Five things to know about autumnal equinoxes

The difference between solstice and equinox, explained

A solstice marks the extremes in the amount of day or night, while the equinoxes come on days with a balance between the two. Learn why with this brief video.

Earth’s tilt and orbit cause the sun to create a figure-eight pattern

The shape—called an analemma—can be obtained by photographing the sun from the same location and time daily for a year. The Earth's eccentricity created the analemma's width, and its tilt shifts the sun's height in the sky over the seasons.

Changes in Earth's orbital cycles influence the timing of ice ages

These cycles include changes in Earth's orbit shape, tilt, and wobble, all of which alter how much solar energy different parts of Earth receive over time. Due to orbital eccentricity, summers in the Northern Hemisphere last about 4.5 days longer than winters.

The science of springtime, 101

Dive into the basics on springtime including the astronomy that brings it about, natural signs of spring's arrival, and some of the cultural approaches to the season.

During the fall, chlorophyll breakdown in leaves produces color changes

With shorter days and less sunlight, the concentration of the green pigment diminishes, revealing yellow and orange pigments. Red leaves result from trapped sugars, producing new pigments called anthocyanins, which weren't present in leaves during the growing season.

There is a template for how to live a better, healthier day, and it includes a digital sunset

Science suggests that early-morning exercise, later-morning peak work or social time, consistent exercise, and a "digital sunset"—starting to turn down the lights in the evening and avoid screens—are important for circadian health.

Daylight saving time, explained

Daylight saving time is supposed to help—but does it? Dive into the history, science, and consequences of this biannual aspect of American life (unless you're from Arizona or Hawaii).

Why meteorologists say summer starts June 1

There are at least two periods called summer: astronomical and meteorological. Astronomical summer mirrors the movement of celestial bodies and begins roughly around June 20, with the summer solstice. Meteorologists designate the beginning of June as the start of summer to make tracking weather patterns from year to year easier.

Life during three months of polar night

In Norway's Svalbard archipelago, night reigns from November to January, as with many communities living within the polar regions. Contrary to popular assumptions about such places, many residents of the region describe the long darkness as peaceful, a time to slow down and draw nearer to neighbors and community. Read more on life in polar night, specifically in the Svalbard town of Longyearbyen, in this essay from a resident there.

One theory claims the retinae of SAD patients may fail to adjust to less light in winter

Most people’s eyes become more sensitive to light in the winter months, but some do not. This failure to adjust causes ripple effects on those individuals’ biological clocks. This Ted-ED video provides a clear, brief, narrative explanation of the condition in six minutes.

Visualize your city’s annual daylight map

Type in your town or region and see sunrise and sunset for each day of the year. A separate view shows the number of hours of day versus night for each day. Search a city far north like Oslo, Norway, and compare its graphs to one near the equator (like Singapore).

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

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.

From seed to pumpkin, a 3-minute time-lapse

Pumpkins are atypically enormous winter squashes, meaning they are harvested in the fall and then remain edible throughout winter. See how it all happens with this mesmerizing, music-backed time-lapse showcasing a pumpkin's 120-day journey from...

Watch the sunset at Stonehenge during the 2025 Summer Solstice

Each year, tens of thousands gathered at Stonehenge to witness the sun’s alignment with the stones during the solstice. Watch a replay of a lifestream of the event from 2025.

See the 25 of the best photos of auroras from around the world.

Moon's visibility is determined by its declination, equivalent to Earth latitude

The Moon's declination varies between approximately +28.7 degrees and -28.7 degrees, ensuring it rises and sets between latitudes of approximately 61.3 degrees north and south. This means there are places on Earth where the Moon is never visible above the horizon and places where it temporarily does not set.

Most tornadoes occur during the afternoon and evening hours

While there is no official national tornado season as with Atlantic hurricanes, many tornadoes form in the presence of thunderstorms, which are fueled by solar heating and the energy released by the condensation of water vapor. The airflow instabilities created from this energy build throughout the day until the sun sets.

See the 25 of the best photos of auroras from around the world.

