Solar System Formation & the Earth

Name the degree of latitude for each of the following lines and points: 1. Equator = 0 2. North Pole = 90° N 3. South Pole = 90° S 4. Tilt of the Earth = 23.5° 5. Tropic of Cancer = 23.5° N 6. Tropic of Capricorn = 23.5° S 7. Arctic Circle = 66.5° N 8. Antarctic Circle = 66.5° S

Solar System Formation Nebular hypothesis 4.6 billion years ago Slowly spinning cloud of dust and gas Objects separated based on density Solar system looked like Saturn with rings Matter collected together as planets As matter condensed, rate of spin increased

Earth’s Formation Started off as a big ball of melted rock The crust cooled to form land Gasses escaped to form the atmosphere The interior is still cooling. How do we know?

Earth’s Density Earth’s average density = 5.5 g/cm 3 Earth’s average crustal density = 2.8 g/cm 3 *Helps to prove that Earth’s interior is more dense than its surface.

Density Effects Earth… Due to different densities Earth’s … interior is layered oceans are layered atmosphere is layered

Earth’s Size Diameter at the Equator = 12,756 km Diameter at the Equator = 12,756 km Diameter at the Poles = 12,714 km Diameter at the Poles = 12,714 km *A relatively small difference effects the shape of the Earth.

Earth’s Shape Because the Earth is spinning, it is not perfectly round. It is an oblate sphereoid. Wider at the equator and shorter at the poles. Does the Earth look round?

Earth’s Interior Inner core solid iron, nickel, sulfur. Why solid? Outer core melted iron, nickel, sulfur Mantle plastic-y iron and silicon; SOLID but acts like a liquid because it’s under extreme pressures.

Earth’s Interior Crust THIN layer not very dense rocks Silicon and oxygen Continents thicker than ocean crust Lithosphere – crust and top of the mantle the “plates” of plate tectonics Asthenosphere – thin layer of the mantle that the lithosphere floats on

How Do We Know? Earthquake

How deep have we drilled?

CHIKYU RESEARCH VESSEL Deep ocean drilling ship current maximum depth: 23,000 ft Deepest mines Tiber well oil well in gulf, by Texas 35,000 ft rock + 4,130 ft ocean =10.7 km of rock +1.2 km ocean

What causes the magnetic field? Because the core is made of mostly a spinning ball of iron.

Rotation What is rotation? Spinning on an axis How long does it take Earth to make one rotation? 1 day 24 hours

Effects of Rotation Day/Night cycle. Why is the line on the right image curved? How do you know these are false color images?

Effects of Rotation Time Zones 24 time zones Each time zone ≈ 15° of longitude 360 ° /24 = 15 °

Effects of Rotation Coriolis Effect Objects traveling over the Earth’s surface do not follow a straight path They are deflected

Evidence for Rotation Stars move through the night 45 minute camera exposure

Evidence for Rotation Foucault’s Pendulum In the morning, the pendulum is swung in a North-South direction. Pegs get knocked down every minutes, seemingly changing directions. By following the path of the pendulum, we “see” the Earth’s rotation.By following the path of the pendulum, we “see” the Earth’s rotation. Pendulum swings on the same path (inertia) and the Earth rotates beneath it.

Revolution What is revolution? One object orbiting another How long does it take for the Earth to go through one revolution? days

Revolution What happens with the.24 of a day? Hint: It happens every 4 years! 0.24 roughly equals ¼ ¼ x 4 = 1 day Every four years, we have “leap year” We add a day to the month of February to “make up” the day. What would happen if we didn’t? What about the 0.01 difference?

Evidence for Revolution Changing constellations and positions of stars through the year.

Evidence for Revolution Parallax – the apparent shift in positions due to differences in distance. (Pencil Demo)

Shape of Earth’s Orbit NOT a “circle” or “oval” Ellipse What’s the difference?

Shape of Earth’s Orbit Avg dist. to Sun = 150 million km closest to the Sun: January 2 farthest from the Sun: July 4 YES: the Sun is FARTHER away during the summer and CLOSER during the winter! The Earth’s distance to the Sun has NOTHING (well, very little) to do with the seasons!

Cause of Seasons The Earth’s tilt is 23.5 degrees to the perpendicular of the orbit of the Earth around the Sun. the Sun’s rays hit more directly at different times of the year.

Leads to long term climate cycles

How might you notice this at home?

