2016, which has been dubbed by many as “the worst year ever,” has a leap second on its last day. That means the year 2016, which for many has been a tough year, is longer by 1 second. But why?
Well, it has to do with our human desire to impose a simple order into a chaotic cosmos.
Here’s the gist. An extra second will be added to Dec. 31, 2016 so that the time in our modern clocks will reflect the cycles of the seasons. We want a clock set in a way that when it reads noon, the sun is near its highest point in the sky. A leap second was also added on June 30, 2015.
Almost all clocks we use in modern life follow the system of time called the Coordinated Universal Time. The clocks on your computers and smartphones are synchronized with UTC. Your local time is derived from it. For example, Philippine Standard Time is UTC plus 8 hours.
It is difficult to overstate the importance of UTC. For one, it allows people, and computers, from different time zones to communicate with each other using a time they all agree on. It is used in global financial transactions and on the internet to provide time stamps. Important events such as the arrival of shipments in a port and the landing and taking off of planes in a busy airport are all scheduled in UTC. Even the Global Positioning System many of us have become dependent on utilizes UTC. It is the clock by which modern civilization ticks, which is why it’s important that it ticks at a very regular pace.
Ever since humans tried keeping the time, we have been searching for things that happen with predictable regularity. The most obvious ones are the cycles in the sky. The sun rises and sets with some regularity, giving us day and night. However, this regularity is not perfect. Sometimes, the day is longer than the night; at other times it’s the opposite.
So people looked at other, longer cycles. For instance, there was one day in the year that was longer than any other. During this day, sunrise happens earlier than on any other day, and sunrise happens later than on any other day. This day was called the summer solstice. The time from one solstice to another was made the basis of a year.
With a year defined, all that’s left is to do is divide it into months, weeks, days, hours, and seconds. Only there were problems.
The biggest was that the seasons drifted across the calendar. This meant that the arrival of a season, say the rainy season, is bound to move across the calendar. If not corrected, there will come a time when summer will be on December. People found that undesirable.
To prevent this drifting, extra days were added now and again. Leap years were invented. Years divisible by four are made leap years and are given 366 days instead of the usual 365. However, years divisible by 100 were not leap years, except those divisible by 400, because those are leap years.
This complicated scheme still does not solve all of the problems, but for a while it seemed good enough. Until we hit another problem—the length of the same day in the year was changing. April 1 in one year seemed to be just a little longer than April 1 of the previous year. The spin of the Earth, it seems, is slowing down. Another way of defining how long a day is had to be invented.
Enter the atomic clock, a clock that ticked with a simpler regularity that did not care for the complexities of the seasonal salsa and the celestial rumba. If we defined a second using this clock, we have defined a unit of time that remained constant throughout history. Add 8640 of these seconds, you get a day.
The atomic clock was the clock for the 21st century. It kept time in a way that was stable enough to form the basis of the modern world.
Except this precise clock did not reflect the cycles people lived by. That had to change; people want to have their cake and eat it, too.
It was out of this desire to have a system of time that was both stable and synchronized with cycles of the seasons and the sun that the UTC was invented. But for it to work, extra seconds have to be added now and again.
However, the addition of the next leap second is very hard to predict. It is a hidden messiness that makes the semblance of order possible, a token of the human desire to establish a simple order in a chaotic cosmos.
I hope you enjoy your extra second of 2016.
Pecier Decierdo is resident physicist and astronomer of The Mind Museum.