Concept 3: Longitude and earth’s rotation

http://www.educypedia.be/education/spacejavaearth.htm

I. Rotation is the spinning of an object on its axis (imaginary line through the poles and center). Our axis is from the north

pole through the south pole.1. Earth rotates at a rate of 360o in 24

hours, or 15o/hr.2. Rotation gives us our daily clock time

and day and night.

3. The earth's true rotation makes the sun 3. The earth's true rotation makes the sun appear to move. This is called the sun's appear to move. This is called the sun's apparent motion.apparent motion. (How fast does the sun (How fast does the sun appear to move each day? The stars? The appear to move each day? The stars? The moon?)moon?)

4. The sun appears to make an 4. The sun appears to make an arcarc through the sky at 15o/hr.through the sky at 15o/hr.

5. Because the earth really rotates from 5. Because the earth really rotates from west to eastwest to east, or counterclockwise, an , or counterclockwise, an observer observer (person standing in one spot on (person standing in one spot on earth)earth) anywhere on earth will see anywhere on earth will see sunrisesunrise (sun appears over horizon in morning)(sun appears over horizon in morning) towards the towards the east east and the and the sunsetsunset (disappear below the horizon in evening)(disappear below the horizon in evening) towards the towards the west.west.

6. Where the sun is during the rest of the 6. Where the sun is during the rest of the day depends on the observer's day depends on the observer's latitudelatitude

7. For New York State, the sun is always 7. For New York State, the sun is always in our in our southernsouthern sky during the day. sky during the day.

8. At 8. At solar noonsolar noon we say the sun has we say the sun has reached its highest point of the day. In reached its highest point of the day. In New York State, the sun is New York State, the sun is never ever never ever everever directly over our heads. directly over our heads. (In other (In other words, the sun is never at words, the sun is never at zenithzenith in New in New York State).York State).

9. Evidence of rotation:9. Evidence of rotation: a. a. Coriolis EffectCoriolis Effect is the is the deflectiondeflection of of

wind and water from straight line motion. wind and water from straight line motion. If the earth did not rotate, winds and water If the earth did not rotate, winds and water would not curve, they’d go in a straight would not curve, they’d go in a straight line.line.

http://www.classzone.com/books/earth_science/terc/content/visualizations/es190 http://www.classzone.com/books/earth_science/terc/content/visualizations/es190

4/es1904page01.cfm?chapter_no=visualization4/es1904page01.cfm?chapter_no=visualization

b. b. Foucault PendulumFoucault Pendulum appears to change appears to change direction in a circle during 24 hours. direction in a circle during 24 hours. However, the pendulum is actually going However, the pendulum is actually going in a straight line, it is the room that is in a straight line, it is the room that is rotating around it!!!rotating around it!!!

http://http://en.wikipedia.org/wiki/File:Pendule_de_Foucault.jpgen.wikipedia.org/wiki/File:Pendule_de_Foucault.jpg

c. Circumpolar constellationsc. Circumpolar constellations ( (always always above the horizonabove the horizon) move around Polaris ) move around Polaris during the night, giving the suggestion that during the night, giving the suggestion that we rotate.we rotate.

http://http://astro.unl.edu/classaction/loader.html?filenameastro.unl.edu/classaction/loader.html?filename=animations/=animations/ancientastro/dipperclock.swf&movieidancientastro/dipperclock.swf&movieid==dipperclock&widthdipperclock&width=850&height=340&version=6.0.0=850&height=340&version=6.0.0

Concept 3: Latitude, seasons Concept 3: Latitude, seasons and revolutionand revolution

1. Revolution1. Revolution is an object moving is an object moving continuously around another object due to continuously around another object due to gravity. gravity.

