3.2 Astronomy

3.2 ASTRONOMY Rotation - the circular motion of an object when it turns around an internal axis about a point in space. Revolution - When an object circles an external axis. Circumpolar - stars that reside above the horizon, which means that they never or rise. Constellations - a group of stars that from figures in the sky, Polaris - the North Star; a star which indicates the north and almost always holds its position while the northern skies turns around it. Foucault pendulum - a pendulum that swings in a constant direction that changes according to Earth’s rotation. Apparent motion - when viewing celestial objects from Earth, it appears as though the objects are moving against the typical direction. GPS - Global Positioning System, uses satellites in space to find your phone, cars, e.g. Heliocentric - the theory/belief that the Sun is the center of the universe. Geocentric - the theory/belief that the Earth is the center of the universe. Horizon - the skyline that separates the Earth from the sky. Zenith - the imaginary point which is above a particular location on the celestial sphere Tilt - to be learning towards one side, like how Earth has a 23.5-degree tilt on its axis. Axis - an imaginary line that passes through Earth's center and the North and South poles. Duration of insolation - the amount of daylight hours. Tropic of cancer - 23.5 degrees north, latitude Tropic of Capricorn - 23.5 degrees south, longitude. Angle of insolation - the angle at which the Sun’s ray strikes Earth. Ellipse - an elongated circle, or oval shape of an orbit. Eclipse - the partial or total blocking of one object in space by another. Major axis - the longest diameter of an ellipse. Minor axis - the shortest diameter of an ellipse. Gravity - the force of attraction between masses in the universe. Equinox - the first day of spring or fall when the sun is directly over the equator. Solstice - the time that Earth's poles are pointing at the greatest angle towards or away from the Sun. Tide - the periodic rise and fall of the sea level due to the gravitational pull caused by the moon. Earth’s Motion ☆ Rotation refers to Earth’s circular motion or spinning that causes day and night. ☆ The rate of rotation determines how many degrees the stars and sun will move across the sky per hour. ☆ Rotation takes place from WEST to EAST (west is EARLIER and east is LATER) ☆ Earth rotates 15 degrees each hour, which creates the 24 time zones. Each time zone consists of 15 degrees. ☆ Revolution refers to the movement of Earth around the Sun on its axis ☆ Also called orbiting ☆ Revolution is responsible for years, seasons, and constellations. ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ Time Zones on Earth: Solar noon is the time of the day when the Sun is at its highest point in the sky for an observer. Longitude lines separate time zones and measure East and West hemispheres. The Prime Meridian is the 0-degree longitude that separates the East and West hemispheres. The International Date Line is located at 180 degrees and marks the beginning of a new day. When the sun shines directly on the Tropic of Cancer (June 21) it marks the first day of summer, or summer solstice, which is also the longest day. When the sun shines directly on the Tropic of Capricorn (December 21) it marks the first day of winter, or the winter solstice, which is also the longest day. September 21 = Fall March 21= Spring Longitude & Latitude: Latitude and longitude is a coordinate “address system” to determine the location of any point on Earth. 1. Latitude - Lines that measure North or South - Also called parallels - Measures from 0 degrees (equator) to 90 degrees. 2. - Longitude Lines that measure East or West of the Prime Meridian Called meridians at 15 degrees apart These lines establish time zones. Moon ☆ ☆ ☆ ☆ Why do we always see the same side of the Moon? The period of rotation and the period of revolution are the same: 29.5 days. So, one rotation is one day and one revolution is one year. The moon has no atmosphere so the skies apply black. The moon is always 50% illuminated by the Sun, but we do not always see that amount lit from Earth because the Moon revolves around the Earth. ☆ The moon rises about 50 minutes later each day since it has moved about 13 degrees since its previous moonrise, delaying the moonrise the following day. Waning - the moon is getting lighter every night; getting closer to a full moon. Waxing - the moon is getting darker; getting closer to a new moon. Crescent - the moon is lit by less than half. Gibbous - the moon is lit by more than half. ☆ The Sun and Moon’s gravitational pull causes the tides. ☆ Most locations experience two high and low tides each day. ☆ Spring tides have a greater tidal range than neap tides because the Sun, Earth, and Moon are aligned. ☆ Spring tides occur during the new and full moon and have the largest difference in water level between high and low tides. ☆ Neap tides occur during the 1st and 3rd quarter and have the smallest difference in water level between high and low tides. ☆ Tides are the highest during a full moon.