Voids in the northern and southern lights are known as black auroras

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

Auroras take place all day long, but are too faint to see during the day

Because the sun constantly emits charged particles into the solar system, Earth's magnetic field deflects them continuously, with a small subset becoming trapped and colliding with atmospheric gases. Daylight, light pollution, and weather prevent the northern and southern lights from being seen most of the time, even for those at higher latitudes.

The sun and Earth's liquid outer core help create the northern and southern lights

Earth's magnetosphere, generated by the movement of molten iron deep within the planet, consists of a magnetic field that deflects charged particles north and south. Some of the particles released by the sun in the solar wind become trapped in this field and are propelled toward the poles, where they produce auroras through collisions with atmospheric particles.

The best location to view auroras is within the auroral oval

Earth's magnetic field pushes trapped particles from the solar wind toward the planet's magnetic poles, where they can descend and collide with atmospheric gases in a ring located between 60 and 75 degrees of latitude. Auroras can also be viewed at lower latitudes—the sub-auroral oval and solar storm zones—if the sun produces powerful solar storms.

High solar activity can produce pink and purple auroras

Although less common, energetic enough charged particles from the sun that descend to an altitude of about 100 kilometers (62 miles) can strike a mixture of ionized and neutral nitrogen molecules, causing them to emit red and blue light, which our eyes perceive as purple.

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.

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

Planeterrellas create artificial auroras that mimic the atmospheric displays of light by setting up an electric field between two metal balls in a jar filled with a small amount of air.

Coronal mass ejections and solar flares produce the most extensive auroras

The most intense geomagnetic storms are produced when massive clouds of plasma—ionized gas—are expelled from the sun's upper atmosphere and interact with the Earth's magnetic field. These storms expand where auroras are bright enough to be seen to regions farther from the poles, particularly during peak periods of the sun's 11-year intensity cycle.

Crackling, popping, and rustling sounds have been reported during auroras

At the altitudes where auroras take place—between 100 and 300 kilometers (62 to 186 miles)—air is not dense enough to efficiently vibrate and carry sound waves to the ground. However, one theory suggests that the geomagnetic energy behind auroras can trigger electrical discharges near the surface, which may be the cause of reported sounds.

Planeterrellas create artificial auroras that mimic the atmospheric displays of light by setting up an electric field between two metal balls in a jar filled with a small amount of air.

View a gallery of various auroral shapes

Auroras can be generally classified as discrete (well-defined shapes) or diffuse (hazy shapes), with light taking various forms, including curtains, arcs, pillars, and rays. Some auroras can also pulsate, particularly after intense periods of auroral activity are winding down.

Aurora-like magenta streaks across the sky may not be auroras

The phenomenon, known as STEVE (Strong Thermal Emission Velocity Enhancement), has only been observed alongside auroras. Rather than light emitted by gases energized by collisions with ionized particles from the sun, STEVE is a high-velocity, high-temperature stream of particles that glows. (Some readers may experience a paywall.)

Rare chance for US states to see Northern Lights

A solar storm in July 2023 offered people in 17 American states, as well as Canada, an unusual chance to witness the Northern Lights, or aurora borealis. The 11-year solar cycle, reaching its peak in 2024, made the lights visible in places further south than usual. Read up on the announcement from the Geophysical Institute at the University of Alaska at Fairbanks here.

The scientific name for northern lights came from two Greco-Roman gods

Although cave paintings may have depicted them millennia earlier, one of the oldest known references to auroras is a Babylonian cuneiform tablet from about 600 BCE. In 1619, Galileo Galilei named the phenomenon in the northern hemisphere "aurora borealis" after the Roman goddess of dawn—Aurora—and the Greek god of the north wind—Boreas.

Auroral myths include Valkyries, firefoxes, and torchlight from giants fishing at night

In Norse mythology, the light displays were considered reflections from the Valkyries' armor as the female warriors brought the souls of heroes to Valhalla. In Finland, firefoxes were thought to move so fast that they created sparks in the sky as their tails brushed against mountains.

Dark stars are hypothetical stars that would have existed in the early universe

Primarily composed of visible matter, this celestial object would also contain a significant amount of dark matter that would annihilate with itself, converting its mass into energy. This energy would prevent the star from collapsing under its own gravity and from triggering nuclear fusion until its dark matter fuel was exhausted.

Light echoes are expanding shells of reflected starlight

Just as sound waves reveal the location of obstacles by reflecting off them, pulses of light emitted by stars illuminate rings of interstellar dust, giving the appearance of ejected material as the light travels outward.

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.

Cloud chambers use alcohol vapor to create trails behind passing cosmic rays

As cosmic rays travel through the air, they collide with molecules to form charged fragments called ions. Vapors in the chamber condense around these ions, creating streaks of tiny droplets that mark the paths where cosmic rays or their secondary particles traveled.

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

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

Watch a lightning storm from the International Space Station

While passing over the Alabama and Georgia regions, NASA astronauts photographed passing thunderstorms from the ISS. The illuminated clouds are described as "nebula-like formations."

Breaking down the ionosphere, which reflects radio waves from Earth's surface

Made up of ionized regions within the mesosphere and thermosphere, the ionosphere contains charged particles produced when solar radiation knocks electrons free from atoms and molecules in the atmosphere. Before satellites, radio operators would bounce signals off these regions to wrap around the planet and extend the range of transmissions.

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.

Most of the observable universe's volume consists of voids and supervoids—enormous regions of space with little to no galaxies, stars, or light.

Black holes do not 'suck' matter and energy in like a vacuum cleaner

Despite its immense magnitude, the force of gravity exerted by black holes acts in the same way as provided by stars and planets, allowing objects to maintain stable orbits around them. Even in cases where tidal forces and friction cause objects to change their orbit and fall towards a black hole, they are more likely to glance by, be whipped around, and get ejected rather than absorbed.

Instabilities in the polar jet stream can bring cold Arctic air southward

The polar jet stream marks the boundary between mid-latitude air and the much colder polar air, which are normally contained by the polar vortex—a ring of strong winds that circles the Arctic around 16 to 50 kilometers (10 to 30 miles) above the Earth's surface. Climate change may be responsible for "blocking patterns" that distort the jet stream, allowing polar air to leak into lower latitudes.

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.

Some North American bats can glow in the dark

After examining 60 museum specimens from six different species, scientists found that all of them emitted light after being exposed to ultraviolet radiation. Researchers are perplexed by this natural phenomenon and are currently unable to deduce the reason behind it.

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.

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

The first image of a black hole was captured by creating an Earth-sized virtual observatory from a network of eight radio telescopes.

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second and are about a billion times as rare.

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.

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.

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.

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.

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.

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.

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

'Silent' fireworks have gained more interest in recent years as a quieter celebratory option.

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

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

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.

Ebola species have historically been named after where they were discovered, stigmatizing residents who live there, including Bundibugyo, in Uganda.

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.

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

Gerrymandering works through two techniques: cracking opposing voters across districts to dilute their power, and packing them into a few to waste their votes in lopsided majorities.