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June 14, 2006
Measuring Time
In previous challenges, we looked at how we experience time ("What's Time to You?"), the idea of traveling through time ("Time Travel"), and some famous science fiction stories about time ("Time Travel" and "Time for Science Fiction"). In all of this, time itself was taken for granted. A second is a second, right? A clock is a clock.
Not really.
Anyone can make a rough estimate of the time by checking the position of the sun in the sky. More precise measurements involve the use of science and technology to make clocks. Clocks themselves have changed over the years, becoming more and more accurate. But what exactly are they measuring?
 | What do clocks really tell us? | |
The second used to be defined as 1/86,400 the length of an average day, determined by when the sun set. In other words, by the rotation of Earth. But Earth's rotation keeps changing. How much has it changed so far? One hundred and fifty million years ago, our "day" was only 22 hours long. Or rather a dinosaur's day. Cool fact, but this makes Earth's rotation a problem for clockmakers.
Enter the atomic clock. It uses the vibrations of certain atoms as the fundamental measure of time. These vibrations give us a very stable second. Great—but. We measure time to help us do things on Earth. These clocks provide a measurement of time that's more precise than the planet itself, which is always changing just that little bit. Left alone, eventually these clocks would say it was noon, but the sun would no longer be directly overhead. Adding time during leap years is one way to keep the time and Earth in sync. Scientists responsible for international time standards are now busy deciding if 2006 will need an extra second. For more, see the article "To Leap or Not to Leap" at http://www.sciencenews.org/articles/20060422/bob8.asp .
It's enough to make your head spin.
Which is a good thing, for a science fiction writer, because we're always looking at how technology and science might affect our everyday lives. It's time to let your imagination take a turn.
Challenge: Time Trouble!
Science fiction writers start with a "what if . . ." question about science to explore in their stories. Here are some for you to think about.
- What if Earth's rotation had become faster instead of slower over the last 150 million years? (Hint: A day would be 22 hours long now.) How old would you be in years?
- What if every government picked its own way to define a second? What problems could this cause?
- Very precise measurements of time are affected by gravity. Clocks on mountaintops, for example, run slightly faster than those at lower elevations. What if a time capsule containing a clock were left on a mountaintop, to be opened in 10,000 years? Would the time on that clock be ahead or behind a clock left at the base of the mountain?
- Many people use their cell phones as clocks. What if one cell phone company accidentally added a leap hour to the time, instead of a leap second?
- What if the only way to tell time on Mars or the moon is to use where the sun is in the sky? How might this affect communication with Earth?
Going Further
Choose one (or more) of the "what if. . ." ideas about time and its measurement listed above, or come up with one of your own. Write a short story or poem to explore the idea for yourself. You could do something funny or serious.
If you wish, send your story or poem to us at scifizone@snkids.com. If we use yours, you may be eligible to win a prize! Please include your first name, age, city or town, and state. If you are under 13 years old, get your parent's permission to write to us.
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