1. “You are here” The Home Planet*
07/16/96
“You are here” The Home Planet
What is position in space of home planet? A little reminder; spatial perspective on our planet’s location
11/17/2018 *

2. several 100 million others*
07/16/96
8.0 x 1017 miles (120,000 light years)
Spiral nebula
100 billion stars (suns)
several 100 million others
Home galaxy is Milky Way
cosmic frisbee; disc-shaped spiral nebula: spiral –shaped collection of some 100 billion stars (each one a sun)
Milky Way is one of several 100 million spiral nebulae
Diameter = 8.0 x miles (120,000 light years)
What is a light year?
A DISTANCE that light travels in one year (6 trillion miles)
11/17/2018 *

3. Sun 30,000 light years from center*
07/16/96
Milky Way revolves around its center of gravity
centrifugal force maintains disk shape
Outer edge of disk has spiral arms (pinwheel)
our sun is a star on one fo those spiral arms 30,000 light years from center of galaxy
Sun 30,000 light years from center
11/17/2018 *

4. Earth is a small satellite of an unimportant star on the periphery of one of millions of spiral nebulae.
11/17/2018

5. Jovian (outer) planets:*
07/16/96
Jovian (outer) planets:
Jupiter
Saturn
Uranus
Neptune
Pluto
Differ in size, density,revolution time, atmospheres, sphericity
11/17/2018 *

6. Terrestrial (inner):
Mercury
Venus
Earth
Mars
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7. The plane in which all planets (except Pluto) orbit the sun is the Plane of the Ecliptic.
11/17/2018

8. distance from sun= 92.5 million miles*
07/16/96
Radius = 4000 miles
distance from sun= 92.5 million miles
nearest star: 2.5 x 1016 miles
Some dimensions
Ask for diameter
Nearest star: Proxima Centauri
Illustrate scale: if sun were beach ball 2 ft diameter, earth would be size of pea 21.5 ft. away; Jupiter size of orange 2000 ft. away; nearest star would be as far away from earth as Rome is from Duluth.
11/17/2018 *

9. oblate ellipsoid flattened at poles bulging at equator*
07/16/96
oblate ellipsoid
flattened at poles
bulging at equator
centrifugal force
Shape of earth
Centrifugal force: force directed away from the axis of a rotating object)
11/17/2018 *

10. Rotational inertia displaces mass equatorward.*
07/16/96
Centrifugal force: too weak to make earth fly apart but does affect shape.
Where speed of rotation is greatest (equator), earth bulges and Where speed is slowest(poles), earth is flattened.
WHY is speed greatest at equator? Circumference = 25,000 mi: At 60 degrees, circumference = 12,500, so speeds are:
25,000 mi/ 24 hr and 12,500 mi per 24 hour
Rotational inertia displaces mass equatorward.
11/17/2018 *

11. Revolution revolution takes 365.24 days
leap year
Path of revolution: counter-clockwise (viewed from a point in space above North Pole)
orbit is “eccentric”
11/17/2018

12. orbit is an “ellipse” circle ellipse 11/17/2018 Circle has one center*
07/16/96
orbit is an “ellipse”
circle ellipse
Circle has one center
Ellipse has two foci
Sun is at one focus of earth’s orbit
11/17/2018 *

13. Definition of an ellipse:
“The sum of distances of each point on the ellipse to the foci is constant”.
11/17/2018

14. Perihelion : 91,500,000 mi.
11/17/2018

15. Aphelion : 94,500,000 mi
Average : 93,000,000 mi.
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16. Perihelion : around January 3 Aphelion : around July 4
11/17/2018

17. Eccentricity = a2 - b2 / a2 “a” is semi-major axis*
07/16/96
Eccentricity = a2 - b2 / a2
“a” is semi-major axis
“b” is semi-minor axis
(eccentricity of earth’s orbit = .017) b
Eccentricity is how much a round shape deviates from a circle a
11/17/2018 *

18. Circumference of earth = 24,900 mi. 247 B.C by Eratosthenes
11/17/2018

19. 4 Today’s Situation Summary of the current situation*
07/16/96
Today’s Situation
Summary of the current situation
Use brief bullets, discuss details verbally
Leader in school of astronomy
Offered proof tat earth was not flat, then calculated circumference 4
11/17/2018 *

