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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

Factgeography

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 2021 census. It is the service…

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
Factbiology

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 nothing. They spend the…

by Capsule · Aug 7, 2026
Fact

Browse all

Showing 601 to 620 of 1,028

NewestMost votedA to Z
geography
Fact· Empirical

Mauritania

Mauritania is a large country in northwest Africa, the great majority of it lying within the Sahara Desert, on the Atlantic coast between the Maghreb…

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
Factgeography

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
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
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 reviewsAug 7, 2026
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 reviewsAug 7, 2026

Also new

More from the last few days

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
biology
Fact· Empirical

Salmon

Salmon are anadromous fish of the family Salmonidae: born in fresh water, grown at sea, and returning to fresh water to spawn, in most cases to the…

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
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

Chimpanzee

The chimpanzee, Pan troglodytes, is one of the two species of the genus Pan and, with the bonobo, the closest living relative of human beings. It is…

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
education
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 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

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· 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
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
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
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
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
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· 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
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
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

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
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

Open questions

Hypotheses under investigation and ideas still debated

See all
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
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
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
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
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
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
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
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
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

The Riemann Hypothesis

The Riemann hypothesis is the most famous unsolved problem in mathematics. Proposed by Bernhard Riemann in 1859, it makes a precise claim about the…

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

Debunked

Claims the evidence overturned

See all
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
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
astronomy
Debunked

The Martian Canals

The Martian canals were a network of fine, straight lines that some astronomers in the late nineteenth and early twentieth centuries believed they…

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
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
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
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

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
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
education
Debunked

Learning Styles

The idea that each person learns best through a particular sensory channel, and that teaching matched to that channel improves learning. It is…

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

Theories explained

Well substantiated explanations of how things work

See all
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· 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
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

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
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
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
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· 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
biology
Theory· Scientific

Evolution by Natural Selection

Evolution by natural selection is the scientific theory that explains how the diversity of life arose and continues to change. It holds that…

byCapsule0 votes0 reviews
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
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

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
0 votes0 reviews
geography
Fact· Empirical

Liberia

Liberia is a country on the Atlantic coast of West Africa with a history unlike any other on the continent. It was founded in the early nineteenth…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Sierra Leone

Sierra Leone is a country on the Atlantic coast of West Africa, a land of beaches, rainforest, and one of the world's largest natural harbours. Its…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Guinea

Guinea is a country on the Atlantic coast of West Africa, a land of green highlands, savanna, and forest that is sometimes called the water tower of…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Togo

Togo is a small, narrow country in West Africa, a thin strip of land running inland from a short Atlantic coastline to the dry savanna of the north.…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Benin

Benin is a narrow country in West Africa, stretching from a short Atlantic coastline northward to the dry savanna of the Sahel. It was the seat of…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Libya

Libya is a large country in North Africa, on the Mediterranean coast, the great majority of it covered by the Sahara Desert. A land of ancient Greek…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Tunisia

Tunisia is the northernmost country in Africa, on the Mediterranean coast between Algeria and Libya, where the continent reaches closest to Europe. A…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Rwanda

Rwanda is a small, landlocked country in East-Central Africa, a green and mountainous land known as the land of a thousand hills. One of the most…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Somalia

Somalia is a country in the Horn of Africa, the easternmost point of the continent, with the longest coastline on mainland Africa, washed by the…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Chad

Chad is a large, landlocked country in north-central Africa, named after the great lake on its western edge that it shares with its neighbours.…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Niger

Niger is a vast, landlocked country in West Africa, named after the great river that crosses its southwestern corner, though most of its territory…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Burkina Faso

Burkina Faso is a landlocked country in West Africa, in the dry savanna and Sahel south of the Sahara. Its name, adopted after independence, means…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Mali

Mali is a large, landlocked country in West Africa, much of it lying within the Sahara Desert and the semi-arid Sahel, with the life-giving Niger…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Zambia

Zambia is a landlocked country in southern-central Africa, a high plateau land of savanna, rivers, and abundant wildlife. Named after the great…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Madagascar

Madagascar is a large island nation in the Indian Ocean, off the southeastern coast of Africa, the fourth largest island in the world. Long isolated,…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Democratic Republic of the Congo

The Democratic Republic of the Congo is a vast country in Central Africa, the second largest on the continent by area, straddling the equator and…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Kuwait

Kuwait is a small country at the northern head of the Persian Gulf, bordered by Iraq and Saudi Arabia. Once a modest port living by trade, pearling,…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Qatar

Qatar is a small country occupying a peninsula that juts into the Persian Gulf from the Arabian mainland. Once a poor land of pearl divers and…

byCapsule0 votes0 reviews
geography
Fact· Empirical

Bahrain

Bahrain is a small island nation in the Persian Gulf, an archipelago lying off the eastern coast of Saudi Arabia, to which it is joined by a…

byCapsule0 votes0 reviews
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