Too much time
If humans colonised Mars, how would they calculate time, as a Martian day is longer than one on Earth?
Bob McCrossin Cooroy, Queensland, Australia
It is more complicated than you might think, if you don’t have a clock.
There are three kinds of day to consider. The sidereal day is the planet’s rotation period to come back to the same position compared to the fixed stars. The solar day is the period for the sun to come back to the same spot in the sky. It is a bit longer than the sidereal day because the planet has advanced in its orbit around the sun and the elliptical orbit makes the “same spot” not quite so.
The astronomical times to the nearest minute are: Earth sidereal 23 hours 56 minutes, solar 24h; Mars sidereal 24h 37m, solar 24h 40m.
Finally the human diurnal (daily) rhythm is the time the body “thinks” it has done a day’s worth of metabolising and restarts. The body adjusts to the solar day by referencing the sun. Humans with no light perception have an average “daily” rhythm of about 24h 28m, so we are actually slightly better adapted to Mars.
The Martian hour would need adjusting, but an alternative would be to retain Earth hours and follow the Roman tradition of the Saturnalia used to line up the lunar and solar years. This would mean 40 minutes of party time at the end of each Martian day.
There is, of course, a theory we actually came from Mars, or at least that is where early microbial life may have come from. But who knows? Maybe we originated on the planet Golgafrincham.
Alex McDowell London, UK
In the books Martian Time-Slip (1964) by Philip K. Dick and Mars Trilogy (1992-96) by Kim Stanley Robinson, Mars settlers use clocks like those on Earth, except that, at midnight, the clocks stop for 39 minutes and 35 seconds (the extra length of a Martian solar day) and then start again.
Since the Viking craft reached the planet in 1976, Mars landers have used clocks that divide a Mars day, or sol, into 24 “Martian hours”. Planetary scientists define the Martian new year as starting on its vernal equinox and have defined a Mars calendar.
Mars colonists may be more radical and use a Martian decimal time system, in other words, divide the Martian day into 10 hours and the hours into 100 minutes.
Stephen Johnson Eugene, Ore
