A question to carry with you
Guided reading paths
Move from a first encounter to the instruments and back to the complete paper. Each stop tells you what to try, what to question, and where to go next.
Choose a route, not a difficulty level. Start with the no-algebra entrance, skip to any stop, or spend as long as you need in a laboratory. No score, timer, account or saved answer is required.
Each page a path reaches says what it shows and where it stops.
The mass-energy paper in fifteen minutes
Einstein's three-page paper of 1905, read without equations: what it claims, how its reasoning works, and the test it proposed.
8 steps · About 12.5 minutes · No equations
You finish able to say: A body that gives off energy becomes less massive by an amount set by that energy, whatever form the energy leaves in, so the mass of a body is a measure of its energy content.
From wandering to a molecular number
Choose what to measure, explain a growing spread, then ask what the observations can actually identify.
7 stops · You read and experiment
It begins at Start with a visible speck and ends at Return to the whole argument.
From entropy to energy packets
Preserve the successes of waves, examine a restricted entropy comparison, and distinguish a hypothesis from its consequences.
8 stops · You read and experiment
It begins at Begin with a counting question and ends at Read the qualifications in the source.
Clocks, coordinate maps and light
Define a measurement before transforming it, then carry the same discipline into the electrodynamic half of the paper.
8 stops · You read and experiment
It begins at One flash and two clocks and ends at Read both halves of the paper.
Two ledgers, one inference
Follow a symmetric emission, subtract two descriptions, and distinguish a derivation from a consistency check.
6 stops · You read, experiment and reconstruct
It begins at Ask what can change when light leaves and ends at Read the short paper without skipping its assumptions.
What is here, and what is not
5 paths, counted from the records that hold them rather than from this sentence. They are the ones that exist: the set is not a plan, and nothing here is a placeholder for a path that has not been written.
Two others are described in this project’s own specification and have not been written: a one-evening path and a full course, both of which would link the capstones rather than the papers. Until they exist the capstone of each paper is reached from that paper, and this page does not list them as though they were here.
Take a detour without losing the question
On a guided page, the navigation above the content offers the previous stop, next stop and full outline. A bookmark link saves only the public reading position. It does not save your laboratory settings, notebook or predictions.
Without JavaScript, every outline, task, explanation and destination link remains readable. Return with your browser's Back command after visiting a stop, or keep the outline open beside the paper.
Explore the longer discovery reconstructions · Choose an instrument directly