Not a Fact Anymore
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Facts have a history.

Knowledge changes.
The record should too.

A catalogue of claims that were once reasonably accepted as factual but were later overturned, replaced, narrowed, reclassified, or corrected by better evidence.

Browse the catalogueSubmit a claim

This is not a collection of myths, failed predictions, or things somebody once said. Every entry must show that the previous claim was genuinely supported or treated as authoritative, and that the present understanding is backed by stronger evidence.

Being wrong is not the failure. Refusing to update is.

Your scientific timeline

What changed since you started school?

See which parts of the scientific record changed during or after your education.

The record through time

Centuries of changing knowledge

Follow a few landmark corrections across the historical record, or explore every entry in chronological order.

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1450The equatorial 'torrid zone' is too hot for humans to inhabit.1610Earth stands motionless at the center while the Sun, planets, and stars revolve around it.1847Puerperal fever is not carried from patient to patient on doctors' hands, so hand disinfection is unnecessary.1956The normal human chromosome number is 48.1998The expansion of the universe is slowing down under the gravitational pull of matter.2024The king cobra is one widespread species, Ophiophagus hannah, found across South and Southeast Asia.

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Three ways into the catalogue

Start with a field, compare how long claims lasted, or look at what happened when institutions acted on them.

SubjectsStart with a field

Medicine, astronomy, physics, archaeology, and more—each with its own timeline and filters.

Browse subjects →LifespansSee what lasted

Compare claims that survived a few years with ideas that held on for centuries.

Compare lifespans →InstitutionsSee what had consequences

Follow claims that shaped medicine, research, law, administration, or public policy.

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Featured entries

Examples where better evidence changed the record

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Not a fact anymore

Peptic ulcers are primarily caused by stress and lifestyle.

What we know now

Most peptic ulcers are caused either by infection with Helicobacter pylori, a bacterium that can live in the stomach, or by nonsteroidal anti-inflammatory drugs (NSAIDs), a common class of pain-relief medicines that can damage the stomach and duodenal lining.

Why it changed

Robin Warren and Barry Marshall found H. pylori living in inflamed stomach tissue and showed that the infection was closely tied to gastritis and ulcer disease. Treating the infection with antibiotics sharply reduced ulcer recurrence, while NSAIDs emerged as another major cause.

Status
Superseded
Category
Medicine
Accepted for
≈32 years
Accepted approximately
Mid-20th century to the 1980s
Changed approximately
1982–1990s

Not a fact anymore

Earth’s continents and ocean basins occupy essentially fixed positions.

What we know now

Earth’s rigid outer layer is divided into tectonic plates that move relative to one another. Continents form parts of these plates and are carried along as the plates move.

Why it changed

Ocean-floor mapping, seafloor spreading, symmetrical magnetic patterns in oceanic crust, the ages of seafloor rocks, and the global distribution of earthquakes and volcanoes produced a unified explanation for continental movement during the 1950s and 1960s.

Status
Superseded
Accepted for
≈115 years
Accepted approximately
19th century to the mid-20th century
Changed approximately
1950s–1960s

Not a fact anymore

Reported rogue waves are physically impossible exaggerations by sailors.

What we know now

Rogue waves are real, rare ocean waves that are much larger than the surrounding sea state. They can arise through nonlinear interactions, current focusing, directional effects, and ordinary statistical extremes.

Why it changed

Reports of isolated walls of water often exceeded expectations from standard linear wave models and were dismissed as unreliable. Instrumental measurements, most famously the Draupner wave recorded in the North Sea in 1995, confirmed that extreme waves can occur.

Status
Overturned
Accepted for
≈45 years
Accepted approximately
Mid-20th century–1995
Changed approximately
1995–2000s

Not a fact anymore

Chemically inert CFCs released near the ground cannot damage the stratospheric ozone layer.

What we know now

CFCs—chlorofluorocarbons once widely used in refrigerants and aerosol propellants—are so stable near the ground that they can survive long enough to reach the stratosphere. There, ultraviolet sunlight breaks them apart and releases chlorine, which can destroy many ozone molecules in repeated chemical reactions.

Why it changed

The same chemical stability that made CFCs seem safe allowed them to persist for years and drift upward. Molina and Rowland showed in 1974 how ultraviolet light could release chlorine from CFCs in the stratosphere. Later measurements and the Antarctic ozone hole confirmed the large-scale effect.

Status
Overturned
Accepted for
≈39 years
Accepted approximately
1930s–1970s
Changed approximately
1974–1980s

Not a fact anymore

Puerperal fever is not carried from patient to patient on doctors' hands, so hand disinfection is unnecessary.

What we know now

Puerperal fever is usually a bacterial infection. Doctors and other medical staff can carry infectious material between patients, making hand hygiene a basic part of infection prevention.

Why it changed

Ignaz Semmelweis found that maternal deaths were much higher in a clinic where doctors and students also performed autopsies. After he required handwashing with chlorinated lime, the death rate fell sharply. Germ theory later explained why it worked.

Status
Overturned
Category
Medicine
Accepted for
≈32 years
Accepted approximately
Early to mid-19th century
Changed approximately
1840s–1880s

Not a fact anymore

Thalidomide is safe to use during pregnancy.

What we know now

Thalidomide is a powerful human teratogen. Exposure during sensitive stages of early pregnancy can cause severe limb, ear, eye, cardiac, and internal-organ defects, and pregnancy must be rigorously prevented during treatment.

Why it changed

Thalidomide was marketed as a sedative and treatment for pregnancy nausea after animal testing failed to reveal its human teratogenicity. In 1961, clinicians independently connected characteristic birth defects with maternal use, leading to withdrawal and major drug-regulation reforms.

Status
Overturned
Category
Medicine
Accepted for
≈4 years
Accepted approximately
1957–1961
Changed approximately
1961–1962

The growing catalogue

Explore all 297 former facts

A varied sample of recently added entries across the catalogue. The full collection can be searched and filtered in either card or compact view.

Open compact index →
The Amazon rainforest was broadly a net carbon sink across the basin.Environmental Science · Narrowed · Lifespan not quantifiedCalifornia was an island separated from mainland North America.Earth Science · Corrected · ≈83 yearsChickens were first domesticated in the Indian subcontinent.Archaeology · Overturned · Lifespan not quantifiedDire wolves were close relatives of gray wolves within the genus Canis.Evolution · Reclassified · Lifespan not quantifiedEquilibrium climate sensitivity to doubled atmospheric CO₂ is likely between 1.5°C and 4.5°C.Atmospheric Science · Narrowed · ≈42 yearsFibonacci leaf spirals were an ancient pattern inherited from the earliest leafy land plants.Botany · Overturned · Lifespan not quantifiedFomalhaut b is a directly imaged exoplanet.Astronomy · Reclassified · ≈12 yearsGermany's Ries and Steinheim craters were formed at the same time by a binary asteroid impact.Geology · Corrected · Lifespan not quantifiedMars became dry mainly because its ancient surface water escaped into space.Planetary Science · Narrowed · Lifespan not quantifiedPterosaurs remained relatively small through the Jurassic and only evolved much larger body sizes in the Cretaceous.Paleontology · Narrowed · Lifespan not quantifiedWoodpecker skulls protect the brain by acting as shock absorbers during pecking.Zoology · Overturned · Lifespan not quantifiedWoody plants obtain their water mainly from soil and use water stored in bedrock only as an emergency reserve during severe drought.Ecology · Narrowed · Lifespan not quantified