{"id":26238,"date":"2021-11-18T11:29:18","date_gmt":"2021-11-18T11:29:18","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/?post_type=purple_issue&p=26238"},"modified":"2021-11-18T11:29:18","modified_gmt":"2021-11-18T11:29:18","slug":"explainer-2","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/2021\/11\/18\/explainer-2\/","title":{"rendered":"Explainer"},"content":{"rendered":"\n
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Johannes Kepler<\/span><\/h4>\n\n

Jane Green looks at the life of the pioneering scientist and his laws of planetary motion<\/p>\n\n

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Johannes Kepler (1571-1630), described by astronomer Carl Sagan as the \u201cfirst astrophysicist and the last scientific astrologer\u201d<\/figcaption><\/figure><\/div>\n\n

Akey figure in the scientific revolution of the 17th century, Johannes Kepler was an astronomer, mathematician, astrologer and staunch Lutheran. He was born on 27 December 1571 into a lower middle-class family in the town of Weil der Stadt (in today\u2019s southern Germany). In a pre-scientific, pre-Enlightenment era \u2013 driven by rival Protestant and Catholic Reformations \u2013 tensions, antagonisms, devil-fearing and witch-hunting were rife. Many people were persecuted for their beliefs. Abandoned by a feckless soldier-of-fortune father,<\/span> Heinrich, and a \u2018generally unpleasant\u2019 mother, Katharina, Kepler was brought up by grandparents. Small, sickly and sensitive, his hands and eyes disabled by smallpox, he took solace in God \u2013 the creator of all things \u2013 as he would throughout life.<\/span><\/p>\n\n

Excelling in grammar, rhetoric, logic, arithmetic, geometry, music, astronomy, Greek and Hebrew in the Latin school system, a three-year theology scholarship at T\u00fcbingen University followed. Here he practised astrology \u2013 the \u2018foolish little daughter of the respectable, reasonable mother astronomy\u2019 \u2013 casting horoscopes for fellow students. He even played King Herod\u2019s wife in an outdoor theatre production.<\/p>\n\n

Aware of Ptolemy and Aristotle\u2019s Earth-centred Universe, it was the teacher and astronomer Michael Maestlin who introduced Kepler to the Sun-centred theory of Copernicus. Its unchanging, divinely-driven \u2018mechanical\u2019 movement sparked a lifelong obsession \u2013a need to mathematically understand God\u2019s divine architecture, the harmony of the heavens.<\/p>\n\n

Epiphany came when he was teaching at a boys\u2019 school in Graz, Austria. While demonstrating the periodic conjunction of Jupiter and Saturn he beheld the geometrical scaffolding on which all known planetary spheres were placed; overwhelmed, he wept. After lengthy calculation (and some fudging) God\u2019s geometrical plan, influenced by Copernicus and respecting the Bible, was revealed in his <\/span>Mysterium <\/em>Cosmographicum. <\/em>Despite being sent a copy, Galileo offered scant approval. However, the great Danish observational astronomer Tycho Brahe was enthusiastic and they began a written correspondence, with Brahe hinting at possible future employment for Kepler.<\/p>\n\n

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Astronomers Tycho Brahe (right) and Johannes Kepler famously worked together in Prague, but not always harmoniously<\/figcaption><\/figure><\/div>\n\n
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A fitting namesake, the Kepler Space Telescope hunted exoplanets from 2009\u20132018<\/figcaption><\/figure><\/div>\n\n
Modelling planetary motion<\/strong><\/h5>\n\n

Kepler proposed that the distance relationships between the six planets known at that time could be understood in terms of the five Platonic solids. In 1597 Kepler married the \u2018weak and annoying\u2019 Barbara M\u00fcller. Solitary, melancholic, somewhat chauvinistic and hydrophobic (he did not bathe for eight years!) Kepler focused on his principal work, <\/span>Harmonices <\/em>Mundi <\/em>\u2013a convoluted discussion of symmetry and cosmic harmony, where he geometrically embedded the five Platonic solids within the orbits of the six known planets and attributed the motions and eccentricities of them to musical intervals. Kepler was often wrong, but his <\/span>Harmonices <\/em>Mundi <\/em>contained the third of his three laws of planetary motion \u2013 in which he states that the cube of the average distance of a planet from the Sun divided by the square of the time to complete one orbit is equal to a constant, a value applicable to all planets \u2013 and in this, as well as his first and second laws, he was proven spectacularly correct.<\/p>\n\n

