Why we have different seasons

Grasp the earth's orbit around the sun with this interactive

See why seasons exist with this interactive simulator. Toggle between different views of the earth in relation to the sun and watch as the earth's axis causes the sun to shine at different angles throughout the year, causing the weather to fluctuate and more. This simulator clarifies a process many take for granted.

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.

Meteorological v. astronomical seasons, explained

Meteorologists and climatologists define seasons differently from “regular” or astronomical spring, summer, fall, and winter. Traditional seasons reflect the movement of celestial objects, known as the astronomical seasons; meteorologists mark seasonal change based on temperature averages.

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.

Wind is the movement of air caused by the sun's uneven heating of Earth

The tilt, curvature, and variations in Earth's surface composition across the globe cause different regions to receive different amounts of solar radiation. As the Earth spins and tries to achieve thermal equilibrium, air masses move and interact, creating wind.

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.

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.

How solar systems form

Learn how our sun, the planets, and other solar system bodies came to be with these videos and an infographic from NASA. Use this resource to visualize how the solar system formed and to model and describe the process.

Visualizing changes in ocean temperatures between 2016 and 2020

How much does the temperature of the sea change in a given year? This visualization helps illustrate the changes by showing sea surface temperature data from January 2016 through March 2020. Sea surface temperature, which refers to water temperature at the sea's surface, plays a significant role in climate and weather.

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).

The ingredients that make up severe weather

A seven-minute video illustrating how a storm is made. These factors—moisture, instability, lift, and shear—are explained through a series of data sets and creative, descriptive diagrams.

Watch a time-lapse from space of photosynthesis across Earth

Using NASA satellite imagery, carbon absorption can be tracked and serves as a proxy for photosynthetic activity on land and in the oceans. Over the course of a year, seasonal changes can be observed as plants become dormant in the fall and active again in the spring.

Explore a series of interdisciplinary explainers on climate science

From animations on the quantum mechanics of greenhouse gases to a photo essay on how scientists acquire climate data, this collection provides detailed explorations of how different branches of science have contributed to our understanding of climatology.

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.

How the moon creates tides

Anyone who has visited large bodies of water virtually anywhere on Earth notices low and high tides occur at regular intervals, a process primarily driven by the moon’s gravitational pull. This explainer details how the motion of the Earth and Moon interact to create tides.

Visualizing the history of Saturn and its rings

Every 13 to 16 years, Saturn's rings become far less visible because its plane becomes exactly even with Earth's. This visual-rich essay explores the history of humanity's perception of Saturn, from Galileo's first sighting (and dubbing the rings "ears") to the idea that the rings won't last more than a few hundred millions years more. Explore this fascinating planet here.

View a diagram of Earth's atmosphere, which is composed of five layers

Starting from the surface, the troposphere is home to Earth's weather, followed by the stratosphere, which houses the ozone layer, and the mesosphere, which burns up most debris from space. Above these layers lies the thermosphere, where auroras are produced, and the exosphere, which lacks a clear outer boundary as it fades into outer space.

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.

An animation illustrating the enormity of the universe

Look around you. Where are you? Where is this place you are occupying? Somewhere in a room, maybe in a city on a continent on a planet orbiting a star in a galaxy among billions. But… where is all of that?

200 million years of tectonic plate movement

The Earth's internal forces have continuously pushed and reshaped how the planet's land masses are arranged. From one supercontinent hundreds of millions of years ago, to present day, the Earth has looked dramatically different throughout the...

The complexity of classifying a tree

It may seem obvious to us when we see a tree, but very specific characteristics cause scientists to distinguish trees from other types of plants. This video provides a visual and verbal explanation of distinctions that separate trees from other plants like shrubs or herbs. See a scientific breakdown of these traits.

Twelve ways the world celebrates springtime

Celebrating the seasonal change is rarely filled with as much relief and hope around the world as spring. This list compiles some famous and lesser-known springtime traditions from diverse cultures.

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.

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.

Watch a pinecone become a pine tree

Sometimes a closer look at an ordinary process can uncover its glory This timelapse video presents the wondrous natural process of a withering pinecone turning into a full sprouted tree. A nearly two year growth, watch the seed turn to seedling and rise over time.

We hear because soundwaves are converted into electrochemical signals in our ears

This science teacher video systematically walks through the biology of the outer, middle, and inner ear. The explanation starts with the auricle, an external part that funnels sound through the auditory canal, and the tympanic membrane (the ear drum), which vibrates when sounds hit it. Beyond that, as the video details, is the eustachian tube, which is connected to the back of our throats and allows air to pass in and out to equalize ear pressure.

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.

This year's first leaf and first bloom in the US, mapped

Spring tends to arrive within a range of dates in the contiguous US. See a map illustrating the most recent year's first leaf and first bloom in relation to historical averages to see how early or late the season arrived.

Five charts that changed the world

Data visualization helps us understand the world, providing a powerful way to communicate complicated information in a quick and efficient way. There are many different ways to create graphs, and these five examples—the pie chart, geographic dot...

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.

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

Explore our favorite visualization of the immense scale of space, from an astronaut to the size of the observable universe

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.

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

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.

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.

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

Poison ivy can cause rashes year-round since all parts of the plant contain urushiol, the oil that triggers our allergic response.

Browse a detailed visual analysis of over 200,000 similes—comparisons that often use 'like' or 'as'—from popular fiction to see how frequently writers the same idiomatic expressions.

Visualize how CRISPR-Cas9—a type of immune system used by single-celled organisms to attack invasive viruses—targets and makes precise changes to a gene's DNA.

After 25 people used virtual reality headsets to practice flying with virtual wings—flapping their arms—their visual cortex responded to the wings almost as if they were real arms, treating them as body parts.

The Great Salt Lake's distinct dual coloration results from high-salinity organisms that only live in the northern portion and produce a purple protein.

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

Children are now three times more likely to say they want to be a YouTuber when they grow up than an astronaut, with some even attending 'YouTube camps' that teach kids how to create content for the platform.

44% of Americans say they pray at least once a day—discover how your state's religiosity stacks up against the rest of the country.

While the first exchange-traded fund (a 'basket' of different assets that can be bought and sold on a stock exchange) in the US only launched in 1993, the global ETF market has grown to more than $10T in the short time since.

In 1945, Surrealist artist Salvador Dalí and legendary animator Walt Disney began collaborating on a short film that was not completed until 2003, years after both men had died.

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

Trace how the Bill of Rights, inspired by centuries of political theory, took shape between 1774 and 1789.