* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download cook - University of Glasgow
International Ultraviolet Explorer wikipedia , lookup
International Year of Astronomy wikipedia , lookup
History of Mars observation wikipedia , lookup
Extraterrestrial life wikipedia , lookup
Theoretical astronomy wikipedia , lookup
Chinese astronomy wikipedia , lookup
Copernican heliocentrism wikipedia , lookup
Astronomy in the medieval Islamic world wikipedia , lookup
Archaeoastronomy wikipedia , lookup
Observational astronomy wikipedia , lookup
Patronage in astronomy wikipedia , lookup
Planets in astrology wikipedia , lookup
Timeline of astronomy wikipedia , lookup
History of astronomy wikipedia , lookup
Venus (Lady Gaga song) wikipedia , lookup
Geocentric model wikipedia , lookup
Comparative planetary science wikipedia , lookup
Dialogue Concerning the Two Chief World Systems wikipedia , lookup
Captain Cook and the Cosmic Yardstick Dr Martin Hendry Dept of Physics and Astronomy, University of Glasgow James Cook (1728 – 1779) Retrograde motion of Mars Early Greek Astronomy The Greeks inherited ideas from Babylonia and Egypt, but approached astronomy in a scientific way Plato (428 – 347 BC): reality a distorted shadow of a Perfect Form. Circle = most perfect form in nature All celestial motions are combinations of circular motions Early Greek Astronomy The Greeks inherited ideas from Babylonia and Egypt, but approached astronomy in a scientific way Aristotle (384 – 322 BC): Universe divided into two parts: Corrupt, changeable Earth Perfect, immutable heavens Ptolemy: 90 – 168 AD Ptolemy proposed a model which could explain planetary motions – including retrograde loops John of Holywood (c. 1200) Author of ‘The Sphere’, standard textbook on spherical trigonometry The Copernican Revolution Nicolaus Copernicus (1473 – 1543) “In the true centre of everything resides the Sun” De Revolutionibus Orbis (1543) The Copernican Revolution Simpler explanation why Venus and Mercury appear close to the Sun Tycho Brahe (1546-1601) Uraniborg observatory Hven, between Denmark and Sweden Tycho Brahe (1546-1601) Uraniborg observatory Hven, between Denmark and Sweden Tycho Brahe (1546-1601) Johannes Kepler (1571-1630) ‘Mysterium Cosmographicum’ published in 1596 ’New Astronomy’ published in 1609 Johannes Kepler (1571-1630) The Spectacle Vendor by Johannes Stradanus, 1582 Hans Lippershey’s 1608 patent of a device for "seeing faraway things as though nearby." Porta’s sketch of a telescope, August 1609 The Observations of Galileo Galileo Galilei: (1564 – 1642) The Observations of Galileo Autumn/Winter 1609, observed: Craters of the Moon Moons of Jupiter Phases of Venus In conflict with Aristotelian / Ptolemaic Universe Galileo Galilei: (1564 – 1642) Published in 1610 ‘Sidereus Nuncius’ (The Starry Messenger) The Observations of Galileo The Moon is an imperfect world with mountains and valleys, just like the Earth The Observations of Galileo Moons of Jupiter: supported idea of Earth moving through space, contradicted Aristotelian view of all motions around Earth The Observations of Galileo Earlier observed phases of Venus The Observations of Galileo Earlier observed phases of Venus Geocentric model Sun The Observations of Galileo Earlier observed phases of Venus Geocentric model Heliocentric model Sun Sun The Observations of Galileo Phases of Venus impossible to explain in geocentric model Clear evidence that the Earth went round the Sun, and not the other way round “Cynthiae figuras aemulatur mater amorum” Getting the Measure of the Solar System In the Heliocentric model it was easy to determine the relative distances of the planets, using the geometry and trigonometry of the Greeks… Sun Earth Venus We can use Pythagoras’ theorem!! Getting the Measure of the Solar System Planet Distance Mercury 0.39 Venus 0.72 Earth 1.00 Mars 1.52 Jupiter 5.20 Saturn 9.54 Getting the Measure of the Solar System Planet Distance Mercury 0.39 Venus 0.72 Earth 1.00 Mars 1.52 Jupiter 5.20 Saturn 9.54 How far is an astronomical unit?