What you learned in school that’s no longer true

ThenThere are nine planets, and Pluto is the ninth.

NowThere are eight planets. Pluto is a dwarf planet.

2006The International Astronomical Union defined “planet” and moved Pluto into a new class of dwarf planets. (NASA, Education Week)

Likely taught to classes up to about 2010; for about 2011 to 2013 it depends on the school. Publishers said most science books would take one to three years to catch up.

ThenMyPlate, a dinner plate divided into food groups.

NowThe official US guide since January 2026: a pyramid that puts protein, dairy, healthy fats, vegetables and fruit first, gives whole grains the least room, and cuts back refined carbs.

2026The US government replaced MyPlate with a new food pyramid in the 2025 to 2030 Dietary Guidelines. (Dietary Guidelines, RealFood.gov)

The Basic Seven: likely taught to classes up to about 1960; for about 1961 to 1963 it depends on the school. The Basic Four: likely taught to the classes of about 1964 to 1996; for about 1997 to 1999 it depends on the school. The Food Guide Pyramid: likely taught to the classes of about 2000 to 2009; for about 2010 to 2012 it depends on the school. MyPyramid: likely taught to the classes of about 2013 to 2015; for about 2016 to 2018 it depends on the school. MyPlate: likely taught to the classes of about 2019 to 2030; for about 2031 to 2033 it depends on the school.

ThenEach part of the tongue tastes one thing: sweet at the tip, bitter at the back, salty and sour on the sides.

NowEvery part of the tongue with taste buds picks up every taste.

1974A careful re-test of the tongue by the researcher Collings found only small differences between areas; the map came from a misread 1942 textbook graph. (Spence 2022, Smithsonian 2017)

Likely taught to classes up to about 2004; for about 2005 to 2021 it depends on the school. Textbooks kept printing the map for decades, and in 2017 a taste researcher wrote that it was still taught in many classrooms.

ThenThere is no Brontosaurus. Its real name is Apatosaurus.

NowBrontosaurus is its own genus again, separate from Apatosaurus.

2015Emanuel Tschopp, Octávio Mateus and Roger Benson compared dozens of skeletons and found Brontosaurus different enough to be its own genus. (PeerJ 2015)

Brontosaurus: likely taught to classes up to about 1986; for about 1987 to 1997 it depends on the school. Apatosaurus: likely taught to the classes of about 1998 to 2022; for about 2023 to 2024 it depends on the school.

ThenDinosaurs were active animals with scaly skin. Birds were a separate group, though some scientists thought they came from dinosaurs.

NowMany small meat-eating dinosaurs had feathers, and birds descend from dinosaurs like them.

1998Pei-ji Chen, Zhi-ming Dong and Shuo-nan Zhen described Sinosauropteryx, a small dinosaur from China covered in fine filaments; in 2010 color cells found in those filaments supported that they were simple feathers. (Nature 1998, Nature 2010, JSTOR Daily)

Slow reptiles: likely taught to classes up to about 1973; for about 1974 to 1989 it depends on the school. Active, scaly dinosaurs: likely taught to the classes of about 1990 to 2002; for about 2003 to 2007 it depends on the school.

ThenAn asteroid may have wiped them out, but scientists still argue about it.

NowAn asteroid impact at Chicxulub, in Mexico, is the accepted main trigger. How much the Deccan Traps volcanoes in India added is still debated. (Science 2010, Science 2010 reply)

201041 scientists writing in Science reviewed the evidence and concluded that the Chicxulub impact triggered the mass extinction. (Science 2010)

An unknown cause: likely taught to classes up to about 1980; for about 1981 to 1990 it depends on the school. A possible asteroid: likely taught to the classes of about 1991 to 2010; for about 2011 to 2012 it depends on the school.

ThenThe continents stay put. The idea that they drift is wrong.

NowThe continents ride on moving plates, and new sea floor forms at ocean ridges.

1963Fred Vine and Drummond Matthews published magnetic patterns over ocean ridges that showed the sea floor spreading. (USGS, Nature 1963)

Likely taught to classes up to about 1966; for about 1967 to 1973 it depends on the school.

ThenHuman cells have 48 chromosomes.

NowHuman cells have 46 chromosomes, in 23 pairs.

1956Joe Hin Tjio and Albert Levan counted 46 with better methods, ending more than 30 years of 48. (Harper 2006)

Likely taught to classes up to about 1956; for about 1957 to 1960 it depends on the school.

ThenHumans have about 100,000 genes.

NowHumans have about 20,000 genes that make proteins. (GENCODE)

2001The Human Genome Project published its first draft and cut the count to 30,000 to 35,000; the finished sequence in 2004 brought it to 20,000 to 25,000. (NHGRI)

Likely taught to the classes of about 1991 to 2001; for about 2002 to 2004 it depends on the school.

ThenStomach ulcers come from stress and an unhealthy lifestyle.

NowMost ulcers are caused by a bacterium, Helicobacter pylori, and antibiotics can cure them.

1982Barry Marshall and Robin Warren found the bacterium in the stomachs of ulcer patients, work that won the 2005 Nobel Prize. (Nobel Prize 2005, Lancet 1984, NIH 1994)

Likely taught to classes up to about 1982; for about 1983 to 1995 it depends on the school. Doctors were not told to treat ulcer patients with antibiotics until a US National Institutes of Health panel in 1994.

ThenNobody knows whether stars like the Sun have planets.

NowMore than 6,000 planets around other stars have been confirmed. (NASA JPL)

1995Michel Mayor and Didier Queloz found the first planet circling a Sun-like star, 51 Pegasi b. (Nobel Prize 2019)

Likely taught to classes up to about 1999; for about 2000 to 2002 it depends on the school.

ThenPeople in 1492 thought the Earth was flat, and Columbus proved it was round.

NowEducated Europeans had known the Earth was round since ancient Greece. The flat-earth story was invented in the 1800s.

1991Historian Jeffrey Burton Russell showed in his book Inventing the Flat Earth that the story came from 1800s writers such as Washington Irving. (Russell 1997)

Likely taught to classes up to about 1995; for about 1996 to 2004 it depends on the school. In 1997 Russell wrote that most schoolchildren were still taught the myth.

ThenModern humans replaced the Neanderthals without mixing with them.

NowNeanderthals had children with our ancestors. People whose families come from outside Africa carry about 2% Neanderthal DNA. (Max Planck 2017)

2010Svante Pääbo’s team published a draft of the Neanderthal genome and found that it had mixed with the ancestors of people outside Africa. (Science 1988, Cell 1997, Science 2010)

Taught to the classes of about 1989 to 2012, but only as one of two views. Schools taught either modern humans replacing the Neanderthals, or groups that mixed.

ThenFind out if you are a visual, auditory or kinesthetic learner, and study that way.

NowCareful studies find no benefit from matching lessons to a learning style.

2008Psychologists Harold Pashler, Mark McDaniel, Doug Rohrer and Robert Bjork reviewed the research and found virtually no evidence for it. (Pashler 2008, Dekker 2012, Newton 2020)

Likely taught to the classes of about 1991 to 2008; from about 2009 on it still depends on the school. In a 2012 survey, 93% of UK and 96% of Dutch teachers believed in it, and a 2020 review of 37 studies found 89% of educators still did, with no sign of decline.