 400 times larger than the Moon! So how can these objects appear to be the same size? Objects that are farther away always look smaller, but a small object and a big object can look the same size if they are the right distances away from you. In fact, the Sun is about 400 times farther away from Earth than the Moon!
Measure Things Far Away
Close one eye and look at an object far away. Stretch out both arms until your fingertips just frame the object. Note how far apart your arms are. Now look at an object that looks bigger and again move your fingers until you frame the object. Your arms should be further apart. Astronomers do something very similar to measure the size of stars, planets, and other bodies appear to us. They call this term “angular diameter” (or “angular size”) for the angle that’s formed by the apparent size of an object you observe from Earth. The angle between your arms is the angular diameter.
Size of the Moon and Sun
The Sun and Moon have roughly the same angular diameter. In fact, sometimes the Moon appears slightly larger than the Sun and sometimes the Sun appears slightly larger than the Moon. This is because the Moon’s noncircular orbit around Earth sometimes brings it closer and sometimes farther away from Earth. It’s just a coincidence that the Sun and Moon appear to be the same size when viewed from Earth. If you were on another planet, its “moons” could have a very different angular size compared with our Sun!
Make a UV Detector (Ages 7 and up)
On a bright, sunny day, use tonic water to detect ultraviolet (UV) light from the Sun.
• two clear cups (plastic or glass)
• tonic water
• tap water
• black piece of paper • pen
• two index cards
• hardcover book
Preparation: 5 minutes
Activity: 5 minutes
Cleanup: 5 minutes
Step 1: Use your pen and paper to make two signs: “Tonic Water” and
“Tap Water.” Tape these signs next to each other at the top of the
sheet of black paper, and tape the black paper to a hardcover book. Place one cup under each sign.
Step 2: Fill each cup to the brim with the kind of water noted on the label.
While you’re indoors, shine a bright flashlight at both full cups.
Do you see any color difference between the cups?
Step 3: Bring your black piece of paper outside, in full sunlight. Prop up the book so that the paper is vertical. Place the two cups in front of the paper. Now what colors are the two liquids?
What’s Going On?
We can see visible light emitted by the Sun. The Sun also emits light we can’t see, including ultraviolet light. Quinine is a substance found in tonic water that is sensitive to ultraviolet light and can absorb ultraviolet light we can’t see and then re-emit visible blue light we can see. This process of converting ultraviolet into visible light is called fluorescence.
When you shined a flashlight at the cups of water indoors, the tonic water did not fluoresce and glow blue. That’s because flashlights and everyday household lights do not emit a significant amount of ultraviolet light.