What the stars once meant to ordinary people

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.

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.

New ways of seeing the cosmos have redrawn the map of human identity

From Galileo’s crude spyglass to the James Webb Space Telescope, each technological leap has expanded our observational reach and redefined philosophical and moral conceptions of our place in the universe. Identifying signs of life through the study of exoplanet atmospheres would represent the next great revolution.

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.

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...

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.

How did Polynesian wayfinders navigate the Pacific Ocean?

Ancient Polynesian navigators used the sun, moon, stars, clouds, currents, and more to sail the seas. People of Southeast Asia began their voyages to the region now known as Polynesia in roughly 1500 BCE. They would settle a vast area of 15 million square miles, including hundreds of islands, moving from islands due to overpopulation or war. Such voyages dwindled in 1300 CE as societies became more rooted.

The medieval meaning of your birthstone

Medieval people viewed birthstones very differently from modern jewelry marketing. Rather than simply being decorative, gems were believed to possess extraordinary magical, medical, and mystical powers. This article breaks down some fascinating insights into medieval gemstone beliefs, including that diamonds could fend off insanity and nightmares.

For the medievals, the moon was a versatile religious symbol

Within the distinct traditions of Christianity and Islam, the moon became a central metaphor and sign for religious teaching. For Christians, its light was used to explain Jesus' humanity with the light of the sun (divinity). For Muslims, the moon represented a cosmic longing for god.

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.

The cosmic dark ages: before stars existed

The theories behind the Big Bang suggest the process of the universe beginning to the creation of stable, neutral atoms took just half a million years. But the transition from such atoms to star formation took surprisingly much longer, upwards of 100 million years. Why? This deep dive explores the science behind the unique physical composition of the so-called cosmic dark ages.

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.'

Shooting stars are streaks of light produced by meteoroids

As these rocks enter Earth's atmosphere at high speeds, friction causes them to burn up, briefly leaving streaks of light. The color of these fireballs can be used to determine the composition of the meteoroid, if it does not reach the ground and become a meteorite for analysis.

A 1919 eclipse validated general relativity and made Albert Einstein a celebrity

According to the theory, starlight should deflect around massive objects due to the warping of spacetime light travels through on its way to Earth. Comparing the locations of stars behind the Sun during the eclipse with their positions at night showed deflections that popularized Einstein's model.

The sun is not as exceptional as once believed, but it remains rarer than most stars

Once believed to be the center of the universe, the sun is a G-class star, the same category to which about 6% of the Milky Way's stars belong. However, the sun is younger than 85%, more massive than 95%, and more metal-rich than about 93% of all stars. Unlike the sun, half of all stars also exist in multi-star systems.

The lifestyles of early humans

For 2.5 million years, humans lived on Earth without leaving a written record of their lives—but they left behind other kinds of remains and artifacts.

See a dying star in different wavelengths

The Crab Nebula is the remnants of a dying star that went supernova . First spotted a thousand years ago by Chinese and Japanese astronomers, and likely Native Americans as well. Its original bright light has long since faded, but you can see it in different light wavelengths through this interactive website.

The world's different calendars, explained

The calendar we use to mark the days, months, and year can feel set in stone, but the history of calendars shows these organization systems can and do change. Parse the fascinating, complex details of the Gregorian, Julian, Chinese, Hebrew, and many more calendars in this comprehensive, well-executed explainer video.

An interactive timeline of history, from beginning to middle

The history of humanity is a long, winding road, and the history of everything else is even more complex and interwoven. This interactive timeline takes users through the history of the world and includes links to related videos, blurbs, and events. Each event in history is represented by a dot, providing users with a glittering horizon filled with moments of intrigue and impact.

See how Stonehenge was built

This short animation shows how human beings managed to lug 30-ton stones over miles of prehistoric English countryside and stand them up The Stone Age engineering involved using giant wooden rollers and carving precisely interlocking tongue-and-groove joints to hold the heavy stones in place.

Read the lyrics for ‘The Star-Spangled Banner,’ annotated by historians

The national anthem features a number of specific references (and outdated sentiments) that might be lost on modern listeners. This resource allows you to decode some of Key’s more complicated lines by reading accompanying notes from three specialists.

Explaining pulsars, the cosmic clocks and lighthouses of the universe

As of 2023, over 3,000 of these rapidly rotating neutron stars have been discovered, which contain magnetic fields along which energized particles accelerate and emit light, including X-rays, gamma rays, visible light, and, most commonly, radio waves. The fastest of these, PSR J1748–2446ad, rotates 716 times per second, meaning its surface equator moves at about 24% the speed of light.

How the Inca used threads to communicate

One of the great mysteries of ancient Peru is that the Inca did not have a system of writing, but communicated with a system of strings tied with knots. This 4-minute video explores its possible uses.

The Michelin Guide, explained

Every year, Michelin—a tire company—transforms the culinary world through its prestigious Michelin Stars. Starting in 1900 as a guide to boost road travel, Michelin evolved into the global authority on fine dining. Today, anonymous inspectors assess restaurants across 30 countries, awarding one to three stars for quality, consistency, and creativity.

The ancient crops we've forgotten how to grow

Roughly half of all world calories today stem from maize, wheat, and rice. But for most of history, plants were domesticated in highly local places. This video dives into the scientists learning about crops no longer highly in use that once fueled entire civilizations in North America. Some forgotten crops include pitseed goosefoot, maygrass, and sumpweed.

TikTok can turn everyday users into stars

TikTok is such a cultural force, it’s now a platform for turning ordinary users into stars. This "Planet Money" podcast episode performs a deep dive into how Tai Verdes went from working a day job and dreaming of becoming a successful musician to using TikTok to gain a following.

Some ads help create ‘symbolic value’ for products

A Rolex watch and a watch from the Dollar Store serve the same purpose: helping the wearer tell the time. But a Rolex is worth thousands of dollars while the Dollar Store watch is costs $1 because of symbolic value, or what the watch says about its wearer. This article helps break down the difference between the two.

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

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

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

Neutron stars, the remains of some massive stars after they explode in a supernova, are the densest directly observable objects in the universe.

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

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

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.

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

Crows are believed to have intelligence on par with a seven-year-old child and demonstrate complex behaviors, from problem-solving with tools to recognizing human faces.

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

Netflix profits when you're not watching, and its movies are designed that way—read a detail-rich critical essay exposing lesser-known Netflix takes

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.

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.

Power lines are dotted with large, brightly colored balls to improve the visibility of these thin wires to helicopters and small planes and help prevent potential crashes.

Hear about the 250-year history of the United States Postal Service, complete with some of its strangest deliveries, important innovations, and the figures that made it an American institution.

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.

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

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.

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.

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

The US Constitution is widely regarded as the longest-standing written national constitution still in force—see how it has influenced rights worldwide.

Memecoins are a type of cryptocurrency—a form of digital currency with a wide variety of uses—created around popular 'memes,' or viral internet jokes.