[LEAPSECS] BBC article

Rob Seaman seaman at noao.edu
Fri Nov 4 21:46:40 EDT 2011

On Nov 4, 2011, at 5:58 PM, Tom Van Baak wrote:

> On Nov 4, 2011, at 11:10 AM, Steve Allen wrote:


>> I think this is because GPS is one of the systems which was designed

>> robustly with the notion that configuration changes are a routine part

>> of the operation, so a leap second is just another routine change.


> It's not just GPS. In general any system today that already has an

> automatic or manual method to handle leap seconds will be fine if

> no leap seconds were to be announced in the future.

I believe this is the exact opposite of the point Steve was making:

>> Malys at futureofutc […] stated that abandoning leap seconds

>> Will require resources to modify existing ICDs and operational software

>> Offers no benefits to NGA or GPS Operations

>> and he gave the cost of creating an ICD for GPS at about $100 million.

Meaning that GPS operations will be rather spectacularly un-fine under such circumstances.

> As you know, the only trouble will be with systems that, for valid or

> accidental reasons, use UTC when they mean UT1,

No, they mean "Universal Time", of which UTC and UT1 are separate realizations.

> or assume that |DUT1| is always less than 1 s.

As the standard has said for four decades.

> But the varying levels of pain that result will be spread very gradually over many decades as DUT1 grows beyond a second, to tens of seconds, to minutes.

No. Astronomy is the canary in the coal mine. Should the miners feel comfortable when the bird keels over at the beginning of the shift, just because the boss up on top calls down to say "no worries"?

> Speculating what will happen to timekeeping over centuries or

> millennia is another matter. We all know even the existing system

> of UTC will become awkward when leap seconds are needed every

> month, or every week, or every day, etc. I have no idea how to

> solve that; or if anyone today has an obligation, or right to.

Of course we have the obligation. Leap seconds aren't the issue. Leap seconds are a feature of one possible solution to time-of-day based civil timekeeping. Eradicating leap seconds won't make mean solar time less of a requirement.

Coordinated Universal Time should remain a type of Universal Time. If the ITU wants a timescale that isn't a type of Universal Time, call it something other than [Adjective] Universal Time. Since it will be modified from TAI, how about "Modified Atomic Time"?


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