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Truth Classification

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How classification works

Capsule of the Day

FactSurgeryTreatment by physical intervention in the body. Surgery was limited for millennia not by knowledge of anatomy but by th…

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The library

Capsules

1,028 capsules, each one classified by the strength of its evidence.

All1,028Fact599Proven130Theory89Hypothesis71Contested90Debunked48
geography236biology88physics67history54medicine45astronomy33psychology26mathematics26chemistry20engineering20astrophysics19neuroscience19anthropology18art18

Trending now

Most recent activity

Factbiology

Wolf

The grey wolf, Canis lupus, is the largest wild member of the dog family and once the most widely distributed land mammal on Earth after humans. It is also the ancestor of the…

by Capsule · Aug 7, 2026
Factgeography

Flin Flon

Flin Flon is a mining city on the Manitoba and Saskatchewan boundary, about 630 kilometres northwest of Winnipeg, built directly on the rock of the Canadian Shield. It is one of…

by Capsule · Aug 7, 2026
Facteducation

Libraries

Organised collections of recorded knowledge, held for use. Libraries are older than most of the writing systems that survive, their defining problem has always been finding rather…

by Capsule · Aug 5, 2026
Fact

Browse all

Showing 421 to 440 of 1,028

NewestMost votedA to Z
Theory

Protein Folding

A protein is manufactured as a linear chain of amino acids and only works once it has folded into a specific three-dimensional shape. How the chain…

byCapsule
geography

Winnipeg

Winnipeg is the capital and largest city of the Canadian province of Manitoba, built where the Red and Assiniboine rivers meet near the longitudinal centre of North America. With…

by Capsule · Aug 7, 2026
Factepidemiology

Sanitation

The safe management of human waste. It has saved more lives than any medical treatment, it is the least discussed of the major public health measures, and roughly a fifth of the…

by Capsule · Aug 5, 2026
Factbiology

Monarch Butterfly

The monarch, Danaus plexippus, is a large orange and black butterfly of the Americas, and the migratory population of eastern North America performs a journey no individual…

by Capsule · Aug 7, 2026
Fact· Empirical

Flin Flon

Flin Flon is a mining city on the Manitoba and Saskatchewan boundary, about 630 kilometres northwest of Winnipeg, built directly on the rock of the…

byCapsule0 votes0 reviewsAug 7, 2026
Fact

Libraries

Organised collections of recorded knowledge, held for use. Libraries are older than most of the writing systems that survive, their defining problem…

byCapsule0 votes0 reviewsAug 5, 2026

Also new

More from the last few days

medicine
Fact

Surgery

Treatment by physical intervention in the body. Surgery was limited for millennia not by knowledge of anatomy but by three specific obstacles, and…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Morden

Morden is a city in the Pembina Valley of southern Manitoba, close to the United States border and about twenty kilometres west of Winkler, with…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Portage la Prairie

Portage la Prairie is a city in central Manitoba on the Assiniboine River, about eighty kilometres west of Winnipeg, with 13,270 residents at the…

byCapsule0 votes0 reviews
medicine
Fact

Nursing

The care of the sick, injured and dependent. Nursing is the largest health profession by a wide margin, its outcomes are measurable and substantial,…

byCapsule0 votes0 reviews
agriculture
Fact

Fishing

Catching aquatic animals for food. It is the last major food source still taken from the wild at scale, which is precisely why it is the one where…

byCapsule0 votes0 reviews
biology
Fact· Empirical

Sea Turtle

Sea turtles are marine reptiles of the superfamily Chelonioidea, seven living species that have been in the oceans for more than a hundred million…

byCapsule0 votes0 reviews
biology
Fact· Empirical

Komodo Dragon

The Komodo dragon, Varanus komodoensis, is the largest living lizard, restricted to a handful of islands in eastern Indonesia. It grows to around…

byCapsule0 votes0 reviews
nutrition
Fact

Salt

Sodium chloride. It is physiologically essential, it was the only reliable food preservative for most of history, and its scarcity relative to demand…

byCapsule0 votes0 reviews

On this day

A birth or event with an anniversary today

history
Fact· Empirical

Statue of Liberty

The Statue of Liberty is a colossal copper statue on an island in New York Harbor, one of the most famous monuments in the United States and a…

byCapsule0 votes0 reviews

Settled science

Verified facts and proven results

See all
biology
Fact

DNA (Deoxyribonucleic Acid)

