History of Astronomy

Astronomy is a large area of ​​science responsible for many scientific advances and its history is full of great names such as Copernicus, Galileo, Kepler and Newton.

History of Astronomy

Astronomy is a natural science that is basically concerned with studying phenomena that occur outside the terrestrial atmosphere and the structure of celestial bodies, such as planets , stars and other cosmological structures ( comets , galaxies and nebulae, for example), and the space itself. The word astronomy comes from the Greek Astron , which means star, and Nomos , which means law.

History of Astronomy

Many ancient civilizations treated the stars as deities. The study of the movements of the planets and stars allowed ancient peoples to distinguish between planting and harvesting times, for example. Some ancient cultures, such as the Mayans, Chinese, Egyptians and Babylonians, were able to create complex calendars based on the movement of the Sun and other stars.

The ancient Greeks also contributed a lot to the advancement of Astronomy . Many Greek philosophers created models to explain the shape of the Earth, the seasons, as well as the movements of the Sun, Moon , and other planets visible to the naked eye.

One of these philosophers was Thales of Miletus (624-546 BC), who considered the Earth to be a flat disk filled with water. Pythagoras of Samos (572-479 BC), in turn, believed that the Earth had a spherical shape. Aristotle of Stagira (384-322 BC) explained that the phases of the Moon depended on solar illumination, by observing the formation of shadows during eclipses , and also defended the hypothesis that the Universe was finite and spherical and that, together with the stars , was immutable: it had always existed and would always exist.

Aristotle’s view of the solar system was qualitative, as he used few mathematical resources to justify his model. His interpretation soon became accepted, accepted and widespread for centuries, contributing to the propagation of erroneous physical and astronomical concepts. Among these misconceptions, we can highlight the ether: the substance proposed by Aristotle that would compose the celestial bodies, whose existence was investigated until the mid-nineteenth century.

Aristarchus of Samos (310-230 BC) was the first philosopher to propose that the Earth moved around the Sun , nearly 2000 years before Copernicus, and he was also able to measure the size of the Sun and Moon relative to the Earth. Eratosthenes of Kyrenia (276-194 BC) calculated, with good accuracy, the diameter of the Earth.

The first attempts to describe the solar system placed the Sun, the Moon and the other stars at the center of the Universe, which would revolve around the Earth. This model of the Earth-centered solar system became known as geocentric .

The apex of the geocentric system was the complex Ptolemaic model, proposed by the Greek scientist Claudius Ptolemy (AD 85-165). This model had several circular orbits, which described with relative precision the movement of the known planets, but it was not able to explain the retrograde motion of some planets, when observed from Earth. The model was used until the time of the Scientific Renaissance, in the 16th century.

In 1608, Galileo Galilei (1564-1642) faced the geocentric ideas of the time , as well as the view of the immutability of the stars proposed by Aristotle, perfected the telescope and used it to observe the craters of the Moon, the phases of Venus and discovered the Jupiter’s natural satellites: Io, Ganymede, Callixtus and Europa.

The first mathematical model capable of predicting planetary orbits with precision, but with great complexity, was attributed to the French astronomer Nicolaus Copernicus (1473-1543). Copernicus abandoned the geocentric view, attributing, in his model, to the Sun the center of the Solar System, in which the Earth would orbit the king star in a circular path, completing one revolution each year. In this representation, the tilt of the Earth’s axis of rotation would be responsible for the division of the seasons, and the retrograde movement of some planets, such as Mars, and the change in luminosity were explained using different orbits.

Copernicus’ planetary model was later corrected by the precise astronomical observations of the Dane Tycho Brahe (1546-1601). In 1599, the brilliant German astronomer and mathematician Johannes Kepler (1571-1630) became Tycho’s assistant and had in his hands an enormous amount of astronomical data of great precision. Kepler revolutionized celestial mechanics when he enunciated three laws that govern planetary orbits, describing them as ellipses, not circles, as previously believed, and established a mathematical relationship between the period and the orbital radius of the planets.

Years later, with the great contributions of Copernicus, Galileo and Kepler, Isaac Newton (1642-1727) elaborated his Law of  Universal Gravitation , explaining the phenomenon of gravity and planetary dynamics in an unprecedented way.

Areas of Astronomy

Astronomy is a very broad area of ​​knowledge with several subdivisions. Among them, we can highlight:

  • Astrobiology : evolution of biological systems in the universe;
  • Astrophysics : study of the physical properties of celestial bodies, such as their density, temperature, luminosity, among others;
  • Planetary astronomy : study of planetary systems, with an emphasis on the solar system, which brings together nuclear physics, geology, meteorology, etc.

world astronomy day

In Brazil, on April 8, the World Astronomy Day is celebrated , unlike the International Astronomy Day, which is celebrated annually on different dates according to the phase of the Moon. The date aims to strengthen ties between enthusiasts and researchers in the area, as well as to promote the dissemination of Science to the general public. In 2009, 400 years after Galileo Galilei’s first telescopic observations, the International Year of Astronomy was celebrated.

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