Units of Measure Earth diameter 12,800 Km Astronomical Unit – avg. distance between Earth/Sun 150,000,000 Km 1 AU Speed of Light (c) 300,000 Km/sec Light year 9.5 x Km 6.3 x 10 4 AU

Earth-Moon Sizes Earth –Radius is 6,378 Km Using earth as 1 Moon –Radius is 1,738 Km 0.27 ~1/4 radius

Earth-Moon Sizes If the Earth were this ball, which of the others could be the Moon? –This ball (Earth) ~ 16 cm –Therefore Moon ~ 4 cm

Earth – Moon System How far away from Earth is the Moon? Take our model Earth and Moon and place them the distance away you think they should be…

Earth – Moon Distance Distance from Earth to Moon –384,400 Km –~30 x Earth’s diameter Using our objects? –If Earth is ~ 16 cm –Distance (30 x 16cm) ~ 480 cm (5 m)

Sun – Earth System How does the size of the Earth compare to the Sun? If this was our Earth, how big would the Sun be?

Sun – Earth Sizes Earth Radius 6378 Km Using Earth as 1  If Earth is 16 cm Sun Radius 6.96 x 10 5 Km (696,000 Km) ~109x Earth ~ 2x Earth-Moon distance The Sun 17 m diameter

Sun – Earth Distance Distance from Earth to Sun 1.5 x 10 8 Km (150,000,000 Km) ~400 x Earth-Moon distance or 8.33 light minutes

Sun – Earth Distance How far away from the Sun is the Earth? Using our model Earth, how far do you think the Sun is? –Earth is 16 cm –About 2 Km from Sun to Earth –About the distance to Westville in New Haven

Earth’s Motions Orbital direction – revolves around the sun counterclockwise Orbital period – days Rotational period – 1 day Tilt of rotation – 23.5 degrees

Earth’s rotation Earth rotates (spins) on its axis about 1700 km/hr (at the equator) and almost 0 km/hr at the poles.rotates Evidence for Earth’s rotation: 1.Foucault’s pendulumpendulum

2. Coriolis Effect- air and water are deflected to the right in the northern hemisphere and to the left in the southern hemisphere due to earth’s rotation video here 3. Star trails

Moon’s Motions Orbital direction – counterclockwise Tilt of orbit – approx. 5 degrees Orbital period – 27.3 days (sidereal month) Rotational period – 27.3 days Synchronous rotation- moon’s rotation equals moon’s rotation equals its revolution its revolution

Tides Influenced by Moon (and Sun) –Moon’s gravity pulls up water on side of Earth facing it –Another high tide occurs on opposite side of Earth 2 high tides and 2 low tides each day Moon rises and sets 50 minutes later each day, so tides occur about 50 minutes later each day

Tides

Earth’s Seasons Caused by Earth’s tilted axis (23.5°) and its orbit (revolution) around the sun Earth’s orbit is an ellipse; Earth is actually closest to the sun during our winter (rather than our summer) –Perihelion- occurs when Earth is closest to sun (in January) –Aphelion- occurs when Earth is farthest from the sun (in July)

Video links Earth’s rotation (day) and revolution (year) Tides

Equinoxes Autumnal (Fall) / Vernal (Spring) Equinoxes- Sun is directly overhead at the equator; equal hours of night and day –Both hemispheres have equal hours of day/night

Spring/Fall Equinoxes

Solstices Summer solstice (June 21)- Northern Hemisphere leans towards sun Northern hemisphere has maximum daylight hours Sun is directly overhead at the Tropic of Cancer (23.5°N)

Summer Solstice Winter Solstice

Solstices cont’d….. Winter Solstice (December 21) Southern hemisphere is tilted towards the sun (Northern hemisphere leans away) Northern hemisphere has least daylight hours Sun is overhead at Tropic of Capricorn (23.5°S)

Angle of Sunlight (or Insolation) Insolation- the amount of incoming solar radiation Angle of light affects temperature Sun is higher in the sky during summer; energy is more concentrated and shadows are short Sun is lower in the sky during winter; energy strikes ground at a slant and is more spread out; less concentrated; longer shadows