Earth review How old is the Earth? Difference between rotation and revolution How long is Earth’s rotation? Revolution? What causes seasons? Answer: 4.54 billion years old Rotation: orbiting movement around an object’s own axis Revolution: orbiting movement around an external axis 3. rotation: 24 hrs; revolution: 365.25 days 4. earth’s tilt: summer north pole tilted towards Sun south pole experience winter as it is tilted away; winter: north pole tilted away from Sun south pole experiences summer as it titled towards

The M N The moon is a natural satellite around our Earth Exomoon: moon around planets that lie beyond our solar system. Moons of extrasolar planet called exomoon How long moon orbits earth? 27.322 days. The moon orbits the Earth once every 27.322 days, measured against background stars. It also takes approximately 27 days for the moon to rotate once on its axis. Tilted 5o Earth tilted axis: 23.5o Moon axis of rotation is titled by 1.5o; virtually no season on moon. This means that some areas are always lit by sunlight, and other places are perpetually draped in shadow. http://www.space.com/55-earths-moon-formation-composition-and-orbit.html

The Moon Large chunk of rock that goes around the Earth in an orbit. Planets orbit stars, Moons orbit a planet First visited by USSR’s robotic spacecraft in 1959 Has no moon of its own; no ring Has a very thin and weak atmosphere + lack water  can’t support life Mass =7.345 × 1022 kg Earth- Moon distance: 384,400 km (how many AU?) Answer= 0.00257 AU. Image courtesy of NASA/JPL Ask students what they know about the moon before revealing bullet points 1. http://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html Lunar Revolution period around Earth with respect to back ground stars (called sidereal period) ?= 27.3 days The sidereal period of the Moon is the time needed for it to return to the same position against the background of stars. Synodic period?= 29.53 days = measuring the motion of the Moon around the Earth relative to the Sun as seen by an observer on the Earth http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question32.html So why are the sidereal and synodic lunar months not equal in length? After one sidereal month after starting at let’s say full moon position, the moon hasn’t got back to its original full moon position because Earth also travels around Sun. The moon has to play catch up; this catching up of the Moon takes an additional 2 days (27.3 to 29.5) 2. The moon moderates Earth's wobble on its axis, leading to a relatively stable climate over billions of years. Meaning? http://moon.nasa.gov/about.cfm How moon was formed? Earth- Moon distance: 384,400 km = 0.00257 AU. The moon takes 27 days to orbit around the earth and spin around its axis Max/min surface temp: -233/123 °C Is the moon titled? USSR: Union of Soviet Socialist Republics or Soviet Union

How was the Moon formed? Over 4.5 billion years ago, a Mars-sized body collided with the still-molten Earth debris from the collision accumulated into Earth’s Moon. Bombarded by asteroids, meteoroids and comets over billions of years  Moon’s surface ground up and “scarred” with craters The newly formed moon was in a molten state. Within about 100 million years, most of the global "magma ocean" had crystallized, with less-dense rocks floating upward and eventually forming the lunar crust. The moon was first visited by the U.S.S.R.'s Luna 1 and Luna 2 in 1959 https://www.nasa.gov/mission_pages/LADEE/news/lunar-atmosphere.html#.VRlEZfnF_1Y Recent studies confirm that our moon does indeed have an atmosphere consisting of some unusual gases, including sodium and potassium, which are not found in the atmospheres of Earth, Mars or Venus.  Source: "How the Moon Formed." : Melbourne Museum. N.p., n.d. Web. 26 Mar. 2015. http://video.nationalgeographic.com/video/101-videos/moon-101-sci

Neil Armstrong, Buzz Aldrin and Mike Collins (Apollo 11) The Moon First human visit: 1969 Neil Armstrong, Buzz Aldrin and Mike Collins (Apollo 11) The Moon Buzz Neil MIke The first human landing on the moon was on 20 July 1969. Astronaut Neil Armstrong and Buzz Aldrin were the first human to walk on the moon's surface. Apollo 11 mission http://moon.nasa.gov/about.cfm How the Moon Got its Name Earth's only natural satellite is simply called the moon because people didn't know other moons existed until Galileo Galilei discovered four moons orbiting Jupiter in 1610. Other moons in our solar system are given names so they won't be confused with each other. We call them moons because, like our own, they are natural satellites orbiting a solar system body (which in turn is orbiting a star). Astronaut’s footprint Thin atmosphere & no moisture  stayed preserved

How the Moon looks depend on where we view it on Earth : Viewed from the North pole from outer space Viewed from the center of its orbit (i.e. from Earth) We see different portions of the lit side of the Moon.

Moon’s synchronous rotation Moon rotates once on its axis every 27.3 days. Time taken the moon to orbit Earth also 27.3 days (i.e. called orbital period)  scientists called this synchronous rotation Speed question: The elliptical nature of the orbit of the moon means its speed varies 27.3 days is an orbital period with respect to the background stars seen by an observer on earth a total of 59 percent of the moon's surface as it orbits us. The moon is rotating synchronously as it orbits around Earth (i.e., it is spinning at the same speed that it is going around Earth). Time for the moon to complete one revolution around Earth= 27.3 days. This is called orbital period The Earth and the Moon rotate and revolve counterclockwise (https://solarsystem.nasa.gov/scitech/display.cfm?ST_ID=490) In other word, a lunar day is a month- long The Earth and the Moon rotate and revolve counterclockwise https://www.youtube.com/watch?v=OZIB_leg75Q

Seen before? When? Only occurs at night? What happens to the Moon in the morning? Answer: no; the moon is always there. In the morning it’s harder to view due to the over-powering brightness of the Sun