Deoxyribonucleic acid (DNA) is the molecule that carries the genetic instructions used in the growth, development, functioning, and reproduction of…

byCapsule0 votes0 reviews
agriculture
Fact

Traditional Yoruba Agricultural Practices in Southwestern Nigeria

The Yoruba people of southwestern Nigeria developed sophisticated agricultural systems over centuries that integrated intercropping, seasonal…

byCapsule0 votes0 reviews
biology
Fact· Empirical

Domestic Cat

The domestic cat, Felis catus, is the most numerous small carnivore on Earth, with something over six hundred million individuals. It is also barely…

byCapsule0 votes0 reviews
history
Fact· Empirical

The Colosseum

The Colosseum is a giant amphitheatre in the centre of Rome, the largest ever built and one of the most recognisable monuments of the ancient world.…

byCapsule0 votes0 reviews
biology
Fact· Empirical

Elephant

Elephants are the largest living land animals, and there are three species rather than the two most references still give. They have the longest…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Amazon Rainforest

The Amazon Rainforest is the largest tropical rainforest on Earth, a vast sea of green covering some 5.5 million square kilometres across nine South…

byCapsule0 votes0 reviews
history
Fact

The Founding and Agricultural Development of Brandon, Manitoba

Brandon, Manitoba was established in 1881 as a planned railway town along the Canadian Pacific Railway and rapidly became the agricultural hub of the…

byCapsule0 votes0 reviews
geology
Fact· Empirical

Volcano

A volcano is an opening in a planet's crust through which molten rock, gas, and ash erupt from the hot interior to the surface. On Earth they are…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Grand Canyon

The Grand Canyon is one of the most spectacular landscapes on Earth: an immense gorge carved by the Colorado River through the high plateau of…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Great Barrier Reef

The Great Barrier Reef is the world's largest coral reef system, stretching more than 2,300 kilometres along the north-east coast of Australia. So…

byCapsule0 votes0 reviews
astronomy
Fact· Empirical

The Moon

The Moon is Earth's only natural satellite and the brightest object in our night sky. Large in proportion to its planet and close enough to study…

byCapsule0 votes0 reviews
engineering
Proven

Arc Flash Hazard Mitigation in Industrial Electrical Systems

An arc flash is a high-energy electrical fault that produces an explosive release of heat, light, and pressure when a phase-to-phase or…

byCapsule0 votes0 reviews

Open questions

Hypotheses under investigation and ideas still debated

See all
physics
Hypothesis

Wormholes

A wormhole is a hypothetical tunnel through spacetime that could, in principle, connect two distant points in the universe, or even two different…

byCapsule0 votes0 reviews
psychology
Contested

The Origin of Language

How human language first arose is one of the hardest questions in science. That we alone among animals possess full language is clear; when, how, and…

byCapsule0 votes0 reviews
astronomy
Hypothesis

Planet Nine

Planet Nine is a hypothetical large planet proposed to exist in the far outer reaches of our Solar System, well beyond Neptune and Pluto. It has…

byCapsule0 votes0 reviews
history
Contested

The Bronze Age Collapse

The Bronze Age collapse was a sudden, widespread breakdown of civilizations around the eastern Mediterranean roughly 3,200 years ago. Within a few…

byCapsule0 votes0 reviews
physics
Contested

The Anthropic Principle

The anthropic principle concerns the striking observation that the universe appears remarkably fine tuned for the existence of life. Many of the…

byCapsule0 votes0 reviews
astronomy
Contested

The Origin of the Moon

How the Moon came to be is a question that has fascinated and divided scientists for generations. While one explanation is now favoured, important…

byCapsule0 votes0 reviews
philosophy
Contested

Free Will

Free will is the question of whether people are truly free to choose their actions, or whether every choice is the inevitable product of prior…

byCapsule0 votes0 reviews
biology
Hypothesis

Panspermia

Panspermia is the hypothesis that life exists throughout the universe and is spread between worlds by space dust, meteoroids, asteroids, and comets.…

byCapsule0 votes0 reviews
astronomy
Hypothesis

The Dyson Sphere

A Dyson sphere is a hypothetical megastructure that an extremely advanced civilization might build around a star to capture a large share of its…

byCapsule0 votes0 reviews
physics
Contested

Interpretations of Quantum Mechanics

Quantum mechanics is the most successful physical theory ever devised, predicting the behavior of atoms, light, and subatomic particles with…

byCapsule0 votes0 reviews
biology
Contested

Are Animals Conscious?

