Planet Earth
Learning Objectives
 Describe the features of Earth that distinguish it from the
other planets in the Solar System.
 To know the size and shape of the Earth and understand how
the Earth’s size was calculated by Eratosthenes.
 To understand the relevant terminology used to describe
locations on the Earth.
 To recall the times taken for the Earth to rotate through
given angles.
Bell Work
 On your piece of paper draw as accurately as you can what
the earth looks like
Discussion
 What features on earth make it distinguishable from other
planets? On the A3 paper in your groups write down your
thoughts.
Describe the features of Earth that distinguish it from the other planets in the Solar System
Answers
 Contains water
 Contains life
 The earth has plate tectonics (earth quakes due to plates)
 It has an atmosphere which shelters us from the sun.
To understand the relevant terminology used to describe locations on the Earth.
Latitude and Longitude
 Latitude - How far a position is north or south of the equator
 Longitude - How far a position is east or west of the Greenwich
Meridian (the imaginary line in the sky between the observers Pole and
Zenith (point in sky above the observer))
Shape of the earth
 The shape of the earth is
actually a Oblate Spheroid
The Earths Tilt
Mini Review
 Try now writing a definition of latitude and longitude into
your books from memory.
To recall the times taken for the Earth to rotate through given angles
Construct your Knowledge
 Key facts about the earth and its rotation.You are going to watch
two animations showing how the earth rotates with the moon,
and around the sun. Before you see these discuss with your
partner if you know firstly, how long it takes for the earth to
orbit the sun, estimate a distance between the earth and the
moon.
Eratosthenes Earth Calculation
 You can figure out the earth's
circumference using a geometric formula
that's over 2,000 years old! Contrary to
popular belief, Christopher Columbus
did not discover that the Earth is round.
Eratosthenes (276–194 B.C.) made that
discovery about 1,700 years before
Columbus.
 Eratosthenes was the head librarian in
Alexandria, Egypt, the centre of learning
in the ancient world.
 He knew that on the summer solstice, the longest day of the
year, the angle of the sun above Syene, Egypt, would be 0°, in
other words, the sun would be directly overhead. So on the
summer solstice, he measured the angle of the sun above
Alexandria by measuring the shadow cast by a pole and got a
7.2° angle.
To know the size and shape of the Earth and understand how the Earth’s size was calculated by Eratosthenes.
 Eratosthenes divided 360° by 7.2° and got 50, which told him
that the distance between Alexandria and Syene (500 miles) was
1/50 of the total distance around the Earth. So he multiplied 500
by 50 to arrive at his estimate of the Earth's circumference:
25,000 miles. This estimate was only 100 miles off the actual
circumference of 24,900 miles!
To know the size and shape of the Earth and understand how the Earth’s size was calculated by Eratosthenes.
Apply Your Knowledge
 Complete the questions on the pupil worksheet
Review