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

Four astronomical discoveries from ancient Greece

Modern astronomy relies on making discoveries without being present on the planets, stars, galaxies, and other objects studied. Imagine the difficulty the ancient Greeks had studying them without computers and telescopes. Yet somehow they calculated precise measurements of planetary distances, sizes, and more. Read this page to learn more about early triumphs in astronomical science.

View depictions of world maps throughout history

The first map to use latitude and longitude positions was created by Ptolemy in 150 CE, over 700 years after the oldest known world map, the Imago Mundi, was made with a Babylonian clay tablet. The Spanish crown created a secret master map from hundreds of sailors’ reports.

Early timekeeping tools included sundials, water clocks, and astrolabes

Astrolabes also provided a person's latitude based on the height of the stars in the sky, thus aiding in navigation. Incense and candle clocks relied on the constant burning rate of fire to track the passage of time based on premarked locations with equal-interval spacing.

The hour originated from an ancient Egyptian astronomical system

The movements of astronomical objects, measured in a day and a year, form the foundation of our sense of time. The Egyptians divided each day and night into 12 time eras, using arbitrarily selected stars as references rather than movements of specific celestial objects.

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.

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.

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 Astronomical Congress designated 88 groups of stars as official constellations

This 1928 decision helped distinguish important groups of stars used in navigation, calendars, and mythological storytelling from miscellaneous collections of stars called asterisms. The Big Dipper is a famous asterism in the constellation Ursa Major.

Earth's circumference was estimated over 2,000 years ago using geometry and shadows

By measuring the angle of the shadow cast in Syene when no shadow was cast in Alexandria, Eratosthenes used the distance between the two cities and trigonometry to estimate the Earth's circumference to within a few percentage points of the actual value.

Halley's comet is named after the astronomer who predicted its next appearance

Edmund Halley realized that historical accounts of a celestial object passing in the night sky in 1531 and 1607 referred to the same object he observed in 1682. By applying Newtonian mechanics to his observational data, he calculated its orbit and accurately predicted its return in 1758.

Explore the night's sky from anywhere

Stellarium Web is a planetarium running in your web browser. It shows a realistic star map, just like what you see with the naked eye, binoculars or a telescope. Using its interface, you can click on object's visible at your location on the Earth...

A data visualization exploring six decades of spacewalks

Astronauts' initial small step for mankind may standout, but how many steps have we taken so far? Space and moonwalks further our understanding of spaceflight, celestial bodies, and space itself. Created to resemble a constellation map, this chart...

Explaining why the Earth wobbles

Astronomers going back to Hipparchus in the 2nd century BCE have noticed our planet has a distinct wobble. More recently, scientists have observed that the Earth is 26 miles wider at the equator than from pole to pole. The wobble results from our...

The Greek city of Alexandria in Egypt helped form the template for modern cities

It was designed by Dinocrates, who studied under Hippodamus, the father of urban planning. Hippodamus preached that urban planning should take into account function, culture, and politics. Dinocrates' design of Alexandria meant applying Hippodamus' teachings on a scale never before attempted.

Hubble's first light test produced an underwhelming photograph

This test represents the first time light travels entirely through an observatory's optical system and reaches its detectors, producing an image. Although the telescope's warped mirror was not discovered and announced until a month after first light, the issue was not responsible for the simplicity of the first light image.

The earliest mention of time travel

Time travel has fascinated humans for centuries. It appears in myths, literature, and science fiction. One of the earliest examples comes from the 400 BCE Hindu epic Mahabharata, describing time dilation long before Einstein’s Theory of Relativity. By the 19th century, stories introduced machines enabling time travel—setting the stage for modern sci-fi.

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

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

The team responsible for the first interplanetary sundials included Bill Nye

While reviewing designs for instruments to be carried by future Mars rovers, Nye suggested adapting the function of a calibration tool, which would be used by the Spirit and Opportunity rovers to help calibrate the brightness and color of their panoramic cameras on the Martian surface.

Who was the world's first author?

This article details the effort to define the world's first author, as supported by current archaeological evidence. Clay disks found in an ancient Sumerian city point to Enheduanna, a high priestess and daughter of Akkadian King Sargon, as the...

The term 'cancer' is 3,000 years old

Around 400 BCE, Hippocrates is said to have named masses of cancerous cells "karkinos"—the Greek word for crab. Science and medical historian Dr. Howard Markel discusses a few hypotheses on why Hippocrates named the disease after a crab and how well cancer was understood in the ancient world.

A Belgian Catholic priest was the first to come up with the idea for the Big Bang

In 1931, Georges Lemaître presented his radical idea that the universe came from a “primeval atom,” challenging the long-held belief that the universe had always existed. Einstein initially dismissed Lemaître’s work as having “abominable” physical insight, only to accept it later.

How a competition honoring a king's birthday uncovered history's first chaotic system

A committee established a contest for King Oscar II's 60th birthday, featuring four unsolved problems in mathematics, including one on proving the stability of a system of more than two objects held together by gravity. Focusing on three celestial objects, Henri Poincaré won the prize for his proof, which he later learned was incorrect and, upon correcting it, instead proved these systems to be unstable.

Sun Ra, a free jazz legend, claimed he was an angel

Sun Ra is one of jazz's most storied cult acts, with a career that spans multiple decades, dozens of hard-to-find self-released albums, and a sound that challenged even the most adventurous listeners. Ra, born Herman Blount, claimed to be from Saturn and once told an interviewer that "Star Wars" was "very accurate."

Vincent Van Gogh's 'The Starry Night' accurately depicts turbulent flow

Analysis of the swirling patterns in the painting found an alignment with the mathematics used to describe turbulence, despite Van Gogh's unfamiliarity with the science. The depiction may indicate he possessed an uncanny ability to capture nature's details.

The USSR launched the world's first satellite, Sputnik 1, into space in 1957

Sputnik, launched by the Soviet Union in 1957, became the world's first artificial satellite. While the technology itself was limited, the launch ignited the space race and signaled that intercontinental missiles and space technology had arrived faster than American leaders expected.

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

Francis Drake: favored English pirate who sailed around the world

Before becoming the global explorer that many know him as today, Sir Francis Drake was a pirate, merchant, and slave trader. This in-depth article dives into the life of Drake, who's commonly credited as the first person to circumnavigate the globe by ship successfully.

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

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.'

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

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.

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

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.

The term 'algorithm' originated from the Latinized name of al-Khwārizmī, a 9th-century mathematician whose works introduced Arabic numerals and the decimal-based numeral system to Europe and whose treatise 'Al-Jabr' gave algebra its name.

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

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.

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.

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

Explore an interactive map built from more than 100,000 survey responses on where people find joy in their lives

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 19th-century painters of the Hudson River School were among the first American romantics, with portraits that displayed the natural beauty of the young country.

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.

One disco producer saw 'Star Wars' four times on its opening weekend and was so inspired that he recorded the album 'Star Wars and Other Intergalactic Funk,' which produced a chart-topping single.

Double world record holder Hunter Ewen helped conquer his fear of balloons, called globophobia, by training to win Guinness World Record titles for balloon inflation.

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.

Jimmy Carter signed a 1978 bill that legalized home brewing, a move credited with kick-starting the craft beer industry.

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

Take a 3D tour of the Hajj, Islam's annual pilgrimage to Mecca, undertaken by over 1.5 million Muslims.

The American cockroach is actually from Africa, an apparent hitchhiker aboard ships carrying enslaved people, with evidence suggesting the bug may have arrived in the New World as early as the 1600s.