With the upcoming solar eclipse I decided to teach a class for local homeschoolers and it filled so fast I ended up teaching three classes! I started out by talking about the scale of our solar system and showed them this picture of the planets and asked them what was wrong with it. Many realized the size of the planets was all wrong compared to each other and the sun. The distances are obviously wrong as well since the planets are very far the sun and they are not equally spaced. To make a model of the solar system to scale, I have a large exercise ball which is half a meter across and we used that as the sun. I then asked the students what size they thought the Earth would have to be for our model. A few kids thought baseball size, a few thought it should be the size of a quarter, but its actually only 0.46 cm across! I then asked the students where should we put the earth if we want our model to be accurate? Should it be right next to the sun (green ball)? A few feet away? In the kitchen? It needs to be at the end of the culde sac across the street! This kind of blows their minds because its sooo small (the tiny blue ball in the photo to the right) and needs to be so far away to be to scale. The other planets are shown to scale with the sun in the photo – but not the right distances. I showed the kids images of my house on google earth with the orbits of the planets drawn on it to scale and for the furthest planets we needed to be looking at a map of the city.
The photo below from wikipedia shows the planets to scale in size but the distances are not correct. Its pretty much impossible to show both the size of the planets and distances in a meaning image that will fit on a piece of paper.
The first activity we did was to make a model of the Earth and moon to scale. We used 1inch foam balls (painted blue and green) for the Earth and 1/4 inch pony beads for the moon. The ball and bead were put on toothpicks and then clamped with bulldog clips to a square dowel (36 inches long, 1/4 inch wide) 30 inches apart. This is roughly to scale. We then went
outside and used the real sun (if it wasn’t cloudy) as our light source. Students were able to make lunar eclipses (photo on right), where the shadow of the earth covers the moon and solar eclipses (photo on left), where the small shadow from the moon makes a small dot on the Earth. We talked about how to see the solar eclipse you have to be standing in the shadow (the black dot on the earth ball, but to see a lunar eclipse you just have to be on the night time side of the earth. This activity can be found in the Solar Eclipse Activity Guide put out by NASA.
Students also made pinhole viewers (directions can again be found in the NASA guide above). Basically you put two hole in one end of the box and tape white paper inside the other end to be your projection screen. Then you cover one of the holes you made with foil and using a tack make a very small round hole in the foil. To use the pinhole viewer you stand with your back to the sun, let sunlight enter the pinhole and fall on the projection screen while looking through the other hole that you made.
Students also made eclipse art, yet another activity from the NASA guide. For this you hold down a circle of cardstock on top of dark paper and then draw around the circle with oil pastel (or chalk) and then using your fingers, smear the pastel outwards to make a corona. The kids made some great eclipse drawings with this method.
Each student was also given a pair of solar eclipse glasses to take home so they can use them to watch the eclipse. I actually bought some plastic onesfor my family so they fit over regular glasses and stay on better (update: just got notified that these might not be safe so Amazon refunded my money). The cardboard ones tend to fall off so you have to hold them on.
Here’s some great videos on solar eclipses.