Pierre Simon Laplace (1749-1827), a French astronomer and mathematician, is famous for having successfully applied Newton's theory of gravitation to planetary movements in the Solar System.

Laplace showed that planetary movements are stable and that the disturbances produced by the mutual influence of planets or by external bodies, such as comets, are only temporary. He tried to give a rational theory of the origin of the Solar System in his nebular hypothesis of stellar evolution.

He was born on March 23, 1749 in Normandy, although in some biographies he appears on 28. At eighteen he already distinguished himself as a teacher and mathematician at the Beaumont military school. He got letters of recommendation and, in 1767, left for Paris to request the help of the distinguished French mathematician D'Alembert. With his help, he later obtained the appointment of a professor of mathematics at the military school in Paris, and his entry into the world of science was assured.

Laplace's first scientific work was his application of mathematics to celestial mechanics. Newton and other astronomers were unable to explain the deviations of the planets from their orbits, predicted mathematically. Thus, for example, it was determined that Jupiter and Saturn sometimes advanced, and others were delayed with respect to the positions they should occupy in their orbits.

Laplace devised a theory, which confirmed with mathematical evidence, that the variations were normal and corrected themselves over the course of long stages of time. It was considered that this theory was of great importance to understand the relationships of the celestial bodies in the Universe, and has endured the test of time without hardly any corrections.

He clarified scientific knowledge about the elemental forces of Nature and the Universe. He wrote articles about the force of gravity, the movement of projectiles and the ebb and flow of tides, the precession of the equinoxes, the shape and rotation of Saturn's rings and other phenomena.

He studied the balance of a rotating liquid mass; He also devised a theory of surface tension that was similar to the modern concept of molecular attraction or cohesion within a liquid.

Working with Lavoisier, he studied the specific heat and combustion of various substances, and laid the foundations for the modern science of thermodynamics. He invented an instrument, known as ice calorimeter, to measure the specific heat of a substance. The calorimeter measured the amount of melted ice by the given weight of a hot substance whose temperature was known. Then, its specific heat could be calculated mathematically.

When studying the gravitational attraction of a spheroid on an external object, he devised what is known today as the Laplace equation, which is used to calculate the potential of a physical magnitude at a given time while in continuous motion. This equation not only has application in gravitation, but also in electricity, hydrodynamics and other aspects of physics.

Between 1799 and 1825, Laplace gathered his writings in a five-volume work, entitled Celestial Mechanics, in which he intended to give a history of astronomy, systematizing the work of generations of astronomers and mathematicians, and offering a complete solution to the problems Solar system mechanics. He later published a volume entitled The System of the World. In 1812 he published his Analytical Theory of Probability, which is a study on the laws of probability.

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