So the wife saw my atomic clock app and asked what it is?
I said, it is the exact / official time.
She: Where is it kept?
Me: There is not just one. (I think)
She: But there must be an official world time.
Me: .............. Google............ no answer.

Is there one official clock in the world somewhere?

 

https://en.wikipedia.org/wiki/Coordinated_Universal_Time

 

The time reference used by most of the world is UTC, which is in turn based on TAI as an absolute reference to which leap seconds are added.

There is no single clock, there are 400:

 

About 50 years ago or so, there were only a few atomic clocks in the world. One of my former professors, Raynor Duncombe, was an astronomer at the US Naval Observatory and director of the Almanac Services. The USNO was in charge of keeping official US time. One of Dr. Duncombe's jobs was to fly the clock to various sites around the US to synchronize their quartz clocks to the atomic clock and determine their drift rate in order to ensure precise time keeping until the next calibration.

The USNO bought the clock a plane ticket so it had a seat beside Duncombe, because they didn't trust it going as cargo. It had a funny name on th ticket, but it escapes me now.

We've come a long way.

 

And of course flying the clock caused an additional error to be introduced...probably not something they could measure at the time maybe...

 

A nice video on topic http://www.theverge.com/2014/2/27/5455514/us-naval-observatory-time-services-atomic-clocks

 

Correct. Earliest they could measure the time dilation effect due to frame dragging with clocks was earlier in this century. They could compare the time on the GPS satellites' atomic clocks with the ground-based atomic clocks. Still took over two decades of measurements and averaging of lots of clock differences for the effect to be measurable.

Interestingly enough, the effect was measured earlier using procession of very high altitude satellite orbits.

 

Wasn't this measured by Hafele & Keating in 1971? Obviously when flying in a plane you introduce both time dilation, as well as gravitational dilation effects.

This was a fun one about gravitational dilation that I read:

http://leapsecond.com/great2005/

 

You're right. I forgot about that first experiment. I was thinking about the more recent ones that had a lower uncertainty.

 

Duh! It's officially time to buy another watch.

 

The current Caesium clocks might just be on the way out soon, the new kid on the block is Strontium!

http://www.iflscience.com/physics/could-this-new-clock-redefine-the-length-of-a-second/

 

For me the "official time" is what ever the watch I happen to be wearing says it is.

 

my wife doesn't give a shit...she says it's her prerogative as a woman to decide what the right time is.

I of course agree....

 

That's very funny!

 

And I always thought it was Big Ben.

 

... which is urgently needed for signal averaging...

 

http://www.timeanddate.com/ is a cool site. I can get lost in there! Timezone news, calendars, Julian date calculators, countdowns, sun and moon information, day length, etc., it just goes on and on. I was using it daily to time all my watches. As of yesterday I set the time display on the computer to include seconds. That works just as good since it is synced with ntp (network time protocol) to 3 separate references.

 

BIH, bureau internationale d'heure, IERS, international earth rotation service. They know what time it is.

And don't mistake GMT, Greenwich Mean Time with UTC, universal coordinated time. They're different. Then there's GMAST, Greenwich Mean astronomic Time, or GAST, Greenwich apparent astronomic time. And as was mentioned, TAI, time atomic international.

USNO broadcast time signals of UTC on WWV short wave radio.

UTC via NTP is very good.

GPS has its own, and it's 17 seconds ahead of UTC.

And there are many more. All official, but qualified.

 

I know that after work today it is time for a beer!

And that's official!