Earth• Rotation- Earth spinning on its axis – Axis- imaginary line that passes through Earth’s center from north to south poles – Rotation causes day and night (clockwise- east to west) – Takes Earth 24 hours (1 day) to rotate once on its axis
Earth• Revolution- movement of one object around another object – One complete revolution around the sun= 1 year – Earth’s path as it revolves around the sun; orbit which is elliptical (oval) – Orbit- the path an object takes around another during a revolution
Earth• Calendar – Earth’s orbit around the sun takes about 365 ¼ days (365.25 days) or 1 year – Leap year every 4 years we make up the extra day. February has 29 days in leap year. (4 x ¼ =1) – The time between one full moon and the next is about 29 ¼ days (12 x 29.25 = 351.0 days)
Seasonso Latitude- Distance north or south from the equator; measured in degrees Equator gets more solar energy (radiation)- straight sun rays Higher latitudes are colder- angled sun rays
Seasons• Earth’s tilt is 23.5˚ North or South making the axis tilt toward the sun part of the year and away from the sun the other part; always points toward the north star• Seasons are determined by how light hits Earth
Seasons• When north is tilted toward the sun, Northern Hemisphere has summer, Southern has winter• When Northern Hemisphere is tilted away from sun, has winter, Southern has summer• Solstice- the two days of the year when the sun is directly overhead
Seasons• Summer- Northern Hemisphere is tilted toward the sun; more hours of daylight – June- Summer solstice, longest day of the year, June 21, first day of summer
Seasons• Winter- Northern hemisphere tilted away from sun, less hours of day light – December- Winter solstice; shortest day of the year, December 21, first day of winter
Seasons• Equinox- equal day and night, sun directly above the equator;• March 21- Vernal equinox, spring• September 23- Autumnal equinox, fall
Moon• The moon is a satellite of Earth: it revolves around the Earth• Moon has almost no atmosphere• Surface- detailed study of moon rocks gathered by astronauts – Craters- cover much of the moon’s surface – Highlands- mountains – Maria- once flooded with molten material; appear as dark, flat areas
Moon• The position of the moon, Earth, and the sun cause the phases of the moon, eclipses, and tides.• The moon’s movement – Moon’s revolution is about 27.3 days – Moon’s rotation is about 27.3 days • The moon’s “year” and “day” take the same amount of time. • The “far side” of the moon always faces away from Earth; you never see it.
Moon• Gravitational pull- the moon and Earth both pull on each other• Moon’s density is about the same density as Earth’s outer layers• Formation- Collision Theory- states that about 4.5 billion years ago a large object collided with Earth; material from this collision was thrown into orbit around Earth, eventually forming the moon.
Moon Phases• Phases: the different shapes of the moon that we see from Earth• What causes the phases? – The moon reflects light from the sun; half of the moon is always lit, and half is dark. – The amount of sunlit side of the moon that faces Earth – As the moon revolves around Earth, the light side of the moon rotates around, changing the amount we see from Earth.
Moon Phases• Full- the entire lit side of the moon is seen• Gibbous- over half of the lit side is seen• Quarter- you can only see half of the lit side of the moon (1st and 3rd/Last)• Crescent- less than half of the lit side is seen; thumbnail shaped• New- the entire dark side is seen
Moon PhasesIt takes about 29.5 days from one new moon to the next : 1 complete cycle• Waxing- the amount of lit side of the moon seen is increasing• Waning- the amount of lit side of the moon seen is decreasing• http://sunshine.chpc.utah.edu/labs/moon/lunar_phase3.swf• http://youtu.be/2aFGNGEcDOk http://youtu.be/3PycZtfns_U
Tides• Tide- the daily rise and fall of Earth’s coastlines• Tidal bulge- the moon’s gravitational pull on the water at the point closest to the moon, and on the opposite side creates a bulge of water; high tide• Low tide- the points between the high tide points have low tide.• There are 4 tides a day; 2 high and 2 low
Tides• Spring tide- at the new and full moons, the sun and moon are lined up. Their combined gravitational pull creates the biggest difference between high and low tides.• Neap tide- at the 1st and 3rd quarters of the moon, the sun and moon pull at right angles to each other. This makes the least difference between the high and low tides.
EclipsesWhen the moon’s shadow hits Earth or the Earth’s shadow hits the moon• Solar Eclipse- the moon passes between Earth and the sun casting a shadow on the Earth; a new moon in which the moon blocks the view of the sun.• Lunar Eclipse- when the Earth passes between the sun and the moon
Eclipses Lunar EclipseUmbra - darkest part of a shadowPenumbra- part of the shadow surrounding the darkest part
Big Bang Theory• The theory that the universe began with a very large explosion, distributing thermal energy and radiation throughout the universe; cosmic background radiation; one of many theories/beliefs.• Scientists discovered the universe is expanding; they began to think there had to be a starting point, where all of the matter in the universe was contained in a small space.
Earth in the Universe
Geocentric• Astronomy- the study of the moon, stars, and other objects in space• Ptolelmy: 140 CE; Greek astronomer who, based on careful mathematical calculations, thought that the Earth was at the center of the universe and the sun and other planets revolved around the Earth.
Heliocentric• Copernicus: 1543; Polish astronomer who came up with the theory that the sun was at the center of the universe, and all of the planets orbited the sun.• Kepler: 1609; Danish; announced that the planets orbited the sun in elliptical orbits.
Gravity• Galileo: 1609; one of the first people to use a telescope to observe objects in the sky, especially the moon.• Discovered craters and mountains on the Earth’s moon.• Isaac Newton: 1687; Laws of Gravity – What goes up must come down – All objects in the universe attract each other through gravitational force
Sun• Energy from the sun lights and heats Earth’s surface• The only star in our solar system• Is a yellow Dwarf star• The corona forms the sun’s outer atmosphere• The photosphere is the visible part of the sun that we see from Earth.• The core is where the sun’s energy is produced.
Sun• Sunspots: cooler dark spots that form in the photosphere when convection activity slows down. Caused by magnetic fields.• Solar flares: regions of very high temperature and brightness. Also caused by magnetic fields. – May erupt sending streams of electrically charged particles into the solar system