Four astronomical discoveries from ancient Greece

Galileo’s discovery of Jupiter’s moons led to multiple scientific advancements

Beyond challenging Earth-centric views upon their discovery in 1610, the Galilean moons were also later analyzed to contribute to early astrometry and astronomical interferometry. Measurements of eclipses were also used to estimate the speed of light.

Meet Hipparchus, the Greek astronomer who created the world's first star map

Astronomer Hipparchus created accurate maps of the night sky way ahead of his time, with coordinates sometimes within a single degree of modern values. Hipparchus founded a new theory of star motion, modeling the sky as a celestial sphere with coordinates similar to latitude and longitude—concepts only recently created in Hipparchus' time.

How do scientists study far away stars?

Astronomy is the only science that is purely observational: meaning, scientists can't study stars in a lab. Here's a breakdown of how modern researchers use new tools to understand objects billions of light years away. As it turns out, the rules of science allow us to identify, categorize, and experiment with phenomena light years away.

The Antikythera mechanism: The oldest-known analog computer

A device now considered the world's oldest computer was pulled from a shipwreck more than 120 years ago. Known as the "Antikythera Mechanism," it is now believed to have allowed precise tracking of astronomical positions, and its sophistication overturned understanding of Ancient Greek capabilities.

How the ancients calculated Earth's size correctly

Watch this seven-minute video to hear Carl Sagan explain how ancient Greek polymath Eratosthenes correctly calculated the size of the Earth in the third century BCE. At some point, Eratosthenes noticed a discrepancy in the length of shadows cast in different cities during the summer solstice. This observation grew into a simple experiment that enabled Eratosthenes, the head librarian at the Library of Alexandria, to calculate the Earth's size precisely.

What the stars once meant to ordinary people

The stars were a crucial aid for ordinary human beings in premodern societies, acting as regular timekeeping phenomena and celestial navigators. Today, light pollution and modern technology have rendered the stars a mere aesthetic delight for most of us, but their significance in history remains. Watch this brief video to learn how premodern humans used the stars for navigation, mathematics, and more.

Researchers once thought Stonehenge functioned as a precise astronomical computer

In the 1960s, scientists used early computers to analyze the stone layout at Stonehenge, arguing it could predict eclipses and other celestial events. This BBC Sky at Night Magazine piece explains how the theory arose—and why scholars now doubt it.

Ancient Greece originated roughly 4,000 years ago around the Aegean Sea

From architectural feats to the Western alphabet, ancient Greece has helped shape modern life. Over centuries, the eastern Mediterranean culture grew as far as India, Egypt, and Spain. Its cultural influence has long since spread beyond any physical boundaries.

The 'Celestial Police' accidentally discovered asteroids while planet hunting

The group was formed in 1800 to find a planet some astronomers believed existed between Mars and Jupiter. Prior to their disbanding in 1815, the group instead discovered Vesta, Juno, and other objects they would call asteroids.

Gaia mapped two billion stars in the Milky Way

Using geometric parallax, the European Space Agency mission made position measurements accurate to 2.78 × 10⁻¹⁰ degrees, revealing large-scale galactic structure and dynamics. Remnants of ancient galactic mergers were also identified within the Milky Way.

The scientific name for northern lights came from two Greco-Roman gods

Although cave paintings may have depicted them millennia earlier, one of the oldest known references to auroras is a Babylonian cuneiform tablet from about 600 BCE. In 1619, Galileo Galilei named the phenomenon in the northern hemisphere "aurora borealis" after the Roman goddess of dawn—Aurora—and the Greek god of the north wind—Boreas.

Bad Ancient: a site to fact-check claims about the ancient world

Peruse popular questions about ancient Rome, Egypt, Greece, and more, from whether Greek boxers were ripped or to what extent Alexander the Great conquered the world.

The breakthrough that changed our perception of the universe

In the 1920s, the Hooker Telescope helped Edwin Hubble make a discovery that forever changed how we see the universe. Building on the work of astronomers like Henrietta Leavitt and Harlow Shapley, Hubble used the telescope to prove that galaxies exist beyond the Milky Way—revealing a vast and expanding universe.

The Greeks weightlifted using massive stones—but viewed muscles differently

Ancient Greek art is replete with humans with muscular physiques, but there is very little evidence they knew much about proper weightlifting. There are just a few stones with inscriptions hinting at their weightlifting use. This article exposes some of our modern assumptions about muscle development, suggesting the Greeks thought differently about strength than we do today.

Ancient Greek told to kick rocks after claiming moon wasn't a deity

About 2,500 years ago, ancient Greek philosopher Anaxagoras theorized that the moon probably wasn't a goddess. This article explains how this belief led to his exile. Anaxagoras also argued the sun was just a burning rock, writing that it was the sun that illuminated the moon. According to this resource, this theory enabled Anaxagoras to accurately explain eclipses and lunar cycles.

What did people do before eyeglasses were invented?

An estimated two-thirds of the world's adults use a form of prescription glasses or contacts, proof spectacles were a godsend when they were invented in 1286 CE. But what did people do before that? Different tools were used for distinct vision problems, but some would use magnifying lenses, clear emeralds, and more. Watch this video for a historical explanation.

Analysis finds dementia was rare in ancient Greece

Ancient medical texts seldom mention severe cognitive decline, suggesting that such conditions were uncommon. This scarcity is attributed to factors like shorter lifespans and active lifestyles, implying that modern environmental and lifestyle changes—along with longer life expectancy—contribute to the current prevalence of dementia.