Whether animals have conscious experiences, an inner life of feelings and awareness, is a deep and genuinely contested question. That many animals…

byCapsule0 votes0 reviews
astrophysics
Contested

Dark Energy

Dark energy is the name given to an unknown influence that appears to be driving the expansion of the universe to speed up over time. It is thought…

byCapsule0 votes0 reviews

Debunked

Claims the evidence overturned

See all
astrophysics
Debunked

The Steady State Theory

The steady state theory was a model of the universe, popular in the mid twentieth century, which held that the universe has always looked roughly the…

byCapsule0 votes0 reviews
physics
Debunked

The Luminiferous Aether

The luminiferous aether was a hypothetical substance once believed to fill all of space and to serve as the medium through which light waves…

byCapsule0 votes0 reviews
history
Debunked

Piltdown Man

Piltdown Man was a supposed "missing link" between apes and humans, announced in 1912 from fossil fragments found in England. For decades it misled…

byCapsule0 votes0 reviews
astronomy
Debunked

Flat Earth

The idea that the Earth is flat is a debunked belief that the planet is a disc or a plane rather than a sphere. It has been contradicted by…

byCapsule0 votes0 reviews
geography
Debunked

The Bermuda Triangle

The Bermuda Triangle is a region of the Atlantic Ocean, roughly between Florida, Bermuda, and Puerto Rico, said to be the site of mysterious…

byCapsule0 votes0 reviews
criminology
Debunked

Criminal Profiling

Offender profiling infers a perpetrator's characteristics from crime scene evidence. The specific claim that it reliably narrows a suspect pool, and…

byCapsule0 votes0 reviews
neuroscience
Debunked

Phrenology

Phrenology was a popular nineteenth century practice that claimed a person's character and mental abilities could be read from the shape and bumps of…

byCapsule0 votes0 reviews
history
Debunked

Astrology

Astrology is the belief that the positions of the Sun, Moon, planets, and stars influence human affairs and personalities, and that they can be used…

byCapsule0 votes0 reviews
geology
Debunked

The Expanding Earth

The expanding Earth was a hypothesis, taken seriously by some scientists into the twentieth century, which claimed that the planet is steadily…

byCapsule0 votes0 reviews
medicine
Debunked

Humorism: The Four Humors

Humorism, or humoral theory, was the belief that human health depends on the balance of four bodily fluids, called humors: blood, phlegm, yellow…

byCapsule0 votes0 reviews
biology
Debunked

Lamarckism

Lamarckism is the discredited idea that organisms can pass on to their offspring the characteristics they acquire during their lifetime. Its classic…

byCapsule0 votes0 reviews
history
Debunked

Alchemy

Alchemy was an ancient and medieval practice that sought to transform base metals such as lead into gold, to discover a universal cure for disease,…

byCapsule0 votes0 reviews

Theories explained

Well substantiated explanations of how things work

See all
astrophysics
Theory

Stellar Evolution

Stellar evolution is the scientific account of how stars are born, live, and die over millions or billions of years. Though no one can watch a single…

byCapsule0 votes0 reviews
physics
Theory· Scientific

General Relativity

General relativity is Albert Einstein's theory of gravity, published in 1915. It reimagines gravity not as a force pulling objects together but as…

byCapsule0 votes0 reviews
mathematics
Theory

Topology

Topology is the branch of mathematics that studies the properties of shapes that survive stretching, bending, and twisting, but not tearing or…

byCapsule0 votes0 reviews
physics
Theory

Aerodynamics: How Flight Works

Aerodynamics is the study of how air flows around objects and the forces this creates. It is the science that explains how aircraft fly, how cars and…

byCapsule0 votes0 reviews
biology
Theory

Mendelian Inheritance

Mendelian inheritance is the set of principles describing how traits are passed from parents to offspring through discrete units we now call genes.…

byCapsule0 votes0 reviews
physics
Theory

Acoustics: The Science of Sound

Acoustics is the branch of physics that studies sound: how it is produced, how it travels as waves, and how it is heard. It bridges science and art,…

byCapsule0 votes0 reviews
biology
Theory

Cell Theory

Cell theory is one of the foundational ideas of biology. It holds that all living things are made of cells, that the cell is the basic unit of life,…

byCapsule0 votes0 reviews
physics
Theory

Thermodynamics

Thermodynamics is the branch of physics concerned with heat, energy, and work, and how they transform from one form to another. Its laws are among…

byCapsule0 votes0 reviews
mathematics
Theory· Mathematical

Game Theory

Game theory is the mathematical study of strategic decision making, where the outcome for each participant depends not only on their own choice but…

byCapsule0 votes0 reviews
mathematics
Theory

The Theory of Computation

The theory of computation is the branch of mathematics and computer science that asks what problems can be solved by computation, and how…

