This Tuesday will take a little second to adjust the measurement of time at the rate of rotation of the Earth. At the risk of disrupting many electronic clocks like was the case in 2012. Explanations.
To follow the ticking of life, the most precise tool in the world meets the sweet name of NIST-F2. It is an atomic clock cesium fountain located in National Institute of Standards and Technology Boulder, Colorado. In the same way that a single platinum-iridium cylinder kept on the NIST campus in Washington is considered kilogram kilograms , the pulses delivered by this clock does not just make a meter time but the meter time par excellence, which are calibrated all other devices.
For decades, the main global time scale, Time Coordinated Universal was calibrated using the data of atomic clocks located around the globe, including the NIST-F2. Since the latter is more accurate than other atomic clocks, it is reasonable to say that this is the most accurate clock ever created by mankind. It is even more accurate than Mother Nature, a statement both true and controversial, for reasons we’ll see in a minute perfectly calculated.
What is a second?
The NIST-F2 works by playing with the electron spin. This machine almost 4 meters high uses lasers to gather nearly 100 million cesium atoms in a small space which slows down their movement and lowers their temperature to almost zero degrees. Other lasers are pushing the group of atoms in a microwave chamber and then gravity takes it back. The precisely calibrated microwave radiation changes the state of the cesium atoms. In the 1950s, scientists have calculated the number of cycles of this radiation that occur in the most precise astronomical definition of a second.
A second, in
the classical sense, does not correspond to one-sixtieth of one minute
or even at a flow
of 86,400 times a day
This number is 9192631770, which for most of us only corresponds to a mass of figures, but enthusiasts recognize it in an instant. A second, in the classical sense, does not correspond to one-sixtieth of a minute or even one of 86,400 times a day. This is “the duration of 9,192,631,770 radiation corresponding to the transition between the two cycles hyperfine levels of the ground state of the cesium 133 atom” .
There is probably nothing more important in our hyper-connected world that a precise calculation of time. Consider the mains: power generation is a very fast and sensitive management between demand and response to the request, which relies on perfect timing to meet the needs. An error of a few microseconds could plunge half a country in the dark.
Atomic Clock vs rotation of the Earth
The problem arises for all systems dominate modern life: air traffic control, stock exchanges, legal documents marked with time code, automated factories, missile guidance, robot-assisted surgery, weather, mobile phone networks, observation Astronomical and car navigation. Our world relies on computers that constantly exchange data packets. To do this, they must agree on the exact time it is and he will be by X seconds. It’s not the money that makes the world. It is the accurate calculation of the time.
But the remarkable precision made possible by atomic clocks poses a singular problem, a problem that is so well melted in our digital infrastructure that pales.
And yet it is important.
The problem is the mixing of two time scales. The time calculated by atomic clocks is not the same as that determined by the first of the clocks: the rotating earth. While current best atomic clocks have an error margin corresponding to approximately one second miscalculated every 100 million years, the Earth, by comparison, is unreliable. This lack of reliability is due to the fact that the rotation of the planet is not regular and gradually slows down. (You may have the impression that time is running at full speed, but the days are getting longer, even slowly.) This gradual deceleration associated with changes in the shorter term of the speed of rotation of the Earth, are of a truly unreliable clock sky.
Before midnight, a 26 th leap second
To prevent our atomic clocks are too far ahead of time determined by the Earth’s rotation, every one or two years the masters of the world time rajoutent one second atomic time before transmitting this time adjusted to the world as the Coordinated Universal Time.
This adjustment is modestly called leap second. Ten of them were added in one go to Universal Time in 1972, and 25 more have been added since. The arrival of the 26 th is scheduled for June 30 in the afternoon, just before midnight. The decision is made every time the difference between the rotation of Earth time and atomic time may exceed 0.9 seconds. In the decades and centuries to come, these adjustments will become more frequent, up to once a month, if not more.
Since
the movement
Earth is unpredictable, we can not predict leap seconds
This change can cause all sorts of problems. In the summer of 2012, clocks haywire ignited Internet. “Bug 2000 2.0: How one second has made the Internet the half lap” headlined Buzzfeed at the time. Temporary failures were found on Reddit, Mozilla, Gawker, LinkedIn, StumbleUpon, Yelp, the Qantas Airlines reservation system, and others. A few years before that, because of the leap second, a pharmaceutical company has lost a stock of drugs remained too long in the production line, and hunters of a US aircraft carrier were not all aligned on the same time scale, to the point of sometimes shifting nearly a minute.
The concern is partly because leap seconds can not be provided on a regular basis, unlike the leap years. These are both adjustments that compensate the fact that the calendar does not correspond perfectly to nature. But since the movement of the Earth is not predictable, we can not predict leap seconds. This means that computer scientists have six months at most to prepare for it.
