The Sun-Earth-Moon System

1. The Sun-Earth-Moon System Rotation Coriolis Effect Tides Revolution Seasons Moon Lunar Eclipse Solar Eclipse

2. Rotation 23.5 ° • Earth is a round, 3-dimensional sphere • AXIS – imaginary vertical line around which earth spins • 23.5 ° from vertical

3. Rotation • ROTATION – the spinning of Earth around its axis

4. Rotation • Effects of ROTATION • Night and day – plants, animals, and people • Daily change in temperature

5. Effects of ROTATION • Earth bulges at the equator • Polar diameter – 7900 miles (12,714 km) • Equatorial diameter – 7927 miles (12,756 km)

6. Rotation • How fast is the Earth spinning around its axis? • At the equator, the Earth's surface moves 40,070 kilometers in 24 hours. That is a speed of about 1040 miles/hr (1670 km/hr or 0.5 km/sec). • [This is calculated by dividing the circumference of the Earth at the equator (about 24,900 miles or 40,070 km) by the number of hours in a day (24).] • As you move toward either pole, this speed decreases to almost zero (since the circumference of the spinning circle at the extreme latitudes approaches zero).

7. Rotation • Effects of ROTATION • CORIOLIS EFFECT • Earth rotates at different speeds at different latitudes • Any moving solid, liquid , or gas is turned to the RIGHT of its intended path in the Northern Hemisphere • Any moving solid, liquid , or gas is turned to the LEFT of its intended path in the Southern Hemisphere • Winds • Ocean currents

8. Effects of ROTATION • CORIOLIS EFFECT

9. Effects of ROTATION • CORIOLIS EFFECT http://topex-www.jpl.nasa.gov/aviso/graphics/general/outreach/tutorial/coriolis.mov

10. Effects of ROTATION • CORIOLIS EFFECT

11. Rotation • Effects of ROTATION • Tides • The gravitational pull of the moon and the sun produces a rhythmic rise and fall of the oceans as the Earth rotates

12. Tides • Effects of ROTATION • Result of the gravitational attraction between the Earth, sun, and moon. • As the moon rotates around the Earth, it pulls the water on the nearest side of the Earth outward into a bulge. • A similar bulge on the opposite side of the Earth is caused by inertia - gravitational attraction of the moon is less water furthest away than on the Earth.

13. TIDES • SPRING TIDE • NEAP TIDE

14. TIDES • SPRING TIDE • During time of the new moon and full moon, the sun and moon are in a straight line • Combined gravitational pull produces spring tides • High tides are very high and low tides are very low.

15. TIDES • NEAP TIDE • When sun and moon are at right angles from the Earth, during the quarter phases of the moon • Gravitational pull on the oceans is less • A smaller difference between high and low tide

16. TIDES Nova Scotia's Hall's Harbour at high tide. The tides have a vertical difference, between high and low tide, of up to 14 metres (48 feet)! And at low tide just six hours later.

17. TIDES - WAVES • Tides are due to GRAVITATIONAL ATTRACTION NOT wind

18. TIDES • A review of tides and the position of the sun and moon

19. Revolution • REVOLUTION – Earth’s yearly orbit around the Sun • 365.25 days • Earth’s orbit is anellipse • Distance between the Earth and Sun changes during the year because the orbit is not a circle! • Average distance is 150,000,000 km • Earth’s tilt on its axis remains in the same direction!

20. Revolution NOTE: This is not to scale; in reality, the sun is a lot bigger to scale, and Earth is a lot further away.

22. Seasons • CAUSES of SEASONS • Tilt of the Earth’s axis • Uneven heating of Earth’s surface • The hemisphere tilted toward the Sun receives more solar energy • Revolution of the Earth around the sun

23. Seasons

24. Seasons • Solstice • Day when the sun reaches its greatest distance north or south of the equator • Northern Hemisphere • SUMMER – June 21 or 22 • WINTER – December 21 or 22

25. Seasons • Equinox • Day when the sun is directly over the equator • Daylight and nighttime are equal • Northern Hemisphere • SPRING (Vernal) • March 21or 22 • FALL (Autumnal) • September 21 or 22

26. Seasons

27. College of Alameda Physical Geography http://members.aol.com/pakulda/emmod.htm

28. MOON • A cold, rocky body about 2,160 miles (3,476 km) in diameter. • It has no light of its own - shines by sunlight reflected from its surface.

29. MOON • Rotates on its axis • Rotation of the moon takes about as long as its revolution • Revolves around the Earth • once every 27⅓ days • The same side of the moon is facing the Earth

30. Phases of the MOON • WAXING • When the moon is between New and Full • Portion of moon visible is INCREASING • WANING • When the moon is between Full and New • Portion of the moon visible is DECREASING

31. PHASES OF THE MOON The photographs show what the moon looks like from Earth. The drawings show what the moon would look like from space.

32. Lunar Eclipse • Earth’s shadow falls on the moon • can only occur at Full Moon • UMBRA – darkest part of the shadow, a region where the Earth blocks all direct sunlight from reaching the Moon. • PENUMBRA – cone of shadow cast by deflected light, a zone where the Earth blocks part but not all of the Sun's rays from reaching the Moon

34. Lunar Eclipse • There is a full moon once a month – why not a lunar eclipse? • All 3 bodies must be in perfect alignment • Must be nighttime when alignment occurs, only half the planet is experiencing night at a given time • During Full Moon phase, the moon usually passes above or below Earth's shadows and misses them entirely. No eclipse takes place. • Two to four times each year, the Moon passes through some portion of the Earth's penumbral or umbral shadows resulting in an eclipse

35. MOON Earth’s orbit around the sun • The moon's orbital plane does not "lie flat" along the ecliptic, but forms an angle of about 5º - affects chances of experiencing an eclipse. (note: the distances in this diagram are not to scale)

36. MOON Path of moon through Earth’s shadow during total eclipse in 2000. Note: the moon does not pass directly through the center of the UMBRA

37. LUNAR ECLIPSE • Partial Lunar Eclipse • A portion of the Moon passes through Earth's umbral shadow. • These events are easy to see, even with the unaided eye. • Total Lunar Eclipse • The entire Moon passes through Earth's umbral shadow. • These events are quite striking for the vibrant range of colors the Moon can take on during the total phase (i.e. - totality).

38. LUNAR ECLIPSE • When an eclipse of the Moon takes place, everyone on the night side of Earth can see it. • About 35% of all eclipses are of the penumbral type which are very difficult to detect, even with a telescope. • 30% are partial eclipses which are easy to see with the unaided eye. • 35% or so are total eclipses, and these are quite extraordinary events to behold.

39. Indirect sunlight still manages to reach and illuminate it. • However, this sunlight must first pass deep through the Earth's atmosphere which filters out most of the blue colored light. • The remaining light is a deep red or orange in color and is much dimmer than pure white sunlight. • Earth's atmosphere also bends or refracts some of this light so that a small fraction of it can reach and illuminate the Moon. LUNAR ECLIPSE

40. LUNAR ECLIPSE • If the Earth had no atmosphere, then the Moon would be completely black during a total eclipse. Instead, the Moon can take on a range of colors. • The filtering and refracting effect of Earth's atmosphere makes the total phase of a lunar eclipse interesting. • The exact appearance depends on how much dust and clouds are present in Earth's atmosphere. • Major volcanic eruptions tend to make total eclipses very dark, since these events dump large amounts of ash into Earth's atmosphere. • During the total lunar eclipse of December 1992, dust from Mount Pinatubo rendered the Moon nearly invisible.

41. SOLAR ECLIPSE • Moon moves directly between Earth and the sun • UMBRA – Dark inner shadow; total eclipses are seen from within this shadow. The track of the Moon's shadow across Earth's surface is called the Path of Totality. It is typically 10,000 miles long but only 100 miles or so wide. • PENUMBRA – Faint outer shadow; partial eclipses are seen from within this shadow.

43. SOLAR ECLIPSE • There is a NEW moon once a month – why not a solar eclipse? • All 3 bodies must be in perfect alignment • During New Moon phase, the moon’s shadow usually passes above or below our planet and misses Earth entirely. No eclipse takes place. • At least twice each year, the 3 bodies line up so that some part of the moon’s shadow falls on Earth’s surface • An eclipse of the Sun is seen from that region

44. SOLAR ECLIPSE 2000 Jul 31: Partial Solar Eclipse http://sunearth.gsfc.nasa.gov/eclipse/OH/OH2000.html

45. QUESTIONS • Describe the two types of planetary motion. • Why does the Earth have tides? • What is the relationship between tides and waves? • What are the characteristics of a wave? • What causes the Coriolis Effect? What is the Coriolis Effect? • Why does the Earth have seasons? • What is the difference between a solstice and an equinox?

46. QUESTIONS • What is the difference between a solar eclipse and a lunar eclipse? • When can you see a total solar eclipse? A total lunar eclipse?