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Truth Classification

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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

Facteconomics

Banking

Institutions that take deposits and make loans. The central fact about banking is that it creates money rather than merely storing it, and almost every difficulty the industry…

by Capsule · Aug 5, 2026
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
Factagriculture

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 the resource has been repeatedly…

by Capsule · Aug 5, 2026
Fact

Browse all

Showing 441 to 460 of 1,028

NewestMost votedA to Z
immunology
Contested

The Hygiene Hypothesis

The hygiene hypothesis is the proposal that reduced exposure to microbes in early childhood leaves the immune system poorly calibrated, and that this…

byCapsule
geography

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 2021 census. Its name records…

by Capsule · Aug 7, 2026
Factbiology

Horse

The horse, Equus ferus caballus, is a large grazing mammal domesticated on the Eurasian steppe and, for roughly four thousand years, the fastest way a human being could travel…

by Capsule · Aug 7, 2026
Factgeography

Winkler

Winkler is the fourth-largest city in Manitoba, in the Pembina Valley about twenty kilometres north of the United States border, with 13,745 residents at the 2021 census. Like…

by Capsule · Aug 7, 2026
Fact· Empirical

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…

byCapsule0 votes0 reviewsAug 7, 2026
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 reviewsAug 5, 2026

Also new

More from the last few days

geography
Fact· Empirical

Dauphin

Dauphin is a city in the Parkland region of western Manitoba, between Riding Mountain National Park and Lake Dauphin, with 8,368 residents at the…

byCapsule0 votes0 reviews
biology
Fact· Empirical

Spider

Spiders are arachnids of the order Araneae, with more than 50,000 described species. All of them produce silk, nearly all of them are venomous, and…

byCapsule0 votes0 reviews
agriculture
Fact

Livestock

Domesticated animals kept for food, fibre, labour and other products. Livestock made agriculture viable on land that grows no crops, and they are now…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Steinbach

Steinbach is the third-largest city in Manitoba, about sixty kilometres southeast of Winnipeg, with 17,806 residents at the 2021 census. Founded by…

byCapsule0 votes0 reviews
biology
Fact· Empirical

Hummingbird

Hummingbirds, the family Trochilidae, are small nectar-feeding birds of the Americas that hover in sustained flight and run the highest mass-specific…

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
biology
Fact· Empirical

Tardigrade

Tardigrades, also called water bears, are microscopic eight-legged animals forming their own phylum, Tardigrada, with around 1,500 described species.…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Thompson

Thompson is the largest city in northern Manitoba, roughly 650 kilometres north of Winnipeg on the Burntwood River, with 13,035 residents at the 2021…

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
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
biology
Fact· Empirical

Penguin

Penguins are flightless seabirds of the southern hemisphere, around eighteen species, which gave up flight in the air for flight underwater. They are…

byCapsule0 votes0 reviews
history
Fact· Empirical

Great Wall of China

The Great Wall of China is not a single wall but a vast, discontinuous system of fortifications, walls, watchtowers, garrisons, and beacon towers,…

byCapsule0 votes0 reviews
chemistry
Fact

Water (H₂O)

Water is a chemical compound with the formula H₂O, consisting of two hydrogen atoms covalently bonded to one oxygen atom. Its bent molecular geometry…

byCapsule0 votes0 reviews
astronomy
Fact· Empirical

The Sun

The Sun is the star at the centre of the Solar System, a vast sphere of hot plasma whose gravity holds the planets in their orbits and whose light…

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
astronomy
Fact· Empirical

The Solar System

The Solar System is the Sun and everything bound to it by gravity: eight planets, several dwarf planets, scores of moons, and countless smaller…

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
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
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
agriculture
Fact

Nitrogen Cycling in Prairie Soils of the Canadian Prairies

Nitrogen cycling in Prairie soils is a well-documented biological and chemical process that determines agricultural productivity across Manitoba,…

byCapsule0 votes0 reviews
geography
Fact· Empirical

The Sahara

The Sahara is the largest hot desert on Earth, a sweep of sand, gravel, and bare rock stretching across northern Africa from the Atlantic Ocean to…

byCapsule0 votes0 reviews

Open questions

Hypotheses under investigation and ideas still debated

See all
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
astrophysics
Contested

