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.

Answers Contains water Contains life 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.

Latitude and Longitude 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.

Construct your Knowledge 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!

Apply Your Knowledge Complete the questions on the pupil worksheet 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