Cosmic rays are thought to be accelerated to near the speed of light by repeatedly bouncing across shockwaves produced by high-energy cosmic events, such as supernovae.

Some cosmic rays possess energies as high as 100,000,000 teraelectron volts—more than 10 million times the energy of particles accelerated in the Large Hadron Collider.

Scientists have determined the properties of cosmic rays by analyzing their trajectories in bubble chambers—containers filled with a vapor that clings to charged particles.

Cosmic rays are evidence of incredibly powerful astronomical events—solar cosmic rays provide information about eruptions and flares on the sun's surface, while galactic cosmic rays shed light on dying stars.

Earth's magnetic field, which deflects charged particles, helps protect us from cosmic rays, but the sensitivity of these particles to magnetic fields also makes it difficult for astronomers to determine their sources.

Research shows that cosmic rays may trigger the cascade of displaced electrons needed to produce lightning, which is also enabled by pointed ice crystals that create strong electric fields.

Antimatter was discovered by examining debris from collisions between atmospheric gases and cosmic rays—high-energy matter particles from space.

If particle accelerators did create black holes by packing tremendous energy into a small volume, then trillions would be created in Earth's atmosphere daily by cosmic rays.

Particles produced in cosmic ray showers that would normally decay long before they reach Earth's surface are observed in ground-based detectors because they experience time more slowly when moving near the speed of light—a phenomenon predicted by special relativity.

In comic books, cosmic rays have been described as capable of accelerating evolution, granting humans superpowers, restoring health and energy, and powering advanced technology.

Cosmic rays can be detected using cloud chambers—containers where alcohol vapor condenses around trails of ions created by these high-speed particles from space.

Objects that move faster than the speed of sound—Mach 1—create shockwaves called sonic booms by building up and forcing sound waves to combine as they lag behind the object.

The deaths of massive stars and the mergers of neutron stars and black holes can produce gamma-ray bursts—jets of particles moving in opposite directions at near-light speed that comprise the universe's most powerful explosions.

Why starquakes may explain various phenomena associated with neutron stars

Fast radio bursts—repeated millisecond-long pulses of enormous energy from neutron stars—are emitted with a timing that resembles the earthquakes and aftershocks seen on Earth when geological activity releases energy from within the planet. Although pulsars should gradually spin more slowly as they lose energy from emitting jets of radiation, sudden increases may result from interior matter moving during starquakes.

Particle accelerators propel matter toward small targets at high speed

Devices like cathode-ray tube televisions were once basic particle accelerators, but modern ones, such as the Large Hadron Collider, use massive magnetic fields and circular tunnels to achieve energies high enough to recreate the conditions just after the big bang.

Learn how to build your own cloud chamber to detect cosmic rays—particles from space that move near the speed of light—at home.

Explaining pulsars, the cosmic clocks and lighthouses of the universe

As of 2023, over 3,000 of these rapidly rotating neutron stars have been discovered, which contain magnetic fields along which energized particles accelerate and emit light, including X-rays, gamma rays, visible light, and, most commonly, radio waves. The fastest of these, PSR J1748–2446ad, rotates 716 times per second, meaning its surface equator moves at about 24% the speed of light.

About 10% of the radiation people are exposed to each year comes from outer space, with higher percentages for those living at higher elevations or who fly often.

Quasars are extremely luminous cores of distant galaxies, powered by supermassive black holes that consume as much as 100 Earth masses of gas and dust per minute.

Antimatter can be created from dark lightning—high-energy light emitted by deflected electrons after they are accelerated to near the speed of light by thunderstorms.

By measuring them in hot-air balloons during a partial solar eclipse and at night, Victor Hess discovered cosmic rays and concluded they came from beyond the solar system.

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

The solar wind engulfs the solar system in a protective bubble called the heliosphere, which was first theorized in the late 1950s based on studies of cosmic rays—high-energy particles traveling through space at near light speed. The heliosphere shields the solar system from much of this ionizing radiation originating elsewhere in the Milky Way.

Listen to the sounds of pulsars, which emit radio pulses up to hundreds of times a second

Just as figure skaters spin faster by tucking in their arms, these celestial objects acquire high rates of spin from the collapse of the cores of massive stars. The star's rotation spins its magnetic field, generating beams of radio waves from its magnetic poles. If either of these poles faces a detector, the signals can be picked up and converted to audio signals.

A nuclear reactor's characteristic blue light is produced from superluminal particles

When light travels through water, its effective speed is 25% lower than its speed in a vacuum. Just as sound waves bunch up and produce a sonic boom when objects move faster than the speed of sound, particles moving faster than this reduced speed generate a shock wave of light, visible as a blue hue.

Before 1932, when particle accelerators were first used for nuclear research, scientists relied on naturally radioactive substances to advance their understanding of the atomic nucleus.

Learn about five of the largest particle accelerators on Earth, which, as of 2026, are led by the Large Hadron Collider at the European Organization for Nuclear Research.

Antimatter's rarity across the cosmos is one of the biggest problems in modern physics because the high-energy environment of the early universe should have produced equal amounts of matter and antimatter.

