by Shane L. Larson
61 seconds is all it takes For the 9 to 5 man to be more than one minute late
So goes the song “61 Seconds” on the 1985 debut album Play Deep, from the British rock band The Outfield. Thirteen times since the release of Play Deep (12 Nov 1985), we humans have added “leap seconds” to our timekeeping, endeavouring as much as possible to keep our continuous record of time aligned with some Cosmic measure of time. In those moments, we had 61 seconds in the “minute.” On the last day of 2016, we will once again add a second to our accounting of time — at 6:59:59 pm EST (that’s 23:59:59 UTC, for all you time nerds out there), a special leap second will be added. For that one moment, we will all live through 6:59:60 pm EDT (23:59:60 UTC) before the time rolls over to 7:00:00 EDT (00:00:00 UTC). An extra second of revelry on New Year’s Eve, 2016.The fundamental reason for the leap second is this: all of our timekeeping is based on repeatable events. Currently, one second (according to us humans) passes for every 9,192,631,770 radiative oscillations of a cesium-133 atom. Originally, however, the second was defined by Persian scholar al-Biruni as 1/86,400 of a solar day, where a solar day is the time it takes the Sun to return to the same meridian on the sky (typically the line from due north to due south). Our innate sense of time, the basis for our calendars and watches and smartphones, is this one that al-Biruni used. But here’s the rub — the solar day is not constant, because the spin of the Earth changes over time.
There are a variety of reasons for why the spin of the Earth is slowly evolving. One is the sloshing of the Earth’s oceans due to the rising and falling of the ocean tides. This is caused by the gravitational influence of the Moon on the Earth. What we observe as rising and falling tides are actually bulges of water created by the Moon. As the solid part of the Earth rotates, it turns under and through these bulges, which resist the spin of the Earth in the same way water resists you trying to push your hand through it. The net result is some of the Earth’s spin is taken away. Other geophysical processes are at work too, including the rebound of the crust since the recession of the ice sheets from the last glacial maximum, the redistribution of water with seasons and long term climate change, crustal displacement from large earthquakes, and so on. The effects are all small, some work together to slow down the Earth, and some work to speed up the Earth. But the net result is this: the actual spin of the Earth is about 0.8 milliseconds (8 ten-thousands of a second) longer than the 86,400 second long days we define with our clocks.
So over time, the spin of the Earth falls behind our clocks, which run ahead a little more every single day. By adding a “leap second”, we are pausing, waiting for the Earth’s spin to catch up. All things being equal, you and I may not notice. Some computers may flip out (they have in the past when we’ve added leap seconds), but largely I expect most of us will continue sipping our beverages as the Sun goes down, waiting for for 2016 to slip into the past and 2017 to arrive. The leap second will pass by, and we might not even stop to notice.
But yesterday I was thumbing through a book of mine, and it made me stop to think about that leap second a little harder. The San Francisco Writers’ Grotto has published a fantastic book of writing prompts designed to provide a bit of creative fodder for you to practice the craft of writing. The very first prompt is this: What can happen in a second?
It’s an interesting thought to ponder. Every now and then, we have one extra second to live through (by our reckoning). What could the Universe do with that one extra second? The answer: amazing things! There are, of course, far too many awesome things that the Cosmos could do, but here are just a few to get you thinking…
• You. Many of the cells in your body are in a constant state of growth and regeneration. To make new cells, your body creates copies of existing cells through a process called “cell division.” In order for this process to proceed, it has to replicate a copy of the genetic material in your cell, which is stored in the long strands of DNA. All told, a human strand of DNA has about 3 billion molecular base pairs — the building blocks of the DNA ladder. If you could stretch a strand out straight, every strand of DNA would be about 2 meters long. The doesn’t sound very long, until you remember that it is all squished inside a cell, which is too small for your eye to see! So suppose your cell is duplicating this DNA strand — molecular machines crawl along the DNA strand, reading it out and making a copy. How many base pairs can it read in 1 second? About 50. If you do some quick math, 3 billion base pairs divided by 50 pairs per second means it should take about 694 days for your body to replicate a single strand of DNA! It doesn’t take this long though, because the replication process involves an entire workforce working on reading out different parts of the DNA in tandem; all told, it takes about one hour to complete the replication process — so in 1 second, the teamwork of all the molecular machines working the strand copies about 830,000 base pairs EVERY SECOND. Is that a lot? If each base pair were like a letter in your genetic alphabet, 830,000 letters is roughly the number of letters in a 600 page novel.
• The Sun is ultimately the source for most of the energy on Earth. It’s energy is released from nuclear fusion deep in its core, where it burns 600 million TONS of hydrogen into helium every second, releasing energy that eventually makes its way to the surface, making the Sun luminous. At that rate, it will burn a mass of hydrogen equal to the mass of the entire Earth in 70,000 years.
