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Science as High AdventureThe Transit of Venus

6 June 2012

Photo taken at PolyU on 8 June 2004

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Outline of the Talk

• What is a Transit of Venus?

• Why is it important?

• Measuring the Solar System

• A Look at Science as High Adventure

• How can I do this at home (school, office, in the park, etc.)?

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In Memorial

Ward A. Hayward 1939 - 2012 Electrical Engineer

Stock TraderAviator

SailorNavigator

Computer ScientistHouse Builder

TeacherFriend

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Transitnoun1 the carrying of people, goods, or materials from one place to another : a painting was damaged in transit.

•Astronomy the passage of an inferior planet across the face of the sun, or of a moon or its shadow across the face of a planet. •Astronomy the apparent passage of a celestial body across the meridian of a place.•Astrology the passage of a celestial body through a specified sign, house, or area of a chart.

2 informal (in full transit theodolite) a tool used by surveyors to measure horizontal angles.

New Oxford American Dictionary

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Gurley Transit (1921, Troy N.Y.)

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Transit with Trunnion(Horizontal Axis)

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What is a Transit of Venus?

• Orbital Planes of Earth & Venus

• Inclination of Planetary Orbits

• Venus’s Silhouette on Solar Disk

• Historical Transits of Venus

• December 6, 1882 Transit

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Orbital Planes of Earth & Venus

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Inclination of Planetary Orbits

NameInclination to Ecliptic

Inclination to Sun's Equator

Mercury 7.01° 3.38°Venus 3.39° 3.86°Earth 0° 7.155°Mars 1.85° 5.65°Jupiter 1.31° 6.09°Saturn 2.49° 5.51°Uranus 0.77° 6.48°Neptune 1.77° 6.43°

Terrestials

Gas Giants

Inclination

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Venus’s Silhouette on Solar Disk

An Earth bound observer will see the silhouette of Venus projected onto and moving across the Solar disk for roughly six hours.

Transit of Venus 2004

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Historical Transits of Venus

Transits occur in 8-year pairs separated by 105.5 or 122.5 years.

1639 4-Dec

1761 6-Jun1769 3-Jun

1874 9-Dec1882 6-Dec

2004 8-Jun2012 6-Jun

2117 11-Dec2125 8-Dec

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December 6, 1882 Transit

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Why is it important?

• The Motions of the Planets

• Ptolemaic Model

• Copernican Model

• Debate: Bruno and Brahe

• Kepler and his Laws of Planetary Motion

• Galileo invents Science

• Newton and Halley

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The Motions of the Planets(the “appearances”)

• Primary motion (prograde), all planets appear to move about the Earth in the same general direction.

• Secondary motion (retrograde), at times the planet appears to move backwards.

• The motions of the stars, Sun, and Moon are less complicated, there are no retrograde motions.

All of these motions are periodic and thus prediction is possible by looking in the rearview mirror.

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Claudius Ptolemy (~85 - ~165 CE)

• Greek-Egyptian Astronomer of the Roman Empire

• Earth-centered (geocentric)

• Principle orbits (deferents)

• Secondary orbits (epicycles)

• Predicts accurately planetary motions.

• Explained the “appearances” but very complicated.

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Nicholas Copernicus (1473-1543 CE)

• Polish Astronomer Monk

• In modern European languages, revolution has two meanings:

(1) A physical turning around such as a planet revolving around the Sun.

(2) A turning around in thinking.

• This dual meaning comes from the (Latin) title of Copernicus’ book De Revolutionibus Orbium Coelestium (The Revolving Celestial Spheres).

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Copernicus(Observations)

Motions of the known planets:

Mercury (swiftest planet) is never seen further than 22.3° away from the Sun

Venus (second swiftest planet) is never seen further than 46.1° away from the Sun

All other known planets (Mars, Jupiter, and Saturn) can be seen up to 180° away from the Sun

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Copernicus(Explanation)

α

β

Mercury

Earth

Venus

0.39 AU

0.72 AU

1.00 AU

Simplest explanation was that the Sun was at the center of the Solar System.

Sun

AU = astronomical unit, the average distance between the Earth and the Sun

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Copernicus: Heliocentric Model

Conclusions:

Mercury and Venus are closer to the Sun than the Earth, orbiting the Sun, not the Earth.

Mars, Jupiter, and Saturn are further away from the Sun than the Earth, orbiting the Sun, not the Earth.

Therefore, the Earth must also orbit the Sun!

