EARTHLINGS who might care to visit other planets in the solar system would find the climates quite inhospitable. But there would be other differences, too, visitors would have to cope with a "daily" and an "annual" rhythm quite different to our own - to such an extent that terms like "day" and "year" would cease to have a meaning in our earthly sense.
Our day, as we know, is as near to 24 hours in length as makes no difference, and our year is about 365 and a quarter of these earthly days. Martian "days", as it happens, are quite similar: Mars takes 24.66 of our hours to rotate upon its axis. The Martian "year", however, is nearly twice as long as ours, since it takes the planet 687 of our days to complete an orbit round the sun.
The inner planets, Mercury and venus, rotate slowly on their axes and have longer "days", but shorter "years", than we do. Mercury, the closest to the sun, rotates on its axis every 59 Earth days, and at 88 Earth days, has a shorter "year" than any of the other planets. Venus has the longest "days" each being 243 of ours in length, but it takes only 225 days to complete its solar orbit.
Most of the outer planets by contrast, rotate much more rapidly than ours upon their axes. One "day" is only 10 hours far Jupiter, 11 hours for Saturn, 17 for Uranus, and 16 hours for Neptune. But it takes them all much longer to make their way around the sun: a Jovian "year" lasts for 4333 Earth days and that of Saturn for 10,740 Uranus's, year is 30,680 days long, and Neptune takes a full 60,000 days, or 165 years, to complete a full orbit around the sun.
When it comes to "days" observed from the surface of a planet, however, that of Uranus would be the strangest of them all. Instead of being "vertical" as Earth is its axis roughly at right angles to its plane or orbit - Uranus lies on its side, with its axis almost "horizontal". As it proceeds on its 84 year journey around the sun, each pole is first exposed to continuous sunlight for 42 years, and then languishes in seeming endless night for the other half of the Uranian year.
If you were to stand at the Uranian north pole in "summertime", you would see the overhead sun revolving in a small circle around the zenith every 17 hours - the length of a Uranian "day". As the planet advanced towards its equivalent of Earth's September equinox, the sun would gradually spiral down the sky, eventually to skim in a circle round the horizon before disappearing completely for nearly half a century.