23:59:60 When a leap second is added, digital clocks tick past 23:59:59 but don’t go directly to 00:00:00.
STILL FINER MEASUREMENTS Even with this refinement, there is still orbital change left over. But now we are talking about temporal shavings that are quite small. At this level of precision, other wobbles in the relation of the Earth’s rotational period (the day) and its revolution period (the year) have to be taken into account. Keeping track of minute effects like this is the job of the International Earth Rotation and Reference Systems Service, which controls the addition (or deletion) of leap seconds. For example, a second was added to Coordinated Universal Time by the service on June 30, 2015, due largely to the slowing of the Earth’s rotation by the gravitational pull of the moon. There are other sources of calendar slip: the 8.9 magnitude earthquake that triggered the Japanese tsunami on March 11, 2011, for example, shifted the planet’s mass distribution enough to decrease the length of a day by 1.8 microseconds. This will add up to about a Christopher Clavius
USING THAT ‘EXTRA’ TIME Personally, I think we should make February 29, leap day, a global holiday. It should be considered a gift to ourselves, like taking that accumulated spare change to the grocery store coin-counting machine, and trading it for some easier-to-spend bills. It should be a day of celebration, a reward for saving that quarter of a day over the last four years, to be spent on something frivolous. Or it could be a special day to realign our sense of hourly routines, weekly trash pickups, the race to fulfill monthly quotas, to the celestial schedule. Without that extra day every fourth year, our ancient friends would begin to miss their annual appointments, and start to fall behind in wishing us prompt birthday greetings, like forgetful Facebook friends. Without February 29, roughly every four years, the “constant stars” would cease to be constant. © The Conversation
second after 1,500 years.
James Hetrick is a professor and chair of the physics department at the University of the Pacific, as well as a professor in Pacific's data analytics master's degree program.
American Consequences DAY
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