How the Universe Will End

The ultimate fate of the universe is one of the deepest questions in science. Cosmologists have proposed several very different endings, and which…

byCapsule0 votes0 reviews
biology
Hypothesis

Abiogenesis: The Origin of Life

Abiogenesis is the natural process by which life is thought to have arisen from non living matter, such as simple chemical compounds. How life first…

byCapsule0 votes0 reviews
astronomy
Contested

The Fermi Paradox

The Fermi paradox is the puzzling contrast between the high apparent likelihood that alien civilizations exist somewhere in our vast galaxy and the…

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
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
earth science
Contested

What Killed the Dinosaurs

Around sixty six million years ago, the dinosaurs and many other forms of life suddenly vanished in one of the great mass extinctions in Earth's…

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
neuroscience
Contested

The Hard Problem of Consciousness

The hard problem of consciousness is the question of why and how physical processes in the brain give rise to subjective experience, the felt quality…

byCapsule0 votes0 reviews
earth science
Hypothesis

The Gaia Hypothesis

The Gaia hypothesis proposes that life and its physical environment on Earth form a single, self regulating system that keeps the planet suitable for…

byCapsule0 votes0 reviews
astronomy
Contested

Is Pluto a Planet?

Whether Pluto should be called a planet is a question that has divided astronomers and captured the public imagination. Discovered in 1930 and…

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

Debunked

Claims the evidence overturned

See all
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
biology
Debunked

Spontaneous Generation

Spontaneous generation was the long held belief that living organisms could arise directly from non living matter. People thought maggots formed from…

byCapsule0 votes0 reviews
literature
Debunked

The Shakespeare Authorship Question

The claim that the works attributed to William Shakespeare were written by someone else. It has attracted eminent supporters for a hundred and…

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
nutrition
Debunked

Breakfast as the Most Important Meal

The claim that eating breakfast is necessary for health and weight control, and that skipping it causes weight gain. The phrase was popularised by…

byCapsule0 votes0 reviews
geology
Debunked

The Hollow Earth

The hollow Earth was the idea that our planet is not solid but hollow, perhaps containing a habitable inner world, or even inner suns and…

byCapsule0 votes0 reviews
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
biology
Debunked

Vitalism

Vitalism was the long held belief that living things contain a special, non physical "vital force" or "life energy" that animates them and that…

byCapsule0 votes0 reviews
astronomy
Debunked

The Geocentric Model

The geocentric model was the ancient belief that the Earth sits motionless at the center of the universe, with the Sun, Moon, planets, and stars all…

byCapsule0 votes0 reviews
physics
Debunked

Perpetual Motion

Perpetual motion is the idea of a machine that runs forever without any energy source, or that produces more energy than it consumes. Inventors have…

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
medicine
Debunked

Do Vaccines Cause Autism?

The claim that vaccines cause autism is one of the most damaging medical myths of modern times. It has been investigated exhaustively and thoroughly…

byCapsule0 votes0 reviews

Theories explained

Well substantiated explanations of how things work

See all
physics
Theory· Scientific

Special Relativity

Special relativity is the theory of space and time that Albert Einstein published in 1905. It revolutionized physics by showing that measurements of…

byCapsule0 votes0 reviews
physics
Theory

Electromagnetism

Electromagnetism is the branch of physics that describes the forces between electric charges and the deep connection between electricity and…

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
chemistry
Theory

Atomic Theory

Atomic theory is the idea that all matter is made up of tiny particles called atoms. It is one of the most important and successful ideas in all of…

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
earth science
Theory

The Greenhouse Effect

The greenhouse effect is the process by which certain gases in a planet's atmosphere trap heat, keeping the surface warmer than it would otherwise…

byCapsule0 votes0 reviews
physics
Theory

Optics

Optics is the branch of physics that studies light: how it travels, how it interacts with matter, and how it can be controlled with lenses and…

