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Why Do We Have Leap Years?
Leap years have been around for a long time.
Leap years are a thing. But why do we need to add a day to the calendar every few years? The simple answer is a calendar year does not equal the amount of time it takes for Earth to make one full trip around the Sun. But why? Well, keep reading to find out!
Calendars have never been correct.
Every calendar ever made has been inaccurate. Some scientists think calendars were first used by people as far back as 20,000 years ago. From that time until today, there have been attempts to correct calendars. Different cultures have tried to create better calendars.
Early Hebrew, Chinese, and Buddhist calendars added entire months. This is because they were based on the Moon’s orbit of Earth and the phases of the moon. While logical, the Moon’s orbit of Earth and Earth’s orbit of the Sun don’t match up.
The Romans got close, but they lacked the technology to accurately measure the true length of a day or the exact orbit of Earth. Then there is the whole thing where a month was added to honor Caesars: Julius, July; Augustine, August… That is why October, with oct referring to eight, is actually the tenth month. But even Caesar knew to add an extra day every four years.
Fun Fact: People born on Leap Day are known as Leaplings.
We should just fix calendars, right?
Ideally, yes, we have the technology to accurately measure the time it takes Earth to orbit the Sun. We know exactly how long it takes for Earth to make one full rotation. But it’s easier to add a day every so often than it is to change calendars and clocks.
Also, even though the calendar is off, it really isn’t off by much. And the amount it is off by is not enough to redo the whole system. What we do works. And it’s worked since Julius Caesar first added a leap day in 46 BCE.
It’s not just a day.
Leap days help to account for the orbit of Earth taking 365.25 days to make it around the Sun. But days are based on the rotation of Earth on its axis. And that has actually changed. Ancient astronomers calculated the length of a day rather accurately. However, the rotation of Earth isn’t constant; it has slowed.
This might not seem like a big deal. And for most people, it isn’t important. But for computers, specifically the ones that run satellites, every second counts. From television to GPS, satellites need to be precisely located. Scientists figure this out by tracking time. If that time gets off, even by a second, it could make the satellite useless. So, on December 31, 2016, a second was added to the clock.
Time is important.
Time is more than just a made-up thing. Tracking time allows us to know where to be and when. It keeps satellites in orbit and computers running on Earth. Time is part of physics if you want to study time when you grow up. And time is part of everything we do.