Smaller than atoms—what are quarks?

Learn about the history of quarks, found deep in the heart of every atom

Independently theorized by American physicists Murray Gell-Mann and George Zweig in 1964, experiments later showed that these particles come in six varieties, named up, down, top, bottom, charm, and strange. Combinations of these quarks, which are held together by mediators of the strong nuclear force—gluons—make up dozens of composite particles, including protons and neutrons in atoms.

The quantum model of the atom resulted from over two millennia of scientific thinking

In 440 BCE, Democritus proposed that everything was made up of tiny particles surrounded by empty space, which varied in size and shape based on the substance's properties. It was not until the 20th century that experimental evidence validated elements of Democritus' model.

The simple grandeur of atomic theory

Is the universe made up of a continuous substance, or a finite amount of tiny, indivisible atoms? The atomic hypothesis, largely vindicated in the 20th century, was forgotten for nearly 2,000 years after first being formulated by the Greek philosopher Democritus. Learn more about the theory and its implications for science and human life with this reflective essay.

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.)

Quantum field theory reveals that particles are ripples in universal fields

Instead of being made of indivisible particles, all visible matter in the universe is built from underlying quantum fields—smooth, invisible entities that behave like waves. The theory suggests these fields are fundamental, and particles are disturbances that move through them.

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.

The deceptively simple proton

Take a visual deep-dive into the proton, a near-fundamental—but deceivingly simple—building block of nature. Among other beguiling characteristics, the particle can't be described by its constituent particles (quarks), but rather exists in a...

What does quark-gluon plasma have in common with tap water?

Quark-gluon plasma is a state of matter that formed shortly, very shortly, after the big bang. At one time filling the universe, scientists describe quark-gluon plasma as being similar to tap water, but only in the manner that such matter flows. Incredibly hot upon its emergence, it swiftly cooled and began forming the early building blocks of the universe.

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.

What is gravity made of?

Our world at very small scales is governed by quantum mechanics, in which forces and energy come in discrete packets. At large scales, our world is governed by gravity, which moves the planets and stars and can create waves in spacetime. To merge...

Axions, a hypothetical subatomic particle, are a leading dark matter candidate

Among the possibilities for what makes up dark matter, some physicists champion axions, which could clump into galaxy-scale quantum states. These states would act as massive, unified superparticles that could explain the observational evidence for the universe's missing matter.

A scale of the universe, from atoms to cosmos

Can you really appreciate just how small protons are, or how massive the universe is? To attempt to grasp it, watch this short video which zooms out from a young woman in California to the very limits of the cosmos using established scales. Then, dive deep into the atoms of her white blood cells for a fully-rounded effect.

Understanding how atomic structure contributes to each element's properties

The outermost layer of electrons in an atom dictates how it will bond to other atoms. These bonds determine whether elements exist as solids, liquids, or gases in the environment and other characteristics. For example, electrons are freely shared between atoms in metallic bonds, allowing them to immediately re-emit light that strikes them, thus making most metals shiny.

Leptons do not experience the strong nuclear force that binds quarks together

Particles like electrons can exist in isolation, enabling them to move more freely. Within circuits, this allows electrons to carry energy across wire surfaces quickly. Contrastingly, light created in the sun's core is delayed by a million years on its way to Earth due to collisions with free electrons.

An explanation of isotopes, which can help scientists trace food, water, and farming choices

Atoms of the same element have the same number of protons, but experiments showed that atoms of the same element can move through electromagnetic fields as if they had different masses. These differences in mass come from variations in the number of neutrons, which contribute to the stability of atoms by providing a buffer to the repulsion between protons.

Create anything from the elements in Little Alchemy 2

Various ancient cultures believed the most abundant substances in the world were its basic elements: earth, water, air, and fire. We may know better now, but you can make almost anything from those four things. Little Alchemy 2 is a fun, cartoonish game that allows users to create more complex items from simple substances.