Moon cycle: 29.5 days (~ one “moonth”; from one new moon to the next) 8 main phases View from space https://solarsystem.nasa.gov/sc The synodic month is 29.5 days. This is the time it takes the Moon to go from one new Moon to the next with respect to the Sun. This is almost equal to one month. In fact, the word month comes from the word "moonth." So, in one week the moon goes through one-quarter of its cycle. itech/display.cfm?ST_ID=490 http://ed.ted.com/on/3ybtW3iS not so good https://www.youtube.com/watch?v=wz01pTvuMa0- good demo Moon phase animation: Animation: http://www.sumanasinc.com/webcontent/animations/content/moonphase.html Moon seems to always has a “dark side” The same half of the Moon is in darkness all the time-i.e. that there is a dark side of the Moon. Reality: The Moon has no side that is constantly dark; the front and back are alternately lit as the Moon rotates. Far side is a more accurate term. 1. The moon revolves about the earth in the same direction as the earth rotates. 2. This motion is completed, relative to the stars, in 27.3 days. Called sidereal month 3. Because the earth is moving about the sun, the time from new moon to new moon is a bit longer – 29.5 days. Synodic month Moon phase explained: 1. https://www.youtube.com/watch?v=wz01pTvuMa0 2. https://www.youtube.com/watch?v=Jip3BbZBpsM

-New moon : when moon between Sun and Earth Play animation http://astro.unl.edu/classaction/animations/lunarcycles/lunarapplet.html Synondic month= period of time elapses between 2 new moons The mean length of the synodic month is 29.53059 days (29d 12h 44m 03s). This is nearly 2.21 days longer than the sidereal month. As the Moon revolves around Earth, both objects also progress in orbit around the Sun. After completing one revolution with respect to the stars, the Moon must continue a little farther along its orbit to catch up to the same position it started from relative to the Sun and Earth. This explains why the mean synodic month is longer than the sidereal month. http://eclipse.gsfc.nasa.gov/SEhelp/moonorbit.html explain why synodic month is longer; it takes moon 27.5 days to rotate to its original point (new moon) but since the earth also complete another portion of its orbit around Sun (30o)the moon is now displaced and thus has to travel an additional distance to be back to its original position for a new moon to take place. When Sun, Earth, and Moon are ~ 180o to each other (all on a straight line):full or new moon When Sun, Earth, Moon are at ~ 90o to each other: 1st and last quarter; moon half lit -New moon : when moon between Sun and Earth -Full moon: when moon behind Earth, with respect to the Sun - Gibbous = between half lit and fully lit - Waxing = increasing; Waning= decreasing

a whole new meaning to moon walking Caption contest Hyperion: Saturn’s moon stands out with its chaotic rotation https://www.youtube.com/watch?v=tk8r85lM3SY Almost all moons in the Solar System keep one face pointed toward their planet. (The only exception we know of is Hyperion, a moon of Saturn.)  http://curious.astro.cornell.edu/physics/44-our-solar-system/the-moon/general-questions/110-does-the-moon-rotate-are-there-other-moons-that-always-keep-one-face-toward-their-planet-intermediate That process is called tidal friction. You probably know that the Moon's gravity affects the Earth's oceans. Well, the Earth's gravity also affects the Moon. It distorts the Moon's shape slightly, squashing it out so that it is elongated along a line that points toward the Earth. We say that the Earth raises "tidal bulges" on the Moon. The Earth's gravity pulls on the closest tidal bulge, trying to keep it aligned with Earth. As the Moon turns, feeling the Earth's gravity, this creates friction within the Moon, slowing the Moon's rotation down until its rotation matches its orbital period exactly, a state we call tidal synchronization. In this state, the Moon's tidal bulge is always aligned with Earth, which means that the Moon always keeps one face toward Earth. The Moon slows the Earth's rotation, too, but at a very slow rate, increasing the length of the day by a couple of milliseconds each century. a whole new meaning to moon walking

Shadow: Umbra and Penumbra Earth’s shadow Moon Umbra = the inner shadow Penumbra = the outer shadow

Make a Moon phase profile with mini-OREO “third quarter“= refers to the Moon being three-fourths of the way to a new moon; not “3/4 of it being lit” Note: "first quarter" = one-quarter of the monthly cycle elapsed; not “¼ of the moon is being lit”  Meaning of “third quarter“? With entertainment: https://www.youtube.com/watch?v=79M2lSVZiY4 https://www.youtube.com/watch?v=ABM_8IVFE6k

Tides, Lunar eclipse vs Solar eclipse Already assigned as homework Textbook page 287-289 Comparison chart from Ms. Pham Today’s HW Read p283-290 Answer p285 #1-4; p288 #5-8; p290 #2-6,8

HW review: Remember: Solar SME Moon passes between Sun and Earth blocking the Sun Earth is in Moon’s umbra (inner shadow)

HW review: Remember: Lunar SEM Similar arrangement of a full moon Earth is between Sun and Moon blocking the Sun Moon is in Earth’s umbra https://www.youtube.com/watch?v=rVE8PFYlwSM

Keeping Time: Origins of the Days of the Week Planet French Monday Moon lundi Tuesday Mars mardi Wednesday Mercury mercredi Thursday Jupiter jeudi Friday Venus vendredi Saturday Saturn samedi Sunday Sun dimanche Why is a week seven days long? Seven days corresponds to the time it takes for a moon to transition between each phase: full, waning half, new and waxing half. Because the moon cycle is 29.53 days long, the Babylonians would insert one or two days into the final week of each month. http://www.livescience.com/45432-days-of-the-week.html

--The end-- Read p283-290 Define: eclipse, lunar eclipse, solar eclipse, gravitational force Copy Figure 7.18 and 7.20 in your notes Recap: could be done on ipad, next day http://www.bbc.co.uk/bitesize/ks3/science/environment_earth_universe/astronomy_space/activity/