高中英语 Unit2Sailing the oceans-Textbook课件 新人

2 Which do you think was easier to work out: latitude or longitude?
Latitude, because it was used to measure how far you had travelled from land on a straight line. It was discovered a long time before longitude.
Explorer
land use of compassቤተ መጻሕፍቲ ባይዱand
landmarks find new places within an
already identified island or continent
Explorer is someone who travels into or through a place in order to learn about it.
3 Can you identify these early navigational instruments seamen used and explain how they are used? 1 _co_m__p_a_s_s_(_in__a_n_ci_e_n_t_C_h_i_n_a_)___ 2 _a_s_tr_o_l_a_b_e_ 3 _s_e_x_ta_n_t___ 4 _s_e_a_/_n_a_u_t_ic_a_l_/_m__a_ri_n_e_c_h_a_r_t _
Very often navigators are also explorers.
Pre-reading
• Look at the pictures. Then answer the questions. 1 How do you think seamen found their way before modern accurate methods of navigation were invented? Kept close to the shore, used nature such as the sun, wind, birds, tide, etc, to help them, and used some of the instruments including a compass, astrolabe, etc.
4 Which ones do you think are still used today? Sea charts are still used today.
Comprehending
1 Read the passage and answer the following questions. 1 What is the use of a bearing circle, astrolabe, quadrant or sextant? (B)
What is the use of a compass? (A) A to set the course of the ship B to measure the position of the ship C to measure the speed of the ship D to tell the time
A navigator explores the sea; an explorer discovers new places on land.
3 Look at these famous people. Are they navigators or explorers? What do you know about them?
2 Why are speed and time important in working out the longitude of a ship?
Speed and time are important in finding out the longitude of a ship because the earth moves fifteen degrees westwards every hour. If you know your direction, speed and time, you can work out the approximate longitude or change in your position in relation to the stars.
Navigator sea nautical instruments
find new islands or continents
Navigator is someone who finds the position and plots the course of a ship, an aircraft, a car, etc, using maps and instruments.
3 Why is the position of the sun and various stars useful for working out latitude?
The position of the sun and stars are useful for working out latitude because they are fixed points in the sky and their movements in relation to the earth are already known. So they can be used to measure a ship's position.
In pairs discuss these questions: 1 What is a navigator?
A navigator explores new routes across the sea. 2 What is the difference between a navigator and an explorer?