“Day” is a vestigial mode of time measurement based on solar cycles. It’s not applicable.
…I didn’t get you anything.
– River Tam, from the “Firefly” episode “Out of Gas”, discussing her brother Simon’s birthday while aboard the spaceship “Serenity”
Several months ago, while watching the television show Caprica, the prequel to the modern Battlestar Galactica series, a thought crossed my mind: how the heck do the Twelve Colonies keep time?
Perhaps a bit of background is in order. In the Battlestar Galactica universe, humans are scattered across twelve planets (well, until the Cylons decide to exterminate the human race, but that’s not important for this topic…). Presumably, it’d be extremely unlikely for these planets to have exactly same rotation rates and orbital parameters. In other words, each planet would have a different length of day and year, just like the planets in our own solar system.
On Earth, we deal with differing times to some extent: while the Sun shines on one side of the Earth, the other side experiences the darkness of night. As most people know, we’ve handled this by slicing the surface of Earth into a series of time zones. For people communicating across different time zones, the problem is resolved either by agreeing on a single time standard, or by taking care in understanding that an offset is in effect.
However, this system works, in part, because the time zones are simply offset from each other. A day is still 24 hours long, no matter which time zone you’re in. Noon in Los Angeles is always 3pm in New York City. Similarly, our calendars maintain a certain meaning; for example, when it’s January (if you follow the Gregorian calendar) we know that it’s Winter in the Northern Hemisphere, and Summer in the Southern. But what happens when times are no longer in lockstep? What happens when, as is likely the case with the Twelve Colonies, two people’s days are no longer the same number of hours, and their years are no longer the same number of days?
Or, to put a practical spin on this, what happens to your clock when you’re living on Mars, and your days are 24 hours, 39 minutes, and 35 seconds long? What happens to your calendar when your years are 668.6 days long? And, of course, I mean 668.6 Mars days – “sols” – not Earth days…see where confusion could already be sneaking in?
How do we deal with that now? Well, so far, all of our explorers to Mars have been robotic. For the Martian orbiters, rovers, and landers, the method of choice for keeping time is to count the number of seconds that have elapsed since a fixed point in time (midnight of the morning of January 1, 1980 in Greenwich, England is a typical choice). So, while 1130773217 o’clock (approximately the number of seconds since 1980-01-01-00:00:00 UTC when I wrote this down) may not have much meaning to you, a robot can easily run a program that’s scheduled according to this time standard. When the robots communicate with Earth, computer programs on the ground convert these times to a more Earth-based time standard, such as Coordinated Universal Time (UTC) or the local time of the mission control center, in order to make them easier for the mission controllers to understand.
But while robots are fine working with a time like 1130773217, it’s not obvious that this particular time corresponds to late morning in Hawaiʻi in mid-Autumn. This is the advantage of the time systems we use: 12:00 reminds us that it’s time for lunch, or December 1 tells us that we should consider wearing something warm if we live in the Northern Hemisphere. But what do these Earth-bound times tell us about conditions on Mars, whose days and years don’t equal ours? Not a whole lot.
So, how will the first astronauts to live on Mars keep time? I can’t say for sure, but I imagine they’ll keep some sort of local clock, so that their version of 12:00 still corresponds to lunchtime. I also imagine, rather than keeping a monthly calendar, they’ll simply count sols since landing. Like our robotic missions, computer programs will make the necessary conversions between the two time standards. For astronauts who will spend less than a Martian year on the surface, communicating mostly with a mission control center, this will be a workable compromise.
But what about the far future? If humans eventually colonize Mars, how will that affect the keeping of time? The first humans born on Mars may not share the same kinship to Earth as their parents. Rather than tying their time standards to a planet they’ve never visited, perhaps they will choose to set their own standards of time – clocks based on their own sunrises and sunsets, and calendars based on their own passage of seasons. In other words, it’s not unreasonable to think that the emergence of a distinct Martian culture might also bring rise to the establishment of a new time standard not easily compatible with Earth’s.
If this happens, how will the cultures of Earth and Mars communicate the time to each other? Will one time standard hold precedence over the other? Or will they choose a third time standard, not based on the motions of either planet, to use for communication? I honestly don’t know the answer, but I do find it a very interesting problem to consider.