History of Early Navigation before 1492 AD

1
History of Early Navigation before 1492 AD

• Montgomery College Planetarium
• at Takoma Park/Silver Spring
• http//montgomerycollege.edu/Departments/planet
• By Dr. Harold Williams

2
Problem

• How to get home after hunting to the wife and
  kids bring the meat home.
• How do you get home after fishing from your boat.
• How do you get to that island or town or city on
  the coast to trade and then get back home.

3
People still have to solve this problem
4
Now
5
Egyptian trading

• Egyptian ship, 1250 B.C. Egyptian ship on the Red
  Sea, showing a rope truss being used to stiffen
  the beam of this ship
• Stern-mounted steering oar of an Egyptian
  riverboat depicted in the Tomb of Menna (c.
  1422-1411 B.C.)

6
Phoenician Glass
7
China Trading

• http//en.wikipedia.org/wiki/Junk_(ship)
• http//en.wikipedia.org/wiki/Zheng_He

8
Arab Trading
9
Data, the sky, Sun first!

• Regularity in day light and dark at night.
• Changes is length of day light and dark at night,
  duration.
• Changes in the position of sunrise and sunset.
• Changes in the length of shadows at noon time
  through out the year. The shortest shadow of the
  day is always at noon time local apparent solar
  time.

10
We can recognize solstices and equinoxes by Suns
path across sky
Summer solstice Highest path, rise and set at
most extreme north of due east. Winter solstice
Lowest path, rise and set at most extreme south
of due east. Equinoxes Sun rises precisely due
east and sets precisely due west.
11
Suns altitude also changes with seasons
Suns position at noon in summer higher
altitude means more direct sunlight.
Suns position at noon in winter lower altitude
means less direct sunlight.
12
Data, the sky, Moon second!

• Regularity in moon light, changing phases.
• Changes is moon rise with phases.
• Changes in moon transit with phases.
• Changes in moon rise with phases.

13
Phases of Moon

• Half of Moon is illuminated by Sun and half is
  dark
• We see a changing combination of the bright and
  dark faces as Moon orbits

14
Moon, anti-Sun

• Does appear in day time, too.
• But phases and moon rise, moon transit, and moon
  set have a one to one correlation.

15
Now we have some time clocks and some directions

• South line with shortest shadow of the day.
• Four cardinal point, 1.) South 2.) Anti-South,
  North (where the sun and moon and planets never
  are) 3.) Eastward (where the sun comes up, but
  it moves around with the yearly seasons) 4.)
  Anti-Eastward, Westward (where the sun goes down,
  but it move around with the yearly seasons)
• For day light when the Sun, Helos, Sol rules.

16
Cardinal DirectionsAzimuth
17
Latitude
18
Thought Question What is the arrow pointing
to?A. the zenithB. the north celestial poleC.
the celestial equator
19
Thought Question What is the arrow pointing
to?A. the zenithB. the north celestial poleC.
the celestial equator
20
Cross Staff
21
Longitude