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• What would you do without all these things?
• Step 1 – figure out what hemisphere you’re inPlenty of ocean to get lost in
• Celestial pole – lucky if you’re in the north, polaris is at the poleLearn your landmarks – the two bears in the north, the southern cross in the southFind the southern pole by drawing a line from acrux and the tip of the cross and between agena and rigelcentaurus, lines intersect at the southern celestial pole
• 20 billionths of an inch4 billion miles
• ### Transcript

• 1. Sailing by Starlight: the Lost Art of Celestial Navigation
Andrew Thaler
• 2. Do you know where you are?
• 3. Finding your way home
• 4. Finding your way home
Southern Sky
Northern Sky
• 5. Finding your way home
How do you travel in a straight line?
Latitude hook
Must be calibrated to a specific location
Polaris above the loop, head south
Polaris below the loop, head north
Kamal
Why does this work?
• 6. Determining Latitude
Polaris
tan θ = x/y
θ = Latitude
X
θ
Horizon
y
• 7. Determining Latitude
Accurate to within 1 Degree
1 degree of latitude = 60 minutes
1 minute = 1 nautical mile
Polaris is 430 light years away
2.5 X 1015 miles
If surveyors were as accurate as Polaris - 0.0000000002 inches
If Polaris was as accurate as a surveyors - 4,000,000,000 miles
• 8. Latitude is θ
Cross staff
Astrolabe
Octant
Sextant
• 9. Longitude
The X-Prize of the millennium
No accurate method until 19th
century
3 puzzle pieces
Rotation of the earth = 15o per hour
Time the sun peaks at prime meridian = 1200
Time (GMT) the sun peaks at your location
• 10. Relative Longitude
Not very accurate!
Find a star near the eastern or western horizon
Measure the altitude of that star at the same time every night
Changes in degrees correspond to movement east or west
2 Caveats
Need to correct for latitude
Need to know what time it is
• 11. What time is it?
The sky is a clock, too
Mariner’s Nocturnal
Measures the angle between Polaris and Ursa Major or Ursa Minor
• 12. Using the Nocturnal
• An analog computer
• 13. Set the dial to the date
• 14. Sight Polaris through the center hole
• 15. Rotate the arm until it lines up with the head of Ursa Major
• Astronomers and Mariners
None of these tools were invented for navigating
We know where we are on earth because we wanted to know where we are in the universe
• 16. Questions?