MMSD FOSS Planetary Science Investigation #2: Round Earth/Flat Earth
The focus of Investigation #2 is: "how do we know the Earth is round?" The investigation explores how shadows are observed on two types of Earth models -- round and flat. The resources we post here are intended to help you verify the shadow observation with shadow photos or data from other parts of the world.
- The EarthDial Project: this project included some live web cameras pointing at sundials at their locations around the world. This project is no longer active, but we've archived photos for one day. Cut out the photos you want to use. Tape them onto a globe in their respective locations (12:00 is pointing north in the northern hemisphere). Archive: we've posted some EarthDial photos from March 11, 2005. You can verify current daylight configurations using Starry Night (see below) or The World Clock. Compare the EarthDial photos from around the world to your own sundial here in Madison (see "Sundial for Madison" below).
- Sundial for Madison, Wisconsin: (preview here) the following sundial has been constructed using a program called Shadows 2.1.0. Simply print out the following PDF files, and make one cut-out, and you are ready to go!
1. Madison Sundial: Madison sundial (PDF 242k) Print out, use a compass to orient the page so that the top (and 12 o'clock) is pointing north, and tape it down outside in the sun. Can you also estimate the date with this sundial? Notice the lines going from left to right across the dial.
2. Style for Madison Sundial: style (PDF 30k) Print out. Hold the page up to the light looking at the back side, and label the corners A and B inside of the triangle. Then cut out the style (black triangle). Use something like poster-puddy to attach the style to the sundial at points A,B. Try to make the style stand up vertically.
3. Equation of Time: Equation Time (PDF 69k) Print out this page if you want to adjust your sundial readout to match the time on your watch.
4. Sundial Data Sheet: Sundial data sheet (PDF 56k) This sheet provides all of the information you might want to know about the sundial.
- The Noon Day Project: even if this project is not running when you are working on this concept, this site is an excellent resource. If you find a partner class you could actually measure the circumference of the Earth like Eratosthenes did!
- MarsDial: there are actually sundials in the Mars rovers! You won't get a live picture, but it's fun to see the same concept on another planet.
- World Map of Time Zones: and you can select specific countries as well.
- Starry Night Earth: follow these procedures to use a computer program called Starry Night to zoom out from Madison to view the Earth from space and look at the Earth from various points of view.
1. Save this settings file to your computer (earth-foss2.snf). Windows: right click on the link, and choose "Save Target As", and save it to your computer. Macintosh: right click (or click and hold and move your mouse a little while holding) and choose "download link to disk", and save it to your computer. NOTE: some web browsers may interpret this file as a web page file and add an extension to the file name ".html": if so, you'll need to change the file name back to "earth-foss2.snf".
2. Start up Starry Night on your computer. Go to the File menu and choose "Open". Find the "earth-foss2.snf" file on your computer, select it, and click Open.
3. Starry Night should now show a view of the Earth as seen from above Wisconsin, at 8:30 AM, October 18.
4. You can change the date and time. Or you can hold down the Shift key and drag your mouse to look at the Earth from a different angle.