Shape of the World

1. Shape of the World The first High-Tech Superpower Rivalries

2. The Impulse Toward Exploration • Tantalizingly brief gap between several medieval events and the European Age of Exploration • China closed itself to outsiders in 1368 • China's great voyages to Asia and Africa ended in 1431 • Last ship to Norse colony in Greenland sailed in 1406 • Columbus sailed in 1492.

3. Circumnavigating the Globe • Ferdinand Magellan (Spain) 1519-22 • Sir Francis Drake (England) 1577-80 • Sir Thomas Cavendish (England) 1586-88 • Simon de Cordes (Holland) 1598-1600 • Oliver Van Noort (Holland) 1598-1601 • George Spilberg (Holland) 1614-17 • James LeMaire and William Cornelius Schouten (Holland) 1615-17

4. Some Observations • Most of these voyages were for military purposes (harassing the Spanish) rather than discovery • This pattern is very similar to the early days of space exploration • Not until the mid-1700’s were there circumnavigations largely aimed at exploration • Drake and his fellow pirates would now be called state-sponsored terrorists

5. A Geographical Oddity • The easiest way to sail around the world is from west to east, with the wind • Almost all early voyages were from east to west around South America • Objective: secrecy in entering the Pacific • Spanish tried and failed to establish settlements at the Straits of Magellan (weather poor, can’t raise crops, etc.)

6. A Geographical Oddity

7. The First Two (Three) -Time Circumnavigator • William Dampier (between 1679 and 1711) seems to have been the first to circumnavigate more than once (three times) • Odds of surviving a circumnavigation were very poor in early voyages • The prevention of scurvy was not discovered until around 1800

8. The First Two -Time Circumnavigating Ship • The Dolphin (1764-66 and 1766-68) was the first ship to circumnavigate the globe twice • It took almost 250 years after Magellan for shipbuilding technology to be able to build a ship capable of surviving two voyages

9. The First Commercial Round-the-World Traveler • By the 1600’s a globe-girdling network of European trade routes was in place • It was rarely necessary to circle the globe • There were only about 25 circumnavigations to 1800 • Giovanni Carreri (1693-98) sailed to Mexico, crossed overland, then booked passage across the Pacific and back to Europe

10. Why Did They Do It? • Why did people risk their lives in tiny boats to trade halfway around the world? • Nowadays: bulk cargo. Ship more valuable than cargo, but cost recovered by many voyages (Exxon Valdez: 10 million gallons = $10 million) • 1600’s: cargo far more valuable than ship • “My ship came in” - one good voyage could set you up for life.

11. The Compass Crisis • Compasses often pointed quite far from true north • Queen Elizabeth offered a prize to anyone who could solve the problem • The court physician, William Gilbert, in 1600 published De Magnete

12. De Magnete, 1600 • Considered the first great work on magnetism • Gilbert deduced the overall form of magnetic fields and concluded that the Earth had two magnetic poles • Earth's magnetic field varies in space and time. It changes measurably in a human lifetime

13. Why Compasses Don’t Point True North • North Magnetic Pole is not at the geographic pole • Declination in Wisconsin is nearly zero • Declination in Maine is 20 degrees West • Declination in Seattle is 20 degrees East

14. The Search For Longitude • The distance north or south of the equator, your latitude, is easy to find in principle. The elevation of the celestial pole above your horizon is your latitude • Distance east and west, or longitude, is another matter altogether. Everybody on earth at a given latitude sees the same sky during a 24-hour day

15. Longitude = Time • The key to longitude turns out to be time. When it's: • noon in New Orleans (90 degrees west) • it's midnight in Calcutta (90 degrees east). • It's 6 P.M. in London (0 degrees) • and 6 A.M. in Fiji (180 degrees) • If you have a clock that keeps accurate time and reads the time of your home port, you can determine local time from the sun and stars and calculate your longitude.

16. Longitude = Accurate Time • Circumference of Earth =25,000 miles, so: • One hour = 1040 miles at the equator • One minute = 17 miles at the equator • One second = 0.3 miles at the equator • Clock has to be accurate to seconds over a span of months, on a rolling ship, in all weather and climate.

17. Eclipses of Moon: Everyone who sees the Moon sees the same thing Too rare for most purposes Eclipses of Jupiter’s moons: frequent but hard to observe Method never panned out Astronomical Methods

18. An Unexpected Spinoff • The Dutch astronomer Roemer found eclipses ran early or late • Discrepancy = time for light to cross Earth’s orbit • First evidence that light had a measurable speed

19. The Final Solution - A Good Clock • One of the great technological stimuli of all time • John Harrison, 1761 • Need high-quality steel for springs • Need accurate tools to make gears and other parts • With good steel and accurate machine tools, what else can you make?

20. Anything at All

21. The Earth is not Round • The Earth is not a sphere - it bulges at the equator • Newton predicted the amount of the bulge • The exact amount provides clues about the makeup of the Earth’s interior • The distortion is about 1/298 of the Earth’s diameter - 29 miles out of a diameter of 7927 miles.

22. How do you Measure Latitude on an Elliptical Earth?

23. The Race to Find the Shape of the Earth • On an elliptical Earth, a degree is slightly longer near the poles • Accurate measurements can determine the shape of the Earth

24. So Who Cares? • This sort of accuracy is useful for steering ICBM’s or using GPS systems • What good was it in the 1700’s?

25. The First High-Tech Superpower Rivalry • Determining the shape of the Earth required the resources of a superpower (for the time) • Effort mostly for political prestige rather than science (sound familiar?) • The French would love to have improved on, better yet, disproven Newton • Unfortunately, the French calculated the wrong shape for the Earth (Mon Dieu!)