How long would it take?

Walk from London to Sydney? Fly it? Send a beam of light? Pick two cities, or enter a distance, to compare.

About these numbers

The distance is the straight line over the Earth's surface (the great-circle distance); roads, rail lines and flight paths are always longer. Each time assumes travelling at the speed shown without stopping, so a real car or train journey takes longer. The speeds are round reference figures: a walker at 5 km/h (the pace in Naismith's rule), a steady cyclist at 20 km/h, motorway driving at 100 km/h, high-speed trains at their 300 km/h service speed, and a jet airliner cruising at about 900 km/h.

The last three are physics. Sound travels about 343 metres a second in air at 20 °C — slower in cold air. The International Space Station orbits at about 28,000 km/h (7.8 km a second), going round the Earth roughly every 90 minutes. Light in a vacuum travels exactly 299,792,458 metres a second (the metre is defined by it), which is why light from the moon takes just over a second to reach us and sunlight about 8 minutes 20 seconds.