Interactives

Animations where you act in order to understand: move through time, change a setting, throw dice, draw to scale. Each one starts from an entry, and its figures have their sources.

• Entry 1.5 · Universe and astronomy Drawing the Solar System The question Can you draw the Solar System to scale, and still see anything? What you do Place the planets at their true distances, then enlarge them step by step until you can see them. Try the evenly spaced distances of the usual diagrams too. Try it →
• Entry 1.6 · Universe and astronomy The far side of the Moon The question Is the far side of the Moon always in darkness? What you do Move the month on, from full Moon to full Moon. Look at the Moon from the Earth, then from the other side: where is the day, where is the night? Try a Moon that does not turn on its axis, too. Try it →
• Entry 1.7 · Universe and astronomy One turn on its axis The question Which planet takes the longest to turn once on its axis? What you do Set time running: the eight planets spin together, all at the same accelerated speed. Count each one’s turns and watch which way its white marker moves. Try it →
• Entry 1.11 · Universe and astronomy Looking far is looking back in time The question When you look at the Sun, do you see it as it is right now? What you do Send out the Sun’s light and watch it reach the planets one by one: the clock counts the journey time. Then choose a body, as far as Earendel: the further away it is, the older what you see. Try it →
• Entry 4.3 · Matter and energy Mendeleev’s wager The question Did Mendeleev win all his bets? What you do Press play: the years run from 1869 to 1923, and the boxes he announced fill up, or do not. Then compare what was predicted for germanium with what was measured. Try it →
• Entry 4.7 · Matter and energy The hammer and the feather The question Does a hammer fall faster than a feather? What you do Choose where to drop the two objects — in air, in Boyle’s vacuum or on the Moon — then let them go. Try it →
• Entry 5.1 · The animal world Rotating a tree The question In this drawing, are mammals more closely related to turtles or to birds? What you do Rotate the branches around their nodes, then answer the question: which is the closest relative of mammals? Try it →
• Entry 5.1 · The animal world How many species? The question How many species live on Earth? What you do First place your own estimate on the scale. Then compare it with what has actually been recorded, and with the researchers’ estimates. Try it →
• Entry 7.2 · Earth and climate At the speed of the plates The question A few centimetres a year: enough to open an ocean? What you do Choose a speed, then let time pass: a year, a lifetime, a million years, a hundred million. Watch the distance travelled. Try it →
• Entry 7.8 · Earth and climate Where do the seasons come from? The question In January, the Earth is closer to the Sun: so why is it winter in the northern hemisphere? What you do Run through the year: the Earth goes round the Sun, its axis always tilted the same way. Change the latitude or the tilt, and watch the height of the Sun, the length of the day and the energy received. Try it →
• Entry 8.7 · The human body How many senses? The question Do we really have five senses? What you do Make the division finer, from three families to thirty-three senses. The body stays the same; only the classification changes. Try it →
• Entry 9.1 · Numbers, measures and techniques One number, three ways of writing it The question To write 9,999, do you need thirty-six signs, or just four? What you do Choose a number, or start the counter. See how many signs Egypt needs, where symbols are added up, and how many places are needed when position gives the value. Try it →
• Entry 9.6 · Numbers, measures and techniques Six dice, or six thousand? The question A die lands on the ace one time in six: is that true over six throws? What you do Throw 6,000 dice one by one and watch the share of aces narrow. Then throw whole series, as many as you like: each one leaves a dot. Try it →
• Entry 9.6 · Numbers, measures and techniques Length or area? The error Nightingale corrected The question Should a number twice as large get a radius twice as long? What you do Make the second number grow, from 1 to 4 times the first. On the left, the drawing of the first version (the radius follows the number); on the right, the corrected version (the area follows the number). Try it →
• Entry 9.13 · Numbers, measures and techniques The origin of printing The question Who invented printing? What you do The five cards are out of order. Arrange them from oldest (at the top) to most recent (at the bottom): drag a card by its handle ⠿, or use the arrows ▲ ▼. Then press “Check”. Try it →

Thumbnail credits 13

• Entry 1.5 · Drawing the Solar System — Saturn in natural colour, from images taken by the Cassini probe (2008). NASA / JPL / Space Science Institute, Public domain, source
• Entry 1.6 · The far side of the Moon — Map of the Moon’s surface, made by NASA’s Scientific Visualization Studio (equirectangular projection). NASA's Scientific Visualization Studio, Public domain, source
• Entry 1.7 · One turn on its axis — Global map of Mars, the MDIM 2.1 colour mosaic made from Viking Orbiter images (equirectangular projection). NASA / Jet Propulsion Lab / USGS, Public domain, source
• Entry 1.11 · Looking far is looking back in time — The star nicknamed Earendel (indicated by an arrow), in its host galaxy, which appears as a red smear; the whole scene is seen through the gravitational lens of a galaxy cluster lying between it and us (Hubble Space Telescope). NASA, ESA, B. Welch (JHU), D. Coe (STScI), A. Pagan (STScI), CC BY 4.0, source
• Entry 4.3 · Mendeleev’s wager — Facsimile of the periodic table of the elements published by Dmitri Mendeleev in 1869. Dmitri Mendeleev, Public domain, source
• Entry 4.7 · The hammer and the feather — 2 August 1971, on the Moon: astronaut David R. Scott, Apollo 15 commander, during the hammer and feather experiment; image from the broadcast of the colour television camera mounted on the lunar rover. NASA Johnson Space Center (S71-43788), Public domain, source
• Entry 5.1 · Rotating a tree — Vulpes vulgaris, the fox: hand-coloured print, between 1818 and 1842 (Iconographia Zoologica, Special Collections, University of Amsterdam). Jacques Christophe Werner and Charles Philibert de Lasteyrie, Public domain, source
• Entry 7.2 · At the speed of the plates — Þingvellir, Iceland: a rift valley that marks the crest of the Mid-Atlantic Ridge, between the North American and Eurasian plates. Bryan Ledgard, CC BY 2.0, source
• Entry 7.8 · Where do the seasons come from? — The Earth seen by the Meteosat satellite on 21 December 2010, 20 March, 21 June and 20 September 2011 (NASA). NASA (Meteosat images), Public domain, source
• Entry 8.7 · How many senses? — The eye in section: engraving from Henry Fox Hewes, Anatomy, Physiology and Hygiene for High Schools, 1900. Henry Fox Hewes, Public domain, source
• Entry 9.1 · One number, three ways of writing it — Tablet YBC 7289, Old Babylonian period: a square, its diagonal and base-60 numbers giving an approximation of the square root of 2 (Yale Peabody Museum). A. Urcia, Yale Peabody Museum of Natural History, CC0, source
• Entry 9.6 · Length or area? The error Nightingale corrected — Florence Nightingale’s “Diagram of the causes of mortality in the army in the East”, sent to Queen Victoria in 1858: each slice is a month; in blue, deaths from preventable diseases, in red those from wounds, in black other causes. Florence Nightingale, Public domain, source
• Entry 9.13 · The origin of printing — Frontispiece of a printed, dated copy of the Diamond Sutra: ink on paper, woodblock print (British Library, Or.8210/P.2). International Dunhuang Project, Public domain, source

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