Why is it that historically the clocks have gotten more accurate, but the trains have been getting later and later?
The force that binds neutrons to an atom's nucleus could be used to create clocks that are 100 times more accurate than today's best atomic clocks, say physicists at the University of New South Wales (UNSW). The nuclear clock outlined in a paper accepted for publication in Physics Letters Review would neither lose nor gain 1/ …
By improvements in (time) management?
Ah yes, but we can measure the lateness of said trains with unprecedented accuracy and thus employ 'Atomic Timing Train Advisory Consultants' (ATTAC's), to burn through a few billion advising the clueless as to how they could reduce said lateness by one orbit of a Neutron.
Quantum uncertainty: the product of the error on the clock and the error in the train schedule is constant.
Because of Heisenberg's trains: the more accurately you know the time, the less accurately you know where the fragging train is.
How on earth did we, way back when, define such a unit as a second if we couldn't even measure it accurately?
How do we know it's 2012 if we've never had an accurate timepiece?
How do we know existing clocks are fast or slow? What do we use to measure the inaccuracy?
How hard is it to use W*kipedia to answer your questions, unless they were purely rhetorical?
Here, have this one on me. http://en.wikipedia.org/wiki/Second
We *define* the second by using atomic clocks, ergo, an average reading of many clocks can never be "slow" or "fast". If you do something odd with a single atomic clock like take it up a mountain, launch it in a satellite, etc, then it will drift, but that's relativity for you.
Why use atomic clock definition? The definition of a second came about because pendulums, the earth's rotation rate and the tropical year cannot be measured with anything like the same accuracy. A physical principle that nothing can ever be exactly measured.
NB: The measurement of metre is now defined by the speed of light (a defined constant) and the definition of a second rather than by using a platinum bar, or measurements of spectral lines, for much the same reasons - we can measure time far more accurately.
> How on earth did we, way back when, define such a unit as a second if we couldn't even measure it accurately?
The same way we defined every unit of measurement we had at the time, as best we could.
> How do we know it's 2012 if we've never had an accurate timepiece?
Because 430 years ago Pope Gregory XIII decided that that year should be called 1582 and everybody agreed with him. Since then the Earth has orbited the Sun 430 times making this year 2012. It doesn't matter how accurate your second is, it is easy to count years which is how we know it is 2012.
> How do we know existing clocks are fast or slow? What do we use to measure the inaccuracy?
Up until 1967 a second was defined in terms of the Earth revolving around the Sun. Since then it has been define as:
"The duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom."
purely rhetorical, but I did wonder who would come it with the most condescending reply.
As it turns out, you,.
Until this reply, of course.
You sound exactly like my three year old nephew. Do you want to build some lego?
>Because 430 years ago Pope Gregory XIII decided that that year should be called 1582 and everybody agreed with him.
Not quite. That's only true if you live in Catholic country. The UK in common with most protestant countries didn't adopt his idea until 1752. The Russians didn't adopt it until the early 20th century.
I read up on this stuff back at the turn of the millennium. A very interesting book - when it comes down to it it's all very arbitrary. Roman emperors for instance sometimes removed a month in order to bring tax collections in a bit early. Maybe that's an idea the ConDem coalition could look as an alternative to spending cuts :)
Something about the old way seems easier.
We don't need to know the time accurately. What mankind REALLY needs is a good excuse for being late.
1 second = The time it takes to grab the remote and change channel when Jedward appear on TV.
Too slow old man, I have a panic button that cuts the power and self destructs the TV...
huh, I can do better than one-second-to-off when the Archers' theme music starts...
(and now I bet you all have Barwick Green going round in your head, teehee)
> I can do better than one-second-to-off when the Archers' theme music starts...
I'm usually driving when I hear it, so I get:
> grab the remote and change channel when Jedward appear on TV.
I see your moronic twins and raise you the fat twat on the insurance adverts...
It will still show the wrong time
Unless we make lots of these clocks and average the results to remove random effects, in 280 billion years the damned thing will be out by 1 second.
Re: It will still show the wrong time
That's all right, our local watchmaker will have it fixed by Thursday.
Does that mean that the whole leap second/day/year debate will have to be re-evaulated based on more accurate timings of the Earth's orbit now? :-\
Re: Leap second
To the rough approximation of a rubidium reference, the answer is: No +/-0.001ppm
The cesium standard answer is: No +/-0.000005ppm
With the proposed neutron standard, the answer is: No +/-1.2E-13ppm
Just so as you know.
"The nuclear clock outlined in a paper accepted for publication in Physics Letters Review would neither lose nor gain 1/20th of a second in 14 billion years, the age of the universe."
That's nothing, my wristwatch also neither loses nor gains 1/20th of a second in 14 billion years - it tends to lose or gain considerably more than that.
Now if they'd said their new fancy clock neither lost nor gained *more than* 1/20th of a second in 14 billion years, that would have been impressive ;-)
What on earth is a Jedward?
Re: What on earth is a Jedward?
A modern method of quantifying 'waste of space'fulness, as in:
Big Brother = 8 jedwards
Celebrity Get me out of here = 10 jedwards
The Catholic Church = ...
well you get the idea.
