Review Question People once believed that all planets and stars orbited around ____. • Mercury • Earth • Venus • Mars
The Rotating Earth • is a sphere, a round 3-dimensional shape • bulges slightly at equator and flattens slightly at poles • Radius: same from all points on the surface • Axis/Tilt: imaginary vertical line through the north and south poles it spins on
What is Earth’s rotation? • Rotation: spinning of earth on its axis, causes days and nights • One complete rotation in 24 hours • completes 365 rotations in a one year journey around the Sun • rotates from west to east
What is a Foucault pendulum? • Weight on a string suspended from a support and swings freely. • Swings in a constant direct but as earth turns it appears the pendulum shifts orientation.
Earths Rotation • Compass always points north is evidence of earth’s magnetic field • Earth’s magnetic axis and rotational axis are not at the same points • Thus, your compass would take you to magnetic north not the north pole • Magnetic north changes and moves around rotational north
What is the Coriollis Effect? • rotation of Earth causes ocean currents and wind belts to curve to the left or right
What is Earths Revolution? Revolution- the motion of a body that travels around another body in space; one complete trip along an orbit • a satellite of Sun • Earth’s orbit around the Sun is an Ellipse, an elongated closed curve • is traveling around the sun at an average speed of 29.8 km/s. • Aphelion: planet is farthest from the sun • Perihelion: planet is closest to the sun.
What causes the changes in seasons ? • is tilted 23.5° • causes our change in seasons • makes daylight longer in summer and shorter in winter • hemisphere tilted toward the Sun has longer hours of daylight and makes summer warmer
What is an Equinox? • Equinox:occurs when the Sun is directly over the equator; causing spring and fall • THINK EQUAL: Hours of daylight and nighttime • Spring equinox is Mar 21 and Fall equinox Sep 22
What is a Solstice? • hemisphere tilted toward the Sun receives and absorbs more solar radiation; causing summer • Solstice:is the day when the Sun rays are at its greatest/least distance from the equator • June 21:longest daylight • Dec 21: shortest daylight
What is the moon? • A natural satellite • Satellite: a natural or artificial body that revolves around planet. • One of more than 96 moons in our Solar System • The only moon of the planet Earth
What is the moons Distance, Size, and Gravity? • About 384,000 km (240,000 miles) from Earth • 3,468 km (2,155 miles) in diameter (about ¼ the size of Earth) • 1/6 of Earths gravity
What is the moons internal structure? • 3 major divisions of the Lunar interior • Crust - average thickness of about 70 kilometers • Mantle • Core - radius is between 300 and 425 kilometers • Determined via seismic data from “moonquakes”
What are some lunar features? • No atmosphere • No liquid water • Extreme temperatures • Daytime = 130C (265°F) • Nighttime = -190C (-310 F)
Lunar Features – Highlands (Terrae) • Mountains up to 7500 m (25,000 ft) tall • Rilles (trenchlike valleys) • Anorthosite: light patches seen on the moon’s surface
Lunar Features - Craters • a bowl-shaped depression that forms on the surface of an object when a falling body strikes the object’s surface or when an explosion occurs] • Up to 2500 km (1,553 miles) across • Most formed by meteorite impact on the Moon • Some formed by volcanic action inside the Moon
Lunar Features - Maria • Originally thought to be “seas” by early astronomers • Darkest parts of lunar landscape • Filled by lava after crash of huge meteorites on lunar surface 3-4 billion years ago • Mostly basalt rock
What is the moons rotation and revolution? • Revolution – Moon orbits the Earth every 29.5days • The moon rises in the east and sets in the west • The moon rises and sets 50 minutes later each day • Rotation – Moon turns on its axis every 29 days • Same side of Moon always faces usarth
What shape is the moons orbit around the sun? • The orbit of the moon around Earth forms an ellipse, the distance between Earth and the moon varies over a month’s time
Apparent Size • The 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.
The near side The Moon rotates in 29.5 days. The Moon orbits Earth in 29.5 days. Because the Moon rotates and revolves at the same rate, we only see one side The NEAR side There is NO DARK SIDE There is a FAR side….
How was the moon formed? • 3 major theories • 1. Capture theory: large object ventured too near the forming earth and got trapped by gravity • 2. Simultaneous formation theory: Earth and moon formed at the same time. • 3. Impact theory: Most widely accepted.
How was the moon formed? • The Giant Impact Hypothesis • 3 stages • 1. began when a large object collided with Earth more than 4 billion years ago • 2. collision ejected chunks of Earth’s mantle into orbit around Earth • 3. debris eventually clumped together to form the moon.
What are phases? • Phase: in astronomy, the change in the illuminated area of one celestial body as seen from another celestial body; are caused by the changing positions of Earth, the sun, and the moon
Why are their phases of the moon? • Moonlight is reflected sunlight • Half the moon’s surface is always reflecting light • From Earth we see different amounts of the Moon’s lit surface • The amount seen is called a “phase” • Synchronous rotation: orbital and rotational periods are equal.
Waxing vs Waning • Waxing – lit side is getting bigger • Waning – lit side is getting smaller • ‘LEFT SIDE IS LIT, THE MOON IS LEAVING’ • Left side, lit, leaving, waning
FOUR MAIN SHAPES FULL CRESCENT QUARTER GIBBOUS
Phases for the month • http://www.moonconnection.com/moon_phases_calendar.phtml
Review question When only a small part of the moon is visible, the moon may be in its • first-quarter phase • waning-crescent phase • new moon phase • last-quarter phase
Why don’t we have eclipses every month? • MOON – SUN – EARTH: All do not travel in the same plane of orbit
What are eclipses? • an event in which the shadow of one celestial body falls on another • Bodies orbiting the sun cast long shadows into space
Penumbra Penumbra What is the shadow structure for an eclipse? UMBRA(Latin for "shadow") is the darkest part of the shadow Umbra PENUMBRA is a partial shadow, grayish outer part of a sunspot
What is a solar eclipse? • A solar eclipse is when the moon comes between the sun and the Earth, so that a viewer is in the moon's shadow. • Total eclipses rare – only once every 360 years from one location!
How do I see a total solar eclipse? • Observers in the “umbra” shadow see a total eclipse (safe to view the Sun); can see the corona • Those in “penumbra” see a partial eclipse—not safe to look directly at Sun • Only lasts a few minutes • Path of Totality about 10,000 miles long, only 100 miles wide