--> all of the planets, including the Earth, orbit the Sun in simple circular orbits and not complicated ones about the Earth

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Copernicus• As we shall see, to claim in Catholic Europe that the Earth

moved was dangerous stuff.

• Copernicus was smart. He completely avoided problems with the Church. He did not publish his ideas until he was on his death bed. He published in Latin so that his ideas were not accessible to the common man but remained with the university professors and Church fathers.

• A great debate opened up. His proposal both “preserved the appearances” and was simpler than Ptolemy’s. Which was right?

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Heliocentric Model Explains Retrograde Motion

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Note: the following slides from Andy Morrall illustrate dynamically Copernicus’ explanation for the “appearances”.

An Earth observer noting the location of a Mars-like planet once a month automatically will see a looping motion “preserving the appearances”.

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Copernicus’ Explanation(click through these rapidly to see the progression in time)

EarthSun

Mars

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Bruno (1548-1600)

• Dominican Monk

• Free thinker

• Active writer and lecturer

• Advocated Copernican view

• Extended it by recognizing that our Sun is also

a star

• He asked, could people live on planets around

such Sun’s?

• The answer of the Catholic Church was to have

the Holy Inquisition (Church Thought Police)

arrest and torture him for 8 years.

• On 17 Feb. 1600, they burnt him alive tied to a

stake.

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Tycho Brahe (1546 - 1601 CE)• Empirically tried to disprove Copernicus.

• Proposed an alternative hypothesis to those of Ptolemy and Copernicus.

• Very modern: he attempted to ask Nature which was right!

• Tycho Brahe was convinced that the key to distinguishing among the three hypotheses was greater precision in measurement.

• He proceeded to design, build, and use the most precise astronomical instruments of the pre-telescope era.

• Later, we will see his influence on Qing China.

Tycho Brahe the astronomer in his observatory Uraniborg, on the island of Hveen, in Denmark. (The Royal Ontario Museum © ROM )

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Tycho’s Alternative

Tycho kept the Earth in the center of the Universe (Ptolemy) but placed all of planets in orbit about the Sun (Copernicus). The Sun and the Moon directly orbit the Earth.

In this model, the Sun has a deferent and the planets follow epicycles based on it.

This too preserved the “appearances”. Which of the three hypotheses could be right (if any)?

In order to find out, Tycho spent his life making observations (c 1571 - 1601 CE).

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Kepler (1571-1630 CE)

• Analyzed data on the orbit of

Mars made by Tycho Brahe

• After a decade of work he

discovered his first two

empirical laws of planetary

motion

• Produced the Rudolphine

Tables

• Defended his mother against

charges of witchcraft

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Kepler’s Laws

Are empirical laws. They are patterns found in the quantitative observations of Tycho Brahe.

Kepler carried on in the tradition of Pythagoras seeking the “Music (Harmony) of the Spheres” convinced that the Heavens were indeed Cosmos (i.e. “ordered”).

He reduced the data on Mars which was particularly accurate. He tried Copernicus’ “perfect” circles only to find that they did not fit. He eventually tried an “imperfect” ellipse and it did fit.

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Kepler’s Laws (1609)

First Law -- A planet orbits the Sun in an Ellipse (not a Circle) with one focus centered on the Sun

Second Law -- A planet sweeps out equal areas in equal times

QuickTime™ and a decompressor

are needed to see this picture.

The Second Law is a direct consequence of the Conservation of Angular Momentum

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Conic Sections

Circle Ellipse Parabola Hyperbola

The intersection of a cone and a plane were well known to the ancient Greeks.

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Kepler’s Third Law (1619)

Third Law -- The period squared of a planet’s orbit (P ) is proportional to the semi-major axis (a ) cubed.

P2

a3 =1

Using “Terrestrial Units” (i.e. Earth-based)P in (Earth) yearsa in Astronomical Units (AU)

(1 AU is the average distance of the Earth from the Sun)

[1, 2, 3 law ;-) ]

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Kepler’s Third Law

The Astronomical Unit or AU is the average distance of the Earth from the Sun. It is used to express the relative sizes of planetary orbits with no conventional reference (ie. to miles, km, etc.).

The orbital periods of the planets are directly measurable and were known in Kepler’s time (and much earlier).

The importance of the AU is that once it could be measured, then using Kepler’s Third Law, one can calculate the distances from the Sun of all the known planets and thus the size of the Solar System!

