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WW
HEADERS_END
This is one of the talks that Colin does.
The aspects touched are:
* The tragedy on October 22nd, 1707
** Admiral Sir Clowdisley Shovell
* Computing your position from bearings
** Using bearings from North
*** Including error allowances
** Using relative bearings between multiple points
*** Generalisation of Thales' Theorem
**** Thales was about 600BC
* Doesn't work over the horizon
** What shape is the Earth?
*** Shadows during Lunar Eclipses show it's a sphere
*** Eratosthenes of Cyrene measured the circumference of the Earth
**** Summer Solstice (not necessary)
**** Reflected in a deep well => Sun overhead - no shadow
**** 7.2 degree shadow in Alexandria, some distance north
**** Divide by EQN:2\pi to get the Radius of the Earth
*** Eratosthenes also invented Latitude and Longitude
** How far is the horizon?
*** "Mountain" 5 metres high
**** How far to get to that point?
***** Uses Pythagoras - about 550BC
****** Pythagoras of Samos - student of Thales
******* Wouldn't accept Irrational Numbers
**** That means from 5m high, distance to horizon is that
**** That means from 5m high, distance to the horizon is that
**** Add answers for total distance
* Out of sight of land
** Measure Latitude with a Sextant or an Octant
*** How does that work?
** Dead reckoning
*** Log / Knots
**** 7 fathoms in 30 seconds = 5040ft/hour
**** 47'3" in 28 seconds = 6075ft/hour
** How do we measure Longitude?
*** That is the £6m question
* Prize offered in 1714 - 6 million pounds in today's money
** Many methods suggested
*** wounded dogs
*** Anchored ships with flares and cannons
*** Measuring the Moon against a fixed star map
**** Parallax
**** Distance to the Moon?
***** Value of /g?/
***** Acceleration due to gravity - value of /g?/
****** Regular dropping - two ticks per second
****** Pendulum timing
*** Clocks
**** Existing clocks were out by minutes per day
***** Robert Hooke had a clock in the late 1600s
***** Required sub-second error
**** John Harrison, 1693-1776
***** H1 - still can be seen in the Worshipful company of Clockmakers Guild Museum
***** H4 - Met the requirement
****** Never given the prize
***** K1 carried by James Cook on his second and third voyages
****** not on hist firstm to Tahiti for the transit of Venus
****** not on his first to Tahiti for the transit of Venus
* Galileo Galilei
** Acceleration is a time squared thingy
** Analysed the pendulum
*** Or was that Isaac Newton?
* CPA / Closest Point Of Approach
* Intercept Problem
* Isaac Newton (1643-????)
* Isaac Newton (1643-1727)
** RoyalMint / Royal Society
** Inverse square law of gravity
*** Acceleration due to gravity
** Reflecting telescope
* GPS / Global Positioning System
** Speedoflight
*** 1638 Galileo Galilei
**** Lanterns
*** 1676 OleRoemer
**** Eclipses of moons of Jupiter
***** Galilean Moons
*** 1767 James Bradley
*** 1728 James Bradley
**** Stellar Aberration (1/200 degrees)
Other pages:
* NewtonsCannon
* OrbitalVelocity
* OrbitalPeriod
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CategoryMaths