IN Lascaux Caves of southwestern France, who are known for 17,000-year-old ornate paintings, the artist’s subject is almost always a large animal.
But hovering over the image of a bull is an unexpected addition: a group of tiny black dots that some scholars interpret like stars. Perhaps these are the alluring Pleiades that Paleolithic hunter-gatherers would have seen vividly in the unpolluted sky.
The claims of prehistoric astronomy are controversial. Even if it is true, we often track our cosmic perspective instead Nicolaus Copernicus, who in 1543 set a steady course by proving that the earth revolved around the sun; to Galileo Galilei and Johannes Kepler, who advanced the heliocentric theory a generation later; and to all their successors, who in just a few centuries (with the considerable advantage of telescopes and other advanced technology) produced an astonishingly detailed map of the universe.
Yet for tens of thousands of years, humans studied the heavens only with the naked eye and ultimately with crude instruments. They got a lot wrong, but ancient astrologers were no slouch, and a few thousand years ago they became surprisingly sophisticated.
“It is no exaggeration to say that astronomy has existed as an exact science for more than five millennia,” wrote the late historian of science John North.
Reading the sky
Traces of these early observers, of how they interpreted the cosmos, have reached us in the form of tantalizing artifacts. For example, dating from approximately 1600 BC, we have what is perhaps the first portrait of the universe: the celestial disc of Nebra.
Nebra’s Sky Disc (Courtesy of: Frank Vincentz/CC BY-SA 4.0/Wikimedia Commons
Discovered just two decades ago in what is now East Germany, this 12-inch bronze circle is inlaid with gold stripes in the shape of the sun, crescent moon and various stars. It may have been used for religious or agricultural purposes, but its significance to those who made it is unclear.
Deeper meanings aside, experts generally agree that the disc is the oldest known concrete image of astronomical phenomena, and that it is more than a vague abstraction. A dense cluster of stars appears to represent the Pleiades (and more accurately from the Lascaux cave painting).
If The Seven Sisters keep popping up at different times and places may not be a coincidence—the cluster has attracted attention throughout recorded history simply by standing out from its lonely neighbors. Some cultures have used it as signal of when to plant and harvest.
Searching for meaning
Around the same time, the ancient Egyptians, who already had a long history of astronomical observation, were developing star charts. These schematic illustrations describe the movements of various stars—probably to keep the priests accurate for their nocturnal rituals, or perhaps to lead the dead to the afterlifeas illustrations often appear in caskets.
Later, probably in the first century BC, the Egyptians became more imaginative with Zodiac sign Dendera. At first this bas-reliefwhich decorated the ceiling of a temple dedicated to the god Osiris, looks like a random menagerie: rams, lions, crocodiles and others arranged in a circle.
Dendersky Zodiac (Credit: Sergey-73/Shutterstock)
But soon after its discovery in 1799, Egyptologists recognized it as a painting of the night sky organized around many of the same constellations we still use today.
The Babylonians of the first millennium BCE recorded their astronomical knowledge in a similar way, inscribing on clay tablets the heliacal rising of important stars—that is, the day on which a star first appeared above the horizon each year. From these lists, they produce “planispheres”, instruments that indicate which stars (and, importantly for their astrological predictions, which constellations) will be visible at any given moment.
Incorporating Greek philosophy
The word “cosmos” comes from ancient Greece, where it means not just the universe, but the universe as a harmonious, well-ordered whole. Although these classical philosophers took what they found useful from the Egyptian and Babylonian traditions, they broke with the supernatural elements of astrology, choosing celestial mechanics based on (more or less rigorous) reasoning and mathematics.
One method of cosmic display at the time was armillary sphere, a globe-like model with several rings to illustrate the movement of the Sun, Moon, and stars. The earth, according to the Greco-Roman reckoning, stood still in the center.
In this case, the sphere is “Ptolemaic,” named after the Alexandrian astronomer Ptolemy, whose geocentric paradigm dominated Western belief until 1500. Spheres that instead show the Earth orbiting the Sun are naturally called “Copernicus.”
Armillary sphere (Credit: Giuseppe Cammino/Shutterstock)
For his sublime picture of the heavens, the Greek philosopher Aristotle took geocentrism to its logical conclusion. As he saw it, the universe consisted of a series of concentric shells revolving around our planet—one for the sun, the moon, each other planet, the fixed stars, and the outermost level for the “prime mover,” a being he concluded that it must have been necessary to set it all in motion.
Moving towards modernity
This godlike vision dovetailed well with the rise of Christianity. During the medieval period this became conventional wisdom – despite the theoretical acrobatics required to equate it with actual astronomical observations (in particular, retrograde motion of the planet).
The combined vision of Aristotle and Ptolemy was in fact so influential that by the 14th century the Italian poet Dante Alighieri structures his world Divine comedy around him. And all he had to do was add a second set of concentric hells.
The Copernican revolution and its aftermath have long since swept away these antiquated notions, of course. But with every scientific advance, every mind-blowing image from deep space from the James Webb Space Telescope, we are expanding our view of space and continuing the process that those cavemen began when they stepped outside to look at the sky.