The Future of Time: UTC and the Leap Second

rlseaman writes "UTC ("Coordinated Universal Time") is very close to being redefined to no longer track Earth rotation. Clocks everywhere — on your wall, wrist, phone or computer — would stop keeping Solar time. 'American Scientist' says: 'Before atomic timekeeping, clocks were set to the skies. But starting in 1972, radio signals began broadcasting atomic seconds and leap seconds have occasionally been added to that stream of atomic seconds to keep the signals synchronized with the actual rotation of Earth. Such adjustments were considered necessary because Earth's rotation is less regular than atomic timekeeping. In January 2012, a United Nations-affiliated organization could permanently break this link by redefining Coordinated Universal Time.'"

Metric Time

[Normal Dan]

As long as we're redoing time I say we convert it to the metric system. This was hard to do before because we kept trying to keep time in line with the rotation/orbit of the earth. But if all that's going out the window, let's just divide everything up into units of 10 and be done with it.

Relativistic Reference Frames?

[bill_mcgonigle]

In 2012, a new definition of time that is only relative to the Earth's reference frame falls short.

Re:Think of the Humans

[zill]

Leap seconds happen at most twice a year, and typically once every few years. If they happen at their maximum permitted frequency, then in 1000 years the difference between midday and noon will be 2000 seconds, or just over half an hour. In other words, for me the drift due to not living exactly on a time zone boundary line will still be more than the difference due to ignoring leap seconds.

It's impossible to predict ahead of time how many leap seconds are necessary. Just because it's been historically ±1 second doesn't mean it will always stay like that in the future. As T increases quadratically, we will eventually see leap minutes and leap hours.

That's not even taking into account of the fact that doomsday style meteor impacts could necessitate adding or removing a whole day every year. That pretty much breaks half of the time-related code that I've written.

Note that this is a wildly pessimistic prediction. It's more likely that we will drift about 5 minutes over the next thousand years. In 1,000 years, if the position of the sun over Greenwich at 12:00 is still of importance to a significant fraction of the human race, then I'll be very surprised.

It's not pessimistic at all. T between the 1000AD and 2000AD was 1600 seconds.

In fact, I'd say that's a very optimistic prediction, since T is monotonically increasing, T for the next 1000 years will be much larger than T for the previous 1000 years.