Understanding why charged particles from the sun protect Earth from more dangerous particles

The sun emits a continuous stream of plasma known as the solar wind

Composed of charged particles—electrons and ions—the solar wind is deflected around the Earth by the planet's magnetic field. More powerful solar storms, known as coronal mass ejections, are short-lived but produce huge clouds of plasma that disrupt technology upon reaching Earth.

An overview of the sun, from its formation to its role in fueling and protecting life on Earth

With a surface gravity almost 28 times Earth's, the sun's mass exerts enough pressure to raise temperatures in its core above 15 million degrees Celsius (27 million degrees Fahrenheit) and enable nuclear fusion. These reactions produce the energy that sustains Earth's photosynthesis-dependent food chains, while the sun's magnetic field protects the solar system from cosmic ionizing radiation.

Cosmic rays are high-energy particles from outside the solar system

Trillions of these particles moving close to the speed of light hit Earth daily, with some originating from beyond our galaxy. While the planet’s magnetic field blocks most, some collide with atoms in the atmosphere, producing cascades of exotic secondary particles.

Learn about the sun's corona, which is nonlethal despite a temperature of millions of degrees

The outermost layer of the sun's atmosphere is best seen during a solar eclipse, when the moon blocks the much brighter (and significantly cooler) solar surface. Despite the high-energy particles in the corona moving fast enough to escape the sun's gravity and gradually become solar wind, their density is too low to contribute meaningfully to the region's overall radiation.

Learn about the Parker Solar Probe, which 'touched' the sun in 2021

Launched in 2018, the probe is named after Eugene Parker, who predicted the existence of the solar wind in the 1950s. The probe's carbon-composite shielding has protected it from significant solar radiation as it has traveled through the sun's corona—the outermost layer of its atmosphere—though it will never reach the sun's surface during successive flybys.

Earth is the only terrestrial planet with a magnetic field

Its magnetosphere emerges from a complex interior process of electrical conduction, heat, and motion known as the geodynamo. The magnetic field shields the Earth from unsafe cosmic radiation, providing one of the many conditions required for life.

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 scientists study Earth's geocorona, the farthest portion of the planet's exosphere

Seen via ultraviolet radiation scattered by neutral hydrogen in the region, observations by the ESA/NASA Solar and Heliospheric Observatory indicate that the geocorona extends roughly 50 times Earth's diameter above its surface. At this distance, the geocorona extends beyond the Moon's orbit.

The history of helioseismology, which studies seismic waves traveling within the sun

Following World War II, scientists began studying the sun's influence on radio waves, the most popular form of mass communication at the time. NASA missions to study the sun's interior have since helped develop explanations for various phenomena in its atmosphere and protect digital infrastructure.

Protecting astronauts against space radiation

Outside the protective atmosphere of Earth, astronauts are constantly bombarded by radiation, which, among other dangers, increases the risk cancer. While those of us on Earth can mitigate the effects of similar radiation by limiting exposure,...

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.

Ozone protects against the sun's UV radiation and enhances the greenhouse effect

In the stratosphere, trioxygen molecules can absorb harmful ultraviolet radiation from the sun, preventing it from reaching Earth's surface, where it can harm organisms and raise surface temperatures. In the lower atmosphere, ozone acts as a greenhouse gas, trapping thermal radiation.

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.

Explaining why solving the solar neutrino problem revealed that neutrinos could transform

Electron neutrinos are byproducts of the nuclear reactions within the sun's core. Based on the sun's energy output, scientists modeled reaction rates and predicted neutrino production, but the observed values were consistently one-third the predicted values. Experiments later showed that these neutrinos could change into other types on their way to Earth, causing the discrepancy.

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.

Why Earth's atmosphere constantly loses the universe's lightest elements to space

The masses of hydrogen and helium are too small for these gases to be held by Earth's gravitational force, particularly when these atoms are given energy from collisions with high-speed particles from the sun. Although the planet loses a meter-wide balloon's worth of hydrogen every second, it will still take billions of years to exhaust the planet of this element.

Why it takes tens of thousands of years for light from the sun's core to reach its surface

Photons take about eight minutes to travel through empty space to Earth after leaving the sun's surface. However, traveling from the core to the surface involves these particles of light undergoing a random walk—scattering off charged particles deep in the sun like a pinball—causing a trip that is more than 200 times shorter to last as long as 170,000 years.

