A Man with Two Watches....

Perhaps that's true, but then neither does a man with one watch for it may not be any more accurate than either of the two watches of the man with two watches.

The man with one watch only know what time the watch indicates.

The man with two watches can use his brain to:

• make a determination if one is faulty and thus rely on the other one
• choose to follow one or the other or some time between what the two indicate if they are sufficiently close in time

How is that a bad thing? Should the two watches indicate the exact same time, then while he may not know the exact time any more than the man with one watch, but he certainly won't be in a worse situation.

Actually, a man with one stopped watch is better of then either.At least twice every 24 hours his watch is exactly right.

Not if it is digital.

;)

I know you are somewhat joking but:

That's not right either. If you are looking for precise exact time relative to something else then you wouldn't be using a watch.

If a watch is exactly right twice a day, it's useless. One would get more use out of a watch that loses a minute a day than one that is stopped.

..At least twice every 24 hours his watch is exactly right.

...yes ! but for how longs is it exactly right?

My guess is that you have to compare two such clocks. If variations in frequency are independent, then the difference between the two should be an indication of the stability of either one.

OK.Even if they remain in sync,how do you measure the frequency without referring to some pre-determined time interval?

Sure,you may have a very accurate "pendulum"(an atom of Cesium,Strontium,etc.),so to speak, but how do you guarantee the accuracy of all of the equipment that measures the frequency of this oscillation?

By referring to a previous standard?

This leapfrogging is sure to introduce errors.

The location and elevation on the Earth can affect time.

And by extension, our position in orbit around the sun, and the moon's orbit around the Earth, the position and velocity (remember the uncertainty principle?) of all the mass in our solar system,the sun's movement through the galaxy,the galaxy's relative motion within our galactic cluster,our cluster's movement through the universe,the expansion of the universe,solar mass ejections,the effect of dark matter,etc.

When they speak of an accuracy of billions of years, all factors must be considered.

Many of which I surely have missed,and that is ok, as long as I don't miss the most important time of all:Suppertime!

It is not necessary to know the exact frequencies, but to compare the difference in phase between the two using some sort of interferometer. If the sources are isolated from each other (important to verify that), then any variation in one should not correlate with a variation in the other. (The standard deviation in the phase difference between the two should be sqrt(2) times the standard deviation of the phase instability of either one.)

OK,they are claiming a loss of only one second in 20 quintillion.How does that copute with the standard deviation?

If they're talking about a Sr Optical Lattice clock, it "vibrates" at about 445 THz (blue). The main source of inaccuracy is thermal motion of the Sr atoms which introduces Doppler shift, and various means are used to cool them.

I'm thinking that if the error is random, the expected amount of error over time would increase as the square root of elapsed time, the so called drunkard's walk. I'm not sure that is how they come up with their answer.

The article you reference is 3 years old. I believe there have been improvements since then.

'...If the sources are isolated from each other (important to verify that)...'

.

Isolated to what extent, and how exactly do you go about verifying such isolation.

.

We have evidence that radioactive decays undergo periodic changes in rate, but we are still lack much certainty about the cause. Is it not possible that a similar, fairly uniform, variation in the characteristic frequency of an isotope occurs periodically? How would we notice if all isotope vibrations were slowing?

Watches became nothing more than jewelry when the cell phone became ubiquitous....Time is only useful if everybody agrees on one defining source, after that it has little meaning in our everyday lives and can become a source of conflict unless there is one agreed upon reference....

What time is it?

I used the old saying merely to introduce the main topic of discussion of time measurment accuracy,not watches,per se.

It's evolving....so is it's method of use in society....

Are you serious - you pull out your cell phone every time you need to know the time, instead of just raising your arm a bit and glancing at the time piece on it?

I thought that texting was an awful waste of time - how much wasted time does using cell phones as watches add to each day?

Thomas Edison, if still alive, would be appalled at the waste of time.

It surprises me just how many people use their phones now instead of a watch. Of course, some of these have their phone permanently in their hand in case an 'important' call or message comes through so it's no more inconvenient than turning your wrist to glance at a watch.

What a waste of a hand.

Absolutely serious, if I am out and about where there is no clock. Stopped wearing my TIMEX digital, since the leather band was causing me to break out in hives.

That Rolex has an aftermarket dial, aftermarket bezel and non-Rolex diamonds on the case.

What makes you think those are diamonds?

They are. I've seen this quality before. If you look closely at the cut, you'll notice that the table (flat area on top) of the diamonds are not consistent. Also, you'll notice a cloudiness in the diamonds (inclusions). Many companies use these diamonds for Rolex parts. When you see what these parts should look like, you'll immediately see the difference.

I sold hundreds of Rolex watches when I owned my jewelry stores. If you don't learn quickly, there are many in the wholesale jewelry business who will take your head off.

hmmm... so, you can tell they are diamonds because the shape is inconsistent and the the clarity isn't good...

^.

^{All kidding aside, I trust you that those are most likely diamonds in the picture.}

And an aftermarket bracelet!

Real Rolex parts are better made, have better cut diamonds, have better set gems/diamonds and the bracelet end caps fit better.

I guess it is the same question about how you check any calibration standard. Either it tracks back to something that is determined by scientific principle or you have an original article to compare your measurements to.

Aren't we back to: One Way Speed of Light ?

