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Units of MeasureUnits of Measure
Earth diameterEarth diameter12,800 Km12,800 Km
Astronomical Astronomical Unit – Unit – avg. distance avg. distance between Earth/Sunbetween Earth/Sun
150,000,000 150,000,000 KmKm
1 AU1 AU
Speed of Light Speed of Light (c)(c)
300,000 300,000 Km/secKm/sec
Light yearLight year 9.5 x 109.5 x 101212 Km Km 6.3 x 106.3 x 1044 AU AU
Earth-Moon SizesEarth-Moon Sizes
EarthEarth – Radius is 6,378 KmRadius is 6,378 Km
Using earth as 1Using earth as 1
MoonMoon
– Radius is 1,738 Km Radius is 1,738 Km
0.27 0.27
~1/4 radius~1/4 radius
Earth-Moon SizesEarth-Moon Sizes
If the Earth were this ball, which of the If the Earth were this ball, which of the others could be the Moon? others could be the Moon?
– This ball (Earth) ~ 16 cm This ball (Earth) ~ 16 cm
– Therefore Moon ~ 4 cmTherefore Moon ~ 4 cm
Earth – Moon SystemEarth – Moon System
How far away from Earth is the Moon? How far away from Earth is the Moon?
Take our model Earth and Moon and Take our model Earth and Moon and place them the distance away you think place them the distance away you think they should be…they should be…
Earth – Moon DistanceEarth – Moon Distance
Distance from Earth to Moon Distance from Earth to Moon – 384,400 Km 384,400 Km – ~30 x Earth’s diameter ~30 x Earth’s diameter
Using our objects? Using our objects? – If Earth is ~ 16 cm If Earth is ~ 16 cm – Distance (30 x 16cm) ~ 480 cm (5 m)Distance (30 x 16cm) ~ 480 cm (5 m)
Sun – Earth SystemSun – Earth System
How does the size of the Earth compare How does the size of the Earth compare to the Sun? to the Sun?
If this was our Earth, how big would the If this was our Earth, how big would the Sun be?Sun be?
Sun – Earth SizesSun – Earth Sizes
Earth Radius Earth Radius 6378 Km6378 Km
Using Earth as 1 Using Earth as 1
If Earth is 16 cmIf Earth is 16 cm
Sun Radius Sun Radius 6.96 x 106.96 x 1055 Km Km (696,000 Km) (696,000 Km)
~109x Earth ~109x Earth ~ 2x Earth-Moon ~ 2x Earth-Moon distance distance The Sun 17 m The Sun 17 m diameter diameter
Sun – Earth DistanceSun – Earth Distance
Distance from Earth to Sun Distance from Earth to Sun
1.5 x 101.5 x 1088 Km (150,000,000 Km) Km (150,000,000 Km)
~400 x Earth-Moon distance ~400 x Earth-Moon distance
or 8.33 light minutesor 8.33 light minutes
Sun – Earth DistanceSun – Earth Distance
How far away from the Sun is the Earth? How far away from the Sun is the Earth?
Using our model Earth, how far do you Using our model Earth, how far do you think the Sun is? think the Sun is? – Earth is 16 cm Earth is 16 cm – About 2 Km from Sun to Earth About 2 Km from Sun to Earth – About the distance to Westville in New Haven About the distance to Westville in New Haven
Earth’s MotionsEarth’s Motions
Orbital direction – revolves around the Orbital direction – revolves around the sun counterclockwise sun counterclockwise
Orbital period – 365.26 days Orbital period – 365.26 days
Rotational period – 1 day Rotational period – 1 day
Tilt of rotation – 23.5 degreesTilt 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.
Evidence for Earth’s rotation:1.Foucault’s pendulum
• 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 MotionsMoon’s Motions
Orbital direction – counterclockwise Orbital direction – counterclockwise
Tilt of orbit – approx. 5 degrees Tilt of orbit – approx. 5 degrees
Orbital period – 27.3 days (sidereal Orbital period – 27.3 days (sidereal month)month)
Rotational period – 27.3 days Rotational period – 27.3 days
Synchronous rotation-Synchronous rotation-
moon’s rotation equalsmoon’s rotation equals
its revolutionits revolution
TidesTides
• 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
TidesTides
Earth’s SeasonsEarth’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
EquinoxesEquinoxes
• 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
SolsticesSolsticesSummer 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…..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 Angle of Sunlight (or Insolation)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