Bringing the Universe to America's Classrooms
(OBS) Illuminating Earth over a Year

Relating the Data to Rotating Earth

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Revisit the graphs that show daytime hours in New York City and Melbourne. Click to view a larger version.

Two double line graphs showing hours of daylight in New York City and Melbourne using the data from the data tables on page 3.
Data points are included for the twenty-first day of each month in 2016 and 2017 for both locations. The y-axis shows daylight hours ranging from 9 and one half to 15 and one half. The x-axis lists the months of January through December. The New York City graph shows two side-by-side lines that rise and then fall, forming an upside-down, rounded V-shape. The lines begin at about 9 hours and 44 minutes and progressively rise until peaking at 14 hours and 38 minutes. From that peak, the lines progressively decrease until ending at 9 hours and 16 minutes. The Melbourne graph shows two side-by-side lines that form a rounded V-shape. The lines begin at about 14 hours and 20 minutes and then progressively decrease to 9 hours and 33 minutes before rising up to 14 hours and 47 minutes.
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This video shows the amount of daytime and nighttime in a different northern hemisphere location (Boston). Boston is just north of New York City.

Keyboard Shortcut Action
Space Pause/Play video playback
Enter Pause/Play video playback
m Mute/Unmute video volume
Up and Down arrows Increase and decrease volume by 10%
Right and Left arrows Seek forward or backward by 5 seconds
0-9 Fast seek to x% of the video.
f Enter or exit fullscreen. (Note: To exit fullscreen in flash press the Esc key.
c Press c to toggle captions on or off

Take Notes

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Compare the New York City data with this video of Boston rotating. Provide evidence from the graphs and the video to explain why a graph of daylight hours in Boston would look more like the graph of New York City than Melbourne.

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