Natural Navigation. Natural Navigation. Jazmine Gaona ASTR Ray Oltion. April 15, Photo Credit:

Transcription

1 Natural Navigation Jazmine Gaona ASTR 1050 Ray Oltion April 15,

2 Introduction When you re lost, what do you do? Most of us rely on our smart phone or GPS device to navigate us to our desired location. But, have you ever pondered how humans used to navigate before such technology? Perhaps you ve thought about natural navigation techniques, and how they were applied. Humans have been using the stars, sun, and man-made inventions to get around the planet ever since the inception of travel. Since the beginning of time, humans wanted to travel the Earth; however, they needed to know where they were going. By trial and error they discovered several natural navigational tools. They started using the night sky, and gave close attention to the stars as they illuminated the sky. Locating Plough, Polaris, Cassiopeia, Orion, and Mintaka greatly helped individuals navigate at night. Polaris, the current North Star, didn t seem to move as much as the others, and eventually became the beacon for night travelers. The sun can also be used to navigate, but requires precise time measurements. Eventually, this led to the invention of several inventions including: the gnomon, the Arabian Kamal, the astrolabe, the cross-staff, the back-staff, the sextant, and the lunar distance method. Navigation Using The Stars Sailors from the Phoenicians to the Polynesians knew the heavens remained the best way to find one s north-south positions (Secrets of Ancient Navigators). By locating Plough (the big dipper), and Polaris (the north star),

3 Cassiopeia, Orion, and Mintaka humans were able to navigate their way around the world. Plough & Polaris The Big Dipper, formally known as Plough or Ursa Major, is an excellent tool located in the twinkling night sky that can be used to help navigate. To do this, first find the pointer stars, the two stars that a liquid would run off if you tipped up the saucepan. These two stars will lead you to Polaris. Polaris, commonly known as the North Star, is directly above true north. This star is the end of the handle on the Little Dipper or Ursa Minor. The North Star will always be five times the distance between these two pointers on the Big Dipper, in the direction that they point (up and away). The Big Dipper rotates counter-clockwise about the North Star, so it will sometimes appear on its side or even upside down. However, its relationship with the North Star never changes and it will always dependably point the way. Also, the elevation of Polaris directly corresponds to the observer s latitude between the North Pole and the equator. When the observer gazes from 90 degrees latitude, the North Pole, Polaris would be

4 located directly overhead at an altitude of 90 degrees. Therefore, if the observer stood at zero degrees latitude, Polaris would be located on the horizon at exactly zero degrees altitude. In ancient times, the navigator who was planning to sail out of sight of land would simply measure the altitude of Polaris as he left homeport, in today s terms measuring the latitude of home port. To return after a long voyage, he needed only to sail north or south, as appropriate, to bring Polaris to the altitude of home port, then turn left or right as appropriate and sail down the latitude, keeping Polaris at a constant angle (The History of the Sextant). Cassiopeia Occasionally Plough isn t as easy to find, because it is low in the sky or obscured. In this case, Cassiopeia is helpful in finding the North Star. Cassiopeia is always on the opposite side of the North Star from the Big Dipper. Orion & Mintaka Orion s Belt or the Belt of Orion is a useful constellation that can be used to help navigate east and west. Orion s

5 belt, the only three bright stars that form a short straight line in the whole night sky, rise very close to due east and set very close to due west. Mintaka is the first star in the Orion belt to rise and set. This star always rises and sets within one degree of true east and west wherever you are in the world. Navigation Using The Sun Many individuals believe that the sun rises in the east, and therefore it is a clear indicator of where east is located. However, this belief is simultaneously right and wrong. In reality, the sun rises due east on only two days of the year, the equinoxes, near March 21 and September 22. This is due to the tilt of the Earth as it travels around the sun. On midsummer s day in the northern hemisphere, around June 21st each year, the summer solstice, the North Pole is tilted as much as it ever will be towards the sun. On midwinter s day, around December 22 each year, the winter solstice, the South Pole is tilted as much as possible towards the sun. How To Use The Sun To Navigate At midday, the shortest shadow cast by a stick each day will form a

6 perfect north-south line anywhere in the world. By marking the tip of a stick s shadow over the course of the middle part of the day, a curve is made. To get an exact north bearing, mark the shadow every few minutes for a hour or so spanning noon (1pm in summer) and determine where the shortest shadow is (Natural Navigation). The closest point on this curve to the stick will be a perfect north/south line. Navigation Using Inventions After centuries of navigating by using the stars and suns, increasingly sophisticated instruments were invented. Many of these devices measure the height of the sun and the stars over the horizon. The gnomon The gnomon is a sun-shadow disk that enables the user to determine their latitude by the length of the sun's shadow cast on a disk. It can be used for finding the declination of the sun through the year. It is one of the first scientific instruments ever made, originating with the Chaldean astronomers of Babylon and from there brought to the Greek world. The ancient Babylonians stuck the gnomon on a stone and, voila, created the sundial.

7 The Arabian Kamal The Arabian Kamal is a rectangular plate that determines latitude. It is used by moving closer or farther from one's face until the distance between the North Star and the horizon exactly corresponded to the plate's upper and lower edges. The distance the plate lay away from the face, measured by a string tied to the center of the plate and held at the other end to the tip of the nose determined the latitude. Notice the knots in the cord attached to the carved mahogany transom. Before leaving homeport, the navigator would tie a knot in the cord so that, by holding it in his teeth, he could sight Polaris along the top of the transom and the horizon along the bottom. To return to homeport, he would sail north or south as needed to bring Polaris to the altitude he d observed when he left home, then sail down the latitude (Secret s of Ancient Navigators). The device originated with Arab navigators of the late 9 th century, and was employed in the Indian Ocean from the 10 th century. Astrolabe The astrolabe is a disc of metal that one held suspended by a small ring.

