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EARTH SCIENCE REGENTS REVIEW UNIT 4 – MOTIONS OF EARTH, MOON AND SUN 1) APPARENT MOTION OF CELESTIAL OBJECTS Most celestial objects appear to rise in the east and set in the west. (This is due to Earth’s rotation which rotates from WEST to EAST – Counterclockwise looking from the north pole). All the motion occurs at a rate of 15° per hour due to Earth’s rotation. THEREFORE EVERYTHING APPEARS TO RISE IN THE EAST AND SET IN THE WEST. 2) APPARENT DAILY MOTION OF THE STARS Polaris appears to be stationary due to the fact that it is directly above the North Pole. Stars that circle Polaris are called circumpolar stars. epod.usra.edu epod.usra.edu epod.usra.edu www.gettyimages. com epod.usra.edu 3) APPARENT MOTION OF PLANETS Over extended periods of time (weeks to months) planets appear to change position. (Ex. Retrograde motion – appears like the object is moving backward). Both planets move in a direct (eastward) motion around the Sun, but the planet with the inside (smaller) orbit moves faster than the planet on the outside (larger) orbit, and when it passes the slower-moving planet, each sees the other one as apparently moving backwards relative to its usual motion around the sky. In this "retrograde" motion, neither planet is actually moving backwards; it only appears that way, during the time that one laps the other. Cseligman.com ap.smu.ca THEORIES OF MOTION GEOCENTRIC MODEL Theory that the Earth was the center of the Universe.by Ptolemy (proved to be incorrect). www.amazing-space.stsci.edu HELIOCENTRIC THEORY Theory that the Sun is the center of the Universe by Copernicus. This model truly explained the motion of the planets. It verified that the planets orbit the sun in an elliptical orbit. (proved to be the center of our solar system). www.amazing-space.stsci.edu 4) ACTUAL MOTIONS OF THE EARTH A) Rotation B) Revolution A) EVIDENCE OF EARTH’S ROTATION Foucault Pendulum Free swinging pendulum that changes its path. The pendulum swings in a fixed direction in space, while the Earth rotates under the pendulum. sciencephoto.com Coriolis Effect The tendency of all particles of matter moving at Earth’s surface to be deflected or curved. (To the right in the northern hemisphere and to the left in the southern hemisphere). williamsclass.com B) EVIDENCE OF EARTH’S REVOLUTION Seasons change throughout the year. www.boqueteweather.com Different constellations are seen throughout the year. (a constellation is a group of stars that form a pattern – ex. (Big Dipper). lpi.usra.edu Changes in apparent diameter. addins.kwwl.com 5) LOCAL TIME (Time of Day) Every 15ºof longitude = 1 hour. (24 time zones). All places on the same longitude line have the same local time. Over the course of a whole year EVERY place on Earth averages out and receives the same amount of daylight hours (different intensity due to the angle of insolation). physicalgeography.net 6 PM NYS DEPT OF EDUCATION To determine the time of day just rotate the Earth counterclockwise. See what section the the point is about to move into. Do not move the day and night, just the point. Point “X” is just about to turn into the night therefore its is 6 PM. (This diagram shows that the terminator line (day and night) cuts through the North Pole. This is a HUGE clue that this is an EQUINOX !!!) 6) APPARENT MOTION OF THE SUN Appears to rise in the east and set in the west. 1. (In N.Y. in the summer the sun rises NORTH OF DUE EAST AND SETS NORTH OF DUE WEST. 2. In the winter the sun rises SOUTH OF DUE EAST AND SETS SOUTH OF DUE WEST). Seasons are caused by the TILT OF THE EARTH. Distance of the Earth to the Sun has no effect on seasons. The Earth is closest to the Sun on Jan.3rd (perihelion) and furthest on July 4th (aphelion). Solar Noon – When the sun reaches its highest position in the sky. 1. Everyday in New York at solar noon the sun is in the SOUTH. Insolation – Incoming Solar Radiation (sunlight). Angle