Leap Second
Leap Second?????
A leap second will be added on June 30, 2015 23:59:60 UTC.
After reading this sentence a lot of queries arise. What is leap second? What is UTC? Why do we have to know about it? And it’s not the same as leap year we know about.
Basically, a second of time, as measured by an atomic clock, added to or omitted from official timekeeping systems periodically to compensate for small changes in the rotation of the earth caused by volcanoes, earthquakes and other natural phenomena and in the length of a solar day.
OR
An extra second (as measured by an atomic clock) added to or subtracted from Greenwich Mean Time in order to compensate for slowing in the Earth's rotation.
I hope you got it!!
The International Earth Rotation and Reference System Service (IERS) in Paris, France observes the Earth's rotation and compares it to atomic time. When the difference between the two approaches 0.9 seconds, they order a leap second to be added worldwide.
If you guessed 86,400 seconds …. It’s correct!!
It’s stated that “A normal day has 86,400 seconds, but in the atomic time scale 1 second is not defined as one 86,400th of the time it takes Earth to rotate around its axis but as the time it takes a Cesium-133 atom at the ground state to oscillate precisely 9,192,631,770 times.”
Earth’s rotation slows down over time which means that days get longer. On average, an Earth day is about 0.002 seconds longer than the daily sum of the 86,400 seconds measured by the atomic clocks. This makes for a discrepancy between TAI and UT1 of around 1 second every 1.5 years. Leap seconds are added to our clocks (UTC) so this discrepancy does not get too large over time and the time we use is synchronized as much as possible with the Earth's rotation. Before the difference between UTC and UT1 exceeds 0.9 seconds, one second is added to UTC. This means that the time difference between TAI and UTC amounts to an integral number of seconds because whole seconds are added, while the time difference between UTC and UT1 is always less than 0.9 seconds.
The last leap second was added at 23:59:60 UTC on June 30, 2012.
Since 1972, a total of 25 seconds have been added. This means that the Earth has slowed down 25 seconds compared to atomic time since then.
This does not mean that days are 25 seconds longer nowadays. Only the days on which the leap seconds are inserted have 86,401 instead of the usual 86,400 seconds.
For computers, a day is 86,400 seconds only, no matter what. Our systems are engineered for data integrity, and some refuse to work if their time is sufficiently wrong. When you try to introduce an extra second that doesn’t fit into the normal format of time (the official leap second timestamp on June 30 will be 23h: 59m: 60s), it can throw off computer systems’ processes. Because leap seconds are not predictable, programmers can't build them into their code the way they do for leap years.
The problem is that during the leap second, the computer clock shows 60 seconds instead of simply rolling over to the next minute, or shows the 59th second twice. The computer sees a leap second as time going backward. The machine registers this as a system error, and the CPU can overload.
Google adds a millisecond to its servers every once in a while throughout the year to solve the problem. The slowed-down servers don't notice when an extra second is slipped in. Another good way to avoid any trouble is to simply shut down a computer system for an hour or two around the leap second.
In particular, apps and programs based on UNIX, a popular open-source operating system, are susceptible to these problems because UNIX exists before the establishment of the leap second. When the last leap second was added in 2012, it caused problems for big companies like Reddit, LinkedIn, Gizmodo and FourSquare. It even led to 400 flight delays in Australia, forcing airport workers to conduct check-ins by hand rather than using computers. However, technical problems related to the leap second are relatively isolated. There’s little chance of a large-scale technological shutdown. But the fact that people spend so much time online now means technical problems related to the leap second could affect more people than in the past.
But many programmers are oblivious to leap seconds, and this can cause problems. The additional seconds happen so infrequently and so irregularly that it makes it difficult for computer companies to catch on to the problem. While Reddit, LinkedIn, Gizmodo and FourSquare will likely remember the lesson they learned three years ago, other sites that didn't experience any issues are likely still unaware.
The atomic time scale has revolutionized technology and stabilized the time but it is slowly drifting out of sync with our actual position in the space.
A leap second will be added on June 30, 2015 23:59:60 UTC.
After reading this sentence a lot of queries arise. What is leap second? What is UTC? Why do we have to know about it? And it’s not the same as leap year we know about.
What are these???
