Astronomy from Prehistory to Galileo

Astronomy and humanitys interest in the sky are almost as old as the history of intelligent life on our planet. As civilizations formed and spread across the continents, their interest in the sky (and what its objects and motions meant) grew as observers kept records of what they saw. Not every record was in writing; some monuments and buildings were created with an eye toward a link with the sky. The pyramids in Egypt, for example, not only housed the remains of their Pharaohs, but some were also aligned with certain star patterns and stars. Nearly every culture had a connection to the sky. Everybody also saw their gods, goddesses, and other heroes and heroines reflected in the constellations. The motions of the Sun, Moon, and stars had ritual meaning, and many tales invented during the ancient epochs are still told today. This fascination with sky objects may date back tens of thousands of years, and some primitive art examples, such as the caves at Lascaux, France, have paintings that appear to show constellations and star patterns. Beyond the ritual and sacred perceptions of the sky, however, people were moving from a simple awe of the sky to an understanding of the motions of celestial objects. They used a connection between the sky and the seasons, and ways to use the sky to create calendars.  Ã‚   Early Neolithic people are thought to have built Stonehenge in England as a connection to the sky. It seems to have a link to Moonrise and Moonset times throughout the year. Orion Lawlor Using the Sky What most historians find quite interesting today is how humanity moved from merely charting and worshipping the sky to actually learning more about celestial objects and our place in the universe. Theres plenty of written evidence of their interest. For example, some of the earliest known charts of the sky date back to 2300 BCE and were created by the Chinese. They were avid skywatchers, and noted such things as comets, guest stars (which turned out to be novae or supernovae), and other sky phenomena.   The ecliptic is the path that the Sun, Moon and planets appear to follow in the sky throughout the year. The constellations that appear along the ecliptic are called the zodiac constellations. These had special meaning to early astrologers, who used them in rituals and to attempt to predict events. Carolyn Collins Petersen The Chinese werent the only early civilizations to keep track of the sky. The Babylonians first charts date back to a couple of thousand years BCE, and the Chaldeans were among the first to recognize the zodiac constellations, which is a backdrop of stars through which the planets, Sun, and Moon appear to move. And, although solar eclipses have occurred throughout history, the Babylonians were the first to record one of these spectacular events in 763 BCE.   Explaining the Sky Scientific interest in the sky gathered steam when the earliest philosophers began pondering what it all meant, both scientifically and mathematically. In 500 BCE the Greek mathematician Pythagoras suggested that Earth was a sphere, rather than a flat object. It wasnt long before people such as Aristarchus of Samos looked to the sky to explain the distances between stars. Euclid, the mathematician from Alexandria, Egypt, introduced concepts of geometry, an important mathematics resource in most of the known sciences. It wasnt long before Eratosthenes of Cyrene calculated Earths size using the new tools of measurement and mathematics. These same tools eventually allowed scientists to measure other worlds and calculate their orbits. Early tools, like the armillary sphere, were sometimes based on incorrect astronomy theories. Aristarchuss calculations on the relative sizes of the Sun, Earth, and Moon. These were done in the 3rd century B.C.E. Public Domain. The very matter of the universe came under scrutiny by Leucippus, and along with his student Democritus, began to explore the existence of the  fundamental particles called atoms. (Atom comes from the Greek word meaning indivisible.) Our modern science of particle physics owes a great deal to their first explorations of the building blocks of the universe.   Our modern attempts to understand the structrure of the atomn (as shown in thise artists concept) are based on ancient Greek explorations of the nature of matter. Science Photo Library/Getty Images Although travelers (particularly sailors) relied on the stars for navigation from the earliest days of Earth exploration, it wasnt until Claudius Ptolemy (more familiarly known simply as Ptolemy) created his first star charts in the year 127 AD that maps of the cosmos became common. He cataloged some 1,022 stars, and his work called The Almagest became the basis for expanded charts and catalogs through the succeeding centuries.   The Renaissance of Astronomical Thought The concepts of the sky created by the ancients were interesting, but not always quite right. Many early philosopher were convinced that Earth was the center of the universe. All else, they reasoned, orbited our planet. This fit well with established religious ideas about the central role of our planet, and humans, in the cosmos. But, they were wrong. It took a Renaissance astronomer named  Nicolaus  Copernicus  to change that thinking. In 1514, he first suggested that Earth actually moves around the Sun, a nod to the idea that the Sun was the center of all creation. This concept, called heliocentrism, didnt last long, as continued observations showed that the Sun was just one of many stars in the galaxy. Copernicus published a treatise explaining his ideas in 1543. It was called  De Revolutionibus Orbium Caoelestium (The Revolutions of the Heavenly Spheres). It was his last and most valuable contribution to astronomy.   The status of Copernicus in front of the Jagiellonian University of Krakow, Poland. photo muguette/Getty Images The idea of a Sun-centered universe didnt sit well with the established Catholic church at the time. Even when astronomer Galileo Galilei used his telescope to show that  Jupiter was a planet with moons of his own, the church didnt approve. His discovery directly contradicted the holy scientific teachings. Those were based on the old assumption of human and Earth superiority over all things. Galileos writings were extensive chronicles of his work, although they were suppressed for a time. That would change, of course, but not until new observations and a flourishing interest in science would show the church how wrong its ideas were.   Galileo Galilei began the era of modern astronomy when he turned a telescope to the sky. His actions unleashed events that reverberated into the 20th century. Library of Congress. However, in Galileos time, the telescopes invention primed the pump for discovery and scientific reason that continue to this day.  His contributions and those of other ancient astronomers remain important in modern astronomy. However, for astronomy to advance, it had to move beyond small telescopes and naked-eye observations. The centuries following Galileos lifetime would bring astronomy into its own as a separate scientific discipline. Key Takeaways People have been interested in astronomy as long as they have been able to look up.The first astronomers used the sky as a calendar and time-keeping device, following as the stars changed daily and over the seasons.Cultural interest in the sky led people to associate constellations and certain stars and planets with their gods, goddesses, heroes and heroines.The Greek, Babylonian, Chinese, and other early astronomers began charting the skies.The Greek astronomy was used by the Romans.The first parents of modern astronomer were Copernicus and Galileo. Sources Krupp, E.  Echoes of the Ancient Skies: the Astronomy of ..  Harper Krupp, 1983.Krupp, E. C.  Skywatchers, Shamans Kings: Astronomy and the Archaeology of Power. Wiley, 1997.â€Å"Prehistoric Cave Art Suggests Ancient Use of Complex Astronomy.†Ã‚  ScienceDaily, ScienceDaily, 27 Nov. 2018, www.sciencedaily.com/releases/2018/11/181127111025.htm.Tang, Yvonne. â€Å"The History of Astronomy.†Ã‚  Home - Curious About Astronomy? Ask an Astronomer, 17 Jan. 2015, curious.astro.cornell.edu/people-and-astronomy/the-history-of-astronomy. Edited and updated by Carolyn Collins Petersen.