The sky at night

For thousands of years the planets were simply the wanderers: bright points that refused to keep still against the fixed stars. Explaining that wandering took us from Ptolemy's nested circles, to Copernicus moving the Sun to the centre, to Kepler discovering that orbits are ellipses, to Newton covering falling apples and falling moons with a single equation — and finally to Einstein, who accounted for the last stubborn wobble in Mercury's orbit. This round covers the lot: perihelion and aphelion, why Earth is nearest the Sun in January yet freezing in the northern hemisphere, the near-flat plane almost every planet shares, tilted axes and backwards spins, and the handful of laws that predict all of it centuries ahead. Ready to wander?

Level: Challenger