• Suppose you use your leap second to shine a laser beam at the Moon. The beam travels at the speed of light, the ultimate speed limit in the Cosmos. It will almost reach the Moon by the time the leap second is over, but will fall just short by about 56,000 miles. It took Apollo astronauts about 4 days to cross the empty gulf between the Earth and the Moon.
• Every second of every day, 4 or 5 babies are born on Earth. About 2 people die at the same time. The population of our small world is growing, even during our extra leap second.
• If you are cruising down the freeway, heading to a New Year’s Eve celebration with your partner or friends, and are travelling at 70 miles per hour (112.6 kilometers per hour), then in a single second you travel 31.3 meters (102 feet and 8 inches). That extra second on the clock gains you an extra hundred feet in your journey.
• You are almost certainly reading this post right now on a mobile device or computer, connected to the vast electronic storehouse of human knowledge called “the Internet.” It is hard to quantify the amount of information on the internet, or what is going on globally at any instant in any kind of meaningful snapshot, but there are Internet Live Stats to give you a sense of the tremendous amount of activity that is jetting electronically around the world. In one second, almost 41,000 GB of data are transferred. That sounds like a lot of information, and it is. Neurologists estimate your brain’s memory capacity to be about one to two million gigabytes — 1 second of time on the internet is roughly 4% of your total brain capacity.
• Like the Moon orbits the Earth, the Earth orbits the Sun, and the Sun orbits the center of the Milky Way. On its journey around the Sun, the Earth is travelling at roughly 108,000 kilometers per hour. In one second, we all travel 30 kilometers farther around the Sun. By contrast, the Sun itself is travelling at about 828,000 kilometers per hour, completing its orbit of the galaxy every quarter billion years. In just one second, you complete 230 kilometers of that journey. When the clocks stall for our leap second on New Year’s Eve, we’ll make it that much farther around our galactic circuit.
• In one second, every 100 Watt light bulb left on in your house, whether you are using it or not, uses 100 Joules of energy. At current electrical energy rates in the United States (about 12 cents per kilowatt hour), that’s less than 1/1000th of a penny, so it doesn’t seem like a lot of energy. Is it? This is about the same amount of energy as a 9-inch cast iron skillet dropped on your head from a height of 33 feet (don’t look up — it’s going to hurt real bad when it hits you, because this is a LOT of energy…). Coincidentally, this is roughly the same amount of energy expended by your metabolism to keep you alive, every second of every day — you are the energy equivalent of a 100 Watt lightbulb.
• A resting human heart will beat just more than once per second (somewhat less than that, if you’re in great athletic shape). By contrast your cat has a heart rate roughly twice that of a human; in the extra leap second, your cat’s heart will beat twice. Dog heart rates vary by size; smaller dogs have rates like cats, bigger dogs have rates like humans. But everyone will get some extra beats in during the leap second.
• Speedcubing is a competitive sport to solve Rubik’s Cube type puzzles in as short a time as possible. To date, there are only 3 successful solves of a classic 3x3x3 cube in less than 5 seconds by a human: Lucas Etter (4.90 sec in 2015), Mats Valk (4.74 sec in 2016) and Feliks Zemdegs (4.73 sec in 2016). Etter and Valk each solved the cube in about 40 turns — just over 8 face turns every second. Zemdegs made 43 turns, a blistering 9 turns per second to capture the world record. Speedcubing is a sport where a leap second is almost an eternity… The current world record held by a robot is just 0.887 seconds — the machines don’t even need a full leap second to solve a Rubik’s Cube…
The list could, of course, go on. You may find it entertaining to think about things that interest you, or ponder things you notice in your life. Ask yourself: what could that extra second be useful for? But after you’ve enjoyed the leap second, sit back in your party hat and puff on your kazoo, and think about the following: time is a real thing. It is clear from the goings on of the Universe around us that time is marching steadily onward; physicists call the evidence of this inexorable stream of time the “Arrows of Time.” But the accounting of time — the division of units of time into units called seconds, and the enumeration of those seconds as they count our way steadily toward tomorrow, are a purely human invention. The Cosmos does not care that there is an extra “leap second” in 2016, not any more than it cares that there is a year called 2016 on some backward blue planet in some forgotten corner of a single small galaxy amidst the 500 billion galaxies that fill the Universe.
The invention of timekeeping, and the invention of the year, and the hour, and the minute, and the second — those are human constructs made with a single purpose in mind: to help us understand the Cosmos around us. These constructs of time are the manifestation of our ability to reason things out, a representation of our ability to consider ideas both complex and abstract and describe and represent them in so simple and understandable of a way that every child, woman and man on the planet can carry a device to tell them how the seconds are passing us by. Which makes me think: it takes about 1 second for me to glance at my watch or smartphone and process what I see. I can waste my extra leap second this year checking the time… 🙂
Happy New Year, everyone. Enjoy your leap second; I’ll see you back here in 2017.