[LEAPSECS] What timekeeping system should the Terra Nova settlers use?

[Rob Seaman]

Sending this from the Super-80 on route to the Philadelphia UTC meeting.

On Oct 3, 2011, at 3:50 AM, Zefram wrote:

Lots of things I agree with.  A couple of comments below.


> Daniel R. Tobias wrote:

>> length of the day, but it was shorter than the current day, which would, I imagine, have an impact on timekeeping in this colony.


I caught some of that episode.  In particular the moon was absolutely colossal in the sky - more like what the Apollo astronauts saw looking back at Earth.  But then once you posit time travel and alternate universes why not move the Moon around? :-)


> The magnitude of this difference is in the same ballpark as the present difference between Terran and Martian days, so exactly the same range of solutions are on the table as for colonisation of Mars.


An interesting equivalence.


> The length of a Martian solar day is currently about 88775.24409 s (per Wikipedia), yielding an average minute length for a UTC equivalent of 61.6494751 s.  On Paleoterra you'll want an average minute length somewhere between 58.0 s and 59.4 s.  So on Mars you'll want about 65% of minutes to be 62 seconds long and the rest 61 seconds long. There'll have to be alternation of minutes within each day, which could be mostly according to a regular pattern, but at least a small part of the pattern will have to be variable on an observational basis.  Likewise, on Paleoterra you'll need to alternate between 58 and 59 seconds or between 59 and 60 seconds per minute, depending on era.


Seems rather unlikely :-)

Stepping back from all our old talking points, ignore UTC and TAI, etc.  Arriving on a new planet it is always going to be the case that the local day is quite different than whatever clocks are onboard the spaceship, time machine, Tardis, vehicle.  What options are available for the colonists?  If not sexagesimal then what?  Could humans actually use a decimal counter productively?  Would the counter have to reset once a day?  Is there some way to indicate time without numbers?  Would they of necessity try to reconcile ship time with planet time (whatever either of these are)?


> Of course, they haven't yet had a need to link precise interval time on the Martian surface to time of day, nor is there any Martian equivalent of the 1 Hz TAI-derived broadcast time signal.  My prediction is that the UTC-equivalent will naturally arise after we land atomic clocks on Mars and set up the Martian equivalent of TAI.


There are a lot of reasons that the Martian equivalent of TAI will be TAI.  First off, all the equipment will be manufactured on Earth for the first few generations.  The Martian equivalent of UTC obviously won't be UTC, however.  To accommodate both they will have to do something different than anything mentioned in the 1999 GPS World article.

I'm taken by your mention of Hertz as the unit of TAI.  That's an interesting way to break the artificial symmetry between the two meanings of the word "second".  Might be some play there.  The unit of atomic time is frequency, the unit of civil time is angles, fractions of a day.  Retire the unit of the "second" entirely.

Rob