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Archive for the ‘astronomy’ Category

photo[4]For some reason after a few years of blogging, my most popular post remains how to make a human sundial. Just last week I received an email from a PTA president in Texas who actually had a human sundial built at their elementary school and was looking for ideas on how it can be incorporated into their curriculum. Even though I don’t teach elementary school any more, building our human sundial (pictured above) was a blast and there’s some great teachable moments that it can provide. Here’s some ideas:

In Kindergarten we have a science unit about sun and shadows, and one of the learning goals is about how the length of shadows changes during the day. The sundial is a great focal point for this, as classes can visit it in the morning, at lunch, and again in the afternoon and observe the difference in the direction and length of the shadow. Depending on the grade, they could even measure the length of the shadow and compare it to the height of the sun in the sky at that time. It’s a clear way of understanding that the higher the sun is, the shorter the shadow, as well as the idea that the sun moves across the sky and the direction of the shadow changes. After observations, we’ve even done drawing assessments where students predict what the shadow would look like given a position of the sun. You could use an actual picture of your sundial for this, and students could then check their predictions the next day to see how accurately they predicted the length and direction of the shadow. Here’s the link to a hands-on science unit you can buy from Delta Science Education that gave me some of these ideas.
In 5th grade our students study the seasons, which is a good opportunity for students to learn about why you need to stand in different places on the sundial depending on the time of the year. It could even be a good opportunity for a long-term study: each day or once a week in the morning, have students observe the sundial at a particular time, noting the position of the sun (measurements could be made with a compass). Students will begin to see how the position of the sun fluctuates with the seasons, which leads to the idea that some seasons have more direct sunlight (and therefore more heat) than others. Another approach which I wish I could try would be to have no date stones on the sundial at all in the beginning of the year and explain to the 5th graders that you aren’t sure how the sundial works. Then you could give the students the job of “calibrating” the sundial, visiting it at the same time each day and marking where they need to stand to make the shadow point to the accurate time. After a few months they would begin to notice the analemma (the shape that represents the changing position of the sun, pictured below) and it’s this shape that allows you to know where to stand exactly to make the sundial work. Here’s a kid’s science site I found about someone who actually tried this with really neat results!

Image from Stanford Solar Center

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Nothing beats the learning potential of a field trip: piling onto a bus in anticipation, stepping out into an unfamiliar environment, the excitement of the experience cementing new learning in lasting memories. But what’s a teacher to do when there are no good options for a field trip? Some of us (especially in the Middle East!) aren’t lucky enough to be surrounded by educational museums or natural wonders, so we have to get a little creative… introducing the Virtual Field Trip.

Our Kindergartners have a unit Objects in the Sky where they learn about the Sun, the Moon, and the stars, and how they relate to our Earth. Though there’s plenty to observe and investigate with shadows, moon phases, and constellations, even these kind of experiences are indirect (heck- we even tell our students NOT to look at the Sun!). No matter how many photos, videos, or stories students look at, the Sun, the Moon, and the stars still remain really far away- both literally and mentally for students.

So why not take a field trip to the Moon? For young students a virtual field trip can be just as exciting and memorable as a real one, and it also fosters the kind of imagination that seems to be sorely lacking in today’s kids. A virtual field trip uses 1 part technology and 2 parts imagination to make it possible to visit inaccessible or even impossible places with your students.

Even though it’s virtual, a virtual field trip starts with the same kind of planning as a real field trip. First you send home permission slips (here’s a permission slip our Kindergarten teachers made for our trip) to make your field trip more “official” and to get families involved in the imaginary adventure. To help share teaching resources we created a virtual field trip website so all our Kindergarten teachers could easily access video clips, handouts, and activity instructions for the trip. We even had our students get ready for the journey by creating their own space helmets. Here they are seriously awaiting their turn to board the rocket ship:

When the big day arrives, you still “take a trip” by travelling to your destination with the help of props and technology. For “international” destinations this means giving students a paper passport to get stamped, a boarding pass to help them find the right seat in the classroom rows of airplane seats, and then watching a video clip of  airplane takeoff. For our extra-terrestrial destination, our science lab carpet was transformed into our rocketship, the lights were turned off, and we watched  this simulated Apollo mission to help us lift-off. It was a blast!