The bug of the year 2015?
Part of the world of computing time think that such problems are the harbingers of a coming disaster. When the leap second was added in 2012, the engineers EGNOS, the European satellite navigation system, reported that they could not predict the impact of change, and that this may require a time-nearly 72 hours to adapt. Luck was on their side because nothing happened horrible, but this episode really does not inspire confidence in our ability to manage the occasional change the time scale that governs almost all modern civilization.
This summer, air traffic controllers of the Copenhagen International Airport decided that the easiest way to handle things at the arrival of a leap second would warn drivers that they will left to themselves for a few minutes, disconnect, reboot the system and get back to the aircraft. Such a system can function in a small European airport, said Poul Henning-Kemp, Danish consultant specialist IT related settings leap seconds.
“But this is not a valid solution for airports in Tokyo or Los Angeles, where leap seconds are added during peak hours.”
Farewell, sun king
Those who are in disfavor of the Leap Second explain that this trick was previously satisfactory and even ingenious turned into a problem at best very expensive, at worst a real time bomb. According, to them, the world should abandon the idea of lock on the position of the sun, and atomic clocks should define the length of the day, period.
Should we abandon
the sun once and for all
and stalling only
the frantic pace
subatomic
particle
In the other camp, there was a small group of astronomers steadfast -and the British government. They argue that the leap second was and is a clever solution and calculate the time without referring to the position of celestial objects is contrary to our understanding of the universe and our place there. We give our all time record straight: for switching to summer time, when changing the time zone, or if an old clock needs to be remounted. So what this particular adjustment is it so horrible?
Whatever his view, the problem became crucial. This fall, in Geneva, the international community responsible for defining a standard notion of time will meet to decide the fate of the leap second. These are mostly bureaucrats, not scientists who will make the decision. Should we abandon the sun once and for all and to tune only the hectic pace of subatomic particles? Or should we continue to rely on the sky, adjusting world clocks from time to time to prevent them from being too out of sync with respect to time determined by Greenwich, England?
The End of Time compromise?
The question probably fascinate the great minds of ancient Egypt. There, there are at least 4,000 years, the division of the day into segments – the invention of hours, fait- was adopted. Synchronization of clocks is then well become necessary later in the nineteenth th century, when the rapid expansion of the railroad helped to understand that the time could not be a measure to local level. In 1884, representatives from around the world gathered in Washington to reach an international agreement on the time and longitude and set a standard. It was at that time that the Greenwich Mean Time was designated as the reference, the basis on which all the world’s clocks would be settled. Each degree of longitude in the world corresponds to a difference of four minutes compared to the average solar time on that green hill east of London.
In the 1950s, the physicist Louis Essen built the first atomic clock. As he wrote, it became clear that the standard for the second time, the rotation of the Earth, “did not correspond adequately to the practical applications of the modern world in the areas of navigation Air and communication “. The latter determined by astronomical observation had had their day.
In 1967, the new standard is adopted permanently, or at least until a better solution comes along.
The atomic clock does not give the time of day, of course, but that is not what is needed
Louis Essen
The atomic clock, notes Essen, “does not give the time of day, of course, but that is not what we need “. This is not necessary because the distribution times of the day is a social concept. Yet as soon as atomic time has become the new standard, a question arose: how to integrate this standard notion of time from the point of view of civilization (or at least incorporate the notion that noon the sun at its zenith are linked)? Essen was convinced that the leap second “was a good compromise” .
The world will then end up with just two notions of time, one determined by atomic clocks, the other by the old method heavenly. They could be slightly offset, but not much. Easy.
The door wide open to error
Easy, yes, except for the GPS. Introduced in the 1970s, satellite guidance technology offers a positional accuracy and unprecedented temporal data. Over the following decades, computer programmers begin to stall many software clocks on the GPS system time instead of Coordinated Universal Time -He who is entitled to the leap second.
In the late 1990s, astronomer Dennis McCarthy, the United States Naval Observatory, learned of a number of bugs and problems related to the implementation of the leap second, and attended a lot of nights chaotic insertion of the leap second at the observatory, so much so that he began to seriously consider simply stop the practice. McCarthy, who rose in rank to become director of the temporal branch of the observatory, began writing and speaking about the possibility that the leap second might have had its day.
The time is
a succession of small events called seconds. We can not afford to interrupt
This sequence
Elisa Felicitas Arias
There are two major categories of problems caused by leap seconds. The first relates to the coexistence between GPS signals and signals UTC (Coordinated Universal Time) in a transmission from GPS satellite, there is a small code segment that roughly explains the difference between time GPS and UTC time is X seconds. Each leap second, that information must be changed in the GPS message. In other words, it is the open door to the error. Another potential danger is related to the interruption of what is supposed to be an uninterrupted sequence.
