Sun-Earth-Moon connections
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
Reasons for Seasons
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
Reasons for Seasons
Incoming solar radiation
The Moon: Properties, history, phases, eclipses, and tides
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
Crater Formation
Crater formation
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
Prominent Maria
Craters vs Maria
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….
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.
Formation of 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
Moon phases
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
For all phases: Note where the sunlight is coming from
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
What is the shadow structure for an eclipse? UMBRA (Latin for "shadow") is the darkest part of the shadow Penumbra 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
The diamond ring
Why not a solar eclipse every month then? Moon's orbit is tilted about 5o with respect to the Earth's orbit (ecliptic), so the shadows usually miss! Moon Earth Ecliptic Moon’s Orbit
What is a lunar eclipse? the passing of the moon through Earth’s shadow at full moon occurs when Earth is positioned between the moon and the sun and when Earth’s shadow crosses the lighted half of the moon
Lunar eclipse Moon’s Path Earth Sun Moon
Why is the Moon red during an eclipse? The Earth’s atmosphere filters some sunlight and allows it to reach the Moon’s surface The blue light is removed—scattered down to make a blue sky over those in daytime Remaining light is red or orange Some of this remaining light is bent or refracted so that a small fraction of it reaches the Moon Exact appearance depends on dust and clouds in the Earth’s atmosphere
What causes the tides? Tides: daily changes in the level of ocean water influenced by the sun and the moon occur in a variety of cycles The combination of gravity and inertia create two bulges of water. High Tide and Low Tide: How often tides occur and the difference in tidal levels depend on the position of the moon as it revolves around the Earth
What causes the tides? The gravitational attraction between the Earth and the moon is strongest on the side of the Earth that happens to be facing the moon, simply because it is closer. This attraction causes the water on this “near side” of Earth to be pulled toward the moon. As gravitational force acts to draw the water closer to the moon, inertial force attempts to keep the water in place. But the gravitational force exceeds it and the water is pulled toward the moon, causing a “bulge” of water on the near side toward the moon
On the opposite side of the Earth, or the “far side,” the gravitational attraction of the moon is less because it is farther away. Here, the inertial force exceeds the gravitational force, and the water tries to keep going in a straight line, moving away from the Earth, also forming a bulge
Tides
Approximately how many days does it take the moon to go through a complete cycle? A. 7 B. 11 C. 26 D. 29.5 ow many days does it take the moon to go through a complete cycle?
When the visible portion of the moon is increasing, the moon is A. waxing B. full C. waning D. waning-crescent
A solar eclipse is most likely to occur when the sun is located between the earth and moon moon is located between the sun and the earth earth is located between the sun and the moon earth and moon are at right angles to each other
Earth has seasons because the temperature of the sun changes Earth rotates on its axis Earth's axis is tilted as it moves around the sun the distance between Earth and the sun changes
The sun appears larger than other stars because it is the biggest star in the universe it is a double star it is the closest star to the earth
A lunar eclipse is most likely to occur when sun is located between the earth and moon moon is located between the sun and the earth earth is located between the sun and the moon earth and moon are at right angles to each other
From new moon to full moon phase you see a decreasing amount of the lighted side of the moon an increasing amount of the lighted side of the moon more of the lighted side, then less of the lighted side of the moon the same amount of the lighted side of the moon
During what moon phase can a lunar eclipse occur? waxing gibbous first quarter new moon full moon