Once we arrived at the Moon, we did a variety of activities to let students experience what the Moon is like:

Searching for “Moon rocks”: Actually samples of basalt buried in the hot sand of our playground, which is not a bad approximation of the sunny side of the Moon this time of year! After discovering their moon rocks, the students observed and drew them for display in a museum when they returned to Earth.

Creating a Moon surface: To experience the surface of the Moon, students got to feel a sample of lunar soil (made with kitty litter! For more info, check out this Moon crater resource by NASA). Then students made a lunar surface of their own out of white clay or moon dust (flour).

Experimenting with craters: With their Moon surfaces ready for action, students simulated meteorites by dropping marbles down on them from different distances. The highest drops made some pretty realistic pock marks with ejecta and all!

At the end of the trip, don’t forget to come home! We re-boarded our space ship and headed back to Earth along with the end of this clip. After splashing down into the ocean, our students had a chance to reflect on their adventures by drawing and writing a story about their trip that they can share with their families.

Done separately these activities would be just that- activities, but when done together as part of an imaginary journey the students readily make connections between the models and their ideas of what the Moon is like. That’s the power of a virtual field trip- it engages students’ imaginations to help them look past the literal and make abstract models come alive.  So next time you dream about a cool field trip that would be impossible to take- make it happen virtually!

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Human sundial

Last year I was lucky enough to receive a grant to build an outdoor classroom at my school, so throughout the school year I’ll be brainstorming ways to make the most of this new learning space. Living in the hot and urban environment of Doha, Qatar, my students don’t have much experience with the outdoors, so I think there’s going to be a ton of opportunities for learning across many different disciplines.

One outdoor classroom project that I’m working on right now is the Human Sundial. It’s similar to the boring old sundials you’re probably familiar with, except that it’s your shadow, and not some little stick’s, that points towards the correct time. Another cool feature of this type of sundial is that it corrects for the change in shadows over the course of the year. For those interested in details, this kind of sundial is technically known as a analemmatic sundial; the analemma is the name of the shape created by the apparent movement of the sun’s location in the sky over the course of the year.

In this post I’ll explain the nuts and bolts of how to make one of these yourself (it’s not hard- I just did it this afternoon!), but first I want to share some ideas for how I’m going to use this as a teacher in (whoops- I mean outside of) the classrom.

Teaching with the sundial

Any time a teacher has a cool tool like the human sundial, there’s the danger that you assume students will just somehow “get it” when you show it off in some classroom demonstration. Even if the demo has a wow-factor, more often than not students will leave remembering the phenomenon, but not the un-wowing explanation that follows it. So how to prevent this?

First of all, I’m not going to show the students the sundial right away. That would be like starting a mystery movie by revealing the culprit in the first scene- boring! First I want students to discover how tricky telling time with the sun actually is. With my kindergarten students, who are mostly focusing on shadows, we could begin by just tracking the shadow of a stationary object (like a flag pole) throughout the day. Maybe have a student mark the end of the shadow every hour, or if we wanted to get hi-tech we could try a time-lapse video. If we have a few classes do this and compare the data, I think the students will readily realize that shadows point in certain directions and have certain lengths at different times of the day. I could then up the ante for comprehension by having a shadow prediction contest (where will this flagpole’s shadow be at 3:30?). The Kgers could then even make their own simple sundial using chalk like I did, and record videos of themselves explaining how it works (assessment, baby!).