of insolation - the angle at which the sunlight is striking a place. The higher the angle of insolation, the greater the intensity of the insolation will be. 1) The highest the angle of insolation can be is 90 degrees. This occurs when the sun is directly overhead. Which can only happen between the tropics. (23.5 *N (Tropic of Cancer) to 23.5 *S (Tropic of Capricorn). Duration of Insolation – This means how many daylight hours the sun is out. Intensity of Insolation – This means the strength of the radiation from the sun. Zenith - The point directly over your head. Shadows (Annually) – Your shadow is longest when the sun is lowest in the sky (Dec 21st). Your shadow is shortest when the sun is highest in the sky (June 21st). (This is at the time of solar noon). Shadows (Daily) – Your shadow is shortest at solar noon and longest at sunrise and sunset. Everyday in New York at solar noon the sun is in the SOUTH, therefore your shadow is always in the NORTH. CELESTIAL SPHERE KEY POINTS • CHECK OVER OBSERVERS HEAD - If the sun can be directly over your head then you MUST be standing at or between the Tropic of Cancer (23 1/2º North) and the Tropic of Capricorn (23 1/2º South). • CHECK WHERE SOLAR NOON IS – If the sun at SOLAR NOON is in the south then you are standing in the northern hemisphere. If the sun at SOLAR NOON is in the north then you are standing in the southern hemisphere. • CHECK YOUR DIRECTIONS – Look at south and north. Sometimes they both say NORTH (that means you are probably standing at the SOUTH POLE). Sometimes they both say SOUTH (that means you are probably standing at the NORTH POLE). • CHECK SUNRISE AND SUNSET – If the sun never sets that means you are standing either at the North or South Poles (or actually above the Arctic Circle 66 ½ degrees north or below the Antarctic Circle 66 ½ degrees south). • EQUINOX – If the sun rises directly DUE EAST and sets directly DUE WEST then it is an Equinox. Everyone on Earth has 12 hours of daylight and 12 hours of darkness. The sun is directly overhead at the Equator at solar noon. EQUINOX = EQUAL DAY AND NIGHT(EVERYBODY) = EQUATOR. • EVERYDAY OF THE YEAR THE EQUATOR HAS 12 HOURS OF DAYLIGHT AND 12 HOURS OF DARKNESS !!!!!!!!!!!!!!!!!!!!!!! AFTERNOON MORNING regentsearth.com NEW YORK STATE SOLAR NOON EQUINOX NYS DEPT OF EDUCATION 6) SEASONS Astronomical Causes of The Seasons 1. Tilt of the Earth’s Axis 23 1/2º with respect to a line perpendicular to the plane of its orbit of the sun. 2. Parallelism of Earth’s Axis Earth’s axis always points in the same direction in space. 3. Revolution of the Earth Around the Sun As Earth revolves around the sun, the direction of the Earth’s axis with respect to the sun varies because of its tilt and parallelism. www.boqueteweather.com NEW YORK STATE DATE (APPROXIM ATE) LATITUDE OF SUN'S DIRECT RAYS DIRECTION OF SUNRISE AND SUNSET ALTITUDE OF NOON SUN LENGTH OF DAYLIGHT Sept. 23 (Autumnal Equinox) Equator (0°) Rises due East Sets due West 48° 12 hours December 21 (Winter Solstice) Tropic of Capricorn (23.5°S) Rises in South East Sets in South West 24.5° (lowest) 8 hours (shortest day) March 21 (Vernal Equinox) Equator (0°) Rises due East Sets due West 48° 12 hours June 21 (Summer Solstice) Tropic of Cancer (23.5°N) Rises in North East Sets in North West 71.5° (highest) 16 hours ( longest day) 12 AND 12 24 HOURS OF DAYLIGHT 24 HOURS OF DARKNESS 12 AND 12 NYS DEPT OF EDUACTION NYS DEPT OF EDUCATION SEASONS KEY POINTS 1) Seasons are caused by the TILT OF THE EARTH. 2) Distance of the Earth to the Sun has no effect on seasons. 