The%20next%20step

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The next step

• England and the great universities

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Problems remaining

• Elliptical orbits why?
• What was the interaction between the Sun and a
  planet?
• What explained the spacing of the planets?

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Why England

• Prosperous times
• Ascendancy of Oxford and Cambridge
• Creation of the Royal Society (1660)
• Philosophical Transactions (1665)
• A widespread curiosity about nature

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Participants

• Robert Hooke - 1635-1703
• Edmond Halley - 1656-1742
• Isaac Newton - 1642-1727
• Christopher Wren - 1632-1723

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Hooke

• Gifted experimentalist
• discovered elasticity
• coined the term cell
• suggested that Jupiter rotated on its axis
• recorded images of Mars
• suggested that a pendulum could be used to
  measure gravity

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• Examined many things with a microscope
• studied snow flakes
• proposed a theory of evolution
• suggested an inverse square law for gravity
• discovered diffraction of light
• wave theory of light
• air made of small particles, widely separated
• fellow of Royal Society 1663

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On motions

• All bodies attract
• attraction weakened with distance 1/r2
• bodies in motion stay in motion straight line

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Halley

• Astronomer and mathematician
• famous for the discovery of the comet
• observed southern stars for the first time
• close to Newton

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Wren

• He, Hooke and Halley tried to find a mechanical
  explanation for the movements of the solar system
• Savilian professor of astronomy at Oxford
• became the greatest architect of the time

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Newton

• Farming family in Lincolnshire
• father dies, mother remarries
• step father dies
• he is a poor student
• uncle gets him enrolled at Trinity College,
  Cambridge, law
• studies philosophy, mathematics, astronomy

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• Isaac Barrow becomes Lucasian Professor of
  mathematics (1663-69), teaches Newton
• 1665 Cambridge closed - plague
• Newton goes back to the farm for 2 years
• discovers differential/integral calculus - 22
  years old
• experiments with light - white light mixture of
  colors
• 1669 - Newton becomes the Lucasian professor

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• Elected fellow of the Royal Society Hooke is
  president based on reflecting telescope
• presents a paper on light at the RS
• Hooke is critical Newton is outraged
• beginning of an ugly relationship
• 1684 Halley asks N about the orbit of a planet
  attracted by 1/r2
• Newton responds - elliptical
• Hooke also working on this problem

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Advantages one curved surface no holes easy to
make
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• But Hooke does not publish
• N sends manuscript to Halley who urges
  publishing Principia appears in 1687
• The description of motions of bodies
• Similar to Hooke who is upset and accuses N of
  theft
• Hooke dies
• N publishes Opticks
• Retires to Royal Mint 1693

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Story of the apple

• Apples fall to Earth
• why doesnt the Moon fall to Earth?
• Newton said it did fall to Earth but missed.

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Newton understanding of why the Moon orbited the
Earth Critical velocity needed Gravitational
force
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Summary of naked eye obs.

• Correct view of the solar system
• proof of the elliptical orbits
• elliptical orbits due to gravity
• inverse square law of gravity
• role of comets
• tides
• precession of the equinoxes
• period and spacing of planets

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Missing

• How old?
• Why are there planets?
• How many planets?
• Composed of?
• Life on the planets?
• History of the solar system.
• Examine the Moon and Mars