How facts, hypotheses, theories, and laws in science differ from everyday language

Distinguishing between scientific theories and laws, and why both are on equal footing

Scientific laws describe outcomes of specific conditions, and scientific theories explain why those outcomes occur. Both are supported by observational and experimental data and can each inform one another, but neither can become the other. Instead, additional data can improve each towards more accurate descriptions and explanations of reality.

Learn why modern scientific patterns have been described as theories rather than laws

After confirming that the accuracy of some laws of physics is limited to certain domains, science became more hesitant to categorize identified mathematical relationships, such as quantum mechanics, as unchanging laws. Instead, these recent, complex frameworks are designated as theories to acknowledge that they are conditional and may be part of a larger, more complete future framework.

Why being able to disprove explanations distinguishes scientific theories from pseudoscience

Introduced by philosopher Karl Popper, falsifiability holds that a scientific theory must make predictions that could be proven inaccurate by future observations. Explanations that cannot make such predictions are not scientific theories. It is scientists' jobs to seek out data to poke holes in scientific theories, thereby potentially strengthening them if they hold up to scrutiny.

Scientific progress works toward absolute truth, but can never reach it

Through the acquisition of scientific knowledge, scientists construct explanations of the world, which are rigorously tested and verified until they narrow down to a leading theory of the natural world. However, because of how science works, these ideas will never become factual, as they must always remain open to be iteratively revision based on new data.

Science is rarely a linear progression of understanding

Particularly at the frontiers, investigations conducted based on established knowledge can provide unexpected results. This opens the door to revising existing models, inspiring new lines of research, and ultimately leading to better future comprehension. For instance, experiments on the speed of light and the expansion of the universe yielded then-confusing data that led to revolutionary insights.

Each scientific study adds incremental knowledge to existing understanding

On its own, no study serves as a source of truth or solves an existing problem indefinitely, though many can be analyzed collectively in a systematic review to build more confidence—the result of more data—in a conclusion. Studies can explore knowledge gaps or test an existing theory, which is always subject to refinement and improvement.

How upheavals in accepted scientific theories helped popularize the term 'paradigm'

When Thomas Kuhn published "The Structure of Scientific Revolutions" in 1962, he described the history of science as comprising periods of "normal science" where these accepted frameworks—paradigms—gradually accumulate anomalies until they cannot describe nature. Revolutionary science, such as the development of a new theory, results in a paradigm shift, another term Kuhn helped popularize. (Some readers may experience a paywall.)

Fantasy and science fiction are distinct genres, though they sometimes overlap

Fantasy stories take place in universes where magic exists; science fiction stories take place in universes that are still grounded in the physics of our world. In science fiction, supernatural powers have scientific explanations. Think of “Spiderman”: Peter Parker gains his powers after being bitten by a radioactive spider.

Conservation laws identify physical properties that remain unchanged in systems

The total amounts of properties like energy, charge, and angular momentum within a system have been experimentally observed to remain constant, even as changes occur. Particle interactions also conserve specific quantities, such as baryon and lepton numbers. Inconsistencies in these values within isolated systems have historically hinted at the existence of new physics.

A list of five scientific theories that were accepted and later disproved

Humoral theory held that everyone's personality derived from different combinations of four bodily fluids: blood, phlegm, yellow bile, and black bile. The phlogiston theory stated that all combustible materials possessed a fire element—phlogiston—that was released and absorbed by the air during burning. When the air became saturated with phlogiston, the fire would go out.

Explore a series of interdisciplinary explainers on climate science

From animations on the quantum mechanics of greenhouse gases to a photo essay on how scientists acquire climate data, this collection provides detailed explorations of how different branches of science have contributed to our understanding of climatology.

How do scientists study far away stars?

Astronomy is the only science that is purely observational: meaning, scientists can't study stars in a lab. Here's a breakdown of how modern researchers use new tools to understand objects billions of light years away. As it turns out, the rules of science allow us to identify, categorize, and experiment with phenomena light years away.

Language is evolution's great mystery

What we call language is something more specific than communication. Language is about sharing what's in our minds: stories, opinions, questions, the past or future, imagined times or places, ideas. So what does language mean for humanity, and how did we come to have it? Watch this brief video to discover more.