How the months of the year got named

Curious about how the months got their names? This article from The Old Farmer's Almanac explores the origins of today’s Gregorian calendar. Based on the ancient Roman lunar calendar, the months were named after Roman gods until winter when the names changed to numerical titles. Read along to learn the significance and intentions behind labeling each lunar cycle.

Thirty weird facts about Christmas trees

From its fascinating origin to how yours is grown today, these incredible Christmas tree facts will add a little bit more wonder to your holiday season.

Everything you need to know about the planets in our solar system

NASA provides a re-introduction to our solar systems's planets, and a few other neighborhood residents. In the Milky Way galaxy, there are more planets than stars. We’ve discovered thousands of planets orbiting distant stars, but it all started with the current lineup of eight planets orbiting our own star—the sun. Learn more here.

Day of the Dead differs from All Souls’ Day in several important ways

The holidays share a calendar date and both honor lost loved ones. However, All Souls’ Day is intended to help guide souls in purgatory to heaven, while Day of the Dead celebrates the temporary return of loved ones’ spirits to Earth.

Babies don't develop a circadian rhythm right away

Newborns don't develop circadian rhythm until they are a few months old, which helps to explain their erratic sleep schedules. When they're around three months old they begin to release melatonin, which influences sleep, and around the same time they develop more regular sleeping routines.

A breakdown of Earth's atmospheric layers, including why it can get colder or hotter with altitude

Gases in the troposphere—the atmosphere's lowest layer—cool with increasing height as they get farther from the thermal energy emitted by Earth's warm surface. In the next layer—the stratosphere—ozone is increasingly heated by the sun's ultraviolet radiation with height. Because cooler air sinks and hotter air rises, the cooler troposphere and hotter stratosphere form a natural boundary keeping Earth's weather in the lowest layer.

A quick technical overview of insomnia

Insomnia is one of the world's most common sleep disorders. Characterized by difficulties falling and staying asleep, long-term struggles with insomnia can prelude or contribute to health difficulties. Treatments range from sleep hygiene management and relaxation therapy, and medication, including antidepressants and melatonin.

The most common birthdays

Nine of the top 10 most common birthdays fall in September, with Sept. 9 being the most common. However, August is the most common birth month, followed by July and December. On the flip side, the least common birthdays are around major holidays, with Christmas Day being the rarest—probably due to doctors scheduling fewer inductions and C-sections on those days. Find out more birthday surprises here.

While El Niño moves warm Pacific Ocean waters east along the equator, La Niña moves them west, shifting where rainfall will become more common for months.

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.

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

Hurricanes, which rely on air consistently spinning in the same direction, cannot cross the equator because air curves in opposite directions north and south of it.

The boiling temperature of water decreases with increasing elevation because the molecules need less energy to overcome the lower atmospheric pressure associated with thinner air.

Learn how your body is, scientifically, like a firework with its own slow, controlled burn.

Discover the catastrophic consequences of a failure of the US electrical grid—something that is more likely than many Americans think.

Chaos theory—informally known as the butterfly effect—is the reason why weather forecasts are presented with probabilities rather than certainties.

According to the physics of black holes, our 4D reality may be a hologram—a projection of information coded on a 2D surface on the edge of the universe.

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

Apollo astronauts left items in the moon's 'toss zone,' including golf balls, family photos, and bags of human waste, to make room for lunar rocks.

Learn how to read a prospectus, the juicy document that any company must file with the SEC before going public.

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.

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.

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.

Between 10 million and 50 million people in the US develop rashes from poison ivy, poison sumac, and poison oak each year.

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

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

The first steps to rebuilding your credit score include getting to know exactly what's on your credit report and figuring out how far you are from the '700 club,' or 'good score' range.

Some coin denominations have ridges etched on their sides, partly to prevent counterfeiting, in a practice called 'reeding.'

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

Famed poet TS Eliot rejected the manuscript for George Orwell's political fable 'Animal Farm,' writing that its criticism of authoritarianism was not 'the right point of view.'