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.

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.

Tiny water droplets can blur a rainbow's colors into a foggy white

When sunlight enters water droplets, it can reflect from the inside and spread out into different colors, producing a series of colorful arcs—supernumerary bows—which we refer to as rainbows. For droplets a few hundredths of a millimeter in size, these arcs overlap onto each other, producing fogbows of white light.

The conditions needed for cloud iridescence, or rainbow clouds

The relatively rare phenomenon occurs when sunlight scatters off tiny water droplets or ice crystals in thin, newly-forming or semi-transparent clouds, such as altocumulus, cirrocumulus, lenticular, and cirrus varieties. This effect is similar to what is seen in soap bubbles and mother-of-pearl shells and produces pastel-like colors.

Rayleigh scattering of light gives the atmosphere its blue skies and red sunsets

Light is deflected from its original path by atmospheric particles, where bluer light is scattered more than other colors. When the sun is at its highest point in the sky, it travels through the thinnest part of the atmosphere, scattering some blue light across the sky. A greater atmospheric path length at sunset scatters more colors, leaving only red, yellow, and orange.

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.

All hurricanes have a central eye where no extreme weather phenomena take place

When standing in the eye of a hurricane, you're likely to experience sunny, cloudless skies surrounded by a wall of intense winds and thunderstorms. The physics behind this formation is the same as what causes water to spiral around a hollow cone as it goes down a drain.

View the ten basic cloud types, categorized by height and composition

Among the features of these types, cirrus clouds can display various colors at sunrise and sunset, while altocumulus clouds can produce a corona phenomenon around the sun or moon. Nimbostratus clouds are thick enough to block out the sun entirely.

Spikes of light around stars are artifacts of light bending around the mirror supports

Through diffraction, electromagnetic waves can bend around obstacles, as observed in the silver linings at the edges of clouds, where light should be blocked. Within reflecting telescopes, starlight diffracts around struts—beams holding a secondary mirror in place—and spreads perpendicular to them, creating pairs of spikes.

Lightning forms when streams of rising and falling charged particles connect

In cloud-to-ground lightning, a buildup of negative charge at the bottom of clouds repels electrons on Earth's surface, leaving behind positively charged particles. When descending negatively charged air—the stepped leader—meets rising positively charged particles—the upward streamer—brightening runs up the connection, producing intense flashes known as return strokes.

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.

From evaporation to precipitation: An overview of the water cycle

The water cycle is a natural process that continuously circulates water throughout Earth's systems. View this diagram from NASA to understand how the water cycle incorporates evaporation, condensation, precipitation, and more. First, the sun's heat...

Rivers in the sky

A short introduction to atmospheric rivers, including a handy illustration on the science behind them, the phenomena that help transport water vapor from the tropics across the globe.

Aurora borealis and auroras australis do not always mirror one another

While the Earth's magnetic field is symmetric across the magnetic north and south poles in isolation, charged particles from the sun distort the field. If the angle of impact between the wave of particles and the Earth's field is such that the distortions are uneven, dissimilar geomagnetic storms and resulting auroras are produced in the northern and southern hemispheres.

Double rainbow appears in New York City on 9/11 anniversary

On the evening of the 9/11 anniversary in 2023, a double rainbow appeared after a thunderstorm across Manhattan, providing inspiration 22 years after the terrorist attacks there. Peruse several amateur images taken of the phenomenon which were shared on social media, including shots from up high in condos overlooking Central Park and from across the Hudson River in New Jersey.

The moon's gravity pulls water from Earth's poles to produce tides

By attracting all parts of the Earth to varying degrees based on their distance from it, the moon produces an overall pressure that drives water toward the opposite sides of the Earth along the Earth-moon axis, not unlike how squeezing a grape causes it to bulge. This creates high tides along the axis on opposite sides of the Earth and low tides along the perpendicular axis. Without significant water to displace, most lakes do not experience noticeable tides.

Color originates from the brain processing light of varying wavelengths

Various geometric models, including Newton's color circle of hue and saturation and the horseshoe-shaped XYZ space for mixing colors via vector mathematics, have been proposed to describe colors accurately. However, these models do not encapsulate the variety of psychological effects that cause perceived colors to differ from mathematical representations.

