Physicopoeia

φυσικοποιΐα
THINGS I WISH I'D KNOWN WHEN I STARTED TEACHING PHYSICS

Explaining Tides

In days gone by, textbooks would sometimes attempt to explain how the Earth's tides are formed. They usually used a very simple gravitational argument to explain how the tidal bulge nearest the Earth was formed but would then fudge an explanation of how the bulge on the other side of the Earth was formed, and hence why we have two high tides per day, not just one. This was fairly unsatisfactory and so it's now rare to see it on syllabuses, which is a shame when it's not that tricky to understand and relates to something many pupils will have experienced at the coast.

 

Also, once you look into it, there are some fascinating feedback effects between the Earth, the Moon and the tidal bulge which are not commonly known about. This presentation takes you through it all - there are some animation effects to help the explanations which should work smoothly on a slideshow: