Earth and Its Moon

1. Earth and Its Moon Chapter 3

2. 3-1 The Earth in Space • Earth rotates on its axis • Axis = imaginary line from North Pole to South Pole • 2 movements of the Earth affect the seasons and both day & night • Rotation • Revolution

3. Day and Night Equator = imaginary line dividing Earth into the Northern Hemisphere and Southern Hemisphere Earth rotates abt 1600 km/hr 24 hours to rotate 1 time on its axis = 1 day Part of Earth faces the sun; other part away from sun in darkness Day and night is caused by the rotation of Earth on its axis

4. Looking down on Earth from North Pole see that rotates in a counterclockwise direction • West to East • Sun rises in East as Earth turns toward it • Sun sets in West as Earth turns away from it • Earth’s day is not constant • Changes b/c Earth’s axis is tilted at a 23½° angle and is not straight up and down • If axis were straight • daylight = 12 hrs and nighttime = 12 hrs, every day of every year • Tilted axis: when North Pole leans toward sun then South Pole leaning away from sun • Daylight hours not constant • Hemisphere that leans toward sun has long days and short night • Hemisphere leaning away from sun has short days and long nights

5. A Year on Earth Earth takes 365.25 days to revolve 1 time around the sun = 1 year Extra ¼ day is left off calendar and added every 4 years to the month of February What is a year with an extra day called?

6. Seasons on Earth 4 seasons: Spring, Summer, Autumn, Winter Mars, Saturn, Uranus, & Neptune all have seasons while other 3 have little to no seasons Why do some planets have seasons and other do not?

7. Planets have seasons because they are tilted on their axis • Different seasons on Earth caused by tilt of Earth’s axis • When hemisphere is tilting toward sun it’s summer and tilting away from sun it’s winter • Hemisphere tilting toward sun receives more direct rays from sun and have longer days • Combination of these results in Earths surface and atmosphere receiving more heat = summer

8. Summer in Northern Hemisphere begins June 20 & 21 • Northern Hemisphere tilted full 23½° toward sun • Northern Hemisphere has longest day • Southern Hemisphere has shortest day • Summer Solstice = longest day of year • Solstice – Latin meaning sun and stop • Sun reaches its highest point in the sky on the summer solstice

9. After summer solstice sun begins to lower in the sky • December 21 & 22 = Winter Solstice • Northern Hemisphere tilted full 23½° away from sun • Shortest day of year in Northern Hemisphere • Longest day of year in Southern Hemisphere

10. Equinoxes- 2 times a year when poles are not tilted toward the sun (Spring & Autumn) • Latin for equal night • Day and night are of equal length all over the world • Vernal Equinox – in Northern Hemisphere spring begins March 20 or 21 • Autumnal Equinox – begins Sept. 22 or 23

11. A Magnet in Space • Magnet Field – invisible lines of force that connect the poles/ends of a magnet • Earth similar to a magnet • Earth has a magnetic field that forms around it • Comes from the movement of materials in the Earth’s inner core • Metals such as Iron and Nickel • Magnetic poles different from geographic poles • Geographic poles - opposite ends of tilted axis • Magnetic poles – ends of lines of force that form the Earth’s magnetic field

12. Magnetosphere – Earth’s magnetic field • Begins at abt 1000km and extends to abt. 64000km on the side facing the sun • On side away from sun is a tail that extends millions of km long caused by a stream of charged particles called the solar wind which continually reshapes the magnetosphere as Earth rotates

13. Van Allen radiation belts – 2 doughnut-shaped regions of charged particles formed as the magnetosphere traps particles in the solar wind • Outer belt contains mostly negatively charged electrons • Inner belt contains mainly positively charged protons • Charged particles travel along magnetic lines of force colliding with the Earth’s upper atmosphere • Aurora – collisions of atmospheric particles that give off visible light that appear as bands of shimmering colored lights • Aurora Borealis – a.k.a. “Northern Lights” near North Pole • Aurora Australis – a.k.a. “Southern Lights” near South Pole

15. 3-2 The Earth’s Moon Lunar – Latin word for moon Neil Armstrong & Buzz Aldrin first men to walk on the moon

16. The Moon’s Characteristics • Moon – 3476km in diameter • ¼ the diameter of Earth • Gravity is 1/6 that on Earth (objects weigh less) • Avg. distance to moon = 384,403km • Measured using a mirror left on moon and bounced a beam of light back to Earth • Moonquakes measured using instruments left on the moon (approx. 3000 occur per year • Crust abt. 60km thick • Inner layer abt 800km thick (denser rock) • Core - melted iron

17. Apollo astronauts brought back moon rocks • Oldest abt 4.6 billions yrs abt. same as age of Earth • Earth and moon appear to have formed abt same time • Moon rocks show no traces of water • Scientist believe moon never has had water • Moon has no atmosphere, therefore no weather • Extreme temperature range 100°C to -175°C • The moon is dry, airless, and barren.

