Library

Learn how to create a clear and easy-to-read graph, and then how to use it to read off values and understand how a physical phenomenon changes over time.

From a falling apple to a rollercoaster, find out why mechanical energy remains constant in the absence of friction, and what happens to it when friction comes into play.

Understand why the momentum of an isolated system is always conserved, and learn to distinguish between elastic and inelastic collisions using practical examples (billiards, railway carriages, road accidents).

Learn how to read, write and calculate using the correct number of significant figures, and how to express the uncertainty of a physical measurement correctly.

Delve into the dynamics of an RC circuit to understand how a capacitor stores and then releases energy, and master the differential equation that governs all analogue electronics.

Applications contractantes, suites itérées et convergence géométrique : le théorème qui donne d'un seul coup l'existence, l'unicité et un algorithme de calcul.

Comprends la continuité uniforme, démontre le théorème de Heine sur un segment et exploite-le pour l'intégrabilité des fonctions continues et le contrôle des erreurs numériques.

Construis pas à pas la sous-suite convergente d'une suite bornée : suites extraites, segments emboîtés, dichotomie, puis les grands théorèmes que ce résultat rend possibles.

Du lemme de Fermat au théorème des accroissements finis : les démonstrations qui justifient enfin le lien entre signe de la dérivée et sens de variation.

The weakest link is usually neither the algorithm nor the key, but the way in which it is selected at random. Why unpredictability is difficult to achieve, and what happens when it is lacking.

What is the difference between ‘encrypted’ and ‘end-to-end encrypted’? What the server can see, what it cannot see, and how modern messaging services protect both the past and the future.

Your browser accepts millions of websites it has never seen before. How does it decide which ones to trust? How certificates and certificate authorities work – and their vulnerabilities.

The little padlock in your browser: what it really guarantees, what it doesn’t guarantee, and how a secure connection is established in a matter of milliseconds.

Two people who have never met can create a shared secret simply by talking out loud, in full view of everyone. The idea that paved the way for modern cryptography.

Traditional ciphers are all cracked on a computer. Here’s how encryption really works today: in blocks, using AES, and why the method matters just as much as the algorithm.

Learn to distinguish between the rate and progress of a reaction, identify the factors that accelerate a reaction, and understand how a chemical system reaches a dynamic equilibrium.

Explore why the carbon atom is capable of forming millions of different molecules, and learn to recognise chains, functional groups and isomers.

Find out how electrons flow between chemical species: oxidising agents, reducing agents, half-reactions, and two everyday examples: the electric cell and rust.

Understand what pH actually measures, Brønsted’s definition of an acid and a base, and why diluting an acid tenfold increases its pH by exactly one unit.

Learn how to distinguish between solute, solvent and solution, how to calculate concentration, and how to prepare a solution by dissolution or dilution without getting the volume wrong.

Find out why chemists count atoms and molecules in huge bundles called moles, and how to easily convert from mass to the number of particles.

Find out how chemists organised all the known elements into a single table, and why this classification still enables us to predict the properties of matter today.

Why burning wood has nothing to do with melting ice, how Lavoisier changed chemistry forever, and how to balance a chemical equation step by step.

From the invisible atom to the chemical formulas H₂O and CO₂, right through to the ions that power your table salt and your batteries: the building block of all chemistry.