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
science
Theory

The Gut-Brain Axis: Microbiome Influence on Mental Health

The gut-brain axis describes the bi-directional signalling between gut microbiota and the central nervous system via the vagus nerve, immune system,…

byCapsule0 votes0 reviews
computer science
Theory· Mathematical

Information Theory

Information theory is the mathematical study of how information is measured, stored, and communicated. It defines what information actually is in…

byCapsule0 votes0 reviews
astronomy
Theory· Scientific

The Big Bang

The Big Bang is the prevailing cosmological theory of how the universe began. It holds that the universe started about 13.8 billion years ago in an…

byCapsule0 votes0 reviews
0 votes0 reviews
immunology
Theory· Scientific

Autoimmunity

Autoimmunity is the immune system attacking the body it belongs to. Around a hundred distinct autoimmune conditions are recognised, together…

byCapsule0 votes0 reviews
immunology
Theory

Herd Immunity

Herd immunity is the protection an unvaccinated person receives when enough of the people around them are immune that a chain of transmission cannot…

byCapsule0 votes0 reviews
climate science
Contested

Climate Tipping Points

A climate tipping point is a threshold beyond which part of the Earth system shifts into a different state, and does not shift back when the forcing…

byCapsule0 votes0 reviews
climate science
Theory· Scientific

Extreme Event Attribution

Extreme event attribution is the field that answers the question people ask after every flood, heatwave, and storm: did climate change cause this?…

byCapsule0 votes0 reviews
climate science
Contested

Climate Sensitivity

Climate sensitivity is the amount of warming that follows from doubling the concentration of carbon dioxide in the atmosphere. It is the single…

byCapsule0 votes0 reviews
genetics
Theory· Scientific

Horizontal Gene Transfer

Horizontal gene transfer is the movement of genetic material between organisms by means other than parent to offspring. It is ordinary among…

byCapsule0 votes0 reviews
genetics
Contested

The Heritability of Intelligence

How much of the variation in measured intelligence is attributable to genetic variation is among the most technically misunderstood questions in…

byCapsule0 votes0 reviews
genetics
Contested

Junk DNA

Only a small fraction of the human genome codes for proteins, something under two per cent. What the rest of it is doing has been argued about for…

byCapsule0 votes0 reviews
genetics
Proven· Replicated

CRISPR Gene Editing

CRISPR is a method for cutting DNA at a chosen location, which makes editing a genome a routine laboratory procedure rather than a specialist feat.…

byCapsule0 votes0 reviews
genetics
Theory· Scientific

Epigenetics

Epigenetics is the study of changes in how genes are used that do not involve changes to the DNA sequence itself. Every cell in a body carries the…

byCapsule0 votes0 reviews
archaeology
Theory

Stratigraphy

Stratigraphy is the study of layers, and the principle that where deposits lie undisturbed the lower ones were laid down before the upper ones. It…

byCapsule0 votes0 reviews
archaeology
Contested

The Indus Script

The Indus Valley Civilisation left behind thousands of inscribed objects, mostly small stone seals, carrying sequences of signs that nobody can read.…

byCapsule0 votes0 reviews
archaeology
Contested

Gobekli Tepe

Gobekli Tepe is a complex of monumental stone enclosures in southeastern Turkey, built around eleven thousand years ago by people who had not yet…

byCapsule0 votes0 reviews
archaeology
Proven· Replicated

Radiocarbon Dating

Radiocarbon dating measures how much carbon-14 remains in something that was once alive, and converts that into an age. Developed by Willard Libby in…

byCapsule0 votes0 reviews
anthropology
Contested

Dunbar's Number

Dunbar's number is the proposal that humans can maintain roughly 150 stable social relationships, and that the limit is set by the size of the brain.…

byCapsule0 votes0 reviews
anthropology
Theory

Kinship Systems

Kinship is the study of how societies organise relatedness, and it was for a long time the central preoccupation of anthropology. The finding that…

byCapsule0 votes0 reviews
anthropology
Contested

Cultural Relativism

Cultural relativism is the principle that a culture should be understood on its own terms rather than judged against the standards of another. It…

byCapsule0 votes0 reviews
sociology
Theory

Anomie

Anomie is the condition of a society whose norms have weakened or become unclear, leaving individuals without adequate guidance about what to want or…

byCapsule0 votes0 reviews
sociology
Contested

The Protestant Ethic Thesis

In 1905 Max Weber argued that the Protestant Reformation, and Calvinism in particular, produced a cultural disposition toward disciplined work and…

byCapsule0 votes0 reviews
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