Earth’s relative motion Motion in the Universe Earth’s relative motion

Daily Review Kepler’s 1st law states that planetary orbits are _________________ shapes? Kepler’s 2nd law states that 2 equal intervals of time an imaginary line connecting a planet and the sun will sweep an equal amount of ___________? Kepler’s third law states that the innermost planets orbit ______________________ than the outermost planets. Rotation is the earth spinning on it’s _________________. One trip around the ______________ is called a revolution.

Essential Standard EEn.1.1 Explain the Earth’s role as a body in space. EEn.1.1.1 Explain the Earth’s motion through space, including precession, nutation, the barycenter, and its path about the galaxy. Explain relative motion of the Earth in the solar system, the solar system in the galaxy, and the galaxy in the universe—including the expanding nature of the universe; Orbital motion (Earth around the Sun- once/year, seasons depend upon an approximate 23.5 degree tilt); Rotation around our axis (day/night,)

Essential Question How do galaxies and planets move in the universe?

Motions of Earth Rotation Revolution Precession Turning or spinning of a body on its axis Revolution Motion of a body along a path around some point in space Precession Slight movement of Earth’s axis 26,000 years

Rotation Results in day and night 24 hours 1,667 km/hr (1,036 mi/hr) Prove Earth is Rotating? OK! Rotation Results in day and night 24 hours 1,667 km/hr (1,036 mi/hr)

revolution Earth moves around the sun in an elliptical orbit Speeds around 107,000 km/hr (66,500 mph) Average distance is 150 million kilometers Perihelion is the point where earth is closest to the sun Aphelion is the point where earth is farthest from the sun

Earth’s axis and Seasons Earth's Seasons Earth’s axis and Seasons Earth’s axis is tilted about 23.5º on its axis This tilt brings the sun 23.5º south of the equator on the winter solstace This tilt bring the sun 23.5º north of the equator on the summer solstace

Precession and polar shift Direction which earth’s axis points changes very slowly over time without a change in tilt Takes about 26,000 years to complete one period Currently the axis points toward Polaris making it the North Star, in 14,000 years Vega will be the North Star.

Earth's not orbiting the sun?! Earth-Sun Motion Earth accompanies the sun as the entire solar system speeds toward a distant star, Vega The sun revolves around the galaxy Over 230 million years At 250 km/sec Now Earth is approaching our nearest galactic neighbor, Andromeda

Motions of the Earth-moon system Earth’s only natural satellite Orbit’s Earth in one month When viewed from the North Pole, the orbit is counterclockwise Average distance is 384,401 kilometers Point close to the Earth is Perigee Point farthest from Earth is Apogee

Phases of the Moon Phases are the amount of moon that appears lit supermoon Phases are the amount of moon that appears lit Half of the moon is always illuminated Phases result from the motion of the moon and the sunlight reflected from its surface Every 29.5 days

Tides (pg 458) Daily elevation changes of the ocean surface. Rhythmic tidal mystery bay of fundy Daily elevation changes of the ocean surface. Rhythmic Caused by gravitational pull of the moon Atmosphere and ocean are fluids and free to move due to this force. The sun is further away resulting in less tug

Nutation The moon pulls on Earth and Earth pulls on the moon gyroscope demo The moon pulls on Earth and Earth pulls on the moon This pull causes the Earth to wobble on its axis by about ½ a degree. Changing in the tilt of the Earth’s axis How does this differ from precession?

Barycenter barycenter animation barycenter Point between 2 or more objects where they balance each other Point where 2 celestial bodies orbit each other

More Barycenter When a moon orbits a planet or a planet orbits a star, both are actually orbiting a point outside the center of the larger body. The moon and earth actually orbit a spot about 1,710 km below earth’s surface.

Earth’s shape

Earth’s shape Not a true sphere Called an oblate spheroid, geoid, or ellipsoid

Circumference and diameter Not equal throughout Poles are squished making a bulge at the equator Diameter and circumference are greater at the equator than at the poles.

Why? Earth’s rotation and gravity Gravity pulls on the mass causing it to contract Rotation causes earth to flatten due to centrifugal force The force that causes objects to move outward, away from the center of gravity We call this the coriolis effect coriolis effect

Local Topography Topography- study of surface shape and feature On a global scale this difference is very small Mt. Everest is about 8,850 m above sea level The Mariana Trench is about 10,900 m below sea level The difference is only about 19,000 m or 12 mi