20. 5 How Did We Get Here? Any relevant historical information
Original assumptions that are no longer valid 5
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21. “If two parallel lines are transected by a diagonal, the alternate interior angles are equal.”
Angle = 7.5 degrees
7.5 degrees is 1/50 of
360 degrees
Distance poles = 500 miles
50 x 500 = 25,000
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22. Polar axis 66.5o tilt (to plane of ecliptic)
23.5o tilt (to line perpendicular to plane of ecliptic)
fixed
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23. 11/17/2018

24. 3 Goal and Objective State the desired goal
State the desired objective
Use multiple points if necessary 3
11/17/2018

25. Graticule: latitude and longitude*
07/16/96
Graticule: latitude and longitude
A grid system to describe the location of a point on a sphere
What is a natural point of reference on this sphere rotating and revolving in space?
11/17/2018 *

26. State the vision and long term direction2
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27. 11/17/2018

28. Latitude greatest circumference equator: 0o, Poles: 90oN, 90oS
arc between location and equator
gives direction North, South of equator
Parallels of latitude are circles, parallel
greatest circumference equator: 0o, Poles: 90oN, 90oS
one degree of latitude is the same all over the globe
11/17/2018

29. To answer your question...
The name of the Milky Way’s spiral arm
in which the earth is located is the
Orion Arm.
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30. 11/17/2018

31.
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32. Longitude Shows direction East, West of Prime Meridian
meridians of longitude are half-circles, not parallel, intersect at poles
Any 2 meridians = circumference of earth
one degree of longitude is not same all over
11/17/2018

33. 11/17/2018

34. 15ْ
30ْ
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35. 1° = 60 minutes (’) 1’ = 60 seconds (”)
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36. Where is UMD?
47o 49’ 00” N, 92o 4’ 45” W
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37. Rectangular survey system*
07/16/96
Rectangular survey system
Legal land description for surveying parcels of land
N-S and E-W reference lines:
range lines and town lines
Creates grid of townships; each 6 miles square; each township designated by the range and town in which it lies
Range lines
Town lines
11/17/2018 *

38. Rectangular survey system*
07/16/96
Rectangular survey system
Legal land description for surveying parcels of land
N-S and E-W reference lines:
range lines and town lines
T3S
Creates grid of townships; each 6 miles square; each township designated by the range and town in which it lies
R2W
Range lines
Town lines
11/17/2018 *

39. Rectangular survey system*
07/16/96
Rectangular survey system
Legal land description for surveying parcels of land
N-S and E-W reference lines:
range lines and town lines
T3S
Creates grid of townships; each 6 miles square; each township designated by the range and town in which it lies
R2W
Range lines
Town lines
36 sections
11/17/2018 *

40. Rectangular survey system*
07/16/96
Rectangular survey system
Legal land description for surveying parcels of land
N-S and E-W reference lines:
range lines and town lines
T3S
Creates grid of townships; each 6 miles square; each township designated by the range and town in which it lies
R2W
Range lines
Town lines
36 sections
11/17/2018 *

41. 9 8 10 15 16 17 20 21
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42. 9 8 10 15 16 17
Section 16, R2W, T3S 20 21
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43. 9 8 10 15 16 17
NW ¼,
Section 16, R2W, T3S 20 21
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44. 9 8 10 15 16 17
NW ¼,
NE ¼,
Section 16, R2W, T3S 20 21
11/17/2018

45. Time based on longitudinal position of sun solar day local time*
07/16/96
Time
based on longitudinal position of sun
solar day
local time
Solar day: time it takes for sun to make an apparent 360 degree circuit in sky
11/17/2018 *

46. Standard time 24 time zones Central Meridian 15 degrees
standard time based on solar time of CM
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47. 11/17/2018

48. 11/17/2018

49. *
07/16/96
Imagine instantaneous travel around world westward back to starting point…
3 am Tuesday
9 am
Monday
9 am
9 pm
Monday
Tuesday
Duluth
North
Pole
Reason for International Date Line: imagine instantaneous travel WESTWARD : (no travel time, no earth spinning time)
3 pm Monday
arrive at same hour, one day earlier.
11/17/2018 *

50. International Date Line*
07/16/96
International Date Line
180o meridian (roughly)
cross eastward: go back a day
cross westward: go forward a day
Solution: have a place on earth where the day changes *

51. e.g. If it is 9am Tuesday in Perth, Australia,
what day and time is it in Vancouver B.C.?
11/17/2018

52. e.g. If it is 9am Tuesday in Perth, Australia, what day and time is it in Vancouver B.C.?
Answer: 5 pm Monday

53. When it is midnight on the International Date Line, it is the same day all over the world.