[LEAPSECS] UTC Redefinition Advanced

Rob Seaman seaman at noao.edu
Mon Oct 25 11:15:47 EDT 2010

On Oct 25, 2010, at 12:29 AM, Poul-Henning Kamp wrote:

> In message <AANLkTinqg5-TKYAPi9nzhcEFcTNiNS8TQvw2SnWpLd1H at mail.gmail.com>, Sanj

> eev Gupta writes:


>> I am still opposed, in principle, to letting NTP time (for example) diverge

>> from The One True Cosmic Time;


> What "One True Cosmic Time" would that be ?

Both sides (assuming this discussion really splits only two ways) are speaking loosely here.

See Einstein, etc, for anything resembling "cosmic time". You will come up empty-handed.

> One where astronauts on Mars would have to monitor earths rotation in order to add or remove spurious seconds to their timescale ?

Astronauts on Mars (in the unlikely event this happens during our lifetimes) will likely keep time just like robots on Mars (and their handlers back on Earth) do - using Martian mean solar time. See previous threads.

Removing the opportunity for intercalary adjustments won't make it easier to synchronize disparate timescales.

> Or one which, given a precise enough frequency standard and knowledge about your relativistic whereabouts you can tell what time it is, without caring what a particular and erratic piece of rock does in another part of the cosmos ?

(Again, see Einstein who himself punted on simultaneity.)

Yet again we've simply established that there are two flavors of timekeeping - intervals and Earth orientation. Adding the orientations of additional planets on the one hand and more stringent space timekeeping requirements on the other only emphasizes that the two things are different.

Civil timekeeping - on Mars or Earth - is tied to the planet's mean diurnal rotation period. Other sorts of timekeeping are tied to different things.

Leap seconds are a means to an end. The end won't vanish when the leap seconds do.


More information about the LEAPSECS mailing list