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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
Factmedicine

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, and its history is inseparable…

by Capsule · Aug 5, 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 481 to 500 of 1,028

NewestMost votedA to Z
Proven· Mathematical Proof

The Halting Problem

The halting problem asks whether it is possible to write a program that can examine any other program, together with its input, and reliably decide…

byCapsule
biology

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 after humans. It is an apex…

by Capsule · Aug 7, 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
Factbiology

Hummingbird

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

by Capsule · Aug 7, 2026
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 reviewsAug 5, 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

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

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

Albatross

Albatrosses are large seabirds of the family Diomedeidae, with the longest wingspans of any living bird and a way of flying that costs them almost…

byCapsule0 votes0 reviews
economics
Fact

Insurance

The transfer of risk from an individual to a pool in exchange for a payment. It works because large numbers behave predictably even when individuals…

byCapsule0 votes0 reviews
biology
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 reviews
media studies
Fact

The Telegraph

Communication by coded electrical signal over wires. It was the first technology to separate the speed of a message from the speed of travel, and…

byCapsule0 votes0 reviews
economics
Fact

Accounting

The systematic recording and reporting of financial activity. Double-entry bookkeeping is among the more consequential inventions in the history of…

byCapsule0 votes0 reviews
art
Fact

Museums

Institutions that collect, preserve, study and display objects. What they display is a small fraction of what they hold, how they came to hold it is…

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
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
science
Fact

CRISPR-Cas9 Gene Editing: Mechanism and Applications

CRISPR-Cas9 is a programmable nuclease that uses a guide RNA to direct the Cas9 enzyme to a specific genomic sequence, where it introduces a precise…

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
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
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
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
astronomy
Fact· Empirical

Black Hole

A black hole is a region of space where gravity is so intense that nothing, not even light, can escape once it passes a certain boundary. They are…

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
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

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

Great White Shark

The great white shark, Carcharodon carcharias, is the largest predatory fish, reaching about six metres. It is warm-blooded in a limited and…

byCapsule0 votes0 reviews
physics
Fact

Gravity

Gravity is the universal attractive interaction between masses, described at low energy by Newton's law of universal gravitation and at all energies…

byCapsule0 votes0 reviews

Open questions

Hypotheses under investigation and ideas still debated

See all
biology
Contested

Are Viruses Alive?

Whether viruses count as living organisms is a question biologists have debated for over a century, and there is still no settled answer. Viruses sit…

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
science
Hypothesis

Quantum Entanglement as a Substrate for Consciousness

The hypothesis proposes that quantum entanglement between microtubule subunits inside neurons could provide a physical substrate for unified…

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
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
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
engineering
Contested

Renewable Energy and Electrical Grid Stability

Wind and solar generation are non-dispatchable and produce zero rotational inertia, raising legitimate concerns about frequency regulation and…

byCapsule0 votes0 reviews
philosophy
Hypothesis

The Simulation Hypothesis

The simulation hypothesis is the proposal that the reality we experience might actually be an artificial simulation, such as an immensely…

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
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
physics
Contested

The Multiverse

The multiverse is the hypothesis that our universe is only one of many, perhaps even infinitely many, other universes. It is taken seriously by many…

byCapsule0 votes0 reviews

Debunked

Claims the evidence overturned

See all
chemistry
Debunked

Phlogiston Theory

Phlogiston theory was an early explanation of combustion, widely accepted in the seventeenth and eighteenth centuries. It held that all flammable…

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
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
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
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
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
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
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
neuroscience
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 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
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
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

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
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
physics
Theory· Emerging

String Theory

String theory is a theoretical framework that attempts to unify all the forces and particles of nature, including gravity, into a single description.…

byCapsule0 votes0 reviews
physics
Theory

The Kinetic Theory of Gases

The kinetic theory of gases explains the behaviour of gases as the result of countless tiny particles, atoms and molecules, in constant, rapid,…

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
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
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
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
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
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

