Why Mars sometimes walks backwards across the sky

Every 26 months or so, Mars slows down, stops, and drifts backwards against the stars for a couple of months before carrying on. Ancient astronomers built elaborate wheels-within-wheels to explain it.

The real reason is simpler: Earth is on the inside lane and overtakes Mars, like passing a slow lorry on the motorway. Drag the Earth around the Sun and watch the loop appear. The next one starts on 10 January 2027.