[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:15.53,0:00:19.16,Default,,0000,0000,0000,,As you can imagine, 400 years ago,
Dialogue: 0,0:00:19.16,0:00:21.100,Default,,0000,0000,0000,,navigating the open ocean was difficult.\N
Dialogue: 0,0:00:21.100,0:00:25.71,Default,,0000,0000,0000,,The winds and currents pushed and pulled ships off course,
Dialogue: 0,0:00:25.71,0:00:29.51,Default,,0000,0000,0000,,and so sailors based their directions on the port they left,
Dialogue: 0,0:00:29.51,0:00:35.08,Default,,0000,0000,0000,,attempting to maintain an accurate record of the ship's direction and the distance sailed.
Dialogue: 0,0:00:35.08,0:00:38.38,Default,,0000,0000,0000,,This process was known as dead reckoning,
Dialogue: 0,0:00:38.38,0:00:46.66,Default,,0000,0000,0000,,because being just half a degree off could result in sailing right past the island that lay several miles just over the horizon.
Dialogue: 0,0:00:46.66,0:00:49.78,Default,,0000,0000,0000,,This was an easy mistake to make.
Dialogue: 0,0:00:49.78,0:00:53.50,Default,,0000,0000,0000,,Thankfully, three inventions made modern navigation possible:
Dialogue: 0,0:00:53.50,0:01:00.86,Default,,0000,0000,0000,,sextants, clocks and the mathematics necessary to perform the required calculations quickly and easily.
Dialogue: 0,0:01:00.86,0:01:08.41,Default,,0000,0000,0000,,All are important. Without the right tools, many sailors would be reluctant to sail too far from the sight of land.
Dialogue: 0,0:01:08.41,0:01:11.36,Default,,0000,0000,0000,,John Bird, an instrument maker in London,
Dialogue: 0,0:01:11.36,0:01:16.83,Default,,0000,0000,0000,,made the first device that could measure the angle between the sun and the horizon during the day,
Dialogue: 0,0:01:16.83,0:01:19.23,Default,,0000,0000,0000,,called a sextant.
Dialogue: 0,0:01:19.23,0:01:26.23,Default,,0000,0000,0000,,Knowing this angle was important, because it could be compared to the angle back in England at the exact same time.
Dialogue: 0,0:01:26.23,0:01:31.95,Default,,0000,0000,0000,,Comparing these two angles was necessary to determine the longitude of the ship.
Dialogue: 0,0:01:31.95,0:01:33.52,Default,,0000,0000,0000,,Clocks came next.
Dialogue: 0,0:01:33.52,0:01:38.50,Default,,0000,0000,0000,,In 1761, John Harrison, an English clockmaker and carpenter,
Dialogue: 0,0:01:38.50,0:01:41.98,Default,,0000,0000,0000,,built a clock that could keep accurate time at sea.
Dialogue: 0,0:01:41.98,0:01:48.48,Default,,0000,0000,0000,,The timepiece that could maintain accurate time while on a pitching, yawing deck in harsh conditions
Dialogue: 0,0:01:48.48,0:01:52.80,Default,,0000,0000,0000,,was necessary in order to know the time back in England.
Dialogue: 0,0:01:52.80,0:01:54.88,Default,,0000,0000,0000,,There was one catch though:
Dialogue: 0,0:01:54.88,0:01:58.71,Default,,0000,0000,0000,,since such a timepiece was handmade, it was very expensive.
Dialogue: 0,0:01:58.71,0:02:05.38,Default,,0000,0000,0000,,So an alternate method using lunar measurements and intense calculations was often used to cut costs.
Dialogue: 0,0:02:05.38,0:02:10.85,Default,,0000,0000,0000,,The calculations to determine a ship's location for each measurement could take hours.
Dialogue: 0,0:02:10.85,0:02:17.71,Default,,0000,0000,0000,,But sextants and clocks weren't useful unless sailors could use these tools to determine their position.
Dialogue: 0,0:02:17.71,0:02:24.16,Default,,0000,0000,0000,,Fortunately, in the 1600s, an amateur mathematician had invented the missing piece.
Dialogue: 0,0:02:24.16,0:02:32.95,Default,,0000,0000,0000,,John Napier toiled for more than 20 years in his castle in Scotland to develop logarithms, a calculation device.
Dialogue: 0,0:02:32.95,0:02:41.43,Default,,0000,0000,0000,,Napier's ideas on logarithms involved the form of one over E and the constant 10 to the seventh power.
Dialogue: 0,0:02:41.43,0:02:45.43,Default,,0000,0000,0000,,Algebra in the early 1600s was not fully developed,
Dialogue: 0,0:02:45.43,0:02:49.13,Default,,0000,0000,0000,,and Napier's logarithm of one did not equal zero.
Dialogue: 0,0:02:49.13,0:02:55.08,Default,,0000,0000,0000,,This made the calculations much less convenient than logarithms with a base of 10.
Dialogue: 0,0:02:55.08,0:02:59.55,Default,,0000,0000,0000,,Henry Briggs, a famous mathematician at Gresham College in London,
Dialogue: 0,0:02:59.55,0:03:07.61,Default,,0000,0000,0000,,read Napier's work in 1614, and the following year made the long journey to Edinburgh to meet Napier.
Dialogue: 0,0:03:07.61,0:03:11.06,Default,,0000,0000,0000,,Briggs showed up unannounced at Napier's castle door
Dialogue: 0,0:03:11.06,0:03:18.41,Default,,0000,0000,0000,,and suggested that John switch the base and form of his logarithms into something much simpler.
Dialogue: 0,0:03:18.41,0:03:23.23,Default,,0000,0000,0000,,They both agreed that a base of 10 with the log of one equal to zero
Dialogue: 0,0:03:23.23,0:03:26.43,Default,,0000,0000,0000,,would greatly simplify everyday calculations.
Dialogue: 0,0:03:26.43,0:03:30.80,Default,,0000,0000,0000,,Today we remember these as Briggs Common Logarithms.
Dialogue: 0,0:03:30.80,0:03:35.10,Default,,0000,0000,0000,,Until the development of electric calculating machines in the 20th century,
Dialogue: 0,0:03:35.10,0:03:44.02,Default,,0000,0000,0000,,any calculations involving multiplication, division, powers, and extraction of roots with large and small numbers
Dialogue: 0,0:03:44.02,0:03:46.73,Default,,0000,0000,0000,,were done using logarithms.
Dialogue: 0,0:03:46.73,0:03:50.18,Default,,0000,0000,0000,,The history of logarithms isn't just a lesson in math.
Dialogue: 0,0:03:50.18,0:03:54.38,Default,,0000,0000,0000,,There were many players responsible for successful navigation.
Dialogue: 0,0:03:54.38,0:03:57.91,Default,,0000,0000,0000,,Instrument makers, astronomers, mathematicians,
Dialogue: 0,0:03:57.91,0:03:59.98,Default,,0000,0000,0000,,and of course sailors.
Dialogue: 0,0:03:59.98,0:04:04.10,Default,,0000,0000,0000,,Creativity isn't only about going deep into one's field of work,
Dialogue: 0,0:04:04.10,0:04:08.56,Default,,0000,0000,0000,,it's about cross-pollination between disciplines too.