Physical Geography Lecture 02 - Earth 092816
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The document discusses key concepts in physical geography, focusing on uniformitarianism, Earth's dimensions, and its shape as an oblate ellipsoid. It also addresses navigation techniques including the use of latitude, longitude, and timekeeping to determine one's position. Notable historical figures such as Eratosthenes and John Harrison are mentioned in relation to measuring Earth and improving navigational accuracy.
![Why is Longitude a Problem?Why is Longitude a Problem?
““The sun, moon, and planets pass almostThe sun, moon, and planets pass almost
directly overhead at the Equator. Likewise thedirectly overhead at the Equator. Likewise the
Tropic of Cancer and the Tropic of Capricorn,Tropic of Cancer and the Tropic of Capricorn,
two other famous parallels, assume theirtwo other famous parallels, assume their
positions at the sun’s command. They mark thepositions at the sun’s command. They mark the
northern and southern boundaries of the sun’snorthern and southern boundaries of the sun’s
apparent motion over the course of the year...”apparent motion over the course of the year...”
““Any sailor worth his salt can gauge hisAny sailor worth his salt can gauge his
latitude well enough by the length of the day, orlatitude well enough by the length of the day, or
by the height of the sun or known guide starsby the height of the sun or known guide stars
above the horizon….The measurement ofabove the horizon….The measurement of
longitude meridians, in comparison, is temperedlongitude meridians, in comparison, is tempered
by time…., [requiring] precise knowledge of theby time…., [requiring] precise knowledge of the
hour in two different places at once….”hour in two different places at once….”
--Dava Sobel,--Dava Sobel, LongitudeLongitude](https://image.slidesharecdn.com/pglecture02-earth092716-161003000751/85/Physical-Geography-Lecture-02-Earth-092816-16-320.jpg)
![Figuring Out Your LongitudeFiguring Out Your Longitude
You need to know:You need to know:
The time back home (or some other known port)The time back home (or some other known port)
The time aboard shipThe time aboard ship
Reset each day at noon (when the sun is at itsReset each day at noon (when the sun is at its zenithzenith))
What’s the time difference?What’s the time difference?
Every hour of difference = 15Every hour of difference = 15°° of longitudeof longitude
Can you do it?Can you do it?
If your clock is set two hours earlier than the time at your home port toIf your clock is set two hours earlier than the time at your home port to
the east, then your ship must be ___the east, then your ship must be ___°° west of your home port.west of your home port.
(Extra credit: If you’re at the equator, what’s your actual distance from(Extra credit: If you’re at the equator, what’s your actual distance from
home?)home?)
The real problem facing the navigators? They didn’t have wristwatches!The real problem facing the navigators? They didn’t have wristwatches!
[Three cheers to John Harrison in 1761!][Three cheers to John Harrison in 1761!]](https://image.slidesharecdn.com/pglecture02-earth092716-161003000751/85/Physical-Geography-Lecture-02-Earth-092816-18-320.jpg)
Physical Geography Lecture 02 - Earth 092816
- 1. Physical Geography: Lecture 2Physical Geography: Lecture 2 EARTHEARTH
- 2. Today’s Very Important Word:Today’s Very Important Word: UniformitarianismUniformitarianism ““The present is the key to the past”The present is the key to the past” How old is the Universe?How old is the Universe? How old is planet Earth?How old is planet Earth? How do we know?How do we know?
- 3. What does Earth look like?What does Earth look like? EratosthenesEratosthenes managed to figure out, inmanaged to figure out, in 247 B.C., Earth’s circumference247 B.C., Earth’s circumference Eratosthenes’ calculation: 28,738 miles (46,250 km) Earth’s actual polar circumference: 24,860 miles (40,008 km)
- 4. 44 Guess what???Guess what??? Earth’s polar circumference:Earth’s polar circumference: • 24,860 miles (40,008 km)24,860 miles (40,008 km) Earth’s equatorial circumference:Earth’s equatorial circumference: • 24,902 miles (40,076 km)24,902 miles (40,076 km) Earth is not a sphere…Earth is not a sphere… ……it’s anit’s an oblate ellipsoidoblate ellipsoid Earth is NOT ROUND!!!Earth is NOT ROUND!!!
- 5. Why isn’t it a sphere?Why isn’t it a sphere? Centrifugal forceCentrifugal force (It’s why the spin cycle in your washing(It’s why the spin cycle in your washing machine gets the extra water out ofmachine gets the extra water out of your clothes)your clothes)
- 6. Centrifugal ForceCentrifugal Force Rotation vs. RevolutionRotation vs. Revolution Both create a bulgeBoth create a bulge around the middle ofaround the middle of the planetthe planet RotationRotation • Earth spinning inEarth spinning in placeplace
- 7. Centrifugal ForceCentrifugal Force RevolutionRevolution • Earth’s orbital movement around the sunEarth’s orbital movement around the sun
- 8. Do you know where you are?Do you know where you are? << Quick! Stand up! >>
- 9. 99 How do you find your way if you don’t have any navigational instruments? What if clouds obscure the sky? Song: “Stand” by R.E.M.
