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   Number 1: Lecture 09: Eclipses of the Sun and Moon

   Among the most amazing sights in the sky, eclipses of the Sun and Moon have long fascinated us. This lecture describes the eclipses of the Sun and Moon, their types, and how often they occur. Recorded 2007 Oct 1 in 1000 McPherson Lab on the Columbus campus of The Ohio State University.

   October 01, 2007·0min
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   Number 2: Lecture 08: The Phases of the Moon

   What are the Phases of the Moon? This lecture introduces the Moon and describes the monthly cycle of phases. Topics include synchronous rotation, apogee and perigee, the cycle of phases, and the sidereal and synodic month. Recorded 2007 Sep 28 in 1000 McPherson Lab on the Columbus campus of The Ohio State University.

   September 28, 2007·0min
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   Number 3: Lecture 07: The Four Seasons

   Why do we have different seasons? This lecture explores the consequences of the tilt of the Earth's rotation axis relative to its orbital plane combined with the apparent annual motions of the Sun around the Ecliptic. The most important factor for determining whether it is hot or cold at a given location at different times in the year is "insolation": how much sunlight is spread out over the ground. This, combined with the different length of the day throughout the year, determines to total solar heating per day and so drives the general weather. It has nothing to do with how far away we are from the Sun at different times of the year. Finally, the direction of the Earth's rotation axis slowly drifts westward, taking 26,000 years to go around the sky. This "Precession of the Equinoxes" represents a tiny change that is still measureable by pre-telescopic observations, and means that at different epochs in human history there is a different North Pole star, or none at all! Recorded 2007 Sep 27 in 1000 McPherson Lab on the Columbus campus of The Ohio State University.

   September 27, 2007·0min
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   Number 4: Lecture 06: Daily and Annual Motions

   Why do celestial objects appear to rise and set every day? How does this depend on where you are on the Earth, or the time of year? In today's lecture we we set the heavens into motion and review the two most basic celestial motions. Apparent Daily Motion reflects the daily rotation of the Earth about its axis. Apparent Annual Motion reflects the Earth's annual orbit around the Sun. We introduce the Ecliptic, the Sun's apparent annual path across the Celestial Sphere, and note four special locations along the Ecliptic: the Solstices and Equinoxes. This sets the stage for many of the topics of the rest of this section. Recorded 2007 Sep 26 in 1000 McPherson Lab on the Columbus campus of The Ohio State University.

   September 26, 2007·0min
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   Number 5: Lecture 05: Mapping Earth & Sky

   Where are we? Where is someplace else? And how do I get there from here? These are questions we need to answer both on the Earth and in the sky to assign a location to a place or celestial object on the surface of a sphere. This lecture includes a review of angular units and the terrestrial system of latitude and longitude on the spherical Earth. We then define the Celestial Sphere, with its Celestial Equator and Poles, and begin to define an analogous coordinate system on the sky. An important wrinkle is that what part of the sky we see at any given time depends on both where we are on the Earth, and what date/time it is. This gives us the elements of the coordinate system we will need to begin our exploration of motions in the sky in the next lectures. Recorded 2007 Sep 25 in 1000 McPherson Lab on the Columbus campus of The Ohio State University.

   September 25, 2007·0min
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