Key Ideas and Terms

1-1 Astronomy is both an ancient cultural practice and a cutting-edge science

1-2 The stars are grouped by constellations

1-3 All of the observed celestial motions can be described if our planet Earth spins once each day while it orbits around our Sun each year

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1-4 The Sun appears to change position over the day and throughout the year, and these changes result in Earth’s seasons

1-5 The Moon appears to change its position in the sky hourly and its phase throughout each month

1-6 Eclipses occur only during rarely observed events when our Sun, Moon, and Earth are perfectly aligned