17 entries
Physics & Chemistry
New elements on the periodic table, redefined kilograms, and particles your textbook called hypothetical.
Changes here run from 1983 to 2025.
- Disproved10
- Updated3
- Refined2
- Replaced2
- UpdatedNot in textbooks yet
The tokamak is the only serious path to fusion; the stellarator is a scientific curiosity
Changed in2025TaughtMagnetic-confinement fusion means the tokamak, the doughnut design that holds every record. The stellarator, with its baroque twisted magnets, is an elegant idea that never kept up. It is a research sideline, not a contender.
NowOn 22 May 2025 the Wendelstein 7-X stellarator held the fusion 'triple product' (the combination of density, temperature and confinement time that gauges how close you are to a power plant) at a record level for 43 seconds, outperforming what any tokamak had sustained for that long.
- Disproved
TaughtTwo-dimensional materials are a carbon curiosity. Graphene works because graphite is already made of weakly bound sheets you can peel apart; a true metal like gold is a three-dimensional lattice and would simply clump up long before you reached a single free-standing atomic layer.
NowIn 2024 researchers at Linköping University made 'goldene': a free-standing sheet of gold exactly one atom thick, the first two-dimensional metal. Cornered into two dimensions, gold even stops behaving like a normal metal and takes on semiconductor-like properties.
- Disproved
TaughtThere is a fundamental physics limit (the Shockley-Queisser limit, about 33.7%) on how much sunlight a single-junction solar cell can turn into electricity. Real silicon panels top out around 27%, and the theoretical ceiling of roughly one-third is a wall you cannot climb over.
NowIn November 2023, LONGi's crystalline-silicon/perovskite tandem cell was certified at 33.9% efficiency by the U.S. National Renewable Energy Laboratory, the first time a solar cell exceeded the 33.7% single-junction Shockley-Queisser limit.
- Disproved
TaughtFusion is the power source of the future and always will be. Every experiment consumes far more energy than the reaction gives back, and breakeven, getting out as much as you put in, has never been reached.
NowOn 5 December 2022 the National Ignition Facility reached ignition: 2.05 megajoules of laser energy delivered to the target produced 3.15 megajoules of fusion energy. It was the first time a controlled fusion reaction returned more energy than was delivered to it.
- Refined
A proton is made of exactly three quarks
Changed in2022TaughtA proton is three quarks, two up and one down, bound by the strong force. That triplet is what a proton is, full stop.
NowIn 2022 the NNPDF collaboration reported the first strong evidence that the proton also carries an 'intrinsic' charm quark component built into its very structure, remarkable because a charm quark is heavier than the whole proton that contains it.
- Disproved
TaughtMatter comes in a fixed handful of phases, and nothing can keep cycling through a repeating motion forever without an energy source, that would be a perpetual-motion machine, which the laws of thermodynamics forbid.
NowIn 2021 physicists built a genuine time crystal, a new phase of matter, on Google's Sycamore quantum processor. Its qubits flip through a pattern that repeats in time indefinitely without absorbing any net energy, and it does so without violating the second law, because its entropy never falls.
- Replaced
A kilogram is defined by a metal cylinder in Paris
Changed in2019TaughtThe kilogram is defined by the International Prototype Kilogram, a platinum-iridium cylinder kept in a vault outside Paris. It is the kilogram by definition.
NowOn 20 May 2019 the kilogram was redefined in terms of the Planck constant. The cylinder is now just an object. No SI base unit depends on a physical artifact any more.
- Updated
The periodic table ends around element 109
Changed in2016TaughtThe periodic table trails off in the hundreds with a few unnamed, provisional elements at the end.
NowThe seventh row was completed in 2016 when nihonium, moscovium, tennessine, and oganesson were named. The table now has 118 elements and no gaps.
- Refined
The Higgs boson is hypothetical and may not exist
Changed in2012TaughtThe Standard Model predicts a particle that gives other particles mass, but it has never been found and might not be there.
NowCERN announced the discovery of the Higgs boson on 4 July 2012. Peter Higgs and François Englert shared the Nobel Prize the following year.
- Disproved
Two-dimensional materials cannot exist
Changed in2004TaughtA one-atom-thick sheet is thermodynamically unstable and would crumple or roll up. Strictly two-dimensional crystals cannot exist at finite temperature.
NowAndre Geim and Konstantin Novoselov isolated graphene in 2004 using adhesive tape and a block of graphite. They won the 2010 Nobel Prize.
- Disproved
You cannot fold a piece of paper more than seven times
Changed in2002TaughtIt is physically impossible to fold any piece of paper in half more than seven times, no matter how big or thin it is.
NowBritney Gallivan, a high school student, folded paper twelve times in 2002 after deriving the equation governing the loss. The limit is about paper dimensions, not a law of nature.
- Disproved
Glass is a liquid that flows very slowly
Changed in1998TaughtGlass is a supercooled liquid. The proof is old cathedral windows, which are thicker at the bottom because the glass has flowed downward over centuries.
NowGlass is an amorphous solid. It does not flow at room temperature on any human or civilizational timescale. Medieval windows are uneven because of how they were made.
- Disproved
Neutrinos have no mass
Changed in1998TaughtNeutrinos are massless particles that travel at the speed of light and pass through matter without interacting.
NowNeutrinos have mass. Super-Kamiokande showed in 1998 that they oscillate between types, which is only possible if they are massive. The Standard Model had to be amended.
- Updated
There are three states of matter
Changed in1995TaughtSolid, liquid, gas. Water is the example: ice, water, steam.
NowPlasma is the fourth and by far the most common state in the universe. Bose-Einstein condensate, predicted in 1924, was finally created in a laboratory in 1995, and other exotic states exist.
- Disproved
Crystals cannot have five-fold symmetry
Changed in1992TaughtA crystal is a periodic repeating lattice. Five-fold rotational symmetry is geometrically impossible in a crystal: you cannot tile a plane with pentagons.
NowQuasicrystals have ordered but non-repeating structures with forbidden symmetries. Dan Shechtman observed one in 1982, was ridiculed for years, and won the 2011 Nobel Prize in Chemistry.
- Disproved
TaughtSuperconductivity requires cooling to near absolute zero with liquid helium, which makes it a laboratory curiosity with no practical use.
NowHigh-temperature superconductors discovered in 1986 and 1987 work above 77 K, the boiling point of liquid nitrogen, which is cheap and easy to handle. Current records exceed 130 K at ambient pressure.
- Replaced
The meter is defined by a metal bar in Paris
Changed in1983TaughtThe meter is defined by the International Prototype Metre, a platinum-iridium bar kept near Paris, or by a specific number of wavelengths of krypton-86 light.
NowSince 1983 the meter has been the distance light travels in a vacuum in 1/299,792,458 of a second. The definition is built from the speed of light, which is now fixed by definition rather than measured.