19-10-27 The Sun, Earth & Moon System The Sun, Earth & Moon System The Sun, Earth & Moon comprise our immediate part of the universe. Their relative motions give us day & night, the seasons, the phases of the moon, eclipses & tides. It is a wonderful dance, choreographed by Mother Nature and Newtonian physics. Novice Astronomy Classes Peterborough Astronomical Association Relative Sizes of the Sun, Earth & Moon Earth’s Rotation & its Orbit of the Sun The sun is 334,000 times more massive than earth. The earth & sun are 150 million kilometers apart. 150 million kilometers = 1 Astronomical Unit (AU) The sun’s light takes 8½ minutes to reach earth. A large pumpkin & a small pea separated by the length of a football field. Earth Moon This picture is to scale. Sun Rises in East, Circular orbit Earth’s tilt is 23.4° Relative sizes and distances apart are to scale. Day & Night. Sets in West. in 365 days. to orbital plane. 1 19-10-27 How Obliquity causes the Seasons Annual Daylight Variations Shadows move from right to left Earth’s tilt (obliquity) is 23.4° Obliquity causes the seasons Peterborough @ 44.3° Angle of incidence is main cause of summer warmth & winter cold (2.5X higher in summer) Length of day is secondary cause At Summer Solstice At Winter Solstice Closeness to sun does not change significantly Stability: Over time, the obliquity has changed: 22.0° to 24.5° At the Spring & Fall Equinoxes In Peterborough (10 hrs vs 16 hrs) Phases of the Moon Orbit of the Moon around the Earth CCW in figure. Hour later each day Dark side vs Far side Once in a Blue Moon Lunar month = 28 days Distance varies from 362,000 km to 405,000 km Track the Moon’s monthly cycle at The Moon orbits the Earth & rotates on its own axis once every lunar month http://sciencenetlinks.com/tools/lunar-cycle-1-calendar/ 2 19-10-27 Tides and other Funky Stuff Profile of a Lunar Eclipse Earth between Bay of Fundy: Sun & Moon 16 meter tides Not to scale! 160B tonnes of sea water Occurs only during a full Moon. Longer Days: Moon in Earth’s 2 ms / 100 yrs ‘shadow’ In 1M yrs no leap year 6 hour days Three forms: Total, Penumbral or Partial Moon Retreating: 1.5” / year 4.5B years ago Visible over wide >15X closer area of Earth & lasts ~5 hours The Moon in Total Eclipse Profile of a Solar Eclipse As the lunar eclipse progresses colours change from deep browns & dark grays to shades of brilliant red and bright orange The next total lunar eclipse visible in Ptbo will be May 15, 2022 Eye protection not required to view a lunar eclipse Total Lunar eclipse in Peterborough, January 20/21, 2019 Photo by PAA member Rick Stankiewicz Moon between Sun & Earth. Moon’s shadow on Earth is very Total eclipse lasts short Occurs only at New Moon phase small, diameter < 200 km time, < 10 minutes 3 19-10-27 The Different Forms of Solar Eclipse Images of Total Solar Eclipses Total It is worth the trip to see at least Eclipse one of these in your lifetime! Partial Eclipse Phenomena of a Total Solar Eclipse Total eclipse shows Sun’s corona. Annular eclipse shows a ring of fire. During the eclipse, birds don’t Partial eclipse shows only a part of the chirp and bees stop flying. Sun’s globe blocked by the Moon. Annular Eclipse Eye protection is required to view a solar eclipse. Total Solar Eclipse with Spectacular Corona The Next North American Total Eclipse of the Sun is … … in Our Backyard! April 8, 2024 …Niagara Falls, Prince Edward County, Kingston , Cornwall… 4 .