VIEWS: 37 PAGES: 4 POSTED ON: 2/11/2010
Earth-Moon-Sun Notes 1. For the first meeting, we try to explain the way Earth's rotation causes Sun to move in sky, leading to night and day, and the fact that the time of day is different in different places on Earth. - First spend 30 minutes with a globe to represent Earth, an overhead projector representing the Sun, and a little figurine you can put on the Earth to represent people. Explain that a globe is a small-scale model of the Earth. Explain that in our pretend game for the day they are huge (bigger than Earth) and out in space. They can pretend they have spacesuits for air. But space is dark (turn off lights). Only light around here comes from Sun (turn on slide projector). If you look at Sun you get blinded, so don't. But when sunlight hits Earth, you can see the Earth. Moreover, people on Earth can now see stuff around them because sunlight illuminates it. But not all people on Earth. Note that only half of Earth illuminated. People on that half can see around them; if they look up (use figurine) they see the Sun. On other side of Earth, it's dark and Sun is not in sky. Let them tell you this is day/night. Now ask them how this situation changes. Get to Earth rotating slowly. Takes a whole day and night to go around - 24 hours. Show them Durham and go through a day and a night in Durham, showing where the Sun seems to be. Explain that Sun looks like it moves in sky - rises, sets, etc. - just as when on carousel things *off* the carousel seem to be spinning. Earth as a merry-go-round (you can tell them we move at 800 mph as it spins if you think it will not take you on a huge tangent). Finally, show how different places on Earth have a different time of day at any given time. If there are kids in the class who have flown far enough to notice (ask teacher about this in advance - it may be her opportunity to let some foreign student who never talks shine) let them talk about jetlag and explain how this works. - Following these (rather dense) 30 minutes they will do a follow-up activity with you and the teacher helping out and monitoring. This is likely to be a good group activity but how they do it is up to the teacher. We will hand out papers with several configurations of a Sun, an Earth (each a circle), with four points marked on Earth. One of these will be red and will represent Durham. Sun will always be on left (say) but Earth will be rotated, so time in Durham is different. Their first goal will be to color (in yellow?) side of Earth illuminated by Sun. Then they try to figure out if it is day or night in Durham. Then to guess what time it is in Durham. Finally, they can go back and try to figure out what time it is at the other points marked on Earth in each of the configurations. This should help nail the concepts. It will also come in handy later when we use the same trick to understand Moon phases. 2. Second weekly meeting we introduce Moon phases. Start by recalling last week’s discussion (5 minutes) and asking for questions. Try to keep these reasonably focused on the subject. Remind them that then they were out in space looking down at the Earth. Start with a discussion of shapes the Moon takes in sky. Establish (they will likely have discussed this) that the Moon itself does not change shape, it is always a ball. Present a moon globe or some other ball to represent Moon today. Today, the students (sitting on carpet in a group) will be on Earth. Overhead, back in corner of room, will be Sun as usual. Show how moon shines by reflecting sunlight (it is not a star or something bright, just a lump of rock, rather like the globe we have here). Now, have someone (teacher or me) man the overhead and keep it pointed at you (unlike Sun it does not illuminate all directions) as you move around students (who are playing Earth). At different points they should be able (if class is dark and overhead bright enough) to see differently-shaped Moons just as we do in the sky. Show them how looking at Moon tells us which way the Sun is (follow illuminated side!). So Moon's orbital motion around Earth creates phases. If you have time, integrate this with previous discussion of rotation - like Sun, Moon will rise and set; you can even try to point out relation between phase and moonrise/set time - both are determined by where in sky moon is relative to sun. Make sure they realize we can see Moon during the day! Full moon is 10/21 so moon rises in late afternoon/early evening this week. Next week, as it wanes, they may be able to see moon and sun in sky at the same time for a real picture to compare with our theory. - The follow-up activity here is a paper worksheet similar to the one used the first time, but the configurations will include Sun, Earth, and Moon. First they can color day/night onto Earth for warmup (depending on time). Then do same for Moon - color in yellow the region illuminated by the Sun. Now color in blue (use color pencils, I guess) the half we can see from Earth (opposite order?). Green overlap is part we see shining when we look at the moon. Note how size of this changes as Moon moves around Earth (Sun still always on left here!). Try to talk them through understanding how the little wedge on their circle becomes a crescent on a sphere. 3. Third meeting to reinforce the phases and introduce eclipses We will start by reviewing the phases stuff from last time. This time we will use a different Sun. We have a naked lightbulb that can illuminate the entire classroom. Start by going over what you did last week – sit them on the carpet with the Sun on one side and walk around them (but not around Sun!) with your moon. Have someone hold up a globe in center of group. You can start with a 30-sec day/night review – just ask where it is day and where night, etc. Then, go around once showing phases. On second time, have someone come up at each of four main phases and point to place on globe where moon is overhead. Have them tell you what time of day it is there – so they see crescent moon will be overhead at noon, waxing/waning quarter in evening/morning and full at midnight. If this is going well, have globe up and get them to see Earth phases as seen from moon. This is a good comprehension test but not our main focus so do not get hung up. Next, have each take a Styrofoam ball “moon” and arrange them in a circle around the Sun (so nobody eclipses their friend). Show them how to turn, holding moon at arm’s length, and watch the phases appear. This is a very powerful and visible demo. Have them do this for a few minutes for themselves, then call out commands and see if they can all do “full moon”, “half (or quarter – whatever you have called it to them) moon”, “banana (C?) moon”, etc. In the process of doing this some will undoubtedly discover eclipses. Promise to get to that soon. When the phases stuff seems to work well, stop them and get their attention. Make sure they can see your shadow on wall behind you. Show them how you can make your full moon disappear, point out on wall that it is entering shadow of your head. Get them to figure out that your head is playing Earth and the entire thing can happen in space, minus the wall. Have them all try to make a lunar eclipse. Make sure they see why this can only happen at full moon – show them other phases and ask them if you can get in the way of the sunlight now.. Show them how if you do it slowly you can see the moon disappear one bit at a time. Now get their attention again. Show them how you make a solar eclipse by getting moon in front of your face. This works best if you hold moon closer to you, and close one eye – so you are looking from the point of totality. Make them look at your face as you do this and notice the dark circle where the Sun is hidden. Make sure they understand that people there will see their day darken – so first that it is day and second that Sun is hidden. Show how people elsewhere can still see Sun (rest of your face is not dark). Turn your head a bit to mimic Earth, show how eclipse moves along Earth. Now have them make solar eclipses, look at each other’s face and see the dark circles. Each of these should take about an hour. Plan time carefully and modify plan on your feet as you go, because both we and they have places to go at specified times! Try to find a minute to talk to teacher before or after to summarize how it went, what to tweak for next time, etc. Try to get them to exchange emails with you as that is a far better way to keep in touch with them.
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