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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

Factbiology

Axolotl

The axolotl, Ambystoma mexicanum, is a salamander that never leaves the larval form. It reaches sexual maturity while keeping its gills and its aquatic body, it regrows amputated…

by Capsule · Aug 7, 2026
Factbiology

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 three metres and 70 to 90…

by Capsule · Aug 7, 2026
Factbiology

Bat

Bats, the order Chiroptera, are the only mammals capable of powered flight. There are more than 1,400 species, roughly a fifth of all mammal species, and they occupy every…

by Capsule · Aug 7, 2026
Fact

Browse all

Showing 521 to 540 of 1,028

NewestMost votedA to Z
biology
Theory· Scientific

The Modern Evolutionary Synthesis

The modern synthesis is the theory, developed in the first half of the twentieth century, that united Charles Darwin's idea of evolution by natural…

byCapsule
media studies

Radio

Communication using electromagnetic waves without a conductor between sender and receiver. It was the first medium to reach a mass audience simultaneously, and it remains the…

by Capsule · Aug 5, 2026
Factnutrition

Salt

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

by Capsule · Aug 5, 2026
Factmedicine

Surgery

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

by Capsule · Aug 5, 2026
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 reviewsAug 7, 2026
Fact· Empirical

Bat

Bats, the order Chiroptera, are the only mammals capable of powered flight. There are more than 1,400 species, roughly a fifth of all mammal species,…

byCapsule0 votes0 reviewsAug 7, 2026

Also new

More from the last few days

geography
Fact· Empirical

Selkirk

Selkirk is a city on the Red River about twenty-two kilometres northeast of Winnipeg, with 10,504 residents at the 2021 census. It came close to…

byCapsule0 votes0 reviews
biology
Fact· Empirical

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…

byCapsule0 votes0 reviews
geography
Fact· Empirical

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…

byCapsule0 votes0 reviews
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

Ant

Ants are eusocial insects of the family Formicidae, with over 14,000 described species and an estimated global population around twenty quadrillion…

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
biology
Fact· Empirical

Orca

The orca, Orcinus orca, also called the killer whale, is the largest member of the dolphin family and the most widely distributed mammal on Earth…

byCapsule0 votes0 reviews
geography
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 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
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
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

Mount Everest

Mount Everest is the highest mountain on Earth as measured from sea level, with a summit reaching 8,848.86 metres (29,031.7 feet) above sea level, a…

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
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
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
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
history
Fact· Historical

French Revolution

The French Revolution (1789–1799) was a period of radical political and social upheaval in France that ended the Bourbon monarchy, abolished feudal…

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
biology
Fact· Empirical

Honey Bee

Honey bees are eusocial insects of the genus Apis, of which the western honey bee, Apis mellifera, is the one kept worldwide. They communicate the…

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
Proven· Replicated

Photosynthesis

Photosynthesis is the process by which plants, algae, and certain bacteria capture the energy of sunlight and use it to turn carbon dioxide and water…

byCapsule0 votes0 reviews

Open questions

Hypotheses under investigation and ideas still debated

See all
psychology
Contested

Nature versus Nurture

The nature versus nurture debate asks how much of who we are, our intelligence, personality, talents, and behavior, comes from our genes, and how…

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
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
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
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
earth science
Contested

What Causes the Ice Ages

Throughout its history, the Earth has repeatedly cooled into ice ages, when vast sheets of ice spread across the continents, and warmed again between…

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
mathematics
Hypothesis

Goldbach's Conjecture

Goldbach's conjecture is one of the oldest and simplest sounding unsolved problems in mathematics. It states that every even whole number greater…

byCapsule0 votes0 reviews
psychology
Hypothesis

Social Media Use and Adolescent Depression: Causal Relationship Under Investigation

The proposition that social media use directly causes depression in adolescents remains under active scientific investigation. While correlational…

byCapsule0 votes0 reviews
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
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
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

Debunked

Claims the evidence overturned

See all
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
medicine
Debunked

Bloodletting

Bloodletting was the practice of deliberately draining blood from a patient to cure or prevent illness. For more than two thousand years it was one…

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
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
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
medicine
Debunked

Miasma Theory

Miasma theory was the belief that diseases such as cholera and the plague were caused by "bad air," a poisonous vapor thought to rise from rotting…