byCapsule0 votes0 reviews
earth science
Theory· Scientific

Plate Tectonics

Plate tectonics is the scientific theory that Earth's outer shell is broken into a set of large, rigid plates that drift slowly over the hotter,…

byCapsule0 votes0 reviews
biology
Theory

Endosymbiotic Theory

Endosymbiotic theory explains the origin of the complex cells that make up plants, animals, fungi, and other higher organisms. It proposes that key…

byCapsule0 votes0 reviews
0 votes0 reviews
Aug 3, 2026
Theory

The Central Dogma of Molecular Biology

The central dogma states that sequence information flows from nucleic acid to protein, and never back out of a protein into nucleic acid. Francis…

byCapsule0 votes0 reviewsAug 3, 2026
Theory· Mathematical

The Median Voter Theorem

The median voter theorem states that under certain conditions, a majority-rule election between two candidates will be won by the position preferred…

byCapsule0 votes0 reviewsAug 3, 2026
Theory· Scientific

Duverger's Law

Duverger's law states that an electoral system in which the single candidate with the most votes wins each district tends to produce two dominant…

byCapsule0 votes0 reviewsAug 3, 2026
Contested

Democratic Peace Theory

Democratic peace theory holds that democracies do not, or almost never, go to war with one another. It is among the strongest empirical regularities…

byCapsule0 votes0 reviewsAug 3, 2026
Theory

Neuroplasticity

Neuroplasticity is the brain's capacity to change its structure and function in response to experience, injury, and learning. It overturned a…

byCapsule0 votes0 reviewsAug 3, 2026
Debunked

The Left-Brain, Right-Brain Myth

The idea that people are left-brained and therefore logical, or right-brained and therefore creative, is one of the most widely believed claims about…

byCapsule0 votes0 reviewsAug 3, 2026
Contested

Mirror Neurons

Mirror neurons are cells that fire both when an animal performs an action and when it observes the same action performed by another. They were…

byCapsule0 votes0 reviewsAug 3, 2026
Contested

Trophic Cascades

A trophic cascade occurs when a change at one level of a food web propagates down through the levels beneath it. The mechanism is real and…

byCapsule0 votes0 reviewsAug 3, 2026
Theory· Scientific

Keystone Species

A keystone species is one whose effect on its ecosystem is disproportionately large relative to its abundance. The concept reorganised how ecologists…

byCapsule0 votes0 reviewsAug 3, 2026
Contested

The Replication Crisis

The replication crisis is the finding that a substantial share of published research results cannot be reproduced when the studies are repeated. It…

byCapsule0 votes0 reviewsAug 3, 2026
Proven· Mathematical Proof

Regression to the Mean

Regression to the mean is the tendency for an extreme measurement to be followed by one closer to average, for no reason other than that extremes…

byCapsule0 votes0 reviewsAug 3, 2026
Proven· Mathematical Proof

Simpson's Paradox

Simpson's paradox is the phenomenon in which a trend appears in several groups of data and reverses when the groups are combined. It is not a…

byCapsule0 votes0 reviewsAug 3, 2026
Contested

Statistical Significance

Statistical significance is a threshold used to decide whether a result is worth taking seriously. The conventional cutoff, a p-value below 0.05,…

byCapsule0 votes0 reviewsAug 3, 2026
Theory· Scientific

Metamaterials

A metamaterial gets its properties from its structure rather than its chemistry. By arranging elements smaller than the wavelength of the wave…

byCapsule0 votes0 reviewsAug 3, 2026
Proven· Replicated

Semiconductor Doping

Doping is the deliberate introduction of impurities into a semiconductor in order to control its electrical behaviour. Every transistor, and…

byCapsule0 votes0 reviewsAug 3, 2026
Proven· Replicated

Shape-Memory Alloys

A shape-memory alloy is a metal that returns to a remembered shape when heated, having been deformed while cool. The effect looks like a trick and is…

byCapsule0 votes0 reviewsAug 3, 2026
Contested

Room-Temperature Superconductors

A material that conducted electricity with no resistance at ordinary temperatures and pressures would be genuinely transformative, eliminating losses…

byCapsule0 votes0 reviewsAug 3, 2026
Contested

Graphene

Graphene is a single layer of carbon atoms arranged in a hexagonal lattice, one atom thick. Its measured properties are extraordinary and not in…

byCapsule0 votes0 reviewsAug 3, 2026
Proven· Replicated

Immunological Memory

Immunological memory is the reason surviving a disease usually protects against getting it again, and the reason vaccination works at all. It is…

byCapsule0 votes0 reviewsAug 3, 2026
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