… Eratosthenes: (c 276 – 195 BC) 1 50 360 Eratosthenes: (c 276 – 195 BC) Syene – Alexandria = 5000 stadia Circumference of the Earth = 250000 stadia 1 50 360 Aristarchus (310 – 230 BC): Earth – Moon distance from eclipse geometry Aristarchus (310 – 230 BC): Earth – Sun distance from phases of the Moon Aristarchus (310 – 230 BC): Earth – Sun distance from phases of the Moon Sound method, but angle between Sun and Moon hard to measure precisely. Aristarchus (310 – 230 BC): Earth – Sun distance from phases of the Moon Sound method, but angle between Sun and Moon hard to measure precisely. Heliocentric model (Sun much larger than the Earth). Not widely accepted, because no parallax shift Parallax Shift A B A and B line up the tree with different mountains, because they see it along different lines of sight Parallax Shift Parallax Shift Parallax Shift Nearby stars do show an annual parallax shift, but it is tiny! First detected only in the mid 19th Century. Parallax Shift Even the nearest star shows a parallax shift of only 1/2000th the width of the full Moon Parallax Shift Even the nearest star shows a parallax shift of only 1/2000th the width of the full Moon But parallax would be the key to measuring the A.U… Johannes Kepler predicted a transit of Mercury on 29th May 1607 Instead, he ‘discovered’ sunspots Johannes Kepler predicted a transit of Mercury on 29th May 1607 Instead, he ‘discovered’ sunspots May 7th 2003: Transit of Mercury Pierre Gassendi (1592 – 1655) Observed a transit of Mercury on 7th November 1631 Predicted by Kepler in 1629, although he didn’t live to see it Pierre Gassendi (1592 – 1655) Observed a transit of Mercury on 7th November 1631 Predicted by Kepler in 1629, although he didn’t live to see it Kepler also predicted a transit of Venus in December 1631, but it occurred after Sunset in Europe November 24th 1639 Jeremiah Horrocks (c1619 – 1641) “The Founder of English Astronomy” (Eyre Crowe, Walker Art Gallery) William Crabtree (1610 - 1644) “Crabtree watching the transit of Venus” (Ford Madox Brown, Manchester Town Hall) Halley travelled to St Helena in 1677, to map the Southern Skies He observed a transit of Mercury on November 7th Edmond Halley (1656 - 1742) Transit observations could measure the astronomical unit! Halley travelled to St Helena in 1677, to map the Southern Skies He observed a transit of Mercury on November 7th Edmond Halley (1656 - 1742) Transit observations could measure the astronomical unit! Method relied on an accurate estimate for the radius of the Earth In 1669 Jean Picard (1620 – 1682) measured RE 6365 km (0.2% error) In 1716 Halley presented a paper to the Royal Society, appealing to astronomers to observe the Venus transits of 1761 and 1769 Edmond Halley (1656 - 1742) “I recommend it, therefore, again and again, to those curious astronomers who (when I am dead) will have an opportunity of observing these things, that they would remember this my admonition, and diligently apply themselves with all their might to the making of this observation; and I earnestly wish them all imaginable Edmond Halley (1656 - 1742) success; in the first place that they may not – by the unseasonable obscurity of a cloudy sky – be deprived of this most desirable sight; and then, that having ascertained with more exactness the magnitudes of the planetary orbits, it may redound to their eternal fame and glory.” In 1716 Halley presented a paper to the Royal Society, appealing to astronomers to observe the Venus transits of 1761 and 1769 Edmond Halley (1656 - 1742) He predicted the astronomical unit could be measured to an accuracy of 1 part in 500 The 6th June 1761 Venus Transit o Observations meticulously planned, for many years o ‘Public outreach’ description by James Ferguson o Franco-British cooperation, despite being at war! o 120 astronomers observed from about 60 locations The 6th June 1761 Venus Transit o Observations meticulously planned, for many years o ‘Public outreach’ description by James Ferguson o Franco-British cooperation, despite being at war! o 120 astronomers observed from about 60 locations o Results were disappointing: Bad weather Poor global coverage ‘Black Drop Effect’ Systematic errors The 6th June 1761 Venus Transit o Observations meticulously planned, for many years o ‘Public outreach’ description by James Ferguson o Franco-British cooperation, despite being at war! o 120 astronomers observed from about 60 locations o Results were disappointing: Bad weather Poor global coverage ‘Black Drop Effect’ Systematic errors o Astronomical Unit lay between 77 million and 97 million miles (20% uncertainty) “I am afraid we must wait till the next transit, in 1769…before astronomers will be able to do justice to Dr Halley’s noble proposal” Neville Maskelyne (1732 - 1811) The 3rd June 