THE EARTH- MOON-SUN SYSTEM CHAP 22

MOTIONS OF EARTH Rotation – turning or spinning of a body on its axis Revolution – the motion of a body (planet) along a path around some point in space. Precession – slight movement of Earth’s axis (takes 26,000 years) Barycenter – the point around which two object orbit

MOTIONS OF EARTH Rotation Causes Day and Night Revolution Elliptical orbit around the Sun Avg. distance from sun 150 million km (varies because the path is an ellipse) Perihelion Earth is closest to the sun (Jan 3) 147 million km away Aphelion Earth is farthest from the sun (July 4) 152 million km away

MOTIONS OF EARTH Seasons Summer - The tilt of the Earth means the Earth will lean towards the Sun Winter – The Earth will lean away from the Sun

MOTIONS OF EARTH Precession Very slow motion Axis maintains the same angle of tilt Direction the axis points changes slowly North Star Polaris – where the axis points now Vega – where the axis will point in years Polaris – where the axis will point in years

MOTIONS OF EARTH Nutation Daily variations in Earth’s rotation caused by the torque that the Moon and Sun exert on the planet

MOTIONS OF EARTH Solar system is moving towards the star Vega The Sun, like other stars, revolves around the galaxy (takes 250 million years at 250km/second) Galaxies are also moving – Milky Way Galaxy is on a collision course with the Andromeda Galaxy

MOTIONS OF MOON Moon Orbit 27 days Elliptical orbit Perigee – moon is closest to Earth Apogee – moon is farthest from Earth

MOTIONS OF THE MOON Phases of the Moon Change in the amount of the moon that appears lit. Caused by the motion of the moon and the sunlight that is reflected from its surface. Takes 29 Days to cycle through phases Takes 27 Days to rotate around the Earth This causes parts of the moon to remain in the sunlight/dark for 2 weeks at a time. Temps range from 127°C (Daylight) to -173°C (Dark side)

MOTIONS OF THE MOON The Moon’s gravitational force pulls on water in the oceans creating a bulge. The Sun’s gravitational force pulls on water in the oceans creating a bulge on the opposite side.

ECLIPSES Solar Eclipse When the moon moves in line directly between Earth and the sun (casts a shadow on Earth) Lunar Eclipse When the moon passes through Earth’s shadow. April 2014 Padre Island The Earth’s atmosphere bends and transmits long-wavelength light (red) into its shadow.

ECLIPSES Why don’t they happen all of the time? The Moon’s orbit is on a slightly different plane than the Earth and Sun. Most of the time the shadow of the moon misses Earth (solar eclipse) Most of the time the shadow of the Earth misses the moon (lunar eclipse) During a new-moon or full-moon phase the moon’s orbit must cross the plane of the ecliptic for an eclipse to take place. (This usually happens twice a year and consist of (2) solar and (2) lunar eclipses.)

ECLIPSES Who can see them? A total lunar eclipse can last up to 4 hours and can be seen by anyone on the side of the Earth facing the moon. A total solar eclipse will only last 7 minutes and the moon will cast a shadow 275km in diameter that can be seen by anyone in the region.

THE SPACE RACE A Cold War competition between the Soviet Union (USSR) and the United States (US) for supremacy in space. ( ) ending with the Apollo 11 Moon landing Originated in Nazi Germany (1930s) with the invention of ballistic missiles. Sputnik (Russian for “traveler”) – world’s 1 st artificial satellite (U.S. was afraid nuclear missiles would be next. Luna 2 (Russian) – 1 st space probe to hit the moon. Yuri Gagarin (Russian) – 1 st person to orbit Earth Apollo 8 (U.S.) – 1 st manned space mission to orbit the moon. Apollo 11 (U.S.) – 1 st lunar landing, Armstrong became the 1 st man to walk on the moon’s surface and ended the race.

EARTH’S MOON Most of our current knowledge about the Moon resulted from the Apollo missions. 6 Apollo spacecraft landed on the moon between Key Facts: Diameter of the Moon (3475km) is 1/4 of Earth’s (12,756km) The gravitational attraction at the lunar surface is 1/6 of Earth’s (150lb person on the Moon would weigh 25lb) Density is 3.3 times that of water. Comparable to mantle rocks found on Earth.

EARTH’S MOON Lunar Surface Galileo was the first to observe surface features of the Moon. (Noticed dark lowlands, and bright highlands.) The Moon is unprotected by an atmosphere and is constantly bombarded by particles from space. Craters – Round depressions in the surface of the moon. Most are produced by the impact of rapidly moving debris. Highlands – mountain ranges Maria – ancient beds of basaltic lava, originated when asteroids punctured the lunar surface, letting magma bleed out. Riles – long channels (valleys or trenches) Regolith – soil like layer (gray debris from meteorites Composed of igneous rocks, glass beads, and fine lunar dust.

EARTH’S MOON How was the Moon formed? The most widely accepted model for the origin of the moon is: When the solar system was forming, a body the size of Mars impacted the Earth. This impact liquefied Earth’s surface and ejected huge quantities of crustal and mantle rock. A portion of this debris entered Earth’s orbit and later combined to form the Moon. Evidence Most of the Moon is made up of crust and mantle material Ejected material would have remained in orbit long enough to have lost water. Higher the crater density, Older the surface

THE SOLAR SYSTEM 99.85% of the mass of our solar system is contained within the Sun. 0.15% of the remaining mass make up everything else (Planets). All planets move in the same direction in an elliptical orbit. Mercury – fastest orbit (48km/second) Neptune – slowest orbit (6km/second)

THE PLANETS Terrestrial Planets – (Mercury, Venus, Earth, and Mars) relatively small and rocky. Jovian Planets – (Jupiter, Saturn, Uranus, and Neptune) are huge gas giants. Differences: Size (Jovian planets are much larger) Density Chemical Makeup Rate of Rotation

THE PLANETS The Interiors of the Planets are made up of 3 substances: 1.The Gases – hydrogen and helium (melting point -273°C or 0 Kelvin) 2.The Rocks – mainly silicate minerals and metallic iron (melting points above 700°C) 3.The Ices – ammonia, methane, carbon dioxide, and water (lower melting points, ex. Water has a melting point at 0° C)

THE PLANETS Atmosphere Jovian planets have a very thick atmosphere hydrogen, helium, methane, and ammonia Large surface gravity Terrestrial planets have a very thin atmosphere Gases can easily escape our atmosphere Small surface gravity Formation of the Solar System Nebular Theory – The sun and planets formed from a rotating disk of dust and gases

THE PLANETS Using your textbook and notebook paper create a chart. This should consist of two columns (Planet and Facts) Give information about Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. Using this information, write a paragraph detailing which planet humans should move to in the future if Earth becomes inhabitable. Turn in your paragraph by the end of class.