Health Warning! This is not necessarily everything you need to know from this lecture! I maintain exactly what you need to
know through the first few lectures as some people add the course late. But these questions are to help with just the most difficult concepts in
some lectures. If you want to discuss any of these concepts more, come see me during office hours.
What are the approximate dates of the Summer and Winter Solstices in the Earth's Northern Hemisphere? What about the Spring (Vernal) and Fall (Autumnal) Equinoxes? Is it summer in both Australia and Laramie on June 21? How many hours of daylight are there everywhere on Earth during the Equinox (Equinox is latin for "equal-night")?
Draw a diagram of the Earth orbiting the Sun with the Earth tilted at 23.5° in its orbit. Draw the Earth as it appears on the Summer and Winter Solstices. By extending out the Earth's equator (which is the same thing as the celestial equator or 0° declination) determine the declination of the Sun on the Summer and Winter Solstices. What is the the declination of the Sun on the "in-between" dates of the Equinoxes?
Recreate the diagram I drew in lectures. In this diagram, the Earth is expressed as a "big rectangle", or 2-D map. The lines at +/- 23.5° (i.e., 23.5°N and 23.5°S) latitude (the tropics) are marked. The declination of the Sun is drawn in the middle of the map, so that it moves from +/-23.5° over the course of a year and crosses 0° on the Spring and Fall Equinoxes. Remember, 90° from your position on Earth in this diagram is your horizon and 0° from your position is zenith (directly over your head).
Imagine you live at the North Pole. How high does the Sun get above your horizon in the middle of the day (local noon) in summer (answer is 23.5°), spring (answer is 0°), fall, winter?
Imagine you live at the North Pole. How high does the Sun get above your horizon in the middle of the night (local midnight) in summer, spring, fall, winter?
How many months of sunlight do people get at the North Pole? How many months of night? When are the cross-over dates between day and night? How many hours of day and night are there on these cross-over dates? (This number of hours is true everywhere on Earth on these dates!)
Imagine you live at the Equator. How high does the Sun get above your horizon in the middle of the day in summer (answer is 66.5°), spring (answer is 90°; it's at zenith), fall, winter?
Imagine you live at the Equator. How high does the Sun get above your horizon in the middle of the night in summer, spring, fall, winter?
Imagine you live in Laramie (40°N). How high does the Sun get above your horizon in the middle of the day in summer, spring, fall, winter?
Imagine you live in Laramie (40°N). How high does the Sun get above your horizon in the middle of the night in summer, spring, fall, winter?
Why are the regions between +/- 23.5° called the tropics? How high is the Sun in the sky through the year in these regions? Why is the region above 66.5°N called the arctic? How high is the Sun in the sky through the year in this region?
Every calculation you have done so far occurs because the tilt of the Earth as it orbits the Sun is 23.5°. Try some of these again for Jupiter. Jupiter has an axial tilt (tilt as it orbits the Sun) of only 3°. Does Jupiter have seasons?