P2

a3 =1

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Some Planetary Properties

Planet Orbital Semi-Major Axis, a Orbital Period, P Orbital Eccentricity(astronomical units) (Earth years)

Mercury 0.387 0.241 0.206 1.002Venus 0.723 0.615 0.007 1.001Earth 1.000 1.000 0.017 1.000Mars 1.524 1.881 0.093 1.000Jupiter 5.203 11.86 0.048 0.999Saturn 9.539 29.46 0.056 1.000Uranus 19.19 84.01 0.046 0.999Neptune 30.06 164.8 0.010 1.000Pluto 39.53 248.6 0.248 1.001

P2

a3 =1

Except Mercury and Pluto, planetary orbits are very nearly circular.

Further planet is away from the Sun (a ), the longer its period (P ) precisely as noted by Kepler

Table 1.1

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Galileo Galilei (1564 - 1642 CE)• 1610 built telescope.

• Discovered

– Sunspots (popularized)

– Craters on Moon

– Phases of Venus

– Moons of Jupiter (a miniature Copernican system)

• Observationally verified Copernicus!

• Worked out the physics of cannon ball

trajectories.

• Historically considered the Father of

Modern Science.

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Galileo Invented Science• Published in Italian instead of Latin so

shopkeepers could read him.

• Demonstrated Ptolemy and Tycho Brahe to be

wrong.

• Was tried by the Holy Inquisition (religious thought

police) TWICE1.

• Spent the rest of his life under house arrest.

• Had his last book, on physics, secretly published

in the Netherlands, not Italy.

• Resulted in Science moving away from the

Mediterranean to England and Northern Europe

where the Catholic Church was not in complete

control.

• Thus, the next generation was dominated by

Newton (English).

• Basically, Galileo discovered the scientific method

which defines the modern world.

1The second time he was turned in by a jealous Jesuit priest who wanted to claim that he, instead of Galileo, had discovered the Sunspots.

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The Climate Necessary for Science… and whereas thereupon was produced the copy of a writing, in form of a letter professedly written by you to a person formerly your pupil, in which, following the hypothesis of Copernicus, you include several propositions contrary to the true sense and authority of the Holy Scriptures; therefore (this Holy Tribunal being desirous of providing against the disorder and mischief which were thence proceeding and increasing to the detriment of the Holy Faith) by the desire of his Holiness and the Most Eminent Lords, Cardinals of this supreme and universal Inquisition, the two propositions of the stability of the sun, and the motion of the earth, were qualified by the Theological Qualifiers as follows:

The proposition that the sun is in the center of the world and immovable from its place is absurd, philosophically false, and formally heretical; because it is expressly contrary to Holy Scriptures.

The proposition that the earth is not the center of the world, nor immovable, but that it moves, and also with a diurnal action, is also absurd, philosophically false, and, theologically considered, at least erroneous in faith.

Therefore . . . , invoking the most holy name of our Lord Jesus Christ and of His Most Glorious Mother Mary, We pronounce this Our final sentence: We pronounce, judge, and declare, that you, the said Galileo . . . have rendered yourself vehemently suspected by this Holy Office of heresy, …

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Isaac Newton (1642 - 1727 CE)

• Completed Galileo’s Laws of Motion

• Discovered the Law of Gravity

• Invented the Calculus

• Derived Kepler’s Laws of Planetary Motion

using calculus and the above first principles

placing them on a sound theoretical basis!

• In doing so, he showed that the same

physical laws held for both the Heavens

and Earth

• (a Cambridge man)

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Edmund Halley (1656 - 1742 CE)• Discovered the periodicity of comets

• Halley’s comet (76 year intervals)

• Proposed how to measure the AU using a

transit of Venus

• (an Oxford man)20 March 106618 April 114528 September 122225 October 130110 November 13789 June 145626 August 153127 October 160715 September 168213 March 175916 November 183520 April 19109 February 198628 July 2061

The reoccurrence of comets is another example of prediction using the rearview mirror.

Scene from the Bayeux tapestry depicting the 1066 invasion of England

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Measuring the Solar System

• Triangulation

• Basic Idea: Parallactic Angle

• Small Angle Trigonometry

• The Ideal Method: Simultaneous Projection

• Distance to the Stars

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Triangulation

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Basic Idea: Parallactic Angle

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Small Angle Trigonometry

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Ideal Method:Simultaneous Projection

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Distance to the Stars

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A Look at Science as High Adventure

• Halley’s Method

• Clocks

• 1761 Transit

• 1769 Transit

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Halley’s Method

• In the 18th Century, how do you make synchronized precision plots of Venus’s silhouette on the Sun?