The field of attribution science seeks to determine whether specific phenomena, such as melting glaciers, droughts, and hurricanes, are driven by Earth's natural climate cycles or by human-caused climate change.

Humans experience the world subjectively. What does that mean for scientific research?

When you close your eyes, do you see static or colorful patterns or an "intrinsic grey" known as Eigengrau in German? This variation of our internal experiences is just the tip of the iceberg, one that scientists are increasingly studying and...

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.

Particle interactions follow rules related to specific quantum properties

Like a business whose purchased inventory matches sold inventory, physicists identified specific patterns across decades of particle accelerator data, which became new conservation laws for elementary particles. These laws help identify which particle decays are expected or forbidden.

Using scientific bets, Hawking challenged and highlighted major physics ideas

Hawking famously placed wagers on high-stakes questions in theoretical physics—such as the Higgs boson—for fun and to draw attention to science. When Hawking lost a bet about Cygnus X-1 being a black hole, he paid up with a magazine subscription.

What Stephen Hawking said about time travel

When renowned theoretical physicist Stephen Hawking did not rule out the possibility of time travel in his posthumous book Brief Answers to the Big Questions, many hopefuls got excited. But, unfortunately for them, Hawking believed that yet-to-be discovered laws of physics will prove time travel impossible. This piece outlines some practicalities about the speed of light and wormholes that lend way to Hawking’s prediction.

How 'vibes' factor into scientists' decisions about using certain units

Although there are absolute quantities from which units can be defined, such as the speed of light and the corresponding light year for distance, the usefulness of units comes from their ability to easily communicate values, rather than how fundamental their origins are. For example, while Kelvin measures absolute temperature, Celsius is scaled to the temperatures of boiling and freezing water, making them more practical for everyday usage.

Quantum mechanical principles are responsible for chemical properties

Besides quantization, the wave-particle duality, and probabilistic features, quantum theory's mathematics introduces the exclusion principle, quantum tunneling, quantum entanglement, and other phenomena foreign to our everyday experiences. Some suggest that all possibilities for a quantum system may also occur across the multiverse.

Fearology, or the study of fear, explores the difference between stress and fear

Our brains involuntarily respond to our environment and signal alarm when that isn't always needed, triggering responses that include goose bumps. But understanding fear and how to talk our brains into calming down can improve daily life.

Critics say Nobel Prizes need updating to reflect how science and society work today

The rules still favor individuals over teams and may reflect outdated views on who does science. In 2013, the Nobel Prize in physics went to two theorists, even though over 5,000 scientists helped confirm the Higgs boson.

Fantasy is heavily influenced by myths, legends, and folk tales

In fantasy, anything is possible, mirroring the supernatural worlds of history’s earliest stories. The narrative voice of fantasy is often similar to early tales, too, with an affinity for the magisterial rather than the contemporary.

Is time travel really possible?

The laws of physics, as currently understood, don’t categorically reject the possibility of time travel. But, scientists are skeptical, especially when it comes to traveling to the past. Hopping between past, present and future would require the world to have some wacky yet-to-be-discovered physical properties like negative mass, negative energy, and infinite density. Time travel also introduces philosophical questions about free will, causality, and chronology.

Classical mechanics describes the motion of and forces on everyday objects

Newton's laws form the core of classical mechanics, suitable for everyday objects and speeds. The term is relatively new, distinguishing the branch of physics from quantum and relativistic mechanics.

By separating light with tools such as prisms, scientists can reveal the presence and composition of celestial matter by identifying color fingerprints unique to specific elements and molecules.

Modern physics suggests that many universes with different physical laws could exist

Physicists suggest that quantum fluctuations in the early universe could have given rise to these universes. Ancient Greek philosophers like Chrysippus proposed a version of the multiverse over 2,000 years ago—millennia before its adoption into various theoretical frameworks today.

Although among the most comprehensive frameworks in science, the Standard Model has numerous gaps, including its inability to explain dark matter, dark energy, or why normal matter is so much more abundant than antimatter.

Because some models of the universe do not incorporate time, it may be an emergent property born from our limited perception of the universe, rather than a fundamental property of reality.

Quantum field theory, which has made predictions accurate to 12 decimal places, explained

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 and extend throughout space and time. The theory suggests these fields are fundamental, and particles are disturbances that move through them.

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.

