The Aztecs synced their solar calendar with a complex 260-day ritual cycle

The Aztecs worshipped a vast pantheon of more than 200 gods

This detailed visualization breaks down how Aztec deities were identified through symbolic cues—colors, garments, poses, and objects—each reflecting specific powers and mythologies. It highlights fearsome figures like Tlaltecuhtli, the earth monster depicted with a gaping maw, said to devour the sun each night.

What were the Aztecs really like?

Does the society live up to its blood-thirsty stereotype? Archaeologist Eduardo Matos Moctezuma answers this question and more in this short article. Moctezuma was the principal excavator of the major Aztec archaeological site Templo Mayor in the 1970s. He shares how the culture grew from a combined emphasis on war and agriculture, and ruled one of the world's largest cities at the time.

Human sacrifice reinforced Aztec political control and religious belief

The Aztecs controlled a vast territory through military might and intimidation. One very key tactic of control was the ritual of human sacrifice. While an effective scare tactic, the ritual was also grounded in deeply held beliefs that the world was sustained by blood.

Using AI to rewrite and revive Aztec tales

Despite being vanquished by the conquering Spaniards in the 16th century, the Aztecs' culture endured through their descendants and rituals, as well as texts that escaped destruction at the hands of the Europeans. These texts, known as codices and preserved in part by Christian monks, revealed intimate details of life as an Aztec in the Middle Ages. Today, AI programs allow students to learn the Aztec's language, Nahuatl, further preserving their heritage.

The Aztec capital fell after a brutal 75-day siege

The violent Spanish conquest ended with a 75-day siege of Tenochtitlan, where thousands died as Spanish forces and their Indigenous allies overwhelmed the city of 200,000. This animated explainer breaks down how those alliances enabled the empire’s collapse.

Watch a traditional Aztec fire-serpent dance rooted in Mexica mythology

This video captures a performance of a Xicauhuatl—or fire-serpent—dance, rooted in Mexica beliefs that these serpents carried the sun across the sky. The performance highlights the fire serpent’s central role in Aztec ritual and storytelling.

The ancient Roman origins of the leap year

The earth's orbit around the sun takes about 365.2422 days, leaving farmer almanacs the awful job of pretending the calendar year fits into a whole number. This article explores the modern origins of the civil solar calendar and its leap year. The Julian calendar, named after the Roman emperor Julius Caesar, cut the calendar year into 365.25 days, gifting the public an extra day every four years. Learn more of the history here.

Teotihuacán was already ancient when the Aztecs encountered it

By the time the Mexica reached Teotihuacán, the vast city had been abandoned for centuries. First settled around 400 BCE, the inhabitants developed monumental temples, canals, and a carefully planned urban grid centered on the Avenue of the Dead.

Ancient civilizations predicted eclipses by tracking different cycles of their recurrence

The periodic nature of the orbits of the sun, moon, and Earth results in several series called saros cycles, in which the geometric configuration of these celestial bodies that produces an eclipse recurs after about 6585 days. Because eclipses are viewable from different locations on Earth, there exist many saros cycles, one for each ecliptic configuration.

New Year's Eve celebrations date back to ancient Babylon

Rather than celebrating in winter, the Babylonians honored the vernal equinox, a day in late March with equal amounts of darkness and light that signaled the start of a new year. They celebrated with Akitu, an 11-day festival.

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.

See a 3D reconstruction of Tenochtitlan, the Aztec capital that was home to an estimated population of 200,000 to 400,000.

The iconic Aztec 'crystal skulls' were 19th-century fakes

The crystal skulls long displayed as Aztec artifacts were actually fabricated in the late 1800s, all linked to French antiquities dealer Eugène Boban. Anthropologist Jane Walsh's investigation exposed their modern origins, overturning a century of mistaken museum lore.

Asia's agriculture-focused set of 24 'small seasons'

In contrast to the four broad seasons and their basis in astronomy and climate, ancient farmers in China and Japan had many more and varied seasons (or "sekki). Take Keichitsu (March 6 to 21), for example: this means "going-out of the worms" when bugs come out from hibernation.

The Maya believed every person is born with a spirit companion

In Maya belief, each person is linked to a spirit or animal companion associated with one of the 20 sacred calendar day signs. Enter your birthday and discover your companion, which is believed to reflect your personality traits.

The Ancient Chinese harnessed solar power for heating and cooling 6,000 years ago

Neolithic Chinese homes faced south for winter sun warmth, while overhangs shielded them from high summer sun. These efforts also influenced urban planning, with cities aligning streets east-west for optimal solar exposure.

