Earth-Moon-Sun Relationship Earthshine Project, BBSO (http://www.bbso.njit.edu/espr/fig10.html

Earth-Moon-Sun Relationship Sphere – a round, three-dimensional object whose surface at all points is the same distance from its center Axis – an imaginary line around which an object spins

Earth-Moon-Sun Relationship Rotation – the spinning of an object around its axis Revolution – the orbiting of one object around another, like Earth revolving around the sun Ellipse – an elongated, closed curve; the shape of planetary orbits

Why do we have Seasons? They are caused by the tilt of Earth’s axis, 23½0 Equinox – when the noon sun is directly overhead at the equator, equal hours of daylight and darkness Solstice – when the noon sun is directly overhead at either 23½0N (Tropic of Cancer) or 23½0S (Tropic of Capricorn) latitude, coincides with the 1st day of summer or winter

Path of the Ecliptic The apparent path of the Sun across the sky. In summer, the Sun's path is longest, and so are the days. In winter, the Sun's path is shortest, and so are the days. http://www.lon-capa.org/~mmp/applist/seasons/cd190b.htm

The Moon 384,000km away, 1/6th the gravity of Earth 1. Earth’s only natural satellite 384,000km away, 1/6th the gravity of Earth Noon temp. of 1300C, night temp. of -1750C Surface features Dark, flat plains called marias Bright areas called highlands

The Moon (cont.) The period of rotation equals the period of revolution around the Earth Apollo 11 put Neil Armstrong and Edwin “Buzz” Aldrin on the moon on July 16th, 1969

Moon Stats No light of its own!! The Moon produces no visible light of its own It shines only by reflected sunlight Surface is very dark, only ~7% reflective 9

The Near Side The Moon rotates in 27.3 days. The Moon orbits Earth in 27.3 days. Because the Moon rotates and revolves at the same rate, we only see one side The Near Side The NEAR side There is NO DARK SIDE There is a FAR side…. The Moon's rotation period is equal to its orbital period: The Moon completes 1 rotation about its axis in the same time as it completes 1 orbit around the Earth. As a consequence, the Moon always keeps the same face towards the Earth. Near Side: hemisphere facing towards the Earth Far Side: hemisphere facing away from the Earth The synchronization of the Moon's rotation and orbit is caused by strong tidal forces from the Earth that effectively "locks" the Moon's orientation relative to the Earth. [Note: The degree of synchronization is not perfect for two reasons. First, the Moon's orbit is elliptical rather than circular, so that the Moon's orbital speed is faster at perigee and slower at apogee. This mis-match in the exact orbital and rotation rates results in an apparent east-west "rocking" motion of the Moon by about 7.9 degress over the course of a month. The second is that the axis of the moon's rotation is tilted by about 7 degrees relative to its orbital plane (like the Earth's 23.5 degrees). This leads to an additional north-south nodding motion over the course of a month. The combined rocking and nodding motion motion is called "libration". You can see libration in the lunation movie below.] 10

Earth and Moon to Scale From http://visibleearth.nasa.gov/view_rec.php?id=1624 This image conveys the distance between Earth and Moon. You can demonstrate a scale model to your audience by providing one of your participants with a tennis ball (Moon) and one with a basketball (Earth).  Ask the audience to determine how far apart the two balls should be about 24 feet. Original Caption Released with Image: 2001 Mars Odyssey's Thermal Emission Imaging System (THEMIS) took this portrait of the Earth and its companion Moon, using the infrared camera, one of two cameras in the instrument. It was taken at a distance of 3,563,735 kilometer s (more than 2 million miles) on April 19, 2001 as the 2001 Mars Odyssey spacecraft left the Earth. From this distance and perspective the camera was able to acquire an image that directly shows the true distance from the Earth to the Moon. The Earth's diameter is about 12,750 km, and the distance from the Earth to the Moon is about 385,000 km, corresponding to 30 Earth diameters. The dark region seen on Earth in the infrared temperature image is the cold south pole, with a temperature of minus 50 degrees Celsius (minus 58 degrees Fahrenheit). The small bright region above it is warm Australia. This image was acquired using the 9.1 µm infrared filter, one of nine filters that the instrument will use to map the mineral composition and temperature of the martian surface. From this great distance, each picture element (pixel) in the image corresponds to a region 900 by 900 kilometers or greater in size or about size of the state of Texas. Once Odyssey reaches Mars orbit each infrared pixel will cover a region only 100 by 100 meters on the surface, about the size of a major league baseball field. If Earth were a basketball, then the Moon would be a tennis ball, 23.5 feet away http://visibleearth.nasa.gov/view_rec.php?id=1624 11

Moon’s Orbit Orbits (revolves around) Earth every 27.3 days Elliptical orbit (not a perfect circle) Near and Far The above illustration, based on Galileo spacecraft images, shows the approximate difference in apparent size between a full moon at perigee (the closest point in the lunar orbit, pictured at left) and a full moon at apogee, the farthest point in the lunar orbit. Image Credit: NASA http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=442 360,000 km 406,000 km 224,000 miles 252,000 miles http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=442 12

Moon Phases New Moon – when the side facing Earth is totally dark First Quarter Moon – when the right half of the moon facing Earth is lit Full Moon – when the side facing Earth is completely lit Third Quarter Moon – when the left half of the moon facing Earth is lit

New moons are not created by the Earth “getting in the way” Misconception Alert!!! New moons are not created by the Earth “getting in the way”

Tides Caused by moon’s gravitational pull Spring Tide – the moon, Earth and sun align Neap Tide – when the moon, Earth and sun form a right angle

Moon Stats Moon’s orbit around Earth is inclined about 5 degrees to Earth’s plane of orbit around the Sun Ecliptic plane Moon’s orbital plane Moon Earth Sun Moon’s orbit around the Earth is elliptical: ~0.15% out of circular. Tilted by 5º from the Ecliptic. Mean Distance: 384,400 km Perigee (Closest Approach): 363,300 km Apogee (Maximum Distance): 405,500 km Appears ~11% larger at Perigee than at Apogee Understanding this is fundamental to understanding why eclipses do not happen every month, or getting the reason for phases confused with eclipses. Image created by LPI staff 19

Earth-Moon Revolutions The earth and moon revolving around the barycenter. Notice how the earth moves slightly.

The Moon (cont.) Lunar Eclipse – when Earth passes between the moon and the sun

The Moon (cont.) Solar Eclipse – when the moon passes between Earth and the sun

Earth’s magnetic field Basically a ‘magnet’, exerting a magnetic field surrounding the earth, which effectively extends several tens of thousands of kilometers into space, is called the magnetosphere.

Earth’s Magnetic Field Magnetosphere protects us from the Solar Wind. http://averyhenderson.files.wordpress.com/2008/12/solarinteraction1.jpeg

http://www. aerospaceweb. org/question/astronomy/magnetic-field/earth http://www.aerospaceweb.org/question/astronomy/magnetic-field/earth.jpg