“Time is a succession of small events called seconds explains Elisa Felicitas Arias, director of the international department Time weights office and Measures in Paris. We can not afford to interrupt this sequence. “
In 2004, a delegation of the International Union of Communications, led by McCarthy, formally proposed to terminate the leap second principle. Reactions were mixed.
“I think when there is a bug, we fix it. That does not mean that redefines the time, “ says Rob Seaman, data specialist at the National Optical Astronomy Observatory in Tucson.
Eye on Mars, the Sun and the Earth
Abandon the leap second will lead to expensive and difficult changes telescopes around the world because they are, of Somehow, clocks that measure time and space. But the biggest criticism of Seaman and other scientists is that set time regardless of the positions of celestial objects returns to separate the sun of our clocks. It is not possible to define a time of the day -a second- just looking at an electronic device. We must also look at the sky.
Take the passage of time on another planet, for example. The days on Mars do not last 24 hours, but they include a sunrise and sunset, and minutes between two, as on Earth. One day is not and can not be arbitrarily determined standard.
Nearly forty years after the introduction of this practice, any kind of bug apocalyptic catastrophe of 2000 under certain occurred
Especially as the leap second works quite well, according to Peter Whibberley, chief researcher of the time and frequency at the National Physical Laboratory in the UK. Nearly forty years after the introduction of this practice, no kind of bug apocalyptic catastrophe of 2000 under certain occurred. “Or if there was, we have not heard about it.”
Whibberley, since we already live in a world governed by the atomic time and not by the rotation of the Earth, the debate about the leap second is not really about the calculation of the time. Atomic clocks do that very well, thank you. But thanks to the leap second, we both know how many seconds have elapsed knowing what the time of day in astronomical terms, or at least with a margin of 0.9 seconds.
“We just change the way we call the time when it appears on our clocks [everyday]” indicates Whibberley.
An English pride misplaced?
If there are compelling reasons to change things, Whibberley has not identified them. Besides that, we should not put the blame on those who want to change things to prove that their new approach will be superior to the status quo, and how to know that this new method will not cause unexpected inconveniences?
Some experts have suggested that the commitment of Britain to the leap second had more to do with national pride and preservation of the prestige of Greenwich Mean Time with a scientific logic, technical or even economic. Whibberley is far from okay with it. To prove it, he expressed a bill before Parliament to pass Britain GMT European time, especially for economic reasons. This does not really look like a political position blinded by nostalgia.
I think that without leap second, we will end
lose the link between time and the experience of the people day and night
Citation
David Willetts, Minister
British Science
But last year, the Minister of Science, David Willetts, warned against the risk of making “the meaningless time” if world leaders decide to remove the leap second.
“I think without leap second, we will eventually lose the link between time and the experience of the people day and night … the relatively frequent but modest corrections better than creating a gap. The Greenwich Mean Time would shift gradually to the West, the United States. I want him to remain in Britain. “
In fact, the first-year pass through Paris, to the east, where Arias the international office of weights and measures is ironic that Britain, the country where the atomic clock was born now so loudly defend what she calls a “imaginary discontinuity of time” .
Difficulties too well hidden?
For people like McCarthy The debate on sunsets lunchtime deviates from the real problem (and the real dangers) in question. The problem is that companies and institutions that are experiencing difficulties because of the leap second has little reason to make these public problems, and have every reason to keep it secret. You feel safe, if, for example, you were told that some elements in the military, or the leaders of the financial markets had trouble staying on time?
In 2008, McCarthy attended a conference at the Naval Observatory, given by Kamp, the Danish consultant. Kamp shared an amazing story with the congregation during a leap second addition of a few years ago, a new radar control system in a certain country (that Kamp would not disclose) has suddenly set to reproduce radar recordings from the year before.
For that to change, it would take something irreversible, short, people dying
McCarthy
McCarthy thought it was the kind evidence he needed to finally win the game against skeptics who think that the second insert is picturesque, safe and pretty cool. But since nothing catastrophic has happened (the radar screens soon returned to normal), McCarthy warnings have again been little heard.
“This is the most frustrating experience of my life, he admits. We can not continue to put that aside and pretend it was not a problem. “
Pending a tragedy
After years of avoidance, blind alleys and false resolutions to further push a little more the problem, 2015 , or at least a good chance to be a real milestone for the United Nations agency charged with agreeing on this.
“If we put aside the 2015 meetings without changing the definition of Coordinated Universal Time, it will not change until a number of years,” think Arias.
But few people are optimistic about the outcome of future deliberations. McCarthy, even having spent countless hours of his life on it, is now convinced that nothing will happen as a tragedy will not force things.
“We need something irreversible, short, people are dying.”
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