• Short answer: you don’t!

• No photography• Clocks of questionable accuracy (land based pendulum okay)• No way to synchronize clocks• Longitude difficult to determine

• Long answer: you measure the transit time of Venus from different latitudes.

• Clock from ingress (2nd contact) to egress (3rd contact)• Elapsed time length of passage across solar disk• Plot multiple lines on a circle with angular separation ratios same

as latitudinal separations on Earth

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Halley’s Method

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Pendulum Clocks

Galileo discovered the isochronicity of the simple pendulum in 1581 while in medical school

t =2πlg

l = pendulum lengthg = acceleration of gravityt = period

Galileo’s 1637 concept drawing

l

m

g

θ

(Answers the question, “what do you do when you have time on your hands?”)

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Pendulum Clocks

Common 19th century school clockFirst practical pendulum clock, 1656, Christiaan Huygens

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Pendulum Clocks & Marine Chronometer

Marine Chronometer H5 (1772) successor to H4 (1761) - expensive at ~ 30% the cost of a ship!

• Pendulum clocks can be carefully adjusted on land to give fairly accurate timing on the order of a fraction of a second error per day or even better if compensated for temperature which effectively changes the length l.

• However, they are next to useless on a rocking ship, which is a pendulum in its own right, and where the local gravity g will be continuously changing.

• Thus they they could not be used as the marine timekeepers needed to clock longitude (east west motion, 1º = 4 min).

• Further, one could not pre-synchronize a pendulum clock then sail to the ends of the Earth to make accurate measurements.

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The 1761 Transit

Observation of the transit of Venus by Chappe d’Auteroche, taken outside outside Tobolsk, Siberia. The locals thought he was a magician.

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Mason and Dixon• Charles Mason and Jeremiah Dixon

• Famous English surveyors

• They intended to observe the 1761 transit from Sumatra but due to an attack by a French Man-of-War (French and Indian War, 1754-63), were delayed so had to settle for making their observations from the Cape of Good Hope in South Africa

• They later surveyed the Mason-Dixon Line between 1763 and 1767 to settle the boundary dispute between the colonies of Pennsylvania (Penn Family) and Maryland (Calvert Family, Lord Baltimore)

The famous Mason-Dixon line which historically formed the boundary between the North & South in USA

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Guillaume Le Gentil • 1761 Paris to Pondicherry, a French colony in

India

• However because of the war, Pondicherry was now in the hands of the British who would not let him land.

• He observed the transit on June 6 from shipboard but his pendulum clock was not useful on board ship – decided to stay in that general part of the world.

• Since he had gone through so much to get out to this part of the world, he decided to hang around for the 1769 transit.

• In the intervening years he mapped the coast of Madagascar

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The 1769 Transit

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Guillaume Le Gentil • Initially went to Manila in the Philippines to observe the 1769 transit. • With Spanish hostility, he returned to Pondicherry (returned to the French

in the treaty of 1763).

• Arriving in March of 1769, he built a small observatory.

• All mornings of previous weeks clear but not the day in question, June 4. • This turn of events drove him to the edge of insanity.

• Eventually recovering, he decided to return home to France.

• Unfortunately the passage home was not uneventful. Delayed by dysentery, he was shipwrecked ending up on Réunion (isle Île Bourbon).

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Guillaume Le Gentil • He had to wait for a Spanish ship eventually returning home in October

1771 having been away 11 years.

• He now discovered that he had been declared legally dead and his position in the Royal Academy of Sciences given to another.

• His wife had remarried and his relatives had plundered his estate.

• Lengthy litigation, intervention on the part of the King, and remarriage eventually normalized his life and he lived another 21 years.

• Moral: it pays to write home occasionally.

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James Cook• Arguably the most important

18th C explorer

• Made three trips explicitly for scientific exploration into the Pacific

• His patron was John Montagu the 4th Earl of Sandwich

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The 4th Earl of Sandwich

• John Montagu, 4th Earl of Sandwich 1718 – 1792

• Succeeded grandfather as 4th Earl at age of ten.

• During his lifetime he held many different government posts.

• Most notable is that he was the First

Lord of the Admiralty (three times, but especially 1771 – 1782).

• His incompetence during the American Revolution (1775 - 1783) makes him a true American Hero

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SandwichIn a famous exchange with the actor Samuel Foote, Sandwich declared, "Foote, I have often wondered what catastrophe would bring you to your end; but I think, that you must either die of the pox, or the halter."

