What causes an eclipse to occur?
Eclipses occur due to the special coincidence of the moon and the Sun being the same angular size. The Sun is 400 times wider than the moon, but it is also 400 times farther away, so they coincidentally appear to be the same size in our sky. This is what allows us the phenomenal beauty of the total solar eclipse. (Note: You can give the audience the experience of the change in apparent size of an object close by and the same object farther away. They can use their hands to measure angular size.)