Our Changing Sun (part 1)

Main Sequence, Red Giant, White Dwarf


In very broad terms, those are stages our Sun will evolve through as it ages and dies. The end won’t commence for 4 or 5 billion years, so we don’t need to panic.

When I began teaching astronomy at Grimsley High School, one activity that was always a hit was the Solar System walk.   The generous folks at the nearby Brunswick Lanes gave me a very used blue bowling ball they were ready to discard.   With the 8” bowling ball as the reference model for the Sun, we would make clay models of the planets to scale.

blue bowling ball
Blue bowling ball as the model for the sSun and clay planet models by the studens

The Sun is about 860,000 miles in diameter, so I rounded down and created a 1 inch : 100,000 miles ratio. Rounding down was for convenience, making the scale easier to remember and deal with. Since the Earth is about 8,000 miles in diameter, our little clay model of our home planet is about 0.08 inches. That’s tiny and students are usually pretty surprised when we compare all the planets to their preconceptions.

After making the models and attaching them to index cards, we go outside and create a scale model of the solar system. We put the sun down, talk about it a bit, then step away to Mercury. Still at the same scale, the first planet is at 10 yards away, Venus is about 19 and Earth is almost 26 yards from the Sun.

At each planet we stop and talk and think. We can confirm that the scale is accurate at the Earth model. We check the apparent angular size of the blue bowling ball 26 yards away and it’s about ½ of a degree. Then we carefully check the apparent angular diameter of the actual Sun and it too is about ½ degree in diameter. Good so far.

clay jupiter
Clay Jupiter model on our solar system walk

After Mars and the asteroids, we look back at the bowling ball, then walk the 95 yards to get to Jupiter. That’s 95 more yards, added to the 39 yards we hiked to get to Mars. I think the physical activity helps students realize how far Jupiter really is, and how much space there is just in our Solar System.



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