Week 1: The Earth as a Rotating & Revolving Planet

  • Earth is not perfectly spherical, it bulges slightly at the equator

    • an oblate ellipsoid

  • Geographic grid

    • Meridians of longitude divide the globe from pole to pole, parallels of latitude divide globe into rings

    • largest parallel is the equator

    • intersection of a parallel and a meridian is called an intersection

    • Great circles bisect the Earth

      • small circles are any other cut through the Earth

    • All meridians are great circles, all parallels but the equator are small circles

    • Parallels are identified from their angular distance from the equator (0-90), and either North or South

    • Meridians are measured how far east or west they are from the prime meridian/Greenwich meridian

      • measured from 0-180 and East or West

    • Fractions of latitude or longitude angles are called minutes (1/60th of a meridian/parallel) and seconds (1/60th of a minute)

    • 41° 27’ 41” N translates to 41.4614° N

    • 60 degrees latitude is 34.5 miles from the equator

  • Environmental effects of the Earth’s rotation

    • feed plants during day

    • animals active during day or night

    • air temperature cycle

    • large motions in the atmosphere and oceans

    • gravitational pull

  • Map projections

    • earliest is mercator, scale increases at top and bottom

      • drawing a straight line anywhere on this map will give u a line of constant compass direction so its good for navigators

      • Mercator’s map can falsely make the shortest distance between two points appear much longer than the compass line joining them.

      • used to show many types of straight line features (wind lines, crustal features, air pressure)

    • polar projection centers on the pole, only one hemisphere, scale increases outward

    • conformal: preserving shape but changing area

    • equal area: shows area correctly, but shapes are distorted

    • winkel tripel projection

      • named after oswald winkel and the german word for triplet

      • minimizing distortion by curving the corners inward

      • a healthy medium

      • only the polar areas grow significantly

  • 15 degrees of longitude equals one hour of time

  • International date line is in Greenwich at the prime meridian

Since the 1950s, the most accurate time has been kept using atomic clocks, which are based on the frequency of microwave energy emission from atoms of the element cesium cooled to near absolute zero. These very accurate clocks keep time to better than one part in | trillion. Atomic time is a universal standard that is not related to the Earth’s rotation. Civil time sources use Coordinated Universal Time (UTC), which is derived from atomic time and provides a day of 86,400 seconds (24 hours) in length to match the Earth’s mean rota- tion rate with respect to the Sun. Coordinated Universal Time is administered by the Bureau International de l Heure, located near Paris.

The Earth’s Revolution around the sun

  • Spring equinox: March 21st

  • Summer solstice (axis tilted towards the sun): June 21st

  • Fall Equinox: Sept 23rd

  • Winter solstice (axis titled away from the sun): Dec 22nd

  • Aphelion (farthest away from the sun): July 4th

  • Perihelion (closest to the sun): January 3rd

  • Earth’s axis is tilted 23 ½ degrees

  • The circle of illumination is the circle that separates the day hemisphere from the night hemisphere.

    • At an equinox, the circle of illumination passes through the north and south poles

  • The subsolar point is the single point on the Earth’s surface where the Sun is directly overhead at a particular moment.