Earth is a Earth is a satellitesatellite (object revolving (object revolving around another object)around another object) of the sun. of the sun.

http://astro.unl.edu/classaction/loader.html?filename=animations/renaissance/http://astro.unl.edu/classaction/loader.html?filename=animations/renaissance/configurationssimulator.swf&movieid=configurationssimulator&width=850&height=680&version=6configurationssimulator.swf&movieid=configurationssimulator&width=850&height=680&version=6

.0.0.0.0 from classaction, planetary motion from classaction, planetary motion

Our Our orbitorbit (path around the sun)(path around the sun) takes us takes us one one yearyear or 365.25 days or 365.25 days (creating leap (creating leap year)year) at a rate of earth’s orbit is 3600/365 at a rate of earth’s orbit is 3600/365 days, or 1 0 /day. days, or 1 0 /day. Think: if our orbital Think: if our orbital radius is 92 million miles, how fast, in radius is 92 million miles, how fast, in miles/day, is our orbit? C=2miles/day, is our orbit? C=2r.)r.) Slide 24Slide 24

3. Ancient proofs of earth's 3. Ancient proofs of earth's revolution:revolution:

a. Seasonsa. Seasons (change in weather in a (change in weather in a cyclic cyclic fashion). fashion).

The size of the sun changes during the The size of the sun changes during the year. We are CLOSER to the sun in year. We are CLOSER to the sun in WINTERWINTER..

ParallaxParallax of stars: of stars:

closer stars seem to shift position relative closer stars seem to shift position relative to farther stars during the year.to farther stars during the year.

Seasonal constellationsSeasonal constellations: the : the constellations we see in fall are different constellations we see in fall are different than those we see in winter, spring, etc. than those we see in winter, spring, etc. The change is cyclicThe change is cyclic

http://phys23p.sl.psu.edu/phys_anim/astro/embederQ4.10060.htmlhttp://phys23p.sl.psu.edu/phys_anim/astro/embederQ4.10060.html earth orbit earth orbit and seasonal starsand seasonal stars

Models of the Solar System (and universe)Models of the Solar System (and universe)

http://http://astro.unl.edu/naap/ssm/ssm.htmlastro.unl.edu/naap/ssm/ssm.html Geocentric Model: earth-centered.Geocentric Model: earth-centered.

Heliocentric Model: sun-centered.Heliocentric Model: sun-centered.(Copernican model)(Copernican model)

retrograde motion and the ptolemic and retrograde motion and the ptolemic and Copernican explanations Copernican explanations http://alpha.lasalle.edu/~smithsc/Astronomy/retrograd.htmlhttp://alpha.lasalle.edu/~smithsc/Astronomy/retrograd.html

ptolemic retrograde ptolemic retrograde http://phys23p.sl.psu.edu/phys_anim/astro/embederQ4.20100.htmlhttp://phys23p.sl.psu.edu/phys_anim/astro/embederQ4.20100.html

copernican retrograde copernican retrograde http://phys23p.sl.psu.edu/phys_anim/astro/embederQ4.20300.htmlhttp://phys23p.sl.psu.edu/phys_anim/astro/embederQ4.20300.html

4. 4. Causes of Seasons;Causes of Seasons;

a. Tilt of axisa. Tilt of axis: our axis is tilted, with reference : our axis is tilted, with reference to the sun's rays, at an angle of 23.5o (look to the sun's rays, at an angle of 23.5o (look at any globe)at any globe)

http://astro.unl.edu/classaction/loader.html?filename=animations/coordsmotion/http://astro.unl.edu/classaction/loader.html?filename=animations/coordsmotion/

obliquity.swf&movieid=obliquity&width=600&height=400&version=6.0.0obliquity.swf&movieid=obliquity&width=600&height=400&version=6.0.0 b. Parallelism of the axisb. Parallelism of the axis: our North : our North

Pole always points toward Polaris. (see Pole always points toward Polaris. (see wall chart)wall chart)

c. Revolutionc. Revolution: We orbit the sun on a tilted planet, causing : We orbit the sun on a tilted planet, causing different parts of the earth to have more light seasonally.different parts of the earth to have more light seasonally.