In 1600 Kepler joined Brahe at Ben\u00e1tky Castle near Prague where, along with Danish astronomer Christen S\u00f8rensen Longomontanus, he observed Mars. Frustrated by Brahe withholding data, Kepler returned to Graz. He would later return to Prague and, forgiven by Brahe, use his data to begin the Rudolphine <\/em>Tables <\/em>\u2013a star catalogue and planetary almanac for Holy Roman Emperor Rudolph II.<\/p>\n\n

After Brahe\u2019s death in October 1601, Kepler became Prague\u2019s Imperial Mathematician and he completed Astronomia <\/em>Nova <\/em>\u2013 the result of his 10-year investigation into the motion of Mars. It included his first and second laws of planetary motion; respectively planets orbit in ellipses with the Sun as one of the two foci (focus points) of each ellipse, and a line drawn from a planet to the Sun sweeps over equal areas in equal time.<\/span><\/p>\n\n

Despite unrelenting heartache \u2013 Barbara\u2019s epilepsy, depression and death, the loss of their favourite son to smallpox, religious persecution, professional rivalry, remarriage and losing many offspring \u2013 he remained ahead of his time, immersing himself in his studies. Areas of interest included optics and optical anatomy; supernovae; Galileo\u2019s Jovian moons; telescope lenses and light transmission; telescope design (he invented a type of refractor); six-cornered snowflakes; and hexagonal packing of spheres and comets. He even defended his mother at a witch trial.<\/span><\/p>\n\n

Kepler died in November 1630, aged 58. He left an astonishing legacy, not least of which proving that planets circle stars in elliptical, not circular, orbits, a theory on which space exploration depends. Isaac Newton\u2019s law of universal gravitation, published in 1687, crowned the cosmic structure Kepler had begun. Kepler was indeed the scientific giant upon whose shoulders other scientists metaphorically stood.<\/p>\n\n

<\/p>\n\n

<\/div>
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Five landmark works<\/h4>\n\n\n\n

A prolific writer, Johannes Kepler\u2019s published writings showcase major aspects of his scientific thinking<\/strong><\/p>\n\n\n\n

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In 1596 Kepler proposed that the distance relationships between the six known planets could be understood in terms of the five Platonic solids<\/figcaption><\/figure><\/div>\n\n\n\n

Mysterium Cosmographicum <\/strong><\/em>(\u2018The Cosmographic Mystery\u2019), 1596 \u2013 the first published defence of the Copernican system, in which Kepler demonstrated his model of the planets using geometric shapes.<\/p>\n\n\n\n

Astronomia Nova <\/strong><\/em>(\u2018New Astronomy\u2019), 1609 \u2013 contains his first and second laws of planetary motion.<\/p>\n\n\n\n

Harmonices Mundi <\/strong><\/em>(\u2018The Harmony of the World\u2019), 1619 \u2013 contains his third law of planetary motion.<\/p>\n\n\n\n

Astronomiae Pars Optica <\/strong><\/em>(\u2018The Optical Part of Astronomy\u2019), 1604 \u2013 Kepler\u2019s exploration into eclipses, looking at the workings of light in reflection and refraction to explain astronomical phenomena.<\/p>\n\n\n\n

De Stella Nova <\/strong><\/em>(\u2018On The New Star\u2019), 1606 \u2013 He wrote the book about the appearance of the supernova SN1604, also known as Kepler\u2019s Nova.<\/p>\n<\/div><\/section>\n\n

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\"\"<\/figure><\/div>\n<\/div>\n\n\n\n
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Jane Green <\/strong>is an astronomy writer and author of the Haynes Astronomy Manual<\/em><\/p>\n<\/div>\n<\/div>\n\n

<\/p>\n\n

PHOTOS: IANDAGNALL COMPUTING\/ALAMY STOCK PHOTO, HISTORIC ILLUSTRATIONS\/ALAMY STOCK PHOTO NASA AMES\/JPL-CALTECH\/T PYLE<\/p>\n","protected":false},"excerpt":{"rendered":"

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