Light waves can interfere and cancel each other out

When light waves travel past one another, their peaks and valleys combine, just as overlapping ripples in water can combine to form a larger ripple. When the peak of a light wave meets the valley of another of the same wavelength and brightness, the waves combine to produce no light.

Meet the Earth's 'radiation donuts'

Radiation donuts might summon up a certain television cartoon character's favorite snack, but they're something else entirely. Also known as Van Allen belts, these zones of radiation arise from charged particles emitted from the sun and subsequently captured by the Earth's magnetic field. Understanding the underlying physics of the Van Allen belts is critical to modern-day telecommunications.

Our brains trick us into seeing an enlarged Moon when on the horizon

Humans perceive the sky as a flattened bowl and judge the size of an object by accounting for its perceived distance away from us. Combined, studies have found that the Moon on the horizon is perceived to be larger because the terrain makes it seem like it is farther away, similar to the Ponzo illusion.

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.

See a lunar eclipse share the night sky with the Milky Way

Photos taken at the Cerro Tololo Inter-American Observatory in Chile in March 2025 captured a blood moon and the Milky Way galaxy within the same field of view. The moon appears red from the bluer parts of its reflected sunlight being scattered by Earth's atmosphere.

'Try to be a rainbow in someone's cloud.'

- Maya Angelou

Chemtrails are formed from condensing water vapor and soot from jet fuel

Conspiracy theories about the phenomenon—also known as contrails—began circulating in the 1990s, but have gained significant traction on social media platforms. Chemtrails are more common in high-humidity conditions, where they persist and form cirrus clouds.

Radio waves are used in broadcasting, weather radar, telecommunications, and GPS

Its ability to bend around obstacles and reflect off the ionosphere—an electrified layer of Earth's upper atmosphere—allows this type of light to travel long distances without damaging living things due to its low energy. MRI scanners, WiFi, and Bluetooth technologies are also applications of this form of light.

Great circles provide the shortest path between two points on a sphere

On Earth, a great circle is formed by slicing through the planet, such that one cuts through the center alongside the two locations from which the shortest distance needs to be found. The resulting arc along the Earth's surface is responsible for curved routes on flight maps, rather than straight trajectories.

Why water towers are built that way

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

Ring galaxies, the rarest kind in the universe

Galaxies come in different sizes, but when it comes to shapes there are just four kinds: spiral, elliptical, irregular, and the rarest kind, ring. Ring galaxies only form in the event of a small galaxy passing through a large one, but there's more to them that that. This page explores these rare and beautiful heavenly bodies.

Listen to samples of 'sounds' produced by the sun's internal vibrations

Sonification can turn otherwise inaudible vibrations into audible sounds, just as scientists colorize images of celestial objects taken outside the visible range into colors our eyes can interpret. This has been used to turn the vibrations within the sun detected by the Parker Solar Probe into audio clips that resemble chirping and whistling.

Massive blooms of microscopic plankton called dinoflagellates produce the neon blue light seen in glowing tides.

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.

Dirty lightning is a thunderstorm created from friction between rising and falling flows of ash and smoke during volcanic eruptions.

Pure water does not conduct electricity because this flow of energy requires the movement of charged particles, and water is a neutral molecule.

See how fireworks are made and learn how metals like magnesium and copper are responsible for different colors.

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.

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

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.

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.

Waves off the coast of Nazaré, Portugal, can reach over 100 feet and are caused by the area's deep underwater canyon geography

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

Coral polyps reproduce via broadcast spawning, where entire reefs simultaneously release reproductive cells for about one hour, once a year.

Dorothy's famous entrance into Oz in 'The Wizard of Oz' relied on analog tricks, including a body double and sepia-toned paint, as much as it did on technology

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

Mid-century modern graphic designers, known for their bright colors and bold lines in advertising, also found success with children's books.

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

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

In 2009, the nation was gripped by the story of a missing young boy who was believed to be floating over Colorado in a homemade balloon, until it was revealed that he was at home the whole time.

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