Why most atoms do not spontaneously break apart, despite protons repelling one another

At small scales, the strong nuclear force overwhelms electromagnetic repulsion between positively charged particles, keeping the nucleus intact. However, because the force's range is limited, it cannot provide the attraction needed to hold onto protons that are spread out across very large atomic nuclei.

Human teleportation through quantum principles raises questions about identity

Through quantum entanglement, particles have been "teleported" by measuring their state in one location and effectively transferring that state to a new location. Doing so for the particles that make up humans would destroy the state of the original particles, killing the person, and effectively creating a clone.

Superconducting qubits have become foundational to today’s quantum computing efforts

Relying on electrons experiencing no friction across metal, these qubits require extremely low temperatures and behave like artificial atoms. The first superconducting qubit, invented in 1999, was large enough to be seen with the naked eye.

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.

Can physics explain where consciousness comes from?

Consciousness is a complex emergent phenomenon of the brain, which is primarily composed of neurons and glial cells. Since all matter is composed of atoms that follow the laws of physics, there may be quantum processes beyond classical electrochemical interactions that can explain where consciousness comes from.

How we know what’s deep inside the Earth, despite never traveling there

We'll likely never see the Earth's core, but we can make educated guesses about what it's like down there. Nearly as hot as the sun's surface and under impossibly high pressure, the inner Earths extreme conditions make it impossible to explore. Yet, seismic waves during earthquakes, volcanic eruptions, and light waves from the sun provide fascinating insights about our planet’s mantle, crust, and core.

Humans have existed for just 0.004% of Earth’s history

Born from the remains of the molecular cloud that birthed the sun, Earth experienced planetary-scale collisions, asteroid impacts, and lava seas. Life became possible after the planet cooled and formed a thin crust, atmosphere, and oceans.

Hear Carl Sagan reflect on the smallness of humanity

13 unanswered questions about black holes

Here's a quick rundown on black hole basics, the cosmic enigmas digesting massive swaths of the universe and destabilizing our fundamental ideas of space, time, and matter. Learn how they got their name, what happens in the unfortunate instance you fall into one, and more with this list of 13 questions about black holes.

The history of the 10 axioms of Zermelo–Fraenkel set theory with choice, regarded as the most universal foundations of math

Like postulates in geometry—accepted truths that form the logical building blocks for formal proofs of more complex theorems—axioms cannot be proven, but set the underlying logic and rules for systems. The ZFC axioms resulted from painstaking work to identify the underlying rules of mathematics and are built on the premise of sets, or well-defined collections of elements.

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

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.

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

Learn more about the history of fireworks, which dates back to an accidental invention during an alchemist's quest for information about immortality.

Against his wishes, Albert Einstein's brain was removed before his cremation, and the pathologist responsible stored it for decades in mason jars within a beer cooler.

SpongeBob exemplifies Aristotle's philosophy for living well because he understands that happiness doesn't come from external factors like money, recognition, or power.

Shooting stars, or meteors, are fragments of asteroids and comets that burn up as they enter Earth's atmosphere, creating streaks in the sky called meteor showers.

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

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

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.

Some Pokémon have been named after real and fictional organisms, while some real-world species have been named after Pokémon, such as Chilicola charizard and Binburrum zapdos.

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.

Corals are themselves not coral reefs—the term refers to the tiny marine invertebrates that build the rigid reef.

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

Researchers believe the brain consolidates memories, processes emotions, and plans for the future during dream states

Lesser-known phobias include turophobia, or the fear of cheese, and nomophobia, the fear of being without your cell phone.

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

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.

In 1963, a basement renovation in Turkey revealed a passageway to a hidden, multilevel underground city that once housed as many as 20,000 people

The rivalry between Alexander Hamilton and Thomas Jefferson centered on federalism—the question of how much power the federal government should hold relative to the states.

The term 'algorithm' originated from the Latinized name of al-Khwārizmī, a 9th-century mathematician whose works introduced Arabic numerals and the decimal-based numeral system to Europe and whose treatise 'Al-Jabr' gave algebra its name.

This poison ivy knowledge quiz—accompanied by photos of the plant's varied forms—may help you identify this common rash-inducing growth.

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