3) EVERYDAY OF THE YEAR THE EQUATOR HAS 12 HOURS OF DAYLIGHT AND 12 HOURS OF DARKNESS !! SUMMER The first day of summer ( June 21st) in the northern hemisphere is called the Summer Solstice. On the Summer Solstice the direct rays of the sun strike 23.5* N (The Tropic of Cancer). The sun rises NORTH of DUE EAST and sets NORTH of DUE WEST. The North Pole has 24 hours of daylight (actually everything above the arctic circle 66 ½ ° north) (South Pole has 24 hours of darkness (actually everything below the antarctic circle 66 ½ ° south). WINTER The first day of winter ( Dec. 21st) in the northern hemisphere is called the Winter Solstice. On the Winter Solstice the direct rays of the sun strike 23.5* S (The Tropic of Capricorn). The sun rises SOUTH of DUE EAST and sets SOUTH of DUE WEST. The North Pole has 24 hours of darkness (actually everything above the arctic circle 66 ½ ° north) (South Pole has 24 hours of daylight (actually everything below the antarctic circle 66 ½ ° south). SPRING AND FALL The first day of spring (Mar. 21st) in the northern hemisphere is called the Spring (Vernal) Equinox. The first day of fall (Sept. 23rd) is called the Fall (Autumnal) Equinox. On both equinoxes the direct rays of the sun strike the Equator. The sun rises directly DUE EAST and sets directly DUE WEST. Everyone on Earth receives 12 hours of daylight and 12 hours of darkness. If the Circle Of Illumination (separating day and night) passes right through the North and South Poles it is an Equinox !!!!! 7) MOTION OF THE MOON MOON PHASES The varying amounts of lighted moon as seen from earth are known as the moon’s phases. Waxing- means getting brighter. When the moon is in a waxing phase the light will be on the right side. Waning – is when less of the moon is becoming lit up. During the waning phases the left side of the moon is lit up. www.astro.virginia.edu PHASES OF THE MOON KEY POINTS We see phases of the moon because the MOON REVOLVES AROUND THE EARTH. The moon is ALWAYS half lit. The moon’s rotation (27.3 days ) is equal to the moon’s revolution around the Earth (27.3 days) (See E.S.R.T). This is called a sidereal month. They are synchronized. Therefore we always see the same side of the moon. It takes 29.5 days for a complete set of phases to occur (full moon to full moon). This is called a synodic month. This 2 day difference is because while the Moon is revolving around the Earth, the Earth is revolving around the sun. APOGEE – When the moon is at its furthest distance. PERIGEE – When the moon is at its closest distance. 8) TIDES - (caused primarily by the gravity of the moon and to a lesser degree the Sun). Tides are cyclic events and very predictable. There is a high tide approximately every 12 hours and 25 minutes. There is a low tide approximately every 12 hours and 25 minutes. There are 2 high tides and 2 low tides approximately every day (every 24 hours). The gravity of the moon pulls on Earth’s waters, creating a bulge of water on the side of the Earth closest to the moon. A tidal bulge forms on the opposite side of Earth as well. Spring Tide: When the Moon and the Sun are in line with the Earth, the gravitational pull is at its greatest causing very HIGH tides and very LOW tides. (FULL MOON AND NEW MOON phases). Neap Tide: When the Moon and the Earth are at 90 degree angles, the gravitational pull causes very average tides. (FIRST QUARTER AND THIRD QUARTER phases). http://www.jochemnet.de/fiu/tide2.jpg www.atlantickayaktours.com NOTE: Look for the MOON to find the high tide !!! 9) ECLIPSES An eclipse is an astronomical event that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it and the viewer. Note : We do not see an eclipse every month because the moon’s orbit is 5° tilted from Earth’s orbit !!!!!!!!!! UMBRA - Area where a total eclipse will occur. PENUMBRA – Area where a partial eclipse will occur. Solar Eclipse: When the Moon passes directly between the Earth and the Sun (NEW MOON phase). THREE TYPES: A. Total – The entire central portion of the Sun is blacked out. B. Partial – Only part of the Sun is blacked out. C. Annular – Only a small ring-like sliver of light is seen (Moon’s shadow does not reach the Earth). astroadventures.net/solar_eclipses.html Lunar Eclipse: When the Earth passes directly between the Moon and the Sun (FULL MOON phase). jrscience.wcp.muohio.edu