Sun Angle also changes with latitude

Seasons

Seasons Chart Start of Season Summer Solstice Winter Solstice Vernal/Autumnal Equinox Date(s) Lat. Where Sun is overhead at noon 66.5 N (Artic Circle) 66.5 S (Antarctic Circle)

Seasons Chart Start of Season Summer Solstice Winter Solstice Vernal/Autumnal Equinox Date(s) 6/21 Lat. Where Sun is overhead at noon 66.5 N (Artic Circle) 66.5 S (Antarctic Circle)

Seasons Chart Start of Season Summer Solstice Winter Solstice Vernal/Autumnal Equinox Date(s) 6/21 Lat. Where Sun is overhead at noon 23.5 N Tropic of Cancer 66.5 N (Artic Circle) 66.5 S (Antarctic Circle)

Seasons Chart Start of Season Summer Solstice Winter Solstice Vernal/Autumnal Equinox Date(s) 6/21 Lat. Where Sun is overhead at noon 23.5 N Tropic of Cancer 66.5 N (Artic Circle) 24 hrs of sunlight 66.5 S (Antarctic Circle)

Seasons Chart Start of Season Summer Solstice Winter Solstice Vernal/Autumnal Equinox Date(s) 6/21 Lat. Where Sun is overhead at noon 23.5 N Tropic of Cancer 66.5 N (Artic Circle) 24 hrs of sunlight 66.5 S (Antarctic Circle) 24 hrs of darkness

Seasons Chart Start of Season Summer Solstice Winter Solstice Vernal/Autumnal Equinox Date(s) 6/2112/21 Lat. Where Sun is overhead at noon 23.5 N Tropic of Cancer 66.5 N (Artic Circle) 24 hrs of sunlight 66.5 S (Antarctic Circle) 24 hrs of darkness

Seasons Chart Start of Season Summer Solstice Winter Solstice Vernal/Autumnal Equinox Date(s) 6/2112/21 Lat. Where Sun is overhead at noon 23.5 N Tropic of Cancer 23.5 S Tropic of Capricorn 66.5 N (Artic Circle) 24 hrs of sunlight 66.5 S (Antarctic Circle) 24 hrs of darkness

Seasons Chart Start of Season Summer Solstice Winter Solstice Vernal/Autumnal Equinox Date(s) 6/2112/21 Lat. Where Sun is overhead at noon 23.5 N Tropic of Cancer 23.5 S Tropic of Capricorn 66.5 N (Artic Circle) 24 hrs of sunlight 24 hrs of darkness 66.5 S (Antarctic Circle) 24 hrs of darkness 24 hrs of sunlight

Seasons Chart Start of Season Summer Solstice Winter Solstice Vernal/Autumnal Equinox Date(s) 6/2112/21March 21/Sept 21 Lat. Where Sun is overhead at noon 23.5 N Tropic of Cancer 23.5 S Tropic of Capricorn 66.5 N (Artic Circle) 24 hrs of sunlight 24 hrs of darkness 66.5 S (Antarctic Circle) 24 hrs of darkness 24 hrs of sunlight

Seasons Chart Start of Season Summer Solstice Winter Solstice Vernal/Autumnal Equinox Date(s) 6/2112/21March 21/Sept 21 Lat. Where Sun is overhead at noon 23.5 N Tropic of Cancer 23.5 S Tropic of Capricorn Equator 66.5 N (Artic Circle) 24 hrs of sunlight 24 hrs of darkness 66.5 S (Antarctic Circle) 24 hrs of darkness 24 hrs of sunlight

Seasons Chart Start of Season Summer Solstice Winter Solstice Vernal/Autumnal Equinox Date(s) 6/2112/21March 21/Sept 21 Lat. Where Sun is overhead at noon 23.5 N Tropic of Cancer 23.5 S Tropic of Capricorn Equator 66.5 N (Artic Circle) 24 hrs of sunlight 24 hrs of darkness Whole Earth has 12 hrs of daylight and 12 hrs of darkness 66.5 S (Antarctic Circle) 24 hrs of darkness 24 hrs of sunlight

Summer Solstice (6/21) The Sun’s rays are most direct; longest day of the year 23.5 N – Tropic of Cancer Sun’s rays are directly overhead at noon 66.5 N – Arctic Circle all points north have 24 hours of sunlight 66.5 S – Antarctic Circle all points south have 24 hours of night

Winter Solstice (12/21) the Sun’s rays are indirect: shortest day of the year 23.5 S – Tropic of Capricorn Sun is directly overhead at noon 66.5 N – 24 hours of darkness 66.5 S – 24 hours of daylight

Equinox Sun’s is directly overhead at noon at the equator 12 hours of daylight, 12 hours of darkness Vernal equinox: March 21 Autumnal equinox: September 22