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
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
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
physics
Debunked

The Caloric Theory

The caloric theory was an explanation of heat, widely accepted into the early nineteenth century, which held that heat is an invisible, weightless…

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
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

Theories explained

Well substantiated explanations of how things work

See all
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
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

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
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
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· Mathematical

Chaos Theory

Chaos theory is the branch of mathematics that studies systems whose behaviour is exquisitely sensitive to their starting conditions. Such systems…

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
mathematics
Theory

Set Theory

Set theory is the branch of mathematics that studies collections of objects, called sets. Though it begins with an idea as simple as grouping things…

byCapsule0 votes0 reviews
physics
Theory

Quantum Mechanics

Quantum mechanics is the branch of physics that describes the behaviour of matter and energy at the smallest scales, those of atoms and subatomic…

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
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
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
0 votes0 reviews
psychology
Theory· Scientific

Operant Conditioning

Operant conditioning is the psychological theory that behaviour is shaped by its consequences: actions followed by rewards become more likely, and…

byCapsule0 votes0 reviews
physics
Theory· Scientific

The Standard Model of Particle Physics

The Standard Model is the theory that describes all the known elementary particles of matter and the forces that act between them, except for…

byCapsule0 votes0 reviews
mathematics
Proven· Mathematical Proof

The Infinitude of Primes

There are infinitely many prime numbers. This was proven more than two thousand years ago by the Greek mathematician Euclid, in an argument so clear…

byCapsule0 votes0 reviews
astrophysics
Proven· Replicated

Black Holes

A black hole is a region of space where gravity is so intense that nothing, not even light, can escape from within it. Once a purely theoretical…

byCapsule0 votes0 reviews
physics
Proven· Replicated

The Equivalence of Mass and Energy

Mass and energy are two forms of the same thing. This is the meaning of the most famous equation in science, which states that the energy contained…

byCapsule0 votes0 reviews
molecular biology
Proven· Replicated

The DNA Double Helix

The double helix is the elegant twisted-ladder shape of the DNA molecule, the chemical that carries the genetic instructions of every living thing.…

byCapsule0 votes0 reviews
earth science
Proven· Replicated

The Spherical Earth

That the Earth is a sphere, very slightly flattened at the poles, is one of the most thoroughly established facts in all of science. It has been…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Western Sahara

Western Sahara is a disputed territory in northwestern Africa, lying on the Atlantic coast between Morocco, Algeria, and Mauritania. A vast, sparsely…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Niue

Niue is a tiny island nation in the South Pacific, a single coral island east of Tonga, often called The Rock for its raised limestone form. One of…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Cook Islands

The Cook Islands is a self-governing island nation in the South Pacific, a scattering of 15 islands spread across a vast area of ocean between French…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Taiwan

Taiwan, officially the Republic of China, is a self-governing island state in East Asia, lying off the southeastern coast of mainland China across…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Palestine

The State of Palestine is a state in the Middle East recognised by a majority of the world's countries and holding non-member observer status at the…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Uruguay

Uruguay is a small country in southeastern South America, lying on the Atlantic coast between its two giant neighbours, Brazil and Argentina. The…

byCapsule0 votes0 reviews
geography
Fact· Empirical

United Arab Emirates

The United Arab Emirates is a country on the southeastern coast of the Arabian Peninsula, on the Persian Gulf, a federation of seven emirates that…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Singapore

Singapore is a city-state at the southern tip of the Malay Peninsula in Southeast Asia, an island nation of remarkable prosperity built on what was,…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Paraguay

Paraguay is a landlocked country in the heart of South America, bordered by Argentina, Brazil, and Bolivia. One of only two landlocked nations on the…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Lebanon

Lebanon is a small country on the eastern shore of the Mediterranean Sea, bordered by Syria and Israel, with a history reaching back to the ancient…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Burundi

Burundi is a small, landlocked country in the Great Lakes region of East Africa, lying just south of the equator between the Democratic Republic of…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Saint Vincent and the Grenadines

Saint Vincent and the Grenadines is an island nation in the eastern Caribbean, among the Windward Islands, made up of the main island of Saint…

byCapsule0 votes0 reviews
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