⇲ The scales of time
An astronaut's watch, a light clock and the edge of the universe are the same story, told at different sizes.
Quantum — the very small
Where time stops being a simple backdrop: photons with no definite path until they're measured, and a whole universe frozen in one state, with time appearing only from inside. The experiments are real; what they mean is still argued over.
Voyages — people and spacecraft
Time as it affects people who travel: astronauts' clocks, conversations with rovers on Mars, how far a crew could go in a lifetime. Everything here is measured or engineering-real, apart from the starship itself.
Physics — the laws underneath
Why clocks disagree, what 'now' means, why time runs one way, what an extra dimension would look like. Small, exact models of the laws themselves.
Cosmos — the universe as a whole
Expansion, horizons, the arrow of time on the largest scale, and why the universe has three space dimensions and one time. Where the biggest open questions live.
The threads
Four questions run across the scales: Clocks disagree, Light and 'now', The arrow of time and Why 3 + 1?. Each lab lists the threads it's on. Tour 2, From the ISS to the edge of the universe, zooms out from astronauts to the whole cosmos; Tour 3, Is time travel possible?, follows one question from clocks to wormholes and time loops.
See it in the labs
Sources: Project structure (D-031).