- 10. A Polynesian map showing wave patterns in the Pacific Ocean
- 11. Great Circles and Small CirclesGreat Circles and Small Circles Another important piece of the navigation puzzle…Another important piece of the navigation puzzle…
- 12. Great CirclesGreat Circles The shortest distance between any two points on a globe lies along a great circle arc
- 13. Distortion of the Great Circle ArcDistortion of the Great Circle Arc on a Flat Mapon a Flat Map
- 14. 1414 The Geographic GridThe Geographic Grid LatitudeLatitude (x-axis)(x-axis) • ParallelsParallels (never touch)(never touch) Always the same distance apartAlways the same distance apart • EquatorEquator is the primary reference line (0º)is the primary reference line (0º) LongitudeLongitude (y-axis)(y-axis) • MeridiansMeridians Meet at the poles (distance between themMeet at the poles (distance between them shrinks)shrinks) • Prime MeridianPrime Meridian is the primary referenceis the primary reference line (0º)line (0º) • International Date Line lies roughly alongInternational Date Line lies roughly along the 180º meridianthe 180º meridian
- 15. Latitude and LongitudeLatitude and Longitude
- 16. Why is Longitude a Problem?Why is Longitude a Problem? ““The sun, moon, and planets pass almostThe sun, moon, and planets pass almost directly overhead at the Equator. Likewise thedirectly overhead at the Equator. Likewise the Tropic of Cancer and the Tropic of Capricorn,Tropic of Cancer and the Tropic of Capricorn, two other famous parallels, assume theirtwo other famous parallels, assume their positions at the sun’s command. They mark thepositions at the sun’s command. They mark the northern and southern boundaries of the sun’snorthern and southern boundaries of the sun’s apparent motion over the course of the year...”apparent motion over the course of the year...” ““Any sailor worth his salt can gauge hisAny sailor worth his salt can gauge his latitude well enough by the length of the day, orlatitude well enough by the length of the day, or by the height of the sun or known guide starsby the height of the sun or known guide stars above the horizon….The measurement ofabove the horizon….The measurement of longitude meridians, in comparison, is temperedlongitude meridians, in comparison, is tempered by time…., [requiring] precise knowledge of theby time…., [requiring] precise knowledge of the hour in two different places at once….”hour in two different places at once….” --Dava Sobel,--Dava Sobel, LongitudeLongitude
- 17. Figuring Out Your LongitudeFiguring Out Your Longitude Earth rotates on its axis, one rotationEarth rotates on its axis, one rotation every 24 hours. The circle of Earth’severy 24 hours. The circle of Earth’s circumference is 360circumference is 360°°, so:, so: 360360°° = __ hours= __ hours 1515°° = __ hour(s)= __ hour(s) 11°° = __ minutes= __ minutes Note: The distance between lines of longitude varies with latitudeNote: The distance between lines of longitude varies with latitude 00°° = 69 mi= 69 mi (111 km)(111 km) 4545°° lat. = 49 milat. = 49 mi (79 km)(79 km) 9090°° = 0 mi= 0 mi (0 km)(0 km)
- 18. Figuring Out Your LongitudeFiguring Out Your Longitude You need to know:You need to know: The time back home (or some other known port)The time back home (or some other known port) The time aboard shipThe time aboard ship Reset each day at noon (when the sun is at itsReset each day at noon (when the sun is at its zenithzenith)) What’s the time difference?What’s the time difference? Every hour of difference = 15Every hour of difference = 15°° of longitudeof longitude Can you do it?Can you do it? If your clock is set two hours earlier than the time at your home port toIf your clock is set two hours earlier than the time at your home port to the east, then your ship must be ___the east, then your ship must be ___°° west of your home port.west of your home port. (Extra credit: If you’re at the equator, what’s your actual distance from(Extra credit: If you’re at the equator, what’s your actual distance from home?)home?) The real problem facing the navigators? They didn’t have wristwatches!The real problem facing the navigators? They didn’t have wristwatches! [Three cheers to John Harrison in 1761!][Three cheers to John Harrison in 1761!]
- 19. Time, Time, Time…Time, Time, Time… Our way of organizing time is directlyOur way of organizing time is directly related to lines of longituderelated to lines of longitude Check this out…Check this out…
- 21. Fiji Is #1!!!Fiji Is #1!!!
- 22. In The ZoneIn The Zone
- 23. Ready for a quick review? 1. What’s the name of the theory that states that “the present is the key to the past”? 2. Who came up with a fairly accurate measurement of Earth’s size in 247 B.C., using only geometry? 3. What is the name for the shape of our planet? 4. What is centrifugal force? What two phenomena cause the centrifugal forces that affect Earth’s shape? 5. The shortest distance between two points on a globe lies along a ___________________.
- 24. 6. The primary reference line of latitude (0°) is ______________. The primary reference line of longitude (0°) is _______________. 7. What’s the most important instrument to have if you need to figure out your longitude? How do you figure it out? 8. True or False? Time zones follow lines of longitude, with exactly 7.5° on either side of the line. 9. If you flew from San Francisco to Sydney, Australia today, on what day would you arrive?
- 25. 10.What time is it RIGHT NOW in: a) New York City? b) Hilo, HI? c) St. Paul, MN? d) Fairbanks, AK? e) Beijing, China?