Henry Cavendish (1731

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Henry Cavendish(1731 1810)

• The Weighing of the Earth

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Personal Life

• As the grandson of the Second Duke of Devonshire,
  he was considered nobility
• He attended Cambridge University from 1749
  1753, but left without earning a degree
• His inherited fortune enabled him to pursue
  scientific studies
• Viewed as solitary and eccentric, he had no
  friends apart from his family
• Aspergers Syndrome account for his unusual
  shyness
• Prohibited from publishing his work until James
  Clerk Maxwell looked through his papers
• Saw credit to most his discoveries had been given
  to others
• Richters Law of Reciprocal Proportions, Ohms
  Law, Daltons Law of Partial Pressures

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Discovery of Hydrogen

• In 1766, In a paper called On Factitious Airs
  Cavendish addresses a inflammable air which
  forms water as a result of combustion.
• Antoine Lavoisier later reproduced the experiment
  giving Cavendishs element the name Hydrogen

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Composition of Atmosphere

• Established an accurate composition of the
  atmosphere
• 79 phlogisticated air (nitrogen and argon)
• 21 dephlogisticated air (oxygen)

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Weighing of Earth

• Cavendish used an torsion balance apparatus to
  complete the experiment in 1797
• Originally created by John Mitchell who died
  before he could put it to use
• Apparatus sent in crates to Cavendish
• The apparatus consisted of a torsion balance to
  measure the gravitational attraction between two
  350 pound lead spheres
• Consisted of a 6-ft wooden rod with metal spheres
  attached to each end, hanging from a wire which
  twisted as a result of the gravitation attraction
  between them
• Wind proof room
• Torsion of wire measure by the telescope

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Gravitation Constant and Mass of Earth

• With G, he could easily calculate the earths
  mass to be 5.9725 billion trillion tons (his
  estimate was 1 off)