DO NowDO Now

1.1. List differences between latitude List differences between latitude and longitudeand longitude

2.2. Why are there time zones on Earth?Why are there time zones on Earth?

3.3. If it 2pm in New York State and If it 2pm in New York State and California is 45 degrees west, what California is 45 degrees west, what time is it in California?time is it in California?

Mapping the EarthMapping the Earth

Measure the EarthMeasure the Earth

Relationship between altitude of Relationship between altitude of Polaris and a persons latitude in the Polaris and a persons latitude in the Northern HemisphereNorthern Hemisphere

The true shape of EarthThe true shape of Earth Observations of the sky are affected Observations of the sky are affected

by Earth rotationsby Earth rotations

Shape of the EarthShape of the Earth

Perfect sphere- Perfect sphere- • Polar diameter Polar diameter

equals equatorial equals equatorial diameter (PD=ED)diameter (PD=ED)

Earth has a slight Earth has a slight bulgebulge

Oblate SpheroidOblate Spheroid flattened slightly at the poles flattened slightly at the poles

and bulging at the equatorand bulging at the equator Polar Diameter=12,715 kmPolar Diameter=12,715 km Equatorial Equatorial

Diameter=12,756kmDiameter=12,756km Therefore ED > PDTherefore ED > PD

Proof that Earth is an Oblate Proof that Earth is an Oblate SpheroidSpheroid

1.1. Photographs from space (most Photographs from space (most direct)direct)

2.2. Altitude of Polaris (north star)Altitude of Polaris (north star)• Polaris is almost located directly over Polaris is almost located directly over

the North Polethe North Pole• As an observer travels north or south As an observer travels north or south

the altitude of Polaris changesthe altitude of Polaris changes

POLARIS (AKA North star)POLARIS (AKA North star)

More ProofMore Proof

3. Gravitational Measurements3. Gravitational Measurements• Differences in weight of an Differences in weight of an

object at the equator and the object at the equator and the polespoles

4. Early Observations4. Early Observations• As a ship sails away from shore As a ship sails away from shore

it appears to disappear from the it appears to disappear from the bottom upbottom up

Determine PolarisDetermine Polaris

1.1. Latitude is equal Latitude is equal to the angle of to the angle of Polaris in the Polaris in the Northern Northern HemisphereHemisphere

What is the latitude of the What is the latitude of the observer?observer?

1.1. 10° North10° North

2.2. 20° North20° North

3.3. 40° North 40° North

4.4. 70° North70° North

PolarisPolaris

Is always north of the north poleIs always north of the north pole It is a celestial objectIt is a celestial object It circumvents the EarthIt circumvents the Earth

Maps & ProjectionsMaps & ProjectionsLatitude and LongitudeLatitude and Longitude