8 Astronomers, navigators, and astrologers historically used it. The disc had a scale with degrees and a ruler for measuring the height of an astronomical body. The astrolabe was popular for more than 200 years because it was reliable and easy to use under the frequently adverse conditions aboard ship (Tools Used in Celestial Navigation and its History). It predicted the positions of the sun, moon, planets, and stars, to determine the local time given the local latitude, and viceversa. Cross-staff The cross-staff was introduced in England in the mid-sixteenth century as a common navigational instrument. It was designed to measure the angles between stars, and to measure the heights of structures or topographical features such as mountains and hills. It is a long staff with a perpendicular vane, which slides back and forth. The device is t-shaped, and the base is held up to ones eye. The suns height is measured by pulling the slide-able top of the T toward one's eye until the sun lay at the top and the horizon at the bottom. The staff is marked with graduated measurements -- calculated by trigonometry. Although it was an effective invention, it had two major problems. Because the device also determined the altitude of the sun, the user was required to look directly into the blinding sun (Secrets of Ancient

9 Navigators). Also, the observer had to look in two directions at once - along the bottom of the transom to the horizon and along the top of the transom to the sun or the star (The History of the Sextant). This made the device difficult and dangerous to use; therefore, the back-staff was developed. Back-staff The back-staff was invented in 1595 by the English explorer John Davis. The back-staff eliminated the problems of parallax and glare of sun sights. The invention enabled users to get the same measurement as the cross-staff, but with one's back to the sun. To use the device, the observer would place the device on ones shoulder and stand with their back to the sun with the horizon vane lined up with the horizon. The half-cross would slide back and forth until the shadow of its vane fell across the slit in the bottom vane, while the horizon was visible through the slit (Secrets of Ancient Navigators). It consisted of a graduated staff, a half-cross in the shape of an arc of a circle on the radius of the staff with a fixed vane, and a brass horizon vane with a slit in it at the fore-end of the staff. The device enabled the observer to see both the sun and horizon without facing the sun.

10 Sextant The sextant is an invention that measures the angle between any two visible objects. It also allowed the user to determine their latitude to within a sea mile or two, even from a swaying deck. The angle, and the time when it was measured, was used to calculate a -navigation position line on a nautical or aeronautical chart. Other uses of the sextant include sighting the sun at solar noon and sighting Polaris at night to find one's latitude. Sailors could employ the sextant to figure longitude using the lunar-distance method, but with the astronomical tables of the 18th century, the process could take several hours to work out one's position (Secrets of Ancient Navigators). The Lunar Distance Method The lunar distance method was created so navigators could determine their longitude. In the 1750s, German astronomer Tobias Mayer developed the method. For centuries the sextant allowed individuals to determine their latitude, however longitude remained This diagram shows the angles and distances measured in the lunar method. an important missing element. According to The History of the Sextant, the lunar

11 distance method allowed the navigator at sea to measure the angle between the moon and a celestial body, calculate the time at which the moon and the celestial body would be precisely at that angular distance, and then compare the ship s chronometer to the time back at the national observatory. The chronometer provided sailors with the accurate time while aboard ships. Once the navigator knew the correct time from the chronometer, they could then determine the longitude. Conclusion There are numerous ways to navigate using the stars and the sun. It was through natural navigation that several inventions came about to help individuals find their way. By locating Plough (the Big Dipper), and Polaris (the North Star), Cassiopeia, Orion, and Mintaka, one would be able to navigate using stars. Also, the sun may be used; however, the tilt of the Earth must be considered, as well as precise time measurements. Over time, inventors, explorers and scientists invented tools such as: the gnomon, the Arabian Kamal, the astrolabe, the crossstaff, the back-staff, and the sextant to determine ones latitude. Next time you re lost and need help navigating, you can consider the techniques once used by human beings. Before the time of smart phones and GPS navigators, relied on the stars, Plough, Polaris, Cassiopeia, Orion, and Mintaka, sun, and inventions such as: the gnomon, the Arabian Kamal, the astrolabe, the cross-staff, the back-staff, the sextant, and the lunar distance

12 method. Incase your batteries were to die on your cell phone; you know how to natural navigate. Bibliography Bradish, S.L. Bright Hub. "Tools Used in Celestial Navigation and its History", 3 Jan Web. 17 Feb Calvert, J.B. Astronomy and Observation. "The Gnomon, Jan Web. 17 Feb Cline, Duane. The Pilgrims & Plymouth Colony: "The Back-Staff", Oct Web. 15 Feb Gooley, Tristan. The Natural Navigator. Natural Navigation, 8 Oct Web. 10 Apr Ifland, Peter. Taking the Stars: Celestial Navigation from Argonauts to Astronauts. The History of the Sextant, 3 Oct Web. 1 Mar National Museum Australia. The Lunar Distance Method, Web. 10 Apr es/european_voyages_to_the_australian_continent/navigation/a_clear_vis ion/the_lunar_distance_method

13 Steinkamp, Shane. The Place With No Name. "A BRIEF HISTORY OF NAVIGATION", Web. 16 Feb Tyson, Peter. Ancient Worlds. "Secrets of Ancient Navigators, 9 Oct Web. 16 Feb