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Galileo Galilei

1564 - 1642

Galileo Galilei

Galileo Galilei, was an Italian scientist whose name is synonymous with the start of the modern scientific method at the beginning of the scientific revolution of the 16-17th centuries.

  • Nationality
  • Italian

  • Subject
  • Physics

  • Fields
  • Mechanics, Astronomy, Mathematics, Inventions

  • Distinctions
  • Appellations of "Father of Modern Physics" and "Father of Observational Astronomy", and even "Father of Science".

  • Posts
  • Professor of Mathematics (and Astrology) at Pisa and Padua Universtities.

    Matematico Primario (first mathematican) to the Gand Duke of Tuscany (Medici).

  • Publications
  • Il Saggiatore (The Assayer), 1623, which discussed the nature of comets, and led to a discussion of the nature of science itself. The Assayer is known as Galileo's manifesto of the scientific method.

    Dialogo sopra i due massimi sistemi del mondo (Dialogue Concerning the Two Chief World Systems), 1632. The two systems Galileo compared in this book were the Copernican heliocentric system and the Ptolemaic (or Tychonic) system, which placed the Earth at the centre of a complicated series of circles.

    Discorsi e Dimostrazioni Matematiche Intorno a Due Nuove Scienze(Discourses and Mathematical Demonstrations Relating to Two New Sciences), 1638. The two new sciences are today called kinematics and strength of materials.

  • Theories
  • Gravitational acceleration

    Pendula and periodic motion

    Heliocentric solar system, providing observation and theoretical confirmation of Copernicus's conjecture that the Sun was the centre of the solar system.

    Theory of tides, which he attempted to use as proof of the motion of the Earth. This theory was shown to be incorrect because it could not explain the two tides which occurred each day.

    He did not accept Kepler's conjecture of elliptical orbits, thinking the circle was the more 'perfect' of shapes for orbits of planets.

  • Equations
  • Although unable to make measurements of time intervals without a precise clock, he derived the acceleration of objects in terms of a geometrical progression. Today we express this relationship as: $d = 1/{2}at^2$, where $d$ is the distance an object falls from rest, $a$ is the acceleration (or $g$ in the case of Earth's gravitational field) in time $t$ (seconds).

  • Experiments/Discoveries
  • Measurement of gravitational acceleration (falling bodies), buoyancy and density, refracting telescope, discovery of moons of Jupiter.

    Observations using the refracting telescope. Although a spyglass of sorts already existed, Galileo was the first to adapt and improve it for astronomical purposes. His observation of the moons of Jupiter demonstrated that not all heavenly bodies orbited the Earth. He also discovered the craters on the Moon, and published detailed drawings.

    Galileo invented a military compass, which he sold through a type of catalogue sales system. He also pioneered a type of thermometer.

    The little balance: a hydrostatic device for measuring the Archimedean density/water displacement principle.

Pendulum in Pisa Cathedral
Galileo is reputed to have hit upon the counter-intuitive idea that the period of swing of a pendulum is independent of the mass, by observing a chandelier swinging in the Pisa Duomo.

Galileo Galilei is commonly referred to by his first name, Galileo, for some reason. He was an inventor and instrument maker as well as radical thinker who applied scientific principles of experiment/observation and the onus of verification (now the empirical method) to challenge long-standing preconceptions.

When these challenges touched on the Church's central dogma, specifically that the Earth was the centre of all the universe, Galileo was arrested, tried for heresy, and placed under house arrest (1633). Nevertheless, his books and his ideas found a more enlightened audience abroad, and inspired a revolution in science.

Galileo was forced to renounce his support of the heliocentric system in a kangaroo trial in Rome. However, he famously murmured 'E pur si muove' (and yet it moves) at the conclusion of his trial, reaffirming his claim that it is the Earth that moves around the Sun, rather than vice-versa. This has come down through history as iconic the ultimate victory of science over religious dogma.

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