"My lord", replied Foote instantaneously, "that will depend upon one of two contingencies; -- whether I embrace your lordship's mistress, or your lordship's principles."

Suggested Epithet: "Seldom has any man held so many offices and accomplished so little."

A notorious gambler, he invented what has since been called the “sandwich”, a slice of meat between two slices of bread, so that he did not have to leave the gambling table in order to eat.

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Cook’s First Voyage 1768 - 71• Promoted to Lieutenant and made

commander of the expedition• Goal: to observe the Transit of

Venus in Tahiti at “Point Venus”• Sailed with

• Charles Green – astronomer• Joseph Banks – botanist

• Rounded cape horn arriving Tahiti on 19 April 1769

• 3 June 1769 observed the Transit of Venus • Sealed orders from Admiralty – to search for purported Terra Australis• First to circumnavigate New Zealand (and map its coast)• First European contact with the east coast of Australia (19 April 1770)• Made first landfall at Kurnell Peninsula (which he named Botany Bay)

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Black Drop Effect

"This day prov'd as favourable to our purpose as we could wish, not a Clowd was to be seen … and the Air was perfectly clear, so that we had every advantage we could desire in Observing the whole of the passage of the Planet Venus over the Suns disk: we very distinctly saw an Atmosphere or dusky shade round the body of the Planet which very much disturbed the times of the contacts particularly the two internal ones."

The Black Drop effect observed by Cook and everyone else

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Cook’s 2nd Voyage 1768 - 71• Promoted to the rank

of Commander

• Main goal: Continue the search for Terra Australis

• Surveyed, mapped, and claimed the South Sandwich Islands (to the SE of South Georgia and to the East of the Falklands Islands) Cook witnessing human sacrifice in Tahiti 1773

• Working out of Tahiti, sailed south and crossed the Antarctic Circle

• Reached 71°10'S on 31 January 1774 almost reaching Antarctica

• Circumnavigated the globe at high southern latitude

• Successfully used the Larcum Kendall K1 chronometer (a duplicate of the Harrison H4) for the first time permitting accurate determination of longitude without the need of Astronomy

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Cook’s 3rd Voyage 1776 - 79• Promoted to Captain

• Main goal to find the Northwest Passage

• Returned to Tahiti to start his explorations of the North

• Sailed north bumping into Hawai`i which he called the Sandwich Islands (Jan. 1778)

• Made detailed coastal maps of Pacific Northwest from Oregon to the Bering Strait

• Returned to Hawai`i in 1779 mapping the islands for eight weeks

• Landed at Kealakekua Bay (on the Big Island) during the Makahiki staying a month

• Cook realized through the similarity of language, that the people of Hawai`i and of Tahiti (Kahiki in Hawaiian) were closely related

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Polynesian Triangle

(1) Hawai`i

(2) Aotearoa (New Zealand)

(3) Rapa Nui (Easter Island)

(4) Samoa

(5) Tahiti

• Fact: the Polynesians, while a people who had no metal, were fantastic sailors who explored and colonized most of the central Pacific long before Europeans arrived. Their North-South travels were guided by the bright stars found in the zenith over their destination

• Hawai`i : hôkû-le`a (lit: star + joy)

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Cook’s 3rd Voyage 1776 - 79• Shortly after sailing for the Northwest again, his mainmast broke and so he returned

to affect repairs

• Wearing out his welcome, following the theft of a small boat, he was killed (on Valentine’s day) and then given the funerary rites of a Hawaiian Chieftain

HMS Endeavour

Hôkû Le`a

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Benjamin Franklin on Cook

• Franklin, as a fellow scientist, fully understood the scientific importance of Cook’s mission so wrote to the Captains of Revolutionary War ships

“...not consider her an enemy, nor suffer any plunder to be made of the effects contained in her, nor obstruct her immediate return to England by detaining her or sending her into any other part of Europe or to America; but that you treat the said Captain Cook and his people with all civility and kindness, . . . as common friends to mankind.”

• Franklin of course did not know that Cook had been killed a month earlier.

• Notable officers who accompanied Cook

William Bligh (3rd voyage – Sailing Master)

George Vancouver (2nd and 3rd voyage – Midshipman)

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How can I do this at home (school, office, in the park, etc.)?

• Today (21st Century)

• Methods for Determining the Parallactic Angle of Venus

• Equipment Needed

• When and Where

• Ke-ala-i-kahiki

• You Can Do This at Home!