For my 5th graders, who also have an astronomy unit and learn about the rotation and revolution of the Earth, I’d like them to learn about the whole analemma effect- how then sun’s apparent location and shadows change over the course of the year. It’s safe to assume they won’t have many prior conceptions about this, and probably think the sun’s path in the sky is relatively constant- so I can exploit that misconception for my own devious learning intentions! I plan on installing the human sundial in the outdoor classroom- but without the analemma date thing to stand on. I’ll just mark the spot that works in September so the students will be none the wiser when they check it out at the beginning of the year. As time marches on though, the sundial will get worse and worse at time-keeping, and by January it should be downright awful. This would be a great time to raise the alarm and have the student’s try to figure out what’s going on. To juice this for all it’s worth I’ll need to make sure there are some grade-level appropriate resources out there that they can use though (any help here would be much appreciated). Then I can use their suggestions and introduce the analemma to fix the sundial…. until next year of course!

Setting up the sundial

I’m no sundial guru, so initially I tried to order up plans for a human sundial from here. Unfortunately, because Qatar’s latitude of 25 degrees North is nearly in the tropics the owner actually refused to sell me the plans, even after repeated requests, because he was worried the sundial’s accuracy and somehow his company’s reputation would be compromised. Whatever. While it’s true that in the tropics shadows aren’t very long in the summer at high noon, we won’t be using our sundial in the summer, and I don’t think Kindergarteners will be too concerned with pinpoint accuracy. At any rate- you definitely don’t need to go out and spend money on plans for a human sundial, because there are plenty of free resources just a click away. So let’s get started…

  1. First you need your exact latitude and longitude. You can use a GPS for this, or you can just go to Google Maps, find your location, and then right-click on it and select “What’s here?”. This will place a little green arrow on your location that you can hover over and get the latitude and longitude. It leaves it up to you to figure out if you’re North or South of the equator and East or West of the prime meridian (good luck with that!).
  2. You also need to know your time zone (how many hours plus or minus Greenwich mean time), and whether you’re currently having daylight savings time. Since Qatar doesn’t bother with daylight savings, this doesn’t affect me, but it will require some alterations to your sundial if you are in a place that does.
  3. Make sure your sundial location is level. You could use one of those bubble-in-liquid carpenter-thingies to do this, or you could do what I did… take a look at your space and say “Looks pretty level to me!”.
  4. Then you need to find true North. No, you can’t use a compass because they point towards magnetic North. There’s a variety of ways to figure out true North, but I think the easiest method is using Solar Noon (when the sun is at its highest point on the horizon), because all you need are some household supplies to make a straight shadow at the time of Solar Noon. Here’s a good explanation of how to do it. Don’t feel like you need to go get all the construction materials though- I hung my weight off an overhead car shade and just traced the shadow with chalk on the pavement.
  5. Once you have a true North/South line set up, then you can start setting up the sundial. To get an idea of what the finished product will look like, I recommend checking out the applet on this website which draws the analemmatic sundial for you when you input the above info (see picture below). You can actually print this out and use it as a mini-sundial as well, just make sure to line it up with your true North/South line.
  6. So far so good? Now on to the human-sized sundial! The math for creating one of this sundials is pretty complicated, so to avoid crunching the numbers yourself, you can use a spreadsheet like this. This spreadsheet might seem a little daunting at first, but the only info you need to input is the cells in blue on the first sheet. Besides the info above you’ll also need to find out your time zone meridian which is the middle longitude for your time zone (you can find this on the picture here, just look at the longitude number above your time zone- for example Qatar’s time zone is +3 so the meridian is 45 degrees East). Finally you need to input the gnomon height, which is simply the height of the thing casting the shadow- you!

When the spreadsheet spits out your numbers, just check the pictured sundial on the sheet called “Layout” and make sure it’s identical to the mini-sundial made by the applet. If it is, you’re ready to start building the real sundial. Start by creating an origin point (like 0,0 on a graph) somewhere in the middle of your true North/South line. Then it’s just like making a giant graph- use the x and y coordinates to plot the hour markers, and the x and “date point Z” coordinates to plot the dates. I did mine in chalk first on the pavement to check if it actually works.

Taken just after 2pm. Boo-ya!

For more information on how you can use a human sundial for some great learning activities, check out my follow-up post here

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