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30 January 2004

Time Machines

by Forrest M. Mims III

Recently a thoughtful young man asked me if it's possible to build a time machine to go back in time.

Of course, I replied. In fact, we don't have to build a time machine. We're surrounded by them. The young man looked a bit surprised, so I began describing some of the time machines in our lives.

A camera is a time machine.

Old photographs of friends and family members are as good as a time machine gets. This is especially so when someone in a photograph is no longer with us. Consider a photograph of a colorful flower that long ago returned to the soil to nourish the next generation. Isn't that a time machine? If still photographs don't meet your time machine expectations, movies and videos of friends and family will. Today's generation of compact video cameras are the fanciest time machines technology can provide.

This cricket is frozen in time inside a lump of amber. Photograph by Forrest M. Mims III. Click image to enlarge.

Nature has many examples of time machines. Consider fossils. On my desk is a nodule of golden amber from the Dominican Republic. It resembles a polished piece of plastic more than fossilized sap that once oozed from an ancient tree. Inside this piece of amber a cricket is frozen in time. Its jumping legs are extended, and its wings are open. It appears to be flying through the amber in which it is entombed.

The cricket was captured when it made the mistake of landing on the soft sap. Trapped by the sticky stuff, it was soon encapsulated by the flowing sap. Thus, amber is a time machine. So are all other fossils. Light is a time machine. That's because light travels only 186,000 miles per second. Because the Sun is around 96 million miles from Earth, sunlight requires nearly nine minutes to reach us. The nearest star other than our Sun is Alpha Centauri, which is actually a small cluster of stars. Alpha Centauri may be close by astronomical standards, but its light requires four years and four months to reach us! That's enough time to get a college degree.

Trees are time machines. Saw into a pine or cedar elm log and you will find very nicely defined rings. Each ring marks a year of growth. Tree rings can reveal to the exact year long ago droughts, floods and even fires.

Computer memories are time machines. So are tape recordings, diaries, books, old newspaper clippings, birth and marriage certificates, high school and college diplomas, year books and a host of other things. But the ultimate time machine is behind your eyes. It's your brain. No other time machine can record the aroma of freshly cut hay, the feeling of accomplishment when you learned to swim and all the powerful emotions we all experience.

All this and more is why I told that young man that we're surrounded by time machines.

Forrest M. Mims III and his science are featured online at www.forrestmims.org.

This feature was originally published in Forrest Mims's weekly science column in the Seguin Gazette-Enterprise, Seguin, Texas. The column is written for a general audience.