Since we're sharing incompetant high school teacher horror stories, I thought I'd share a few of my own. (Then I'll ask a question about planetary gravity that's been kinda bugging me. I promise.)
I had a couple of really bad teachers that just never taught the subject at all. I'm not sure if they were always that bad or if I just caught them at a bad time because I usually seemed to have the worst teachers during the very last period of the day. So maybe the kids in the earlier periods got good education but by the end the teachers just stopped caring. Or maybe they just sucked because they were a bit out of their field.
My regular freshman year chem-physics teacher went on maternity leave for most of the 2nd semester, which was the chemistry portion. Her long-term substitute was a biology major. He tried to teach the class for the first couple days, then he just gave up. He spent the next several months playing around with the geiger counter he found in the lab and showing us his vast collection of cheesy old sci-fi movies (Fiend Without a Face, It!, Them!, Creature from the Black Lagoon,
My senior year, I took government/economics with "Coach" Hoffmeyer, which probably tells you all he knew about government or economics. (He was a really nice guy, though.) Mostly, we watched movies. To his credit, many of them did have something to do with government, like All the President's Men
or The Candidate.
But when we got to Remember the Titans,
I felt like he was reaching. He was still better than one of his substitutes though, who kept insisting that Animal Farm
was about Nazi Germany, not Soviet Russia.
Then there was Mr. Draper, who I had for a one-semester elective called "Criminal Justice." In reality, the whole class was just a bunch of his paranoid rants about how high school was not really meant to educate us but to socialize us into doing the same boring jobs that our parents did.
Although, oddly, the weirdest teacher I had was when I went to ASU and took a lower level economics course. The class was taught by a racist Welshman, who went on leave for some surgery, and left his class in the hands of his TA, who was a younger, even more racist Welshman. And the crazy thing was the way he was able to smoothly integrate his racism into his class examples. Like, when he would explain the principle of specialization: Canadians are big, so they can make a lot of lumber, but they're dumb, so they can't make computers. The Chinese are smart, so they can make computers, but they're short, so they can't chop down trees. So the Canadians sell lumber to China and the Chinese sell computers to Canada.
He really couldn't understand why everyone was so shocked by this example, especially the Chinese girl sitting in the front row. I tried to help him dig himself out of this hole (or at least get everyone else to jump down in it with him) by suggesting, "Say something bad about Wales." And, without missing a beat, he just shrugged and said, "Well, there's nothing bad to say."
Over short ranges at least, gravity is subject to the inverse square law. That means the farther you get from the center, the less its gravity affects you. From the nebula/ball example above, this means that the force of gravity half a light year away from the center is considerably less than it would be half a mile from the center. Just as important to understand, however, is that you can only be pulled in by the gravity of something BELOW you, so if you are INSIDE the gas cloud, you will not be affected by any mass that is farther away from the center than you are.
This brings me to a question I have. I just came back from seeing the remake of Total Recall.
Now, I know I'm not supposed to take any of its science seriously, but it did make me think. In the movie, there's this transportation device called "The Fall" which literally takes you through the center of the Earth to ferry commuters from Australia to London. Now, when they reach the middle of the planet, they briefly become weightless while the entire apparatus shifts to point the other way. My question is, would the effect of gravity in the exact center of the planet be like weightlessness? Or, being so close to the Earth's gravitational center, would the force of gravity be so strong that it would cause harm (or at least be noticibly uncomfortable)?