I was standing at the edge of a cliff in the Grand Canyon and I saw a spectacular sunrise. It was so amazingly beautiful that I wanted to see it again, so I jumped on the ground (of the cliff, not off the cliff) and laid flat – about 1.68m below. What do you know, I was able to see that spectacular sunrise a second time about 10 seconds later.
What’s the radius of the Earth???
Try it…an awesome geometry/trigonometry problem that you have to draw out and problem solve (and my students end up loving it). You may think that seeing a sunrise and finding the radius of the Earth has nothing to do with one another, but this is an easy way to prove the earth is round (oh, and also get excommunicated by the Catholic Church in the 1500’s).