I thought this was more likely about the MythBusters metrognome experiment(lots of garden gnomes all swaying back and forth in synchrony on a light weight roller suspension. (Actually, that was a joke, son, they really did work with metronomes to see if they would "sync up".

If the metronomes (about 200 as I recall) rest on a flat lightweight rigid sheet that rests on an air hockey table, they will not synchronize oscillation.

If the lightweight rigid sheet rests on two round pieces of pipe (depends on how round?), the whole assembly rocks back and forth, and the perturbation will force pendulum synchrony.

Now if we could only do that with crystal oscillators....

'....Now if we could only do that with crystal oscillators......'

.

Seems like that is exactly what you wouldn't want to be possible, in something you intend to use as a dependable regular reference for the passage of time.

Good explanation, GA from me

Precisely the answer I was looking for.I just never thought of it that way.

Thanks! A GA from me.

I think you have begun to develop an excellent answer, but some problems need to be worked out.

.

The problems are easiest to see by considering what could do very well on the described evaluation, yet be of very little use... with the exception of being used as an example here.

.

Ten clocks a built in a similar way allowing readout in incredibly small divisions and the readout for the last smallest digit is analog with micrometer scale.... ya, know, to eleven.

.

Oh, almost forgot a very important detail... all the clocks begin at 0000.00.00.00.00000000000000000......0000000000000000000000 whateverunits

and a solidly built to never turn or alter any digit ever. Perfect consistency. Perfect precision. Perfectly useless.

.

Of course, a clock that doesn't differ with time isn't realistic, but it should illustrate some problems.

.

There are a number of ways that clocks need to be consistent other than minimizing deviation from other similarly constructed and treated clocks. All similar clocks could maintain minimal deviation, yet fail to be regular with respect to what we have decided are reliably regular observable phenomena. The utility of a clock is severely diminished if the increments are mismatched with regular phenomena to a degree that predictions cannot be made without excessive complication.... even if all the same clocks strongly agree on that exact wavering scale.

Did you get the impression I was taking your word for it?

.

.

....wait a minute. It sounds like maybe you are just paraphrasing NIST's explanation and haven't actually evaluated the explanation yourself..... 'anyone can do that'.

So long as we are talking about wrist watches that are maintained and worn appropriately as intended...one per wrist, the man wearing two watches shouldn't have difficulty knowing the right time.....

...from the left.

...the punitentiary?

Now was this a pointless blog or what!!!

No one is better off or more clever (or more ontime either!) than he was before it was started.

But what if Mr. Jackson has two sheds?

Your contribution to furthering the attributes you see in this blog has been duly noted.

.

If it weren't for your cowardly anonymous nature, you could receive the adulation due for providing such a great example of someone who is clearly no better off and certainly not more clever.

A Man with Two Watches.... is guilty of conspicuous consumption!

...of what? Time?

.

Anyway, it isn't necessarily conspicuous. He might be using some trick to covertly consume his time.... you never know, he might have something up his sleeve...

Your sig line reminds me of the agnostic, dyslexic, insomniac who stayed awake at night pondering the existence of a Dog.

Me too.

.

I wonder if text were written in a palindromic style if it would be useful to those who have trouble reading regular text because of dyslexia?

How about the dyslexic,suicidal twin that shot his brother by mistake?

My computer spellchecker is dixlesic.

No where, that I read in the question, does it say the man is wearing both watches at the same time. Maybe he left both of them at home and has to rely on other method(s) of telling time.

There is a sense where time keeping with a clock is boring, it is routine carried to the limit. I have wondered about the methods of estimating elapsed time used before modern clocks and watches. I know that a barbarian chief challenged the Rabbi Hillel, a contemporary of Jesus, to explain the Torah "whole standing on one leg". I was amused but soon saw that it was his way to indicate the time he allowed for the explanation.

I wondered if anyone ever put together something along the lines of the beautiful Beaufort Scale of wind speeds, but instead, for the passage of time.

BTW. Rabbi Hillel thought about the challenge, summoned the barbarian chief and said, "The Torah says, "Do not do unto others, that which you would not want done to you. The rest is all commentary." The chief and his tribe converted to Judaism.

That's a lot of commentary for a one sentence rule!

.

That is an interesting story thanks for relating it.

The man who sounded the local factory hooter, at start of work in the morning and again in the evening to stop work, was talking to the vicar.

"I set my watch to the church clock at 8.00am"

"That's interesting" says the vicar "I set the church clock to the works hooter at 6.00pm".

The idea of vicars claiming to be paying attention to hooters in order to set their clocks, is pretty funny on its own.

.

...of course 'hooters', here in the US, doesn't refer to a whistle or horn used to signal the end of the workday.

It would seem we would need a leap-second every 10 billion years. I can hardly wait.

Nothing in the article mentions making the rotation of the Earth more regular.

1972 - 1998 period averaged a little under one leap second per year.

1999-present period averages a little under one leap second every five years.

Clocks have been far more accurate for a long time, but the Earth refuses to be tied down to a consistent polar moment of inertia. Oh, and the moon is kind of a drag, too.

I have only just a minute, only sixty seconds in it.

Forced upon me, can't refuse it. Didn't seek it, didn't choose it.

But it's up to me to use it.

I must suffer if I lose it. Give account if I abuse it.

Just a tiny little minute, but eternity is in it. (Dr. Benjamin E. Mays)

jt.

As I walked my dog through the cemetery a man said to me, " 'morning."
Er... no, I said, just walking the dog.