natural navigation final -...
TRANSCRIPT
Natural Navigation
Natural Navigation
Jazmine Gaona
ASTR 1050
Ray Oltion
April 15, 2013
Photo Credit: http://www.universetoday.com
Natural Navigation
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),
Natural Navigation
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
Photo Credit: http://www.universetoday.com
Natural Navigation
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
Photo Credit: http://www.universetoday.com
Photo Credit: http://www.universetoday.com
Natural Navigation
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
Photo Credit: http://www.naturalnavigator.com
Photo Credit: http://www.naturalnavigator.com
Natural Navigation
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.
Photo Credit: http://mysite.du.edu
Natural Navigation
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 9th century, and was employed in the Indian Ocean from
the 10th century.
Astrolabe
The astrolabe is a disc of metal that
one held suspended by a small ring.
Photo Credit: http://airandspace.si.edu
Photo Credit: http://www.saudiaramcoworld.com
Natural Navigation
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 vice-
versa.
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
Photo Credit: http://astronomy.swin.edu.au
Natural Navigation
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.
Photo Credit: http://odock.blogspot.com/2011/02/history-
of-navigation-in-verse.html
Natural Navigation
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
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
an important missing element. According to The History of the Sextant, the lunar
1
This diagram shows the angles and distances measured in the lunar method.
Photo Credit: http://www.nma.gov.au
2
Photo Credit: http://www.marineinsight.com/misc/marine
-navigation
Natural Navigation
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 cross-
staff, 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
Natural Navigation
method. Incase your batteries were to die on your cell phone; you know how to
natural navigate.
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Natural Navigation
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