How did early Sailors navigate the Oceans?

the early ocean voyages were probably big mistakes a vessel could be thrown off course by a sudden storm or error by the helmsman so how did the early sailors navigate the oceans long before the magnetic compass reached Europe the Vikings were sailing across oceans to both the east and west discovering new lands in the West such as Iceland and Greenland and even discovering America nearly 500 years before Christopher Columbus these brave Vikings were creative in compensating for their lack of technology floki vulgar darson a great Viking Explorer credited with the discovery of Iceland carried aboard a cage of ravens when he thought land should be near he would release one of the birds if it circled the boat without purpose bland was not near but if it took off in a certain direction that boat followed knowing the bird was headed toward land the early Pacific Polynesians were the first to use the motion of the stars whether the position of certain wildlife species or the size of waves to find the path from one island to another using the motion of stars imagine one night you call a friend who's a few thousand miles away and ask them to name the star which is directly over their head you could then find that star in the night sky and the point on the horizon directly below that star would be their exact direction from you at that moment unfortunately a few minutes later that star would have moved and so you'd need a new one with this method it would take a lot of phone calls for every new star fortunately there is one star in the night sky that does not appear to move it's called Polaris the North Star the easiest method for finding the North Star is by finding the plow an easy to identify a group of seven stars it is known as the Big Dipper to the Americans and the saucepan to many others the plow rotates anti-clockwise about the North Star so it will sometimes appear on its side or even upside down however its relationship to the north star never changes and it will always dependably point the way to it the first useful invention to help was the magnetic compass with that you could hold a steady direction as you sailed and with something called a dead reckoning sailors estimated their ship's speed by noting the time it took for a woodchip a bubble or a piece of seaweed to pass along the length of their vessel but since the time was measured with a sandglass these early calculations were often way off to determine a position on Earth's surface it is necessary and sufficient to know the latitude longitude and altitude altitude considerations can of course be ignored for vessels operating at sea level if you have a compass know the date and have a set of prepared navigation tables showing how high the Sun should be at local noon then you can determine your latitude easily but to calculate your longitude you need oddly enough a very accurate clock which is calibrated to Greenwich Mean Time or GMT here's why we know that Earth revolves about its axis once every 24 hours in other words the Sun completes its apparent revolution of 360 degrees in 24 hours so in 1 hour the Sun appears to move 15 degrees in 4 minutes it appears to move 1 degree in 1 minute it appears to move 15 arc minutes in 4 seconds it appears to move 1 arcminute and so on if you're sailing in it's 1800 hours GMT and the local time is 800 hours then you get a time difference of minus 10 hours minus 10 hours is minus 150 degrees therefore you are 10 hours behind GMT which means your longitude is 150 degrees west in 1714 the British government offered a prize to anyone who could perfect and demonstrate a clock that would be accurate enough over long voyages to give the desired precision and locating a ship this type of clock was called a chronometer but the problem was that all the clocks of the time were making they were upset by changes in temperature humidity vibration corrosion etc in 1775 Captain Cook returned from a three-year voyage having used when the chronometer submitted by Larkin Kendall which was a copy of h4 clock paid by John Harrison upon comparing it to local reference clocks it was found to have been accurate to within eight seconds per day nowadays of course navigating is much simpler all large ships today rely on Global Positioning System marine GPS receivers don't show streets they give longitude and latitude and typically also show maps of any nearby coastlines harbors lighthouses etc many also display the approximate depth of the water as well many marine GPS units now have a Man Overboard button if someone falls overboard the captain or other crew member presses that button the GPS unit then marks that spot in the ocean and typically displays a directional arrow pointing to it along with a distance reading to that spot that lets the captain turn the ship around and return to the spot where the person fell into the water I suspect most ships even now carry a sextant a handheld instrument used to measure angles between the Sun and Moon and horizon as a backup to their GPS systems with that and an accurate wristwatch and navigation tables a competent navigator can still find where he is on the ocean even if the modern GPS unit fails so when you're sailing you might not save time but time just might save you

Channel: thecuriousengineer

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Keywords: sea navigation, history of navigation, christopher columbus, polynesia, polynesian navigation, Ocean (Geographical Feature Category), Navigation (Organization Sector), viking navigation, Leif Erikson (Deceased Person), magnetic compass, north star, Polaris (Celestial Object), plough, big dipper, how to navigate using the stars, Captain Cook, navigation tables, Global Positioning System (Industry), greenwich mean time, find latitude and longitude

Id: 4DlNhbkPiYY

Length: 6min 20sec (380 seconds)

Published: Sun Oct 05 2014