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Today (21st Century)• We have very accurate clocks

• We can easily synchronize them

– Internet

– WWV or WWVH NIST time signals (on 2.5, 5, 10, 15 and 20 MHz.)

• We know exactly our observation positions (latitude & especially longitude)

• Digital photography

– Synchronized photographic plotting possible

– Video of ingress and egress to minimize the black drop problem

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Methods for Determining the Parallactic Angle of Venus

• Halley’s traditional method of timing the transit– Use videography to record ingress and egress– Later play back carefully to accurately determine contact

times

• Direct synchronous plotting of Venusian silhouette

• Determine transit paths by plotting multiple points along transit (not necessarily synchronized)

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Equipment Needed

• Safe telescope– Galileo discovered the sunspots– And later went blind

• Synchronized clock (for synchronized and elapsed timing)– Internet-worked or synchronized computer – iPhone

• Digital camera (for synchronized photo plotting)

• Digital video recorder (to record ingress and egress)

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When and Where• In Hong Kong the transit will begin early in the morning just after sunrise and

continue to around 1 PM as the Sun climbs towards the Zenith.

• Since this is close to the Summer Solstice (21 Jun), the Sun will start out near the horizon and end very high in the sky because we (22° 16’ 42” N) are just south of the Tropic of Cancer (23° 26’ 16” N).

• The observation site will need a good view of the Eastern horizon.

Latitude 22° 18' 10".9 N Longitude 114° 10' 47".5 EDate 6-Jun-12 Clouds 73%

Contact Event Local Time Horizontal Azimuth (from N)

Sunrise 5:42:30

I External Ingress 6:11:53 6°.1 113°II Internal Ingress 6:29:37 9°.9 110°.5Mid Midpoint 9:31:29 50°.6 100°III Internal Egress 12:31:26 87°.9 260°IV External Egress 12:48:49 83°.0 265°.2

Sunset 19:04:19

http://transitofvenus.nl/wp/where-when/local-transit-times/

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Ke-ala-i-kahiki

Parallel to the Hong Kong observations, I will record the transit in Hawai`i (21° 24’ 33” N).

I am also arranging for colleagues in other universities as far north as Alaska and south as Australia to follow the transit.

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You Can Do This at Home!

A pinhole camera is easily made by poking a small hole in a piece of cardboard and projecting the inverted image on a nearby wall or other screen.

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How to Do This at Home (or in a park, etc.)

1. Fully charge all battery-operated devices. If spare batteries are an option, be sure to charge those too.

2. Time calibrate off the Internet (or WWV / WWVH radio signals) digital still and video cameras as close as possible. This will assure that the metadata stamp of all recordings is close to the actual time and will minimize confusion later. It will also assure that the elapse time from ingress to egress can be measured. If possible, determine the error for later correction.

3. Identify positions to be manned and the people to fill those positions– telescope operator / guide– still photographer– video photographer– data recorder

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How to Do This at Home (or in a park, etc.)

4. Fully practice all procedures at the actual observation site chosen to be sure that nothing is left to chance

5. Videographing during ingress and egress

The basic idea, in order to compensate for the black drop effect, is to have a continuously running video camera starting before and ending after the contact event to assure that they have been recorded along with the time. At the beginning and end of the continuous run, film a synchronized digital clock. With this embedded in the video sequence, there should be no ambiguity as to the exact time of each video frame.

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How to Do This at Home (or in a park, etc.)

6. Still photography

Between the contact sequences digital photos should be taken of the solar disk at predetermined precise five-minute intervals. By themselves, they will allow precise plotting of the transit from the point of view of the observation site. Together with photos taken at the same time from different observation sites, they will allow ideal synchronous plotting that was not possible in past centuries. The transit is long (over six hours) so it is best to have multiple people taking the photos in shifts. With Hong Kong’s cloudy skies, it is very probable that not all possible photos can be taken but hopefully enough to do the plotting.

Hopefully, this data, carefully taken, will be preserved so that interested parties in December 2017 CE will be able to access the archive.

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Reminder

• In Hong Kong, the Transit of Venus will begin just after sunrise on 6 June 2012

• Miss it, and you will have to wait until December 2117

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Polytechnique

Rensselaer Polytechnic InstituteThe Hong Kong Polytechnic University

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15 April 1912

RMS Titanic sunk and the Great Leader Comrade 김일성 born

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Maya Apocalypse?

Winter Solstice, 21 Dec 2012 - Stay Tuned!