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Earth’s Moon Chapter 25.2. Moon Facts: Distance from Earth: 384,400 km (238,855 miles) Size: 27% or 1/3 or 1/4 of Earth (~4 moons would fit across Earth)

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Presentation on theme: "Earth’s Moon Chapter 25.2. Moon Facts: Distance from Earth: 384,400 km (238,855 miles) Size: 27% or 1/3 or 1/4 of Earth (~4 moons would fit across Earth)"— Presentation transcript:

1 Earth’s Moon Chapter 25.2

2 Moon Facts: Distance from Earth: 384,400 km (238,855 miles) Size: 27% or 1/3 or 1/4 of Earth (~4 moons would fit across Earth) Near side = side ALWAYS facing Earth (Moon spins so slowly) Far side = side NEVER facing Earth. Rotation (day): Time to spin 360 on its axis = 27.3 days The moon rotates at the same rate as it revolves! Sidereal Revolution : Amount of time to complete a 360 orbit around Earth = 27.3 days Lunar Revolution: Amount of time it takes for the moon to cycle thru. All it its phases (new  new) = 29.5 days Temps: Extreme Hot or Cold (-170/ 110 °C) b/c no atmosphere to trap heat Gravitational Pull: 17 % (1/6) of Earth’s - too weak to hold onto an atmosphere Visited: Neil Armstrong and Buzz Aldrin (on NASA's Apollo 11 mission, which also included Michael Collins) were the first people to walk on the moon, on July 20, Apollo 17 was the last mission.Neil Armstrong

3 Moon Motion Rotation: Make one complete turn on an axis (a “day”) Revolution: The motion of an object around a closed orbit, following a circular or elliptical path. Sidereal Month or Revolution: The time required for the moon to complete a 360 degree revolution around Earth. (27.3 days) Link to Moon Motion Animations: ipse/eclipses.htm ipse/eclipses.htm

4 Lunar Phases As moon orbits Earth, ½ is always lit … but we do not always see the entire lit ½. Phases are caused by changes in relative positions of the moon, sun, & earth as the moon revolves around earth. Takes the moon 27.3 days to complete an orbit but 29.5days for us to see it complete a cycle of phases (b/c Earth is moving too!)

5 Moon Activity #1 Objective: To observe and model the moon’s ROTATION & REVOLUTION around Earth. Conclusion Write-Up (Paragraph) Compare/Contrast the Moon’s rotation and revolution to Earth’s. How does this affect the view we have of the moon? How does this relate to length of day (for both)? Length of year (for both)?

6 MOON PHASES Nearside = side facing us Far side = never facing us Why: Moon rotates so slowly that we always see the same face. It rotates at the same speed that it revolves. Blue Moon = 2 nd Full moon of a month isamples/astronomy/moonphase.html

7 Lunar Phases Even though ½ of the moon is always lit by the sun, we see different portions of this lit ½ as the moon revolves around Earth. Phases depend on the moon’s position relative to Earth and the sun. It takes 29.5 days for the moon to go through its cycle of phases (Longer than 27.3 days…because Earth is moving around the sun and the moon has to “catch up”).

8 Solar Eclipse – Sun is blocked Umbra = Dark shadow Locations w/in Umbra will see a total eclipse Penumbra = “lighter” shadow Partial eclipse viewed here Link to Eclipse Animations: ehall/ph/eclipse/eclipses.htm ehall/ph/eclipse/eclipses.htm

9 Eclipses don’t happen every NEW and FULL moon because the moon’s orbit is not in the same plane as the Earth’s (ecliptic). The sun, Earth, and moon have to line up in the same plane for an eclipse to happen.

10 LUNAR ECLIPSE – MOON IS BLOCKED Link to Eclipse Animations: lipse/eclipses.htm lipse/eclipses.htm


12 Moon appears reddish during a lunar eclipse b/c light is bent as it travels past Earth. When light is “bent” it appears more red.

13 Tides are caused by the gravitational pull of the moon on Earth. High tides – 2 x a day Low tide – 2 x a day New + Full = Spring (High tides HIGH and low tides LOW). Sun & Moon work together. Quarter moons = Neap (Not as much diff. b/w high & low tide). Sun & Moon work against each other. The sun is also “pulling” on Earth’s water. (Remember gravity depends on mass and distance. The sun is farther from Earth … but its mass is so tremendous that it pull’s on Earth’s water too). The sun has a smaller influence on tides than the moon. BUT when the moon and sun are lined up with Earth – they combine pulling forces to create HIGHER TIDES.