A leap second is a second which is added to Coordinated Universal Time (UTC) in order to synchronize atomic clocks with astronomical time to within 0.9 seconds. Coordinated Universal Time (UTC) is the primary time standard by which the whole world regulates time. UTC is the time standard used to determine local times in time zones worldwide. It is primarily based on the combined output of several highly precise atomic clocks, a statistical time scale called International Atomic Time (TAI).Basically, a second of time, as measured by an atomic clock, added to or omitted from official timekeeping systems periodically to compensate for small changes in the rotation of the earth caused by volcanoes, earthquakes and other natural phenomena and in the length of a solar day.
OR
An extra second (as measured by an atomic clock) added to or subtracted from Greenwich Mean Time in order to compensate for slowing in the Earth's rotation.
I hope you got it!!
Why Do We Need Leap Seconds?
As the atomic clocks are programmed to tick away at the same speed over millions of years ago compared to the Earth's rotation (which determines the length of a day) they are simply too accurate. Now as the Earth's rotation around its own axis is gradually slowing down, very slowly, so in order to maintain the time we have to add a second every now and then.Leap Second 2015 and Internet Crash
How many seconds are in a day?If you guessed 86,400 seconds …. It’s correct!!
It’s stated that “A normal day has 86,400 seconds, but in the atomic time scale 1 second is not defined as one 86,400th of the time it takes Earth to rotate around its axis but as the time it takes a Cesium-133 atom at the ground state to oscillate precisely 9,192,631,770 times.”
Earth’s rotation slows down over time which means that days get longer. On average, an Earth day is about 0.002 seconds longer than the daily sum of the 86,400 seconds measured by the atomic clocks. This makes for a discrepancy between TAI and UT1 of around 1 second every 1.5 years. Leap seconds are added to our clocks (UTC) so this discrepancy does not get too large over time and the time we use is synchronized as much as possible with the Earth's rotation. Before the difference between UTC and UT1 exceeds 0.9 seconds, one second is added to UTC. This means that the time difference between TAI and UTC amounts to an integral number of seconds because whole seconds are added, while the time difference between UTC and UT1 is always less than 0.9 seconds.
The last leap second was added at 23:59:60 UTC on June 30, 2012.
Since 1972, a total of 25 seconds have been added. This means that the Earth has slowed down 25 seconds compared to atomic time since then.
This does not mean that days are 25 seconds longer nowadays. Only the days on which the leap seconds are inserted have 86,401 instead of the usual 86,400 seconds.
For computers, a day is 86,400 seconds only, no matter what. Our systems are engineered for data integrity, and some refuse to work if their time is sufficiently wrong. When you try to introduce an extra second that doesn’t fit into the normal format of time (the official leap second timestamp on June 30 will be 23h: 59m: 60s), it can throw off computer systems’ processes. Because leap seconds are not predictable, programmers can't build them into their code the way they do for leap years.
The problem is that during the leap second, the computer clock shows 60 seconds instead of simply rolling over to the next minute, or shows the 59th second twice. The computer sees a leap second as time going backward. The machine registers this as a system error, and the CPU can overload.
Google adds a millisecond to its servers every once in a while throughout the year to solve the problem. The slowed-down servers don't notice when an extra second is slipped in. Another good way to avoid any trouble is to simply shut down a computer system for an hour or two around the leap second.
In particular, apps and programs based on UNIX, a popular open-source operating system, are susceptible to these problems because UNIX exists before the establishment of the leap second. When the last leap second was added in 2012, it caused problems for big companies like Reddit, LinkedIn, Gizmodo and FourSquare. It even led to 400 flight delays in Australia, forcing airport workers to conduct check-ins by hand rather than using computers. However, technical problems related to the leap second are relatively isolated. There’s little chance of a large-scale technological shutdown. But the fact that people spend so much time online now means technical problems related to the leap second could affect more people than in the past.
But many programmers are oblivious to leap seconds, and this can cause problems. The additional seconds happen so infrequently and so irregularly that it makes it difficult for computer companies to catch on to the problem. While Reddit, LinkedIn, Gizmodo and FourSquare will likely remember the lesson they learned three years ago, other sites that didn't experience any issues are likely still unaware.
The atomic time scale has revolutionized technology and stabilized the time but it is slowly drifting out of sync with our actual position in the space.
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