Wonders of the Solar System Text Only. Andrew Cohen

hours. The length of the day at a particular place on the Earth’s surface is dictated by the precise angle of our planet in relation to the Sun.

      We have seasons here, too, due to the fact that the Earth’s axis is tilted by twenty-three degrees. As we journey around the Sun this angle creates the changing dynamic that defines the cycles of many of the creatures that live both on the land and in the oceans. In the Northern Hemisphere the summer months coincide with the North Pole leaning towards the Sun; when, at this time of year, the angle favours the northern half of our planet with extra energy from our star. By winter the dynamic has changed; the North Pole is pointing away from the Sun and the Southern Hemisphere is bathed in additional sunlight.

      It’s wonderful to think that across the planet the rhythms of our lives are governed by our journey through space. From waking up to going to bed, wearing a jumper one month and a T-shirt the next, eating strawberries in July or a tangerine in December, each of these everyday events is intimately connected to a journey through space that catapults us at 108,000 kilometres (67,000 miles) per hour around a star, but leaves most of us completely unaware of this rollercoaster ride through the cosmos.

      It’s not only Earth that is subject to these rhythms – the whole Solar System is full of these cycles, with each planet orbiting the Sun at its own distinct tempo. Mercury is the fastest; closest to the Sun, it reaches speeds of 200,000 kilometres (124,000 miles) per hour, completing its orbit in just eighty-eight days. Venus rotates so slowly that it takes longer to spin on its axis (225 days) than it does to go around the Sun, so that on Venus (and also on Mercury) a day is longer than a year. Further out, the planets orbit more and more slowly. Mars completes one orbit of the Sun every 687 days, just a couple of months short of two Earth years. Jupiter, the largest planet, takes twelve Earth years to complete each orbit, Saturn almost thirty years, Uranus eighty-four years and at the very furthest reaches of the Solar System, four and a half billion kilometres from the Sun, Neptune travels so slowly that by 2009 it hadn’t completed a single orbit since it was discovered in 1846.