15 The Moon Affects Earth’s Rotation! Gravity works both ways! Earth pulls on the Moon – keeping it in orbit. The Moon pulls on Earth to produce tides. The Moon pulls on Earth’s tidal bulge. This slows down Earth’s rotation. This is due to friction (a pulling force opposing motion). Earth slows down by fractions a second each year. But some of its momentum is transferred to the moon – which uses it to move farther from Earth. So the moon is slowing us down & the moon is drifting away (3.8 cm /year)!


17 Moon’s Formation: Collision Theory  Most widely accepted theory  Mars-sized object made an off-center collision. Debris from Earth (ejecta) and pulverized Mars-sized object pull together (gravity) to form the Moon.  Moon’s composition has similarities AND differences to Earth rocks – this theory supports that observation.

18 Moon Geology Highlands – lighter areas, Mts., older Mare (Maria) – Low lying, made fr. Cooled lava (basalt rock), younger Regolith – powdery rock surface formed by impacts Craters – Main surface feature of moon – tells us that the early s.system was full of impact collisions (very violent) Rilles – Cooled lava channels UNLIKE EARTH, THE MOON HAS NOT CHANGED MUCH IN THE LAST 3 + BILLION YEARS.

19 Water on the Moon? Very small amounts of frozen water at poles – not enough to support life L-Cross mission just “bombed” the south pole of the moon to look for water under the surface. L-cross Mission Bgy21XohI L-cross mission (PBS) cl8Uo Moon’s surface has not changed much b/c there is no weather, atmosphere, or plate tectonics.

20 Web links Solar Views Website Moon Phase Changes hase.html

21 1. Which choice represents the most widely accepted scientific theory on the moon’s formation? a.The moon formed from the debris of a collision of a Mars-sized planet and Earth. b.The moon formed somewhere else in the universe and while passing Earth it was captured by Earth’s gravity and pulled into orbit. c.The moon formed from a ‘splash’ or part of Earth was tossed off while Earth was still molten and spinning very rapidly. d.The moon formed at the same time and the same way that Earth did.

22 2. Which letter is pointing to the highland regions of the moon? 3. Which letter represents MARIA REGIONS? 4. People once thought that the darker areas were seas or oceans. This turned out to be false, but how did these darker regions form? A. B.

23 5a. Draw in the tidal bulge to show how the moon’s gravity affects Earth’s water. 5b. How many high tides a day? 5c. What causes tides? Earth M

24 6. Which choice best describes temperatures on the moon? a.Very hot all the time b. Very cold all the time c. Very hot or very cold extremes d. Moderate temperatures

25 7. What type of eclipse is being shown in the diagram: Solar or Lunar? 8.From Earth, will a total or partial eclipse be seen? 9.What moon phase is it? Earth moon

26 10. Which statement is true about spring tides? a. They occur during quarter moon phases. b. They occur during new and full moon phases. c. They occur during the waxing phases of the moon. d. They occur only in the spring season. 11. Neap tides occur during ______ phases of the moon.

27 12The powdery rock that forms the surface layer of the moon is known as: a. Regolith b. Craters c. Penumbra d. Maria

28 13. How does the moon’s mass compare to Earth? a.It has the same mass. b.It is ¾ Earth’s mass. c.It is ½ Earth’s mass. d.It is 1/3 Earth’s mass. e.It is 1/16 Earth’s mass. 14. How does the moon’s gravity compare to Earth’s? a.It is 6 times greater. b.It is the same as Earth’s gravity. c.It is 1/6 Earth’s gravity. d.There is no gravity on the moon.

29 15. If you are in the UMBRA you will see a __________ eclipse (total or partial) 16. What will the tides be like when the moon is in this position? Extreme/strong

30 True or False 17. ________The moon’s pull on Earth’s tidal bulge causes Earth to speed up in its rotation. 18. ___The moon is the only location beyond Earth, that humans have visited. 19. ________The moon is geologically active.

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