Astronomy in our Early History

galileo and telescope
Galileo offering his telescope to three young women seated on a throne. Painting by unknown artist. Library of Congress.

Astronomy and our interest in the sky are almost as old as human history. 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. People were moving from a simple "awe" of the sky to an understanding of the motions of celestial objects, a connection between the sky and the seasons, and ways to "use" the sky to create calendars.


Nearly every culture had a connection to the sky, often as a calendrical tool. Nearly all also saw their gods, goddesses, and other heroes and heroines reflected in the constellations, or in the motions of the
Sun, Moon, and stars. Many tales invented during the ancient epochs are still told today.

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. There's 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 Chinese weren't 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 wasn't 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 wasn't long before Eratosthenes of Cyrene calculated Earth's size using the new tools of measurement and mathematics. These same tools eventually allowed scientists to measure other worlds and calculate their orbits.

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. 

Although travelers (particularly sailors) relied on the stars for navigation from the earliest days of Earth exploration, it wasn't 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", didn't 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 idea of a Sun-centered universe didn't sit well with the established Catholic church at the time. Even when Galileon Galilei used his telescope to show that  Jupiter was a planet with moons of his own, the church didn't approve. His discovery directly contradicted its own holy scientific teachings, which were based on the old assumption of human and Earth superiority over all things. 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. 

However, in Galileo's time, the telescope's invention primed the pump for discovery and scientific reason that continue to this day. 

Edited and updated by Carolyn Collins Petersen.