Corrections

This page lists changes to exhibits that were already published: a wrong fact or number, or a model or control that did not work as described. Small wording and layout fixes are not listed one by one.

How to report a problem

Every page has a Report a problem button near the bottom. It sends us the page address, the language and any text you have selected. Tell us what is wrong and, for a fact, where you read the correct value. You can also write to contact@explorehall.com.

What happens to a report

We open the exhibit and reproduce the problem on a computer and a phone.
For a fact or a number, we check it against the sources listed in the exhibit's commentary, and against the exhibit's own number checks.
If it is wrong, we fix the model and the commentary in every language the exhibit is published in, and add a row below.

Date	Exhibit	What changed
2026-10-24	How big a crater would an asteroid make	The commentary used 7,800 kg/m³ for iron while the model uses 8,000 kg/m³; the text now matches the model (about 200,000 Mt for a 1 km iron body). The "Try it" steps now use the exact control names on the stage. Fixed in all 14 languages.
2026-10-24	How deep is the ocean? A walk down to the Mariana Trench	A "Try it" step told readers to switch the lamp off at 300 m to compare. The lamp only works below about 140 m; the step now compares 300 m and 3,000 m and says the switch does nothing near the surface.
2026-10-23	How a wind turbine works	The Korean page gave the main-shaft torque as 4.18 million N·m; the English page and the model give about 4.2 million N·m. The Korean text now matches.
2026-10-23	Walk a scale model of the solar system	The comparison with the Voyage model in Sweden said our scale was half of theirs and the walk twice as long. It is one tenth, and ten times. Fixed in all 14 languages.
2026-10-23	How a lithium-ion battery works	The text treated 100 Wh as an absolute limit for carrying batteries on planes. With airline approval, up to two spare batteries between 100 and 160 Wh are allowed, carried in the cabin with the terminals protected. Fixed in all 7 languages.
2026-10-23	How the Enigma machine works	An encyclopedia source for the plugboard count was replaced with Cornell University combinatorics notes in all 7 languages.
2026-10-23	How CRISPR-Cas9 gene editing works	The text implied that the odds for a random 20-letter guide prove a target is unique in the genome. They do not; real genomes repeat, so guides are checked against the actual sequence. Fixed in all 7 languages.
2026-10-23	How a mechanical watch works	The text had the effect of a higher beat rate backwards: a given shock is a larger share of a faster, shorter swing, not a smaller one. A claim that a higher beat rate always means more wear was softened. Fixed in all 7 languages.
2026-10-23	Why we have seasons	A 0.2° change in the Sun's height was given without its time span; it is over half a day. Encyclopedia sources were removed from all 7 languages.
2026-10-23	How a manual typewriter works	Encyclopedia sources were replaced with museum and manufacturer records in all 7 languages. The text now separates character pitch from the model's six-lines-per-inch spacing, and Kong Byung-woo's 1948 development, 1949 award and 1950 improved prototype.
2026-10-23	How tides work	The Bay of Fundy resonance is now credited to the Canadian Hydrographic Service rather than to a NOAA page that does not discuss it. Five Korean numbers that did not match the English were fixed.
2026-10-23	How a four-stroke engine works	The table of real engines cited an encyclopedia. It now cites manufacturers and SAE papers. Two values were wrong: the Classic 350 makes 14.87 kW (not 15.1) and the 1GD displaces 2,754 cc (not 2,755). Fifteen rows and one paragraph about engine sound that we could not verify were removed. Fixed in all 14 languages.
2026-10-23	How a vinyl record stores sound	A groove width of 657 nm, a groove length of 19 km and a 40× comparison for the CED video disc could not be confirmed and were removed in all 14 languages, on the page and on the stage. The museum-backed 12-inch disc and 60 minutes per side remain.
2026-10-23	How a wing makes lift	An encyclopedia source was replaced with the Cessna 172R information manual in all 7 languages. The text now keeps the published stall speeds (51 and 47 KCAS) apart from the model's approximate 97 km/h, and limits the 6.5% winglet saving to the specific Boeing 707 test.
2026-10-23	How a pin tumbler lock works	Dates that rested on an encyclopedia were replaced; the text now keeps ancient wooden locks, the modern Yale cylinder and a museum reconstruction made around 1912 apart. 79,666 is now described as the number of key cuts allowed by the MACS rule, not a security rating. Fixed in all 7 languages.
2026-10-23	How a car differential works	An encyclopedia source for tyre sizes was replaced with Bridgestone technical guidance in all 7 languages, and an exact year for Pecqueur's patent that our source does not state was not used.
