高中英语 Unit2Sailing the oceansReading课件 新人教选修9.ppt

Reading,The four basic instruments for navigation:Sinan,Inch Astrolabe,Sextant and nautical map.,Sinan,the ancient Chinese compass.,It was invented by Zhang Heng in the Han dynasty.It is made up of a bronze foundation(青铜地盘)and magnetic spoon(磁勺)which is made of natural magnet,positioned right in the central of the foundation.,The handle of the spoon points to the south,while the other side points to the north.When the Sinan is in the still,the handle of the spoon points to the south because of influence of the terrestrial magnetism(地磁).,It has 17 stars listed as well as a map of the sky overhead(for 37 degrees)and the ecliptic(黄道).The time of day or night is on the outside edge with noon at the top of the Astrolabe and midnight at the bottom.It comes with a carrying chain,a pouch,and a book on its use.The reverse side has a sight for measuring the elevations of the heavenly bodies.,astrolabe,sextant,The sextant is a navigational 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 eyepiece.,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 only measure angles from 0 to 90 degrees.,nautical chart,Nautical 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 and has continued to be updated ever since.These charts were not available to Captain Bligh or Zheng He.,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.,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 identify these early navigational instruments seamen used and explain how they are used?,1)compass(in ancient China)2)astrolabe3)sextant4)sea/nautical/marine chart,4.Which ones do you think are still used today?,Sea charts are still used today.,1.Where do these materials come from?2.What did the early navigator use to help them navigate?3.What natural objects were used to assist the navigation?4.Is it easier to measure longitude or latitude?5.Do the astrolabe,the quadrant and the sextant mean the same thing?,Read and answer these questions.,Comprehending,1.Read the passage and answer the following 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 time,A,B,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.,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 ships position.,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?,Wait till the storm is over,and then find your new position and return to your original course.,3.Read the chart below and fill in your plans of action to deal with them.,Use knots to find your speed and work out your approximate longitude.,Use the compass and the astrolabe,quadrant or sextant to find out your position,return to your former course.,Follow nesting birds to shore;look for special cloud formations or fog over streams to find land.,Use a compass.,Measure 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 analyze the navigational skills.,1.To find the ships position at sea a sailor used the North Star and the sun.2.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 winds,4.There were two methods to find longitude:1)_ 2)_,Using instruments,measuring time and speed,compass and complicated mathematical tables,5 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 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 position).,5.Imagine you are on a boat with twenty-nine other people.You have a small box for your personal things but it can only hole ten items.What would you need for a weeks journey across the North Sea to England?,soap,blanket,cards,chess,shirt,trousers,knife,scissors,sea-sick tablets,cold medicine,novels,essay collections,waterproof boots,Read the passage(Reading)and decide whether the following statements are true(T)or false(F).1.An early method of calculating longitude was to use a knotted rope tied to a log.2.The astrolabe was the first instrument to measure the suns position.3.The quadrant was more precise and simplified than the astrolabe,but still had its shortcoming.,T,F,T,4.Up till now,the most accurate and reliable navigational instrument is the sextant.5.The astrolabe,quadrant and sextant are different kinds of navigational instruments and they have nothing to do with each other.,F,F,Type of writing and summary of SAILING THE OCEAN.,exposition,Finding longitude,Finding latitude,Keeping alongside the coastline,using celestial bodies,using wildlife,using the weather,using the sea,Homework,1.Review this passage.2.Preview Learning about language.,