Can You Play Cricket on Mars? by Sir Patrick Moore

Author:Sir Patrick Moore
Language: eng
Format: epub
ISBN: 9780752469416
Publisher: The History Press
Published: 2011-02-10T16:00:00+00:00

How long is a year on Uranus?

Uranus takes eighty-four Earth years to complete one journey round the Sun, so that Herschel discovered it less than three Uranian years ago. But the axial rotation period is short; only 17 hours 14.4 minutes. This means that there are almost 43,000 days in every Uranian ‘year’.

The planet’s calendar is made even more complicated by the fact that the rotational axis is tilted to the orbital plane by ninety-eight degrees – more than a right angle. Our tilt is 23.5 degrees, which is why we have our seasons, but Uranus ‘rolls’ along; sometimes one or other of the poles is pointed directly toward the Sun, and a polar night can last for twenty-one Earth years. We do not know why Uranus is tilted in this extraordinary way. It used to be thought that long ago Uranus was hit by a massive impactor and literally knocked sideways, but this is rather difficult to believe, and more probably the tilt was gradually increased by gravitational interactions with the other planets. But why should Uranus be so unlike the other giant planets in this respect? Again we have to confess that we do not know. In some ways Uranus is very much of an enigma.

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