Transcript A time exposure photograph was taken for 8 hours. During that time

Measuring Earth
Midterm Review
Topics:
•Earth’s true shape & evidence
•Positions on Earth (Latitude, Longitude, Angle of Polaris)
•Time Zones
Earth’s true shape & evidence
1. Earth’s True Shape: Oblate Spheroid
-bulging at Equator, flattened at poles
-due to Earth’s rotation
2.Evidence:
a. Weight of an object is greater on the
North Pole than the equator
WHY?- Closer to Earth’s center on
Poles so force of gravity is greater
2.Evidence:
b. Ships seem to sink below the horizon
due to Earth’s curved surface (sphere)
2.Evidence:
c. Earth’s shadow during an eclipse is
curved
2.Evidence:
d. Photographs from space
Remember:
Equatorial Diameter= 12,756 km
Polar Diameter= 12,715 km
-Earth is almost perfectly round, so it appear
to be a perfect sphere!
Positions on Earth (Latitude,
Longitude, Angle of Polaris)
1. Latitude lines
- run West to East around globe
-Measure degrees north and south of Equator
-LAT is fLAT
Up to 90o N
Up to 90o S
Angle of Polaris and Latitude
► Polaris
can only be seen in Northern
Hemisphere
► Angle of Polaris from horizon= Latitude
Polaris at center of Star Trails
► Polaris
is stationary- does not move in sky
Star Trail Times
► Earth
rotates once in 24 hrs
► To rotate, it must travel 360o
► 360o =
24 hrs
15o/hour
Practice 1:
During the time exposure of a photograph, the
stars appear to have moved through an arc of
60° around Polaris. How many hours did this
time exposure take?
4 hrs
Practice 2:
A time exposure photograph was taken for 8
hours. During that time, how many
degrees of an arc did the stars appear to
have moved?
120o
2. Longitude lines
- run North to South around globe
-Measure degrees West and East of Prime
Meridian (Greenwhich, England)
-Prime Meridian is 0o
-LONGitude- LONG lines
180o
W of
Prime Meridian
180o E of Prime
Meridian
Degrees to Minutes to Seconds
► Minutes
and Seconds are a break down of
degree Latitude and Longitude
► Each
degree is broken down into 60
minutes or 60 '
► Each minute is broken down into 60
seconds or 60"
► (It's just like cm and mm on a ruler)
Time Zones
► We
know from Star Trails that Earth rotates
15o/hr
► We know that the sun rises in the East and
sets in the West
SO…
► West of the Prime Meridian is earlier
► East of the Prime Meridian is later
In the U.S.
Remember: The
Earth is rotating
The sun does not
actually move
around the Earth