The ancient Greeks and Romans viewed comets and meteors as divine omens

Both considered the appearance of a comet or its fragments as a precursor to significant events, such as the birth of a notable figure or the death of a ruler. One observed in 44 BCE was believed to be a sign of the deification of Julius Caesar after his assassination.

Examine a 3D model of the Rosetta Stone

One of the most famous archaeological finds of all time, the 1799 discovery of the Rosetta Stone helped unlock the secrets of ancient Egypt. Inscribed on the granite slab was the same passage in three languages: hieroglyphics, Old Egyptian, and Greek, which enabled scholars to decode the ancient language. Take an up-close look with this 3D model made up of more than 200 composite photos.

Cecilia Payne-Gaposchkin discovered stars are mostly made of hydrogen and helium

At 25, her doctoral thesis challenged the then-common belief that stars were composed similarly to Earth. Several years later, Henry Norris Russell, who had initially dismissed her findings, independently made the same discovery and received credit for it.

Explore the known asteroids, comets, and spacecraft involved in asteroid studies within our solar system with 'Eyes on Asteroids,' a 3D visualization from NASA.

Modern physics suggests that many universes with different physical laws could exist

Physicists suggest that quantum fluctuations in the early universe could have given rise to these universes. Ancient Greek philosophers like Chrysippus proposed a version of the multiverse over 2,000 years ago—millennia before its adoption into various theoretical frameworks today.

The Four Great Inventions are historically significant Chinese technological advancements

The inventions of paper, gunpowder, printing, and the compass advanced civilizations worldwide by spreading knowledge, enhancing warfare, and improving navigation.

The first interferometric gravitational wave detector was invented in 1972

Robert Weiss completed the designs after his students asked about an earlier apparatus that used stretched aluminum cylinders to detect passing gravitational waves. Unfamiliar with general relativity and hoping to keep the course focused on experimental tests rather than mathematics, Reiss later asked his students to consider his device for homework. (Some readers may experience a paywall.)

An interactive look at Neptune, the distant planet

Dark, cold, and whipped by supersonic winds, Neptune is a gas giant made of hydrogen, helium, ammonia, and methane, and was the first planet discovered through mathematics rather than direct observation. It's also the smallest of the gas planets on the periphery of the solar system. Learn more about the last planet in the solar system through the NASA site.

The art of 'undiscovering' phantom islands

Centuries of maps include islands and isles that appear to only exist on atlases. This article explores the discovery and "undiscovery" of such landscapes, which still persist despite modern technology. As recently as 2012, Google Maps showed an...

Stanford built a Google Maps for the Roman Empire, revealing how much it cost to travel in the ancient world

The first image of a black hole was captured by creating an Earth-sized virtual observatory from a network of eight radio telescopes.

Track the location of the Voyager probes, currently between 13 and 15 billion miles away from Earth.

Visualize the path of every solar eclipse from 1900 to 2099 and see what each looks like when observed from different locations on Earth.

Explore the archaeological treasures of Pompeii, the city buried under volcanic ash when Mount Vesuvius erupted in 79 CE.

Learn more about the history of fireworks, which dates back to an accidental invention during an alchemist's quest for information about immortality.

Stars appear to twinkle because turbulence in the motion of molecules in Earth's atmosphere causes light to bend and wiggle rapidly on its way to the surface—a phenomenon called scintillation.

Most of the observable universe's volume consists of voids and supervoids—enormous regions of space with little to no galaxies, stars, or light.

While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

Before humans, the Soviet Union and the United States sent animals—including apes, dogs, and cats—to space during the Space Race.

After NASA's Voyager 1 captured Earth as a single pixel as it left the solar system in 1990, astronomer Carl Sagan used the image to reflect on humanity's fragility and the responsibility to protect 'the only world we've ever known.'

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

English mathematician Ada Lovelace wrote the first computer algorithm a century before computers existed and hypothesized that computing devices would one day be able to compose music—foreseeing the generative AI systems of today.

Clever Hans was a 1900s horse that was believed to be able to solve math equations, tell time, and read and comprehend German, until a psychology student discovered how he got his answers.

See photos of Meteora, a mountainous site in central Greece, home to 14th-century monasteries perched atop soaring outcroppings.

The Mona Lisa's celebrity status and repeated restorations have obscured what made the painting so revolutionary for its time

The first horror movie is believed to be George Méliès' 1986 short 'The Haunted Castle,' which pioneered the use of special effects

As of 2025, the most cited papers in science include a review of graphene, methods to improve image recognition, streamlining electron density calculations, and optimizing protein studies.

Long before Major League Baseball began allowing instant replay for balls and strikes, an umpire reluctantly used the technology to determine whether a hit was a home run, a move that inadvertently ushered in a new era for the sport.

For centuries, it was common to sleep in two shifts: a few hours at the beginning of the night, and a longer period beginning around midnight

The Brothers Grimm were lawyers before they were storytellers, but became interested in fairy tales as they began investigating how rules and customs had been passed down through cultures.

Meet the 56 signers of the Declaration of Independence—most of whom didn't put pen to paper until August 2, 1776—and see their original signatures.

SpongeBob exemplifies Aristotle's philosophy for living well because he understands that happiness doesn't come from external factors like money, recognition, or power.

Lesser-known phobias include turophobia, or the fear of cheese, and nomophobia, the fear of being without your cell phone.