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 2:29 AM | Comments (2)
April 2, 2005
Science Activity 1 - Leapin' Lizards
Crocodiles are survivors from the dinosaur age. A crocodile then looked very much like it does now. Crocodiles belong to a reptile family that did not become extinct like most dinosaurs 65 million years ago.
The features of the crocodile today are very similar to what they were 15 million years ago. A crocodile's armor-plated skin is made up of tough scales called scutes. These are reinforced from bony plates just below the surface.
Prehistoric crocodiles were giants, some up to 40 feet (13 meters) long! They preyed on other reptiles, including small dinosaurs. Other prehistoric crocodiles were as small as lizards.
Crocodiles have been honored throughout history. Egyptians in the town of Crocodilopolis had a crocodile god. The ancient Egyptian god of water, Sobek, was in the shape of a crocodile. Alligators, from the same reptilian family as crocodiles, got their name from 'el lagarto,' the Spanish word for lizard!
The estuarine (saltwater) crocodile from Australia, Indonesia, and Southeast Asia is the biggest of all crocs! This massive croc is the only one to swim in the sea. They live in estuaries along the coast and can grow BIGGGGG! The largest saltwater crocodile on record was 27 feet (9 meters) in length and weighed two tons!
With the coming of the European colonists, crocodile habitats became crowded with humans. Both enjoyed the living conditions along the Australian coastal areas. Unfortunately, they couldn't cohabitate as both were creating a problem for the other! No only did crocodiles hunt their prey from the rivers as animals came to drink, they also have the ability to leap as much as 9 feet (3 meters) out of the water after a meal! Crocs began feeding on livestock and then humans nearly hunted the crocs out of existence.
In 1972, crocodile hunting was banned in Australia. It is believed that around 270,000 saltwater crocodile skins and between 200,000 and 300,000 freshwater crocodile skins were exported from Australia before the ban. To meet consumer needs for their meat and their skins, crocodile farms now raise crocs. Poaching of these reptiles has become less of a problem. The croc farms have also become a major tourist attraction, especially at feeding time!
Here's the first scientific challenge for the research assistants...
Use these links to help you research:
Crocodiles.com>
Aborginal Crocs
Marine Bio
Species List
Alligators & Crocs
Posted by april at 4:51 PM | Comments (4)