18. Features of the Moon • Galileo first person to see the moon through a telescope • Highlands – mountain ranges soaring thousands of meters into the black sky • Maria - broad, smooth lowland plains; appear as dark areas • Latin word for seas • Craters are scattered across moon’s surface • Range in size from microscopic to hundreds of km • Copernicus is one of the largest craters on the moon (91km across) • Most craters located in highlands, very few in the maria

19. Craters formed from blasts of meteorites and some from volcanic activity • Maria filled with hardened rock from volcanic activity billions of years ago • Rilles – long valleys that crisscross much of the moon’s surface, Hadley Rille – 113 km long • Scientists unsure what made rilles, some possibilies: • Evidence that there were active volcanoes • Cut by rivers of flowing lava or • Cracks in surface from moonquakes • Moon’s hot surface cooling and shrinking • All is evidence that the moon was once hot and active

20. Movement of the Moon • Earth revolves around sun and at same time moon revolves around the Earth • Perigee – point of the moon’s orbit closest to the Earth (abt. 350,000 km) • Apogee – point of the moon’s orbit farthest from Earth (abt. 400,000 km) • Moon moves west across the sky, apparent movement caused by Earth’s rotation • When viewed amongst the stars, movement of moon eastward is observed

21. Earth rotates on axis 1 time every 24 hrs • Moon rotates 1 time on axis every 27.3 days • Moon revolves 1 time around Earth every 27.3 days • Moon’s Period of Rotation = Period of Revolution • Same side of moon always faces the Earth • Apollo 8 astronauts were first humans to view the dark side of the moon

22. Origin of the Moon • Moon was “born” when a giant asteroid the size of Mars struck the young Earth, tearing away a chunk of material • The Pacific Ocean possibly could be the hole what was left • Evidence based from moon rocks and explains why moon is so similar to Earth • Water would have vaporized as it was torn from the Earth

23. 3-3 The Earth, the Moon, & the Sun • Relative motions of the Earth, the moon, and the sun result in the changing appearance of the moon as seen from the Earth and the occasional blocking of the sun’s light

24. Phases of the Moon • Moon revolves around the Earth • Moon’s revolution causes moon to appear to change shape in the sky • Different shapes called Phases of the Moon • Goes through all phases in 29.5 days • Moon reflects sunlight toward the Earth, has no light of its own • Phase depends on where moon is in relation to sun and Earth

25. New Moon – moon has no visible light, btwn the sun and the Earth • Sometimes faintly visible due to earthshine (sunlight reflected off the Earth) • Waxing Crescent Phase – more of the lighted side of the moon is visible, a slim curved slice appears • Moon is “waxing” when lighted area appears to grow larger • Moon is “waning” when lighted area appears to grow smaller

26. First Quarter Moon – moon appears ½ lit • 1 week after new moon , moon traveled ¼ the way around the Earth • Waxing Gibbous Phase – days after First Quarter Phase and more of the lighted side of the Moon appears • Full Moon – 2 wks after New Moon Phase • Entire lighted side of moon is visible • Earth is btwn the Moon and Sun • 2 weeks more and the Moon moves through the Waning-Gibbous, Last Quarter, & Waning-Crescent Phases & back the New Moon Phases

27. Eclipses • Movement of the Earth, the Sun, and the Moon lining up in the sky blocking out light or casting shadows • 2 types of Eclipses • Depends which body is blocked Sun or Moon • Solar Eclipse – new moon comes directly btwn moon’s shadow, sunlight blocked from reaching the Earth • Shadow has 2 parts: Umbra and Penumbra • Umbra – small, inner shadow • Penumbra – larger, outer shadow • Only people directly in the path of the umbra can see a total solar eclipse (sun completely blocked) • Never look directly into the sun during a total solar eclipse

28. Why isn’t there a solar eclipse every time there is a new moon? • Lunar Eclipse – Earth comes directly btwn sun and the Full Moon Phase • Moon passes through the Earth’s shadow • Total Lunar Eclipse – moon passes through umbra • Partial Lunar Eclipse – moon passes through penumbra • dims moon’s glow to a reddish color when sunlight is reflected off moon and is bent as it passes through the atmosphere

30. Tides • Gravitational attraction btwn Moon and Earth due to closeness • Gravitational pull of Earth on moon results in a bulging of the Moon surface facing the Earth • Moon also exerts gravitational pull on Earth pulling results in the rise and fall of the oceans as the Moon moves around the Earth • Tides – rise and fall of oceans

31. 2 places on Earth that bulge due to the Moon’s gravitational pull causing high tides: • Side of Earth facing the Moon • Side of Earth facing away from the Moon • Low Tides occur btwn the bulges • 2 high tides and 2 low tides occur every 24 hrs • High and low tides occur abt 50 min. later each day due to the moon’s risng 50 min. later • Spring Tides – higher than normal during full and new moon phases • Due to sun and moon being in direct line with the Earth and increased effect of sun’s gravity on Earth

32. Neap Tides – high tides that are lower that usual • Occur during the first and last quarter phases, gravitational pull on oceans is partially canceled by sun’s gravitational pull • Sun and moon at right angles of the Earth