COVID-19 disruptions revived ancient chinampa farming in Mexico City

When the pandemic disrupted food supply chains, chinamperos—farmers who cultivate the Aztec-era “floating gardens” built atop shallow lakebeds—shifted to direct sales in the city, boosting their visibility and reconnecting residents with a longstanding local agricultural tradition.

The holiday has evolved alongside its participants' cultural identities

The Day of the Dead blends various traditions, including Aztec myth, Mexican heritage and Chicano identity. That makes for a complex and evolving holiday. This conversation between Cynthia Vidaurri, a Smithsonian folklorist, and Lalo Alcaraz, a cultural consultant for “Coco,” analyzes how the varied influences have created the modern holiday.

Artificial lighting and modern practices like working late are linked with sleep shifts

An analysis of five adults participating in a German reality program that tasked them with living in a Stone-Age-like settlement for 2.5 months, provided some insights into how modern conditions may have shifted our circadian rhythms. The participants slept about 90 minutes more under these conditions, and went to bed earlier and rose earlier, raising questions about how circadian rhythms, sleep, and sleep quality are affected by modern lifestyles.

One researcher posed a theory that aliens played a significant role in human evolution

Researcher Zecharia Sitchin proposed that Sumerian cuneiform tablets revealed that Sumerian gods were aliens who landed on Earth in Mesopotamia and influenced the creation of modern humans. While his ideas gained cultural interest, they are widely rejected by mainstream scholars.

How the brain processes a calendar year

When most of us picture a calendar year, we have a foggy image in our minds of the months, in rough, calendar-like grids. But for some folks, that picture is a whole lot more clear. Around 1 percent of the population has a strange ability known as "calendar synaesthesia," which means they're able to visualize in crisp detail an elaborate calendar of the months of the year. Learn how it works here.

Is the sun aligned with Stonehenge right now?

Twice a year, during the longest day and night, the sun’s path aligns ever so gently with the ruins of Stonehenge. During the summer solstice, viewers can see the sun’s rise crest the central heel stone. The winter solstice sees the sun set across the site’s altar stone. Use this interactive to tour the historic site and check its current skyscape.

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.

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.

The calendars of the 'Lord of the Rings'

JRR Tolkien's epic fantasy trilogy "The Lord of the Rings" is a seminal work in the history of literature partly due to its creator's obsessive focus on systematic detail—including the calendars used in the world. Take a fantastic dive into the minutiae of Tolkien's creation by learning the different approaches to time organization in the Shire or Rivendell with this dense, comprehensive resource based on Tolkien's appendices.

The 2012 Maya-predicted apocalypse didn't really stem from the ancient Mayans

On Dec. 20, 2012, fears of a Mayan-predicted apocalypse gripped Earth, causing panic in some parts of the world, including the stockpiling of vodka in Russia. In this podcast, Maya expert David Stuart—who helped translate some of the relevant Mayan texts—debunks the notion, arguing the Mayan calendar's end marked a cycle, not doomsday.

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

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.

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

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.

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

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 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.

El Niño, Spanish for 'the boy,' was named after Jesus Christ because the phenomenon resembled the weather changes observed around Christmastime.

See how each of the more than two million known species relates to each other—and to common ancestors—in this zoomable tree of life.

Explore chaos in this simulation of two double pendulums, where small differences in the release angles produce wildly different outcomes.

Salvador Dalí believed he was his own dead brother, who had died nine months before he was born

The syncytiotrophoblast is the outer layer of the placenta and the largest human cell, spanning an area about twice that of a king-sized bedsheet.

Apeirophobia is an overwhelming fear of living forever, perhaps stemming from the brain's inability to conceptualize an infinite life.

Sunflowers have long been a symbol of nuclear disarmament because they can extract large amounts of radioactive cesium from soil.

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

A 2019 Facebook event called on attendees to "Storm Area 51, They Can't Stop All of Us," resulting in countless memes, the creation of a music festival, and eventually the arrests of those who did try to approach the area.

In 2018, 26-year-old missionary John Allen Chau was killed by tribesmen after attempting to reach and evangelize on India's isolated North Sentinel Island

Coral reefs get their colors from zooxanthellae—microorganisms that line corals' digestive tracts and provide them with sugars in exchange for a home within this protective tissue.

Volcanic activity may have triggered the Black Death by spewing gases that led to crop failures in Europe, thus forcing the import of grain ships with plague-infested fleas.

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.

Budweiser stores yeast derived from the original 1800s strain in a secret bunker, which only the Head of Yeast Management can access—not even the CEO

US housing costs have risen by roughly 175% between 1991 and 2026—but a growing number of Gen Zers are becoming homeowners anyway. In 2025, 4% of homebuyers were Gen Z, up from 3% the year before.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.