2026-10-23	How a gyroscope works	The Coriolis force was written with the wrong form; it is −2m(Ω × v). Fixed in English, Korean and Spanish.
2026-10-23	Why every snowflake looks different	The text now separates growth from vapour from riming (droplets freezing on the crystal), limits the 60° and 120° angles to the outline of the flat face, and says the count of possible shapes is an illustration, not a measured chance of two matching flakes. Two retired NOAA links were replaced.
2026-10-23	How do bats see with sound? Echolocation explained	The difference in the speed of sound between 0 and 30 °C was given as about 3%; it is about 5%. The text now says the model narrows the beam during the final buzz while real bats widen it, and that wavelength is not a minimum insect size.
2026-10-23	How a solar panel works	An FAQ answer said bypass diodes fully protect a shaded cell; they limit the loss, and the cell can still heat up. The text also says a cloudy sky can still let some direct light through, and that 61° is a theoretical tilt beyond the 60° slider.
2026-10-23	How a slide rule works	A relative-error formula for a finite slip of the slide was written as an equality; it is an approximation. The exact factor is 10^(Δx/250 mm) − 1.
2026-10-23	How a capacitive touchscreen finds your finger	The 0.1 mm figure was presented as accuracy; it is the step of the reported position. Johnson's 1965 work at RRE is now kept apart from his 1969 patent.
2026-10-23	How fibre optics and submarine cables work	A sentence saying satellites carry only a small share of international traffic had no source and was removed. The graded-index sentence now cites the Fiber Optic Association and says some modal dispersion remains.
2026-10-23	What is under the street	A claim that steep sewers leave solids behind was removed; the text now describes pipe wear and energy at joints. The 0.637 m figure is now described as a horizontal wall clearance, not a measured crossing clearance.
2026-10-23	How a microwave oven works: the magnetron and the standing wave inside	58 °C was described as the average shown on screen; it is the energy calculation before the 100 °C cap. The brown colour above the cap marks excess energy and is not a browning simulation.
2026-10-23	Reaction time test: how many milliseconds do you take?	A claim that hearing is always the fastest sense was removed. The text now says frame timestamps do not measure when light leaves the screen, and that the 231 ms study value already includes the study's equipment delay.
2026-10-23	How a hanok is put together and heated	A 4-in-10 roof pitch was given as 23°; it is 21.8°. The text now keeps wind pressure apart from earthquake inertia and damping ratio apart from energy lost per cycle, and an unverified claim of 28 columns and 216 m² was removed.
2026-10-23	How photosynthesis works	"Today's 426 ppm" now says it is the model's default value. An FAQ answer that traced the oxygen atoms of CO₂ one by one was removed, and the text now says green light can drive photosynthesis deep in the leaf.
2026-10-23	Where volcanoes and earthquakes happen	The depth at the ridge centre was given as 2.5 km; with the model's axial valley it is 3.5 km. The scale note now mentions the enlarged volcano, a statement about distance circles was corrected (the squared radius grows by a fixed amount), and the tenfold amplitude rule is limited to local magnitude.
2026-10-23	How DNA replication works	FEN1 and RNase H were treated as the same enzyme; they are different. The text now says each of the two E. coli forks copies about half of the chromosome.
2026-10-22	How fibre optics and submarine cables work	Corning's first low-loss fibre was dated 1970; the Nobel Foundation source we cite gives 1971 for the 1 km fibre. Two figures that rested only on an encyclopedia (first submarine use of erbium amplifiers in 1995, 0.17 dB/km for pure-silica-core fibre) were removed or marked as typical values.
2026-10-22	How arches and bridges carry weight	The parts panel said the stone arch has 14 voussoirs. The model has 15 (12 degrees each, 180 degrees in all), as the commentary says. Fixed.
2026-10-22	How a piano works: the grand action and equal temperament	The commentary dated Pape's felt hammers to 1826 only. It now gives 1826 (Smithsonian Steinway history) for the first felt and 1839 for layered, tapered felt (Smithsonian piano catalogue).
2026-10-19	Braille, semaphore and signal flags	The sea-flags tab opened on the bare mast, so the 40-flag board was out of view. The camera now shows the board and the hoisted flag together.
2026-10-19	The Jagyeokru water clock	Clicking parts of the 3D model did not always select the part under the pointer. Fixed.
2026-10-18	How animals see	The sharpness (acuity) view through the telescope zoom was corrected.
2026-10-18	Why we have seasons (French)	A label was cut off on phones. Shortened so it fits.
2026-10-17	How a vinyl record stores sound (Arabic)	In the right-to-left layout, speeds such as 33⅓ and their units were split or reordered. They now stay together.