Breaking down sunlight and why the sun appears yellow despite emitting green light the most

This peak intensity is produced alongside a spectrum of other colors, which, when combined, make the sun appear white in space. Since Earth's atmosphere scatters bluer and greener wavelengths of light more than red and orange wavelengths, sunlight reaching Earth's surface appears yellow, while the sky appears blue. (Some readers may experience a paywall.)

Comets serve as time capsules of the early solar system

The frozen objects preserve the molecular composition of the solar system's formation, dating back about 4.6 billion years. Spectral analysis of the gases they release when heated upon approaching the sun in eccentric orbits reveals this composition and helps assess solar system formation models.

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.

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.

Explaining the galaxy-sized gas bubbles hovering around the Milky Way

Depth perception is hard to achieve when looking out into space. For decades, two camps of astrophysicists have disagreed over the nature of the North Polar Spur, a radio-wave emitting arc above the Milky Way galaxy's plane. Was it close and relatively small? Or was it faraway and much more massive? New research utilizing X-ray mapping of the galaxy has helped clarify the existence of both so-called smaller Fermi bubbles and larger X-ray ones.

The one-electron theory describes the universe as having only one electron

The thought experiment explains why every electron has the same charge and mass as every other electron, and describes every positron—the antimatter version of the electron—as that same electron traveling backwards in time. Among other foundational challenges, the model suggests that the universe contains equal numbers of electrons and positrons, yet normal matter is much more common than antimatter.

Faraday cages protect enclosed objects by redirecting electrical currents

Constructed from conductive materials, the cage allows electrons to distribute themselves evenly throughout its surface and travel to ground, keeping the interior neutrally charged and preventing any internal electricity. The same principle blocks electromagnetic waves by redirecting the electric field component, preventing telecommunication signals from entering the apparatus.

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.

Jupiter may have affected the trajectory of the asteroid that wiped out the dinosaurs

Despite its reputation as Earth’s cosmic shield, Jupiter’s gravity pulls more asteroids into Earth-crossing orbits. Simulations show that Earth experiences over three times more asteroid impacts because of Jupiter’s influence than if Jupiter didn’t exist.

Solar energy alone can fully power the world if transmission hurdles can be resolved

When light strikes a photovoltaic cell, electrons are loosened, which travel through a circuit where the energy can be used. Distributing energy from high solar intensity regions and storing energy for non-daylight hours is logistically challenging and costly.

Demystifying sunscreen

Sunscreen is helpful all year round. Experts argue a minimum level of protection is SPF 30. There are two kinds of sunscreen: mineral (a physical barrier) and chemical (absorbs UV light). No new sunscreen ingredients have been approved in the US in decades, so foreign products are common.

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.

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

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.

After NASA's Voyager 1 captured Earth as a single pixel as it left the solar system in 1990, astronomer Carl Sagan used the image to reflect on humanity's fragility and the responsibility to protect 'the only world we've ever known.'

How fusion—which releases energy when two lighter atoms combine to form a heavier atom—differs from fission

Neutron stars, the remains of some massive stars after they explode in a supernova, are the densest directly observable objects in the universe.

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.

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.

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

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.

Visualize the path of every solar eclipse from 1900 to 2099 and see what each looks like when observed from different locations on Earth.

Radioactive elements can introduce software errors because the ionizing radiation they produce can detach electrons from atoms, and computer code relies on the distribution of electrons.

Larger animals like giraffes, elephants, and blue whales have developed a unique defense against cancer, a phenomenon known as Peto's Paradox

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

An investigation suggests a Scottish island became awash in forever chemicals via seafoam and seaspray—raising questions about what that means for the safety of other coastal areas.

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.

SpaceX's S-1 or 'prospectus' revealed many previously unknown details about the company, including its unprofitability despite doing $18.7B in revenue in 2025, exactly how many voting shares Elon Musk will have in the company (roughly 85%), and more.

As of 2025, the most cited papers in science include a review of graphene, methods to improve image recognition, streamlining electron density calculations, and optimizing protein studies.

Volcanoes 'die' when their supply of magma runs out, if they are shifted away from their underlying magma reservoir, or if they get clogged by collapsing or their magma cooling back into rock.

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

Watch the cumbersome, but necessary, precautions healthcare workers must take to care for and protect themselves while caring for Ebola patients.