Miscellaneous announcements… • Get started on your first observing project. • Anyone interested in the astrophotography project? • No class Monday (happy Labor Day). • First homework is due Wednesday.
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Miscellaneous announcements…• Get started on your first observing project.
• Anyone interested in the astrophotography project?
• No class Monday (happy Labor Day).
• First homework is due Wednesday.
The Stars from Different Latitudes
1 September 2006
Today:
• How the stars change as you move to different latitudes on earth
• Using the stars to measure the size of the earth
From other locations…
• Longitude (E-W location) doesn’t matter, except to determine time of day
• Latitude matters: For every 70 miles traveled north, northern stars get 1º higher, southern stars 1º lower
• So a 360º shift would presumably take 360 x 70 miles, or 25,000 miles: the earth’s circumference!
The Two-Sphere Universe
• The earth is a much smaller sphere at the center of the celestial sphere.
• As you move around on the earth, your horizon changes orientation so you see a different half of the celestial sphere.
• This model dates back to ancient Greece, 2500 years ago.
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