人新课标选修9课件优秀备选reading

1、Unit 2 Sailing oceansReadingLead-inCompass (Sinan)指南针A compass consists of a small magnet balanced on a point so that it can move round in a circle. The magnet is generally called a needle because it is shaped like a needle. One end of the needle is often marked “N” for north, or coloured in some wa

2、y to indicate that it points toward north.Astrolabe星盘The astrolabe measures the height and position of the sun. If you can measure this accurately, a sailor can tell how many degrees the boat is from the North Pole. From this he can tell where the boat is in the ocean.Sextant 六分仪The sextant is a nav

3、igational instrument for measuring the angle between the horizon and some object in the sky. First a sailor looks at the horizon through an eyepiece. At the same time he can see light from the sun or a star reflected off a small mirror on top of the instrument, onto a second mirror and into the eyep

4、iece. The navigator can then see two images, the horizon and the sun side by side. He can then measure the angle between them on a scale at the bottom of the instrument. The scale goes from 0 to 120 degrees. An earlier instrument, called a quadrant, measured in angle in the same way but it could onl

5、y measure angles from 0 to 90 degrees.nautical chartNautical charts are maps of the depth of the sea and the currents of the oceans. They provide modern sailors with routes through the seas, rather like roads through the countryside. The information began to be collected in the nineteenth century an

6、d has continued to be updated ever since. These charts were not available to Captain Bligh or Zheng He.Discuss1. 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 th

7、em, and used some of the instruments including a compass, astrolabe, etc.2. Which do you think was easier to work out: latitude or longitude?Latitude, because it was used to measure how far you had traveled from land on a straight line. It was discovered a long time before longitude.3. Can you ident

8、ify these early navigational instruments seamen used and explain how they are used?1) compass ( in ancient China)2) astrolabe3) sextant4) sea / nautical / marine chart4. Which ones do you think are still used today?Sea charts are still used today.Comprehending1. Read the passage and answer the follo

9、wing questions.What is the use of a bearing circle, astrolabe, quadrant or sextant? ( ) What is the use of a compass? ( )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 timeAB2) Why are speed and time important in working out

10、 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.3) Why

11、 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 ships positio

12、n.2. Suppose you were a sea captain aiming to sail round Africa. Discuss in groups:1) What skills would you seek in your sailors?2) What problems would you anticipate for this journey?3. What would you do if you came across the following problems during your voyage? Read the chart below and fill in

13、your plans of action to deal with them.What would you do if :Plan of actionYou were far from land and a storm arose.Wait till the storm is over, and then find your new position and return to your original course. What would you do if :Plan of actionYou knew your latitude but didnt know your longitud

14、e.Use knots to find your speed and work out your approximate longitude.What would you do if :Plan of actionYou were blown off-course.Use the compass and the astrolabe , quadrant or sextant to find out your position , return to your former course. What would you do if :Plan of actionYou were offshore

15、 but you needed more food and water.Follow nesting birds to shore ;look for special cloud formations or fog over streams to find land. What would you do if :Plan of actionYou wanted to keep a straight course. Use a compass.What would you do if :Plan of actionYou were lost with no land in sight. Meas

16、ure your position using the sun or stars; look for sea birds, cloud formations, fog or seaweed to show that land is nearby.4. Read the passage again and use the information to analyse the navigational skills.Using nature1. To find the ships position at sea a sailor used the North Star and the sun.2.

17、 A sailor knew that land was nearby if he saw _ _.3. Sailors used _ _to increase their speed. fresh seaweed, nesting birds returning home in the evening or fog sea currents or tides and winds4. There were two methods to find longitude: 1)_ 2)_ Using instrumentsmeasuring time and speedcompass and com

18、plicated mathematical tables5 Write down the working principles of the following instruments: Bearing circle: Astrolabe: to compare the height of the sun now with the position of the sun at midday. to compare the position of the ship in relation to some stars or the sun Quadrant: a more precise form

19、 of the astrolabe, to measure how high stars are above the horizon, and compare that measurement with previous measurements (using the ship as one of the fixed points to find its position) Sextant:an updated version of the quadrant and so it was more accurate, to measure the angle between two fixed points outside the ship (using two mirrors to find the ships posi