Oscillating matter in the early universe left behind patterns detailing cosmic expansion

As gravity tried to bring matter closer together in the early universe, its high temperature produced an outward pressure that caused it to expand. These competing forces caused matter to vibrate and produce the equivalent of sound waves, which spread outward as the universe expanded and cooled, serving as relics of dark energy's history.

The hypothetical matter that neutron stars' cores may contain, including strange quarks

Models of the extreme pressures and energies in neutron stars suggest conditions resembling those believed to have existed within a fraction of a second after the Big Bang. In these environments, the quarks that make up protons and neutrons in trios may instead form pairs that combine to form one quantum object. (Some readers may experience a paywall.)

In 2017, a hidden chamber was found in the Great Pyramid of Giza by measuring particles created in the collisions between cosmic rays and atmospheric particles.

A beam of neutrinos can be created by firing a beam of high-energy protons at a target to produce unstable particles that decay into neutrinos.

Interactions between solar storms and Earth's magnetic field create auroras

Solar storms on the Sun's surface produce clouds of electrically charged particles, some of which make their way to Earth. Those trapped in Earth's magnetic field accelerate toward the north and south poles, colliding with atmospheric atoms and molecules in the process, which produces light.

Fritz Zwicky predicted the existence of dark matter and neutron stars

The former resulted from analyzing the motion of galaxies in the Coma Cluster, a subset of the approximately 30,000 galaxies he cataloged during his life. When hypothesizing an origin for observed high-energy particles called cosmic rays, Zwicky and colleague Walter Baade thought they could come from exploding stars, or supernovae—a term he coined—which would leave behind a collapsed star made entirely of neutrons.

In 1997, the Compton Gamma Ray Observatory identified 'positron geysers'—fountains of antimatter particles—emerging from near the center of the Milky Way.

Dark energy causes 97% of the galaxies to move faster than light

Although special relativity prevents objects from moving faster than the speed of light, the expansion of the universe, which increases with distance between objects, produces observed superluminal motion. This does not violate the theory because galaxies are moving with the expanding space, rather than through it.

It may be possible to create dark matter in particle accelerators

In high-energy collisions, exotic forms of matter can be produced by directly converting energy into mass according to *E = mc*². Even though a dark matter particle would not be directly observable, its creation would result in unaccounted-for mass, which can be compared to potential dark matter candidates for indirect detection.

View a timeline of the universe's major events, according to the Big Bang model.

According to the equivalence principle, objects in a closed space cannot tell the difference between whether they are accelerating or experiencing a uniform gravitational field.

The cosmic microwave background radiation is the oldest light in the universe

Just after the Big Bang, the high-density universe prevented light from traveling very far before being absorbed and emitted repeatedly by free-floating particles. As the universe expanded, electrons and protons combined to form hydrogen, thereby freeing up space for light to travel unimpeded, creating the background light we observe today.

The universe's expansion is accelerating due to a mysterious force called dark energy

Astronomers discovered in the late 1990s that galaxies move apart faster over time, contradicting expectations that gravity should slow cosmic expansion. This prompted the revival of the "cosmological constant," a form of repulsive gravity first proposed by Albert Einstein.

After photons—particles of light—neutrinos are the most abundant particles in the universe.

Cyclotrons move particles in spiral paths of increasing radius

After particles are injected into the center of the device, an alternating electric field and a constant magnetic field energize the particles as they spiral outward toward a target. Cyclotrons are common in hospitals that perform molecular imaging, which relies on radioactive components that decay within hours.

Through sonoluminescence, concentrated sound waves can produce short, high-intensity flashes of light by rapidly collapsing microscopic bubbles to temperatures up to twice that of the sun's surface.

Cosmogenic nuclide dating reveals how long a surface has been exposed to air by measuring the abundance of rare isotopes produced when cosmic rays interact with minerals.

Photons do not experience distance or the passage of time.

Light takes approximately eight minutes to travel from the sun's surface to Earth, but it takes thousands of years to reach the star's surface from its core—a distance more than 200 times shorter.

The hypothetical particle that travels faster than light

Astrophysicists inspired by science fiction developed the theory of the tachyon—a Greek word for "fast"—which is a field or particle hypothetically able to travel faster than light. Although no experiments have confirmed any part of it, it's a fun theory to consider.

As seen in the dark region of the Horsehead Nebula, clouds of space dust can block some forms of light from reaching telescopes, impairing observations and data collection.

Particle accelerators detect subatomic particles using millions of sensors

Calorimeters measure the energy of particles. Tracking devices can measure momentum and charge from the trajectory of particles, which is determined by recording tiny electrical signals. Time-of-flight detectors provide particle velocities directly and particle mass indirectly, giving physicists a suite of properties to compare with those of known matter.

Under the Big Rip scenario, dark energy becomes strong enough to tear atoms apart

If the density of dark energy, which produces a repulsive effect through the expansion of space, increases with time, then all structures of matter, including galaxies, stars, planets, and atoms, will be pulled apart once the strength of dark energy surpasses the magnitude of the forces holding those structures together, including the gravitational and electromagnetic forces.

At the Large Hadron Collider, protons are accelerated so close to the speed of light that they would lag behind a laser by just 10 feet after 14 minutes of travel.