http://http://astro.unl.edu/classaction/loader.html?filenameastro.unl.edu/classaction/loader.html?filename=animations/=animations/coordsmotion/eclipticsimulator.swf&movieidcoordsmotion/eclipticsimulator.swf&movieid==

eclipticsimulator&widtheclipticsimulator&width=970&height=710&version=6.0.0=970&height=710&version=6.0.0

5. Important dates:5. Important dates:

Equinoxes: “equal night”. Sun is Equinoxes: “equal night”. Sun is overhead at equator. September 22 and overhead at equator. September 22 and March 21March 21

Solstice: ‘sun stop’. Sun is either at Solstice: ‘sun stop’. Sun is either at Tropic of Capricorn (winter begins Tropic of Capricorn (winter begins December 21) or Tropic of Cancer December 21) or Tropic of Cancer (summer begins June 21).(summer begins June 21).

Each day, the sun seems to move a little Each day, the sun seems to move a little bit between 23.5 North and 23.5 Southbit between 23.5 North and 23.5 South

Actual position of sunrise changes with Actual position of sunrise changes with seasons, but is always eastseasons, but is always east

Position of sunset changes with seasons, Position of sunset changes with seasons, but is always west.but is always west.

http://http://alpha.lasalle.edu/~smithsc/Astronomy/retrograd.htmlalpha.lasalle.edu/~smithsc/Astronomy/retrograd.html retrograde motion and the retrograde motion and the ptolemic and Copernican explanationsptolemic and Copernican explanations

http://phys23p.sl.psu.edu/phys_anim/astro/embederQ4.20100.html ptolemic http://phys23p.sl.psu.edu/phys_anim/astro/embederQ4.20100.html ptolemic retrograderetrograde

http://phys23p.sl.psu.edu/phys_anim/astro/embederQ4.20300.html copernican http://phys23p.sl.psu.edu/phys_anim/astro/embederQ4.20300.html copernican retrograderetrograde

http://astro.unl.edu/classaction/loader.html?filename=animations/renaissance/http://astro.unl.edu/classaction/loader.html?filename=animations/renaissance/configurationssimulator.swf&movieid=configurationssimulator&width=850&height=68configurationssimulator.swf&movieid=configurationssimulator&width=850&height=680&version=6.0.0 from classaction, planetary motion0&version=6.0.0 from classaction, planetary motion

http://astro.unl.edu/classaction/loader.html?filename=animations/renaissance/http://astro.unl.edu/classaction/loader.html?filename=animations/renaissance/ptolemaic.swf&movieid=ptolemaic&width=900&height=660&version=6.0.0 ptolemic ptolemaic.swf&movieid=ptolemaic&width=900&height=660&version=6.0.0 ptolemic phases of venusphases of venus

http://astro.unl.edu/classaction/loader.html?filename=animations/renaissance/http://astro.unl.edu/classaction/loader.html?filename=animations/renaissance/retrograde.swf&movieid=retrograde&width=700&height=600&version=6.0.0 retrograde.swf&movieid=retrograde&width=700&height=600&version=6.0.0 retrograde animationretrograde animation

http://phys23p.sl.psu.edu/phys_anim/astro/indexer_astro.html physics animations http://phys23p.sl.psu.edu/phys_anim/astro/indexer_astro.html physics animations http://phys23p.sl.psu.edu/phys_anim/astro/embederQ4.10060.html earth orbit and http://phys23p.sl.psu.edu/phys_anim/astro/embederQ4.10060.html earth orbit and

seasonal starsseasonal stars

C= 2 x 92 million x 3.14 = 580 million miles orbitC= 2 x 92 million x 3.14 = 580 million miles orbit Speed of orbit = 580 million miles / 365 days = Speed of orbit = 580 million miles / 365 days =

1.6 million miles / day1.6 million miles / day Hours in a day = 24Hours in a day = 24 Speed per hour = 1.6 million miles/ day x 1day/ Speed per hour = 1.6 million miles/ day x 1day/

24 hours = 67, 000 mph24 hours = 67, 000 mph