1769 Venus Transit Captain James Cook set sail for Tahiti in August 1768, onboard the Endeavour with astronomer Charles Green Captain James Cook John Harrison ‘H4’ 1763 The 3rd June 1769 Venus Transit Endeavour arrived in Tahiti on 13th April 1769 – constructed a fort, and an observatory, at Point Venus Captain James Cook The 3rd June 1769 Venus Transit Endeavour arrived in Tahiti on 13th April 1769 – constructed a fort, and an observatory, at Point Venus Transit observed by Cook, Green and Solander Captain James Cook The 3rd June 1769 Venus Transit: Tahiti Captain James Cook The 3rd June 1769 Venus Transit Endeavour arrived in Tahiti on 13th April 1769 – constructed a fort, and an observatory, at Point Venus The Endeavour explored for two more years, before returning to Britain. During the voyage Charles Captain James CookGreen died of malaria. The 3rd June 1769 Venus Transit Endeavour arrived in Tahiti on 13th April 1769 – constructed a fort, and an observatory, at Point Venus The Endeavour explored for two more years, before returning to Britain. During the voyage Charles Captain James CookGreen died of malaria. Jean Baptiste Chappe d’Auteroche died of typhus on 1st August 1769, in Baja California The 3rd June 1769 Venus Transit Endeavour arrived in Tahiti on 13th April 1769 – constructed a fort, and an observatory, at Point Venus The Endeavour explored for two more years, before returning to Britain. During the voyage Charles Captain James CookGreen died of malaria. Jean Baptiste Chappe d’Auteroche died of typhus on 1st August 1769, in Baja California Guillaume-Joseph-Hyacinthe-Jean-Baptiste Le Gentil wins the award for the unluckiest astronomer! The 3rd June 1769 Venus Transit: Vardö, in Lapland Captain James Cook The 3rd June 1769 Venus Transit Father Maxmilian Hell (1720-1792) observed the transit from Lapland 3rd June 1769 20:34 UT Internal contact at Vardö… 3rd June 1769 20:34 UT Internal contact at Vardö… …meanwhile in Tahiti… 3rd June 1769 20:43 UT Internal contact in Tahiti… 3rd June 1769 20:45 UT Internal contact in Tahiti… …meanwhile at Vardö… 4th June 1769 02:22 UT Internal contact in Tahiti… 4th June 1769 02:22 UT Internal contact in Tahiti… …meanwhile at Vardö… 4th June 1769 02:33 UT Internal contact in at Vardö… 4th June 1769 02:33 UT Internal contact in at Vardö… …meanwhile in Tahiti… The 3rd June 1769 Venus Transit The 3rd June 1769 Venus Transit After years of analysis, the results of the 1769 observations were published. e.g. Thomas Hornsby (1771):1 A.U. = 93,726,900 miles (between 90 and 94 million miles) Captain James Cook Cassini de Thury “Happy is our Century, to which has been reserved the glory of being witness to an event which will render it memorable in the annals of the Sciences!” Venus Abandoned In the 19th Century, astronomers’ attention switched to Mars. o o o o Easier to measure positions at night! Mars appeared smaller in size No ‘time limit’ on observations No black drop or atmospheric effects Captain James Cook o o View from 0 N, 0 W o o View from 0 N, 180 W (opposite side of the Earth) Venus Abandoned Captain James Cook David Gill (1843 – 1914) Measured the parallax of Mars from Ascension Island in 1877 Venus Abandoned Captain James Cook David Gill (1843 – 1914) Measured the parallax of Mars from Ascension Island in 1877 Venus Abandoned Gill’s observations narrowed the range for 1 A.U.:- Captain James Cook David Gill (1843 – 1914) Measured the parallax of Mars from Ascension Island in 1877 Between 92,981,000 miles and 93,235,600 miles Superceded the photographic observations of Venus transits in 1874 and 1882 Venus Reclaimed Captain James Cook Observations of the Near-Earth asteroid Eros allowed even greater precision Venus Reclaimed Captain James Cook Observations of the Near-Earth asteroid Eros allowed even greater precision Harold Spencer Jones (1900 – 1960) 1 A.U. = 93,005,000 miles (less than 0.1% uncertainty) Venus Reclaimed Captain James Cook Irwin Shapiro Bounced RADAR echoes from Venus in 1968 Venus Reclaimed Captain James Cook Irwin Shapiro Bounced RADAR echoes from Venus in 1968 In 1976 IAU adopted:- 1 A.U. = 92,958,329 miles = 149,597,870 km Venus Reclaimed Captain James Cook Irwin Shapiro Bounced RADAR echoes from Venus in 1968 ‘Shapiro Effect’ time delay also a test of General Relativity In 1976 IAU adopted:- 1 A.U. = 92,958,329 miles = 149,597,870 km Faro – Helsinki, 3479 km Waikoloa, Hawaii