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Madison Metropolitan School District

MMSD FOSS Planetary Science Investigation #3: Day and Night

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The focus of Investigation #3 is to explore the celestial geometry and motions that cause day and night on the Earth. The concept seems simple at first, but without a thorough understanding of this concept, students will likely have misconceptions which will hinder their understanding of this concept, and related concepts such as day and night on other worlds, and phases of the moon. The resources provided here are intended to supplement or replace some of the resources provided in the FOSS Planetary Science curriculum, and may add to the relevance of this activity for the students.

  • Geostationary Satellite Images of Western Hemisphere: It may be helpful for the students to see actual photographs of the Earth throughout a 24-hour period. The Space Science and Engineering Center at the UW-Madison provides images from a satellite called GOES EAST which orbits above the Earth's equator and the western hemisphere. Geostationary means that it orbits at just the right speed so that it stays above the same location on the Earth all of the time. These satellites orbit at altitudes around 22,300 miles (35,900 km). Below are two options: a set of images assembled for you on April 10, 2007; or follow the instructions to view current images.

    A. Geostationary Satellite Images for April 9-10, 2007: while viewing current images may be best, we've compiled the images for this 24-hour period in various formats in case you find this easier. Choose the file format that works best for you and your students.
    PowerPoint: day-night-goes.ppt
    Interactive Quicktime File: [7 MB] (click on the image to go to the next image)
    Quicktime Movie File: [7 MB] (pauses for 3 seconds on each image, play and pause as needed)
    PDF File: day-night-goes.pdf

    B. Current Geostationary Satellite Images: The Geostationary Image Browser allows you to view the most recent images from this satellite and others. Follow these instructions:
    1. Go to
    2. Click on the following options: 8 Image Animation, Full Disk, Visible, Lower/Small. The images will begin to load.
    3. Rather than allowing the animation to run, try clicking the "Stop" button. The blue and green squares at the top of the page indicate which image you are looking at in the 8-image sequence: blue square shows the one you are currently viewing.
    4. Explore: use the ">" button in the browser window to toggle through the images one at a time. The date listed at the top of the images is in the order of day, month, year. The time listed at the top of the images is in Universal Time (a.k.a. Greenwich Mean Time). It's the time in England, on a 24-hour clock. To translate into the time here in Wisconsin, subtract 6 hours for Central Standard Time, and subtract 5 hours for Central Daylight Time (example: 17:45 UT = 12:45 PM CDT). You'll explore 8 black and white images of the western hemisphere taken in 3-hour intervals, covering a 24-hour period. The image closest to midnight is skipped in visible light images because it would be dark.
    5. Explore some of the other options of the viewer as well.
  • Video clips of Earth from Space: Images taken by spacecraft passing Earth: the images are looped together to make a video clip.
    1. The NEAR spacecraft took these images as it passed by the Earth on its way to an asteroid. The video clip covers a day and a half, and shows Earth rotating (Antarctica), pans over to the moon, and pans back to Earth.
    Clip info: January 1998; 1 minute; 8 MB. earth_swby_lgNEAR.mpg
    Credit: Near Earth Asteroid Rendezvous; JHUAPL
    2. The MESSENGER spacecraft captured these images as it passed by the Earth in August, 2005. Watch the Earth seem to get smaller as the spacecraft speeds away. The video covers a 24-hour period.
    Clip info: August 2005; 11 seconds; 5 MB.
    Credit: Messenger mission, NASA, JHU/APL.
  • Webcams: use live webcams from around the world to show that it is nighttime on the other side of the Earth while we have daytime. The EarthCam Network is a good source.