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April 17, 2005
Science Activity 2 - Celestial Reasonings
The Expedition 360 team have a Sat-phone to help them in their navigation, but how did the old explorers find their way around? In this lesson you will explore the old time methods so that you can explain to Jason what he can do if his Sat-phone doesn't work.
Once they had left land behind them, navigators of the early explorers relied on navigational instruments from many cultures.
One of the most important instruments, the astrolabe, was a metal disk developed by Greek astronomers 2,000 years ago. It was held vertically and a movable pointer was aimed at the sun. The pointer would then indicate the sailor's degree of latitude.
The compass-invented by the Chinese to determine direction and widely used by the Arabs-had come into use in Europe only about a century before Columbus.
Today, expedition navigators have access to ocean charts, sextants, compasses and a GPS, which gives longitude/latitude coordinates from satellites orbiting the earth.
The quadrant, like its modern descendant the sextant, was derived from an Arabic instrument, the kamal. It was used to determine latitude by measuring the altitude of the North Star or the sun above the horizon.
Since there were no clocks at sea, explorers relied on a sandglass, which had to be turned eight times during each four hour watch.
Most early explorers relied primarily on 'dead reckoning' (see nautical glossary: social studies blog). They essentially guessed the distance traveled by estimating the ship's speed and how far sideways the wind had blown it each day.
Modern expedition navigators have access to ocean charts, compasses, and a GPS, which indicates longitude and latitude coordinates, reading information from satellites orbiting the earth.
Lesson Activities: Take a Bearing
Materials:
compasses
circle marked in 360 degree units
paper and pencil
Download Worksheet (Right click and choose Save target as to save it on your computer.)
Preparation:
Become familiar with the readings on a compass. Identify north at 0 degrees or 360 degrees. East is 90 degrees, south is 180 degrees and west is 270 degrees.
Identify intercardinal directions by their compass reading, example: northeast would be found at 45 degrees and so on.
Procedure:
Using the downloaded worksheet, begin at the 'X' and take a bearing (reading) on your compass or circle marked in 360 degrees. From 0 degrees, determine the bearing from X to each letter. Go from the center of the X to the center of each letter.
Post the correct compass reading from the X to each letter using the comment function of this blog:
X to A_____
X to B_____
X to C_____
X to D_____
X to E_____
X to F_____
(You can copy the above questions, then paste them into the comment box, then add your answers before posting).
Informational Links:
Orienteering Lesson
How Celestial Navigation Works
The Mariner's Museum Online Exhibitions
Posted by april at April 17, 2005 2:29 AM
Comments
X to A__304___
X to B___250__
X to C___211__
X to D__111___
X to E___75__
X to F___61__
Posted by: Dalton, Leslie, Tim, Jaimie, Sam at May 6, 2005 8:43 PM
testing adding comments
Posted by: Barb at April 24, 2005 9:49 PM
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