English chemist Rosalind Franklin (1920 - 1958) on the importance of science

"Science and everyday life cannot and should not be separated. Science, for me, gives a partial explanation of life."

Explore an interactive map of the unified theories of everything

This interactive concisely describes many highly complex theories ranging from quantum gravity and black holes to dark matter and energy. Supplementary resources, key questions, and possible solutions accompany each description. As of 2026, no developed theory provides an accepted explanation of all observed phenomena in the universe at all scales.

The Standard Model reveals an underlying organization to the universe

Using the framework of quantum field theory, it structures all known particles into 12 matter particles, alongside five particles that carry three of the four fundamental forces. Although remarkably precise and predictive, it cannot yet explain gravity, dark matter, or dark energy.

Statistically speaking, aliens likely exist, but we still haven't found any evidence of them

The Fermi paradox addresses this discrepancy between the lack of evidence of alien life despite the high likelihood of its existence. Physicist Brian Cox offers various theories, like the extinguished civilizations hypothesis, for why we have never found any extraterrestrial neighbors.

Authentic storytelling and audience awareness drive effective science communication

Bill Nye suggests that making people care about science requires limits on technical jargon, ensuring content is relatable to viewers, and injecting some comedy to help make the ideas stick. Having clear learning objectives can help educators stay on track and efficiently write content.

Explore a simulation of ideal gas behavior, which can be explained by kinetic molecular theory

The theory describes particles as moving in random directions, with a distribution of velocities determined by the gas's temperature. The particles collide elastically like billiard balls, are negligibly small, and do not exert forces on one another. The gas laws can be derived from these principles using statistics or observed via this interactive.

How science explains déjà vu

Take a fun look at the science explaining the odd experience of déjà vu, which some theories suggest is actually a sign of a healthy brain.

According to Bill Nye, science is under threat from an erosion in critical thinking

He states that conducting research online cannot replace consulting with scientific experts who have spent their entire lives intimately studying a field. The former science education show host argues that deepening cynicism towards scientific institutions has been fueled by leaders embracing debunked and unsupported claims.

Scientists are experimenting with ways to probe the multiverse theory

Researchers are simulating vacuum bubbles—the theorized starting points of universes—using quantum computers, digital models, and exotic lab setups to study how they form, expand, and possibly collide. One experiment aims to "blow" artificial universe-like bubbles inside ultra-cold quantum gases, potentially capturing real-time glimpses of cosmic birth processes in a lab.

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.

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

Linguistics professors believe memes are a language

It's generally agreed upon that languages exhibit at least some of the following characteristics: compositionality, social transmission, arbitrariness of form and meaning, and accomplishment of linguistic functions like asking questions and expressing emotions, among other qualities. Memes fulfill these basic requirements, giving them linguistic legitimacy.

Human anatomy provides evidence for evolution

Throughout history, scientists have used anatomy to support the Theory of Evolution in three main ways. Homologous structures, or similar physical features in organisms that serve different functions, can help scientists understand common ancestors....

Research studies can be conducted inside or outside of living samples

While "in vitro" experiments occur outside living organisms for cost-effectiveness, "in vivo" experiments take place inside them, providing real-life insights at a higher cost and with increased ethical concerns. Alternatively, "in silico" methods use computational simulations.

The Big Bang theory describes how the universe began and continues to expand

Rooted in Lemaître’s 1927 idea of a growing universe and confirmed by Hubble’s redshift data, the theory is backed by evidence like cosmic microwave background radiation—remnants of the universe’s fiery birth detected in the 1960s. The radiation was first misidentified as interference from pigeon droppings inside a telescope antenna.

Probability waves govern particles like electrons in the quantum space

Just as waves are extended objects whose heights change across space, quantum waves dictate that the probability of an object existing in different locations across space varies. Like water waves, the probability waves can combine, changing the heights—and therefore probabilities—in different locations.

What's the difference between weather and climate?

A five-minute TedEd video exploring the differences between weather and climate – what they are, how we predict them, and what those predictions can tell us.

Paleontologists apply rules about rock layering, fossilization, and radioactivity to date geological samples

Concepts such as the understanding that older rock layers will form beneath newer ones allow scientists to compare the ages of samples from various layers. Although no geological site preserves evidence across all time, samples can be combined with fossils of known age, such as those dated by analyzing the decay of their radioactive isotopes, to reconstruct Earth's timeline.