Earth, Moon, and Sun System

Earth’s Magnetic Field Earth has a magnetic field that protects us from harmful radiation from the sun.

Earth’s Magnetic Field Earth’s magnetic field is: Concentrated at two ends of an imaginary magnetic axis running from Earth’s north magnetic pole to its south. Tilted about 11.5 degrees from the geographic axis

Earth’s Magnetic Field Changes slowly over time. Called the magnetosphere Responsible for auroras.

Earth’s Magnetic Field What are auroras? The magnetosphere deflects harmful radiation from the Sun, a stream of particles called solar wind.

Earth’s Magnetic Field What are auroras? These particles from the Sun produce charged particles in Earth’s atmosphere that spiral along Earth’s magnetic field lines towards the magnetic poles and collide with atoms in the atmosphere. These collisions cause atoms to emit light.

Earth Orbits the Sun Earth’s orbit is slightly elliptical. An ellipse is like a slightly flattened circle or egg-shaped.

Earth As a Planet Earth is the only planet with characteristics that make it possible for life as we know it to survive.

Earth as a Planet Earth resembles Venus more than any other planet in: Size Both have atmospheres with carbon dioxide

Time and Seasons Humans have used movements of Earth, the Moon, and the Sun to measure time for thousands of years. Earth makes a complete rotational turn once in about 24 hours. Earth’s actual rotation is 23 hours, 56 minutes, and 4 seconds.

Time and Seasons Revolution Measures Years The time that it takes to make a complete rotation or orbit around the sun is 365 days which is our Earth year.

Time and Seasons Why do seasons change? They change primarily due to the tilt of the Earth on its axis in relationship to the sun (changes in the angle of sunlight hitting certain parts of Earth). In short, Earth’s seasons are influenced by Earth’s rotation, revolution, and tilt of its axis.

Time and Seasons Why do we have more daylight in summer than winter? The hemisphere of the Earth that is tilted toward the Sun receives more hours of daylight…another reason it is warmer in the summer.

Time and Seasons Equinoxes and Solstices Two times a year, the sun is directly over the Earth’s equator. This is called an equinox.

Time and Seasons During an equinox, the number of daylight hours equals the number of nighttime hours all over the world. These occur around March 20th or 21st, and September 22nd or 23rd.

Time and Seasons The solstice is the point at which the Sun reaches its greatest distance, north or south of the equator, and it appears to “stand”, or stop moving. This occurs on June 21st or 22nd, and December 21st or 22nd. During summer solstice, there are more hours of daylight than during any other day of the year, and during winter solstice, it is the shortest daylight day of the year. http://www.materialworlds.com/sims/SolarSystem/FourSeasons1View/install.html

Movement of the Moon It takes 27.3 days for the Moon to revolve once around earth and two more days for the Moon to line up with Earth and the Sun again, thus a complete lunar phase takes 29.5 days (a synodic month)

Movement of the Moon The same side of the moon always appears toward Earth because it takes 27.3 days to rotate once on its axis, the same amount of time it takes to revolve once around Earth.

How does the moon affect Earth? TIDES Tides are caused by a giant wave produced by the gravitational pulls of the Sun and the Moon. The actual wave is only 1-2 m, but has a wavelength of thousands of kilometers.

How does the moon affect Earth? TIDES Even though it is smaller than the sun, the moon has a greater effect on tides than the sun because it is closer.

How does the moon affect Earth? TIDES When the moon and sun line up, high tides are much higher and low tides are much lower. This is called a spring tide.

How does the moon affect Earth? TIDES When the moon and sun are at right angles to each other, the high tide is not as high and the low tide is not as low, producing a neap tide.

Phases of the Moon The moon “shines” because it is reflecting sunlight from its surface. Moon phases are the changing appearances of the Moon as seen from Earth.

Phases of the Moon New Moon Moon is between the Earth and the Sun. Cannot be seen (except during a special alignment)

Phases of the Moon Waxing Phases Lighted portion that we see appears to be larger each night. Said to be in the waxing gibbous phase until it reaches the full moon phase.

Phases of the Moon Waning Phases The lighted portion that we see appears to be smaller each night.

Eclipses Solar Eclipse Occurs when the moon moves directly between the Sun and Earth and casts a shadow on part of Earth. The darkest portion of the Moon’s shadow is called the umbra.

Eclipses Solar Eclipse The lighter shadow cast on Earth’s surface is called the penumbra.

Lunar Eclipse Occurs when Earth’s shadow falls on the moon. Eclipses Lunar Eclipse Occurs when Earth’s shadow falls on the moon.

Moon’s Surface Craters, Maria, and Mountains Many depressions (craters) were formed by meteorites, asteroids, and comets striking the surface of the moon.

Moon’s Surface Maria Dark-colored relatively flat regions on the Moon’s surface. Regolith Debris on the Moon’s surface.

Moon’s Interior The moon’s interior is believed to have a crust, upper mantle, lower mantle, and a core.

Moon’s Origin Capture Theory The moon was captured by Earth’s gravity. Binary Accretion Theory The moon condensed from the same material that formed the Earth.

Moon’s Origin Fission Theory A glob of molten material was ejected from Earth while it was still in its molten stage.

Moon’s Origin Giant Impact Theory A Mars sized object collided with Earth. The cores of the 2 bodies combined and settled toward the center of the larger object. Gas and debris condensed into a large mass forming the moon.