I am getting ready for classes. One class I am teaching is a physics course for elementary education majors. I really enjoy this class. There is hardly any math and the students learn by doing some experiments and then creating models. These models are then shared and discussed among the class. The basic points of the class are:
- Help students learn the nature of science by doing sciency things.
- Learn some science content by doing stuff (instead of listening to me talk about stuff)
- Learn about how to teach science in elementary schools.
- Explore the nature of learning.
I didn't really make this course up. Instead, I am using a curriculum from Fred Goldberg called Physics and Everyday Thinking.
So, what is my point? The point is that to learn stuff, students can't just come in and wait to be fed. If it were that easy, I would totally do that. Most students don't believe me when I tell them this. Some are quite frustrated that I don't just tell them that a constant force makes an object change its speed (even though I actually do tell them this). So, to start off class I am going to ask the following questions (they can answer anonymously).
- Why is it warmer in the summer than in the winter? (for the Northern hemisphere)
- If you apply a constant force on an object, what will it do?
- What causes the phases of the moon?
- Which has a larger density, a marble or a gallon of water?
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All of these questions have something in common. All of these are on topics that they have (at least in theory) covered at some point in one of their classes. If you look at the Grade Level Expectations (or whatever they are called in your state), you will find seasons, forces, density and phases of the moon. I am fairly certain that the students have covered these concepts at some point. Further, many of these students have taken introductory astronomy in college, then they will have covered these again.
I am also fairly certain that most students will get these questions wrong. You know it as well as I do. These are complicated ideas and they can't be understood or even just "memorized". So, the point is: here are some ideas you were just told, but still don't understand. Maybe they will get it, maybe not (the point I mean).
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Why is it warmer in the summer than in the winter? (for the Northern hemisphere)
All four hemispheres have summer and winter for the same reason: orbital inclination. Earth aphelion is ~152,097,701 km, hard by 04 January. Earth perihlion is ~147,098,074 km, hard by 04 July. Those are trimmed by where you are on the planet, time of day, and moon's phase (system barycenter vs. Earth's surface). Other planets' positions trim the trim. The solar constant slightly varies over time. Add precession (Platonic Year) plus nutation (longitude and obliquity) and polar wander (e.g., Chandler wobble, annual circle, polar wander). If you run GPS, reality is a dirty place.
eccentricity = sqrt[1-(b/a)^2]
focus offset = sqrt[(a^2 - b^2)]
for Earth,
e = 0.016710219
a = 149597887.5 km
b = 149576999.8 km
f = 2499815.1 km
GM = 1.32712440018x10^20 m^3/sec^2
1) It's warmer in summer than in winter in the Northern Hemisphere because we call the warm season "summer" and the cold season "winter". The same reason why we call the warm season "summer" in the Southern Hemisphere. If the angle of the Earth's axis to the ecliptic was such that the solstice was in March, we'd probably call March "summer", and not "spring".
2) I'm applying a constant force downward on my chair, and it's not doing anything. I can apply a small, constant force sideways on the coke can on my desk and it moves at constant speed on the surface. So one of the things which can happen when I apply a constant force on an object is nothing.