1 million kilometers from the sun this occurs on or

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Unformatted text preview: (from Greek for “far-Sun”), Earth is 152.1 Million kilometers from the Sun. This occurs on or about July 5th! Although a 5 million km variation in distance sounds like a lot, its really only a 3% change from maximum distance to minimum distance. That’s not enough to cause seasons, and remember, the Earth is closer to the Sun in northern winter! The diagram above exaggerates the ellipticity of Earth’s orbit. In reality, Earth’s orbit is nearly circular. So what does cause the seasons? 4 So what does cause seasons? Earth’s axial 8lt 23.5º September 23.5º 23.5º June 23.5º December March Richard Pogge ‣ ‣ Earth’s rotation axis is tilted to its orbit around the Sun by 23.5° Axis points in the same direction in space as we orbit the Sun - towards Polaris Monday, October 22, 12 The Earth's rotation axis is tilted relative to the plane of its orbit around the Sun (also called the ecliptic plane). Tilt is about 23.5 degrees from perpendicular relative to the ecliptic plane. Note that the Earth's axis points towards the same direction in space as it orbits around the Sun - toward Polaris. So lets look at how the tilt causes seasons... 5 Eclip8c on the celes8al sphere NCP Sun is on the celestial equator Sun is north of the celestial equator ic lipt c E 3.5º 2 CEq ~ Sun is south of the celestial equator SCP Richard Pogge Monday, October 22, 12 6 To explore the cause of seasons, we need to consider the Sun’s daily path in the sky and how it changes over the course of the year due to the Earth’s axis title. So,...
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This note was uploaded on 10/23/2013 for the course ASTR 100 taught by Professor Dunne during the Fall '12 term at University of Illinois, Urbana Champaign.

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