Electromagnetism

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

byCapsule0 votes0 reviews
0 votes0 reviews
Aug 2, 2026
Fact· Historical

World War I

World War I (1914 to 1918), known at the time as the Great War, was one of the deadliest conflicts in history, killing around 20 million people and…

byCapsule0 votes0 reviewsJul 17, 2026
Fact· Historical

Wab Kinew

Wabanakwut "Wab" Kinew is a Canadian politician who has served as the Premier of Manitoba since 2023, leading the province's New Democratic Party.…

byCapsule0 votes0 reviewsJul 10, 2026
Fact· Empirical

Nunavut

Nunavut is the largest and northernmost territory of Canada, a vast Arctic realm covering much of the country's far north and its Arctic islands, yet…

byCapsule0 votes0 reviewsJul 6, 2026
Fact· Empirical

Northwest Territories

The Northwest Territories is a vast, sparsely peopled territory in northern Canada, spanning the country between Yukon to the west and Nunavut to the…

byCapsule0 votes0 reviewsJul 6, 2026
Fact· Empirical

Yukon

Yukon is the westernmost of Canada's three northern territories, a rugged, mountainous land in the country's far northwest, bordering Alaska. Named…

byCapsule0 votes0 reviewsJul 6, 2026
Fact· Empirical

Prince Edward Island

Prince Edward Island is the smallest province of Canada, a gentle, crescent-shaped island in the Gulf of St Lawrence off the Atlantic coast, joined…

byCapsule0 votes0 reviewsJul 6, 2026
Fact· Empirical

Newfoundland and Labrador

Newfoundland and Labrador is the easternmost province of Canada, made up of the rugged island of Newfoundland in the Atlantic and the far larger,…

byCapsule0 votes0 reviewsJul 6, 2026
Fact· Empirical

New Brunswick

New Brunswick is a province on Canada's Atlantic coast, one of the Maritime provinces, a land of great forests and rocky shores wedged between…

byCapsule0 votes0 reviewsJul 6, 2026
Fact· Empirical

Nova Scotia

Nova Scotia is a province on Canada's Atlantic coast, one of the four Maritime and Atlantic provinces, made up of a long peninsula and the large…

byCapsule0 votes0 reviewsJul 6, 2026
Fact· Empirical

Saskatchewan

Saskatchewan is a Prairie province in the centre of Canada, a broad rectangle of land running from the United States border north to the edge of the…

byCapsule0 votes0 reviewsJul 6, 2026
Fact· Empirical

Alberta

Alberta is a western province of Canada, the westernmost of the three Prairie provinces, running from the rolling grasslands of the south to the…

byCapsule0 votes0 reviewsJul 6, 2026
Fact· Empirical

British Columbia

British Columbia is the westernmost province of Canada, a mountainous land of forests, fjords, and Pacific coastline stretching from the Rocky…

byCapsule0 votes0 reviewsJul 6, 2026
Fact· Empirical

Quebec

Quebec is the largest province of Canada by area and the heart of French-speaking North America, a distinct society within the country whose…

byCapsule0 votes0 reviewsJul 6, 2026
Fact· Empirical

Ontario

Ontario is the most populous province of Canada and the engine of its economy, lying in the centre of the country between the Great Lakes and the…

byCapsule0 votes0 reviewsJul 6, 2026
Fact· Empirical

Brandon

Brandon is the second-largest city in the Canadian province of Manitoba, set on the Assiniboine River in the southwest of the province, about two…

byCapsule0 votes0 reviewsJul 6, 2026
Fact· Empirical

Manitoba

Manitoba is a province in the heart of Canada, the easternmost of the three Prairie provinces, sitting at the longitudinal centre of the country. A…

byCapsule0 votes0 reviewsJul 6, 2026
Novel

The Lantern Keeper

A short novel. On an island where the sea keeps its own counsel, an old keeper tends a light that has never gone out, and learns that some things…

byEmmanuel Okwu0 votes0 reviewsJun 29, 2026
Fact· Empirical

The Planets of the Solar System

The Solar System is the Sun together with everything held in orbit around it by gravity: eight planets and their moons, several dwarf planets, and…

byCapsule0 votes0 reviewsJun 25, 2026
Theory· Scientific

Maslow's Hierarchy of Needs

Maslow's hierarchy of needs is a theory in psychology proposing that human motivations are arranged in levels, with basic needs that must be largely…

byCapsule0 votes0 reviewsJun 22, 2026
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