Big Brother equivalence?
``Big Brother = 8 jedwards''
Are you confusing this with the USian measure of intrusiveness, the Jedgar?
Have probably already patented it so those boffins will get the asses sued if they build one!!
of extreme density.
Re: A measure
This should have been a reply to "What is a Jedward?"
Excuse my ignorance, but...
how do atomic clocks tie into high-bandwidth data transfer?
I seem to remember Stephen Fry being flamed here for his assertion regarding a (very) similar topic. Living in SA, "high bandwidth" means over 4Mbps, so have no experience re "high bandwidth".
Re: Excuse my ignorance, but...
The trick with high bandwidth stuff isn't knowing what the time is, its to do with recognising the pulses on the line. If you are generating a signal on a fibre optic line at N GHz, you need a clock source on the receiving end which has EXACTLY the same frequency to interpret the signals so you know if the bit is on or off. If one or the other drifts you'll introduce errors into the signals. Even a small drift can be bad as it upsets not only the bit in flow at the time, but also all subsequent bits which will probably overcome the ECC until the receiver figures out something is wrong and finds the next frame/packet boundary. Its one reason why, even though its mostly hidden, AFAIK high speed telco grade optical networks still use framing. (the other being that they're still based on the concept of carrying voice channels)
You can use a 2nd fibre to get around this (i.e. put the clock pulses down the 2nd fibre to let you interpret the signals on the first) but (a) that gets more difficult the higher the clocks go and (b) telco's really don't like that as it uses up a lot of fibre they could use to sell overpriced bandwidth to people.
Fry got laughed at for suggesting that packet switching networks need to know what the time is. I've yet to meet a router (or other packet processing device, other than some mobile phone standards which use clocks for encryption related things) that won't run if it doesn't know what time it is. Likewise I've never seen a SONET mux with a time source. But they all have clock sources built in.
(Note I haven't worked in the telco field for a few years, but while the speeds have increased I don't think the fundamentals have changed)
need more accuracy
at that rate of accuracy if i dont check and reset for 19600 billion years I could be 5 mins late for work!
Re: need more accuracy
Don't worry. You pension will kick in in about 19599 billion, 999 million, 999 thousand, 995 years anyway.
Chimes are one thing
Now if only those boffins could apply as much effort into getting the BBC pips properly aligned with reality on a digital radio.
Re: Chimes are one thing
Fundamentally impossible unfortunately, DAB simply cannot do real-time transmission or reception.
FM only suffers speed-of-light delay, DAB adds huge compression and decompression delays, and as each 'block' is compressed separately it's impossible to reduce the delay to less than one block of time, even if the processors at the BBC and in your radio could do it instantly.
Which it can't - and your radio is probably really slow.
All I want to know
Is that more or less accurate than my casio?
Re: All I want to know
(Less facetiously, yes, unless they hook your local transmitter up to it, in which case, it will be as accurate (so long as you account for light-speed lag from the base station, anyway...)
I want one....
But while a lot of the commentards are ranting and raving about the accuracy...
Think about the technology required to actually build one, and then build one that would be practical for any of the mentioned uses. (Except trying to keep the trains on time. I don't think its possible.)
Yeah I'm one of those guys who wears an automatic watch because I think its cool to have a timepiece made up of hundreds of mechanical moving parts costing $$$ and being hand made, when an electric watch costing $ is probably more accurate.
Sometimes the journey is more important than the destination itself.
Re: I want one....
"Sometimes the journey is more important than the destination itself."
Very insightful of you sir! I doff my cap! (Well, I would if I had one).
To bad HP isn't in the watch business any more
They made so nice Cesium wrist watches like the 5071A.
Re: To bad HP isn't in the watch business any more
While a joke, the smallest atomic clocks are the size of cigarette packs and are used in Satellites. Note that they may be smaller, but I don't think that civilians can either buy them, or afford them.
The real problem
The real problem is that time itself in a mystery. How do we know that ten seconds measured today (accurate to 14 decimal places) is the same amount of whatever time might be, as ten seconds measured yesterday? Or last century? Or in the age of the dinosaurs? Or "seconds" after the start of the universe?
We don't. We know only that multiple clocks involving different vibrating entities that agreed on a number yesterday, also do so today, within their individual limits of accuracy (whatever that means). We can't take today's clock back to double-check yesterday's measurement. Time goes forwards only.
IT angle: in a computer or other clocked logic, the exact frequency or regularity of the clock is fairly unimportant. The presence or absence of skew between the clock here and the clock there is critical to the correct operation of the whole thing. A wild speculation: the universe ends when it expands so far that "clock skew" prevents it from working.
Does anybody really know what time it is?
Does any body really care?
> Does anybody really know what time it is?
I do. I've got it written down 'ere on a piece of paper. A nice man wrote the time down for me this morning.
If anyone ever asks me the time, I simply show him the piece of paper.
Let me hold that piece of paper to my ear would you? 'Ere. This piece of paper ain't goin'
Sorry, Vic, Eccles was there before you.
> Eccles was there before you.
Err - yes. That's why I quoted from the script.
I was kinda hoping someone would feed the next line, but it seems there aren't too many Goon Show fans left :-(