BY TOM SNEDDON, P.GEOL.
BY TOM SNEDDON, P.GEOL.
APEGGA Manager, Geoscience Affairs
Like all geoscientists, I am obsessed with time. It makes perfect sense, then, that one of my favourite novels is Douglas Adams’ Restaurant at the End of the Universe.
We geo folks rarely care much about the end of the universe, but we sure use up the clock considering conditions at its beginning. Since we do a lot of worrying about what came first, we intuitively think of now as the end of time, which by definition it is.
A thing that separates us from the engineers is their preoccupation and worry about the future. They’re thinking
Will the bridge fall down in 15 years?
What will be the maximum probable flood?
How many cars will pass by in five, 10 and 15 years?
What is the maximum live load?
And so on.
We of the geoscience persuasion are preoccupied with and worry about the past.
What is the first arrival time?
When was it laid down?
What is the arrival time of this event?
When did the last magnetic reversal occur?
How long has it been since the time clock in this zircon crystal was reset?
And thus it goes.
About 30 years ago, I had the privilege of hearing Rear Admiral Grace Hopper, the mother of the digital computer, talk about time intervals. Her presentation made a lasting impression.
When she was assigned by the U.S. Navy to the Harvard Mark I team, Dr. Hopper said, she found everyone talking about milliseconds, nanoseconds and seconds, on top of all the usual computer jargon. She knew what a second was, but she realized she had little understanding of their tiny brethren.
Being a sound professional, she set out to conceptualize that which she did not know.
In a thought experiment, she could see an electron drifting along a copper wire. The electron would move with the speed of light through a vacuum, and somewhat slower along a real substance.
She started with the microsecond and calculated the distance travelled to be about one foot (sorry about the old-speak measure — Grace was from a previous generation). During her public appearances, she would actually produce a foot of copper wire from her uniform pocket. A nanosecond would clearly be 1/1000th of a foot or about the size of a grain of pepper, so out came a baggie, a grain of pepper inside it.
Dr. Hopper apologized for not having a millisecond to show, since a millisecond would then be 1,000 times longer than a microsecond or nearly 1,000 feet — a quantity of copper just a bit too large for a lady of 70 to carry on an airliner.
Geoscientists often have to explain their time units to the curious but uninitiated. Like Grace Hopper, everyone can understand the concepts of year and decade without much of a mind stretch. Century has meaning to those of us who have been through half of one, and even millennium can be conceptualized, sort of. A million years and ten million years are beyond most people and a billion years is unfathomable.
As we cognoscenti know, it is easy for the public to confuse the time of dinosaurs with that of early humans and Pleistocene sabre-toothed cats — despite a 90-million-year separation. Timelines help put things in the right sequence, but they’re as tough to pull from your pocket in correct scale as Grace Hopper’s millisecond.
To complicate matters, we also know that the models we use to make sense out of geophysical and geological data have scale problems for us, let alone the rest of the public. Geological processes work at all time scales and the laws of geophysics are taught as dimensionless entities for good reason (remember tau, the time surrogate?).
Geological processes are also independent of physical materials. You can build a real-time delta in a wheel barrow using a