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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

Factbiology

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 a forest and woodland ape of…

by Capsule · Aug 7, 2026
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

Ant

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

by Capsule · Aug 7, 2026
Fact

Browse all

Showing 341 to 360 of 1,028

NewestMost votedA to Z
Hypothesis

The Alkaline Vent Hypothesis

The proposal that life began in alkaline hydrothermal vents on the ocean floor, where mineral chimneys provided compartments and a natural proton…

byCapsule
biology

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
Factbiology

Seahorse

Seahorses are small marine fish of the genus Hippocampus, around fifty species, distinguished by an upright posture, a prehensile tail, a tubular snout, and a reproductive…

by Capsule · Aug 7, 2026
Factmedia 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
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 reviewsAug 7, 2026
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 reviewsAug 7, 2026

Also new

More from the last few days

biology
Fact· Empirical

Axolotl

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

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
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
economics
Fact

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…

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

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
biology
Fact· Empirical

Common Raven

The common raven, Corvus corax, is the largest songbird in the world and among the most widely distributed birds on Earth, occupying the whole…

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
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
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

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
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
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
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

Lion

The lion, Panthera leo, is the only truly social cat and the second largest after the tiger. It once ranged from southern Africa through the Middle…

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
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

Octopus

Octopuses are eight-armed cephalopod molluscs, around three hundred species, found in every ocean. They have three hearts, blue blood, no skeleton,…

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
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
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
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
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
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

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
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
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
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
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
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

The Rare Earth Hypothesis

The Rare Earth hypothesis proposes that complex, multicellular life, of the kind found on Earth, is extremely rare in the universe, because it…

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

Debunked

Claims the evidence overturned

See all
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
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
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
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 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
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
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
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
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
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
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
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

Theories explained

Well substantiated explanations of how things work

See all
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
mathematics
Theory

Graph Theory

Graph theory is the branch of mathematics that studies networks of connected objects. A graph is simply a collection of points, called vertices,…

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
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
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
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

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
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
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· 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
0 votes0 reviews
Aug 3, 2026
Hypothesis

The RNA World Hypothesis

The proposal that early life used RNA for both heredity and catalysis, before DNA and proteins divided those jobs between them. It solves a genuine…

byCapsule0 votes0 reviewsAug 3, 2026
Proven

Error-Correcting Codes

Adding structured redundancy to a message so that errors introduced in storage or transmission can be detected and repaired without asking for a…

byCapsule0 votes0 reviewsAug 3, 2026
Proven

Semmelweis and Handwashing

A Hungarian obstetrician worked out in 1847 that doctors were killing women in childbirth by carrying something on their hands from the dissection…

byCapsule0 votes0 reviewsAug 3, 2026
Proven

Spectroscopy

Every element absorbs and emits light at a unique set of wavelengths. Reading those wavelengths identifies what something is made of without touching…

byCapsule0 votes0 reviewsAug 3, 2026
Proven

The Expansion of the Universe

Distant galaxies recede from us, and the further away they are the faster they go. The observation established that the universe has a history rather…

byCapsule0 votes0 reviewsAug 3, 2026
Proven

Nuclear Fission

Splitting a heavy nucleus releases about a hundred million times more energy per atom than a chemical reaction. It was discovered by accident in…

byCapsule0 votes0 reviewsAug 3, 2026
Proven

Rutherford Scattering

Firing alpha particles at gold foil and finding that a few bounced back. The result destroyed the prevailing model of the atom, established that…

byCapsule0 votes0 reviewsAug 3, 2026
Proven

Osmosis

Water moves across a membrane from where solutes are dilute to where they are concentrated. It requires no pump and no energy input, it generates…

byCapsule0 votes0 reviewsAug 3, 2026
Proven

Enzyme Catalysis

Enzymes speed up chemical reactions by factors that reach ten to the power of seventeen, at body temperature and neutral pH, without being consumed.…

byCapsule0 votes0 reviewsAug 3, 2026
Proven

The Laser

A device that produces light in which every wave is in step, travelling in one direction at one wavelength. It was built in 1960 with no application…

byCapsule0 votes0 reviewsAug 3, 2026
Hypothesis

The Zoo Hypothesis

The proposal that extraterrestrial civilisations exist, know we are here, and are deliberately not making contact. It is among the oldest proposed…

byCapsule0 votes0 reviewsAug 3, 2026
Hypothesis

The Self-Domestication Hypothesis

The proposal that humans domesticated themselves, selecting over many generations against aggression and for tolerance, and that this produced our…

byCapsule0 votes0 reviewsAug 3, 2026
Hypothesis

Modified Newtonian Dynamics

Galaxies rotate faster at their edges than the visible matter can explain. The standard answer is that unseen dark matter supplies the extra gravity.…

byCapsule0 votes0 reviewsAug 3, 2026
Hypothesis

The Endurance Running Hypothesis

The proposal that humans evolved to run long distances, and that running down prey over hours in the heat was how our ancestors hunted before…

byCapsule0 votes0 reviewsAug 3, 2026
Hypothesis

The Bicameral Mind

Julian Jaynes proposed in 1976 that people three thousand years ago were not conscious in the way we are, that they experienced their own thoughts as…

byCapsule0 votes0 reviewsAug 3, 2026
Hypothesis

The Great Filter

If the universe should be full of civilisations and appears empty, something must be preventing them. Robin Hanson's proposal is that at least one…

byCapsule0 votes0 reviewsAug 3, 2026
Hypothesis

The Toba Catastrophe Hypothesis

The proposal that a supervolcanic eruption in Sumatra about 74,000 years ago caused a volcanic winter that nearly exterminated the human species,…

byCapsule0 votes0 reviewsAug 3, 2026
Hypothesis

The Obstetrical Dilemma

The proposal that human childbirth is difficult because walking upright narrowed the pelvis while brains grew larger, leaving birth as a compromise…

byCapsule0 votes0 reviewsAug 3, 2026
Hypothesis

The Serotonin Hypothesis of Depression

The proposal that depression is caused by low serotonin, and that antidepressants work by correcting it. The popular version of this claim is not…

byCapsule0 votes0 reviewsAug 3, 2026
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