Cosmic Chronicles: A Journey Through Astronomical Discoveries

Ancient Astronomical Observations

Early astronomers peered into the sky month by month, as part of a religious ritual. They noted that certain stars appear just before the sun and disappear immediately after it. These observations were repeated over the years, with meticulous measurements and annotations of the times and positions these phenomena occurred in the sky. This led to the conclusion that these cycles were repeated cyclically with each season. The sky, in essence, provided a large celestial schedule that allowed them to predict seasons favorable for hunting and navigation.

For the Egyptians, when the star Sirius appeared above the horizon before dawn, it signaled the approach of the planting season. The Babylonians, meanwhile, developed astrology and laid the foundations of modern astronomy. To describe the motion of the sun, moon, and planets, they invented the sexagesimal system and established the Zodiac and the first calendars.

Precession of the Equinoxes and Astrological Misinterpretations

The Earth's axis undergoes a movement, similar to a wobble or "pitch," which is called the Precession of the Equinoxes. This movement is responsible for the phenomenon where, approximately every 2160 years, the beginning of spring and all the horoscope signs shift back one position. While precession is a real astronomical phenomenon, its application to astrological predictions falls under pseudoscience.

Greek Contributions to Astronomy

In Greek culture, the understanding of the cosmos gradually shifted. Little by little, mythological explanations involving gods were replaced by mathematical reasoning and physical laws that tried to explain the nature of things and the behavior of natural phenomena. Greek culture thus laid the physical and mathematical foundations of modern astronomy.

Influential Greek Astronomers

• Aristotle (384-322 BC), a Greek philosopher, considered the Earth to be the center of the universe, imagining a geocentric universe.
• Aristarchus of Samos (310-230 BC), an Ionian scientist, was the first to establish the heliocentric model of the universe, proposing that the Earth and planets revolve around the Sun.
• Eratosthenes (276-194 BC) famously demonstrated the sphericity of the Earth and calculated its perimeter and terrestrial radius with remarkable precision.
• Hipparchus (190-120 BC), a mathematician and astronomer, developed the first comprehensive star map.
• Ptolemy (100-170 AD) reviewed the ideas of Aristotle and, in his influential work Almagest, reinforced the geocentric model, which remained dominant for over a millennium.

The Scientific Revolution in Astronomy

Pioneering Figures

• Nicolaus Copernicus (1473-1543) had the courage to deny the apparent evidence that the sun rises from the east and sets in the west. His solid mathematical calculations established the modern heliocentric model.
• Johannes Kepler (1571-1630), based on the careful calculations of Tycho Brahe, discovered that the orbits of the planets were elliptical, formulating his three laws of planetary motion.
• Galileo Galilei (1564-1642) built the first astronomical telescope and made groundbreaking observations that supported the heliocentric model, leading to significant conflicts with the established views.
• Isaac Newton (1642-1727) explained the cause of motion of the planets orbiting the sun through his theory of universal gravitation in 1667, providing a comprehensive physical framework for celestial mechanics.