This week at SET

Today, we finished up our discussion of orbits and Earth's tilt by discussing the impact of the moon on Earth's rotation and stability, and how the very creation of the moon involved an impact!

At the end of class, I also showed them some solar bodies to give them an idea of the scale involved when dealing with planetary bodies, because a lot of them were struggling with the size and weight of the moon, Earth and our sun. A quicker comparison of solar sizes can be seen here, with the advantage of keeping everything within the frame.

Despite the sun's immense size, from Earth it appears almost exactly the same size as the moon does, which is why Earth has the phenomenon of solar eclipses, something the other rocky planets around us do not. Mercury and Venus lack moons and Mars does not have a large enough one. You'd have to go all the way out to the gas giants to see eclipses on other planets, but if you did, they'd happen all the time. And although Pluto would seem a good bet for eclipses all the time due to its large, close moon and extreme distance from the sun, its odd orbit and rotation means it only happens every 120 years - but when it does, for several years Pluto experiences a eclipse about once a week.

In addition, a lot of the kids didn't know it's bad to stare directly at the sun. I explained that this permanently damages the eyes, but you may want to repeat that to them a few more times to make sure they remember.

For homework, look at the moon! The moon waxes (the lighted part grows bigger) until the side we see is all lit up, then wanes (the lighted part grows smaller) down to a new moon where it's entirely black. It isn't immediately apparent which direction the moon is going in, so look at it for a few nights in a row and see if it's getting bigger or smaller. If it's getting bigger, it's a waxing moon, and smaller is a waning moon.

(And our weather unit may have concluded, but there's always more interesting things to learn about! For example, there's a very hard to catch phenomenon of lightning bursts that go up from the clouds rather than down, producing a brief but beautiful effect known as sprites. For many years these were known only to a lucky few high-altitude pilots who glimpsed them and scientists weren't even sure they existed, but modern film has now managed to capture numerous sprites in increasing detail.)

Also, Christmas vacation is coming up. As you can see from the schedule we won't be meeting for the last two weeks of December, the 24th and 31st. That isn't the end of this session, however! Fall session for SET school continues meeting through January, with the spring session only beginning in February.