One would think that time was simple. But it is not.
Let’s take something as simple as a year: that’s the time it takes for the earth to orbit the sun.
The problem is that that journey takes 365 days and 6 hours – or 365.2422 days to be exact. The calendar, on the other hand, has only 365 days.
That’s why we have a “leap year” every four years where we harvest the extra hours and create an extra day.
A day is not 24 hours
Not even one day is easy.
A day is the time it takes for the earth to rotate around its axis. We call it 24 hours or 86,400 seconds.
But the terrain doesn’t take the same amount of time each time. The speed of rotation of the Earth is not uniform. Some days are shorter, while other days are longer.
In recent decades, most days have been a bit longer than 86,400 seconds.
This causes our exceptionally accurate atomic clocks, which determine Universal Time (UTC), to be out of sync with the Earth’s rotation.
What exactly is a second?
A second was originally defined as 1/86,400th part of a day.
It was based on a day with 24 hours, each of which had 60 minutes, which itself consisted of 60 seconds.
24 * 60 * 60 = 86,400
But that definition wasn’t precise enough when you really had to do things precisely.
In the 1960s it was decided to formally define a second based on the fluctuations of a cesium atomespecially caesium-133, which is very stable.
One second is defined as the time it takes for caesium-133 to complete 9,192,631,770 oscillations.
It is important that the official and hyper-accurate world time is actually correct. Much of modern computer technology, and especially that which has to do with satellites in one way or another, depends on exact time. And no less important everyone agrees about what time it is actually.
It is therefore decided that whenever the earth’s rotation (solar time) and the official time (atomic time) differ by more than 0.8 seconds, the official time must be adjusted.
Since 1972, so-called “leap seconds” have been used to make this correction. It has been done many times: Total In total, the time was adjusted by almost half a minute.
This takes place by introducing a time that does not normally exist: 23.59.60 on New Year’s Eve, to then move on to 00.00.00 on the following day. The last time this happened was in 2017.
It means you uncorked the bottle of champagne at the wrong time…
It has important consequences
But adjusting the official clock by one second is not right. The last few times this has been done it has resulted in massive outages in the world’s computer systems. Things have simply gone haywire because times have changed in ways that computer systems aren’t designed to handle.
Facebook engineers wrote earlier this year how difficult it was in practice.
Or as the standardization organization BIPM (Burau International des Pids et Mesures) writes:
– The introduction of leap seconds creates time leaps that risk leading to major failures in critical digital infrastructure, including global navigation systems, telecommunications and energy transmission.
Time passes faster, which no one thought about
A fundamental problem with leap seconds is that you don’t know when they will occur. You can’t just say you add a second every 5 years to New Years in computer systems. The rotation of the Earth is irregular and adjustment occurs when necessary. It is announced with six months notice.
Very few have experience with this, and it requires the effort of many. The change must be painless and take effect everywhere at the same time.
But that’s not all: the Earth is about to spin faster than before. Time literally goes faster.
This can lead to the next time a second needs to be adjusted, so you have to to remove a second.
This has never happened before and it worries the BIPM:
– Recent observations of the Earth’s rotation indicate the possible need for the first negative leap second, the introduction of which has never been foreseen or tested.
Facebook is equally concerned:
– The consequences of a negative leap second have never been tested on a large scale, they can have devastating effects on software, they write.
When something you’ve done many times causes problems, only your imagination can limit the possible consequences of something you’ve never tried before.
At its general meeting in early November, therefore, the BIPM GCPM group adopted what is called Resolution 4. This meant that they would work to abolish the entire leap second system by 2035 and find a system that meant that the time adjustment would not be necessary for the next 100 years.
The most likely way this will be done is that the time will not adjust until a full minute has elapsed.
Still a lot of work to do
Chief engineer Harald Hauglin, head of time and frequency at the Swedish Regulatory Agency, tells Nettavisen the decision is not final.
– Resolution 4 on the leap second adopted last week by the General Conference on Weights and Measures (CGPM) is not a final decision, but advocates increasing the maximum allowable deviation between UT1 and UT1 “standard time” by 2035 atomic clock time UTC. However, GCPM is not the only organization with a say. The current maximum value for UT1 – UTC is determined by the United Nations body ITU – the International Telecommunication Union. The ITU decided that the UT1 – UTC deviation should be no more than 0.8 seconds.
– Resolution 4 asks the International the Committee for Weights and Measures (CIPM) to further work with the ITU to determine a new, larger maximum value for UT1 – UTC and create a plan on how the new value can be used by 2035. Proposals for a new maximum value and plan for the introduction is to be presented and possibly adopted by the General Conference on Measurement and Weight in 2026. For this change to be final, the corresponding proposals must also be presented and adopted during the “general conference” of the World Radiocommunication Conference ( WRC) of the ITU, which is held every three to four years. The next WRC is in 2023. It is the National Communications Authority (Nkom) that represents Norway in the WRC, while Justervesenet represents Norway in the CGPM, he says.
If the job runs, able to whether the world has gone through its last leap second. Right now, the weather is pretty much exactly where it should be, after around 2020 the earth started spinning faster than it used to before.
– It is true that it is not relevant to have a positive leap second for a while. This is because in recent years the earth has rotated much faster than it otherwise has since the leap second system was introduced. It is the International Agency for the Rotation of the Earth (IERS) which monitors the orientation of the Earth in space. IERS provides both historical data for UT1 – UTC, but also calculations of how UT1 – UTC is thought to be up to a year ahead. There is no chance of a leap second – either positive or negative – during the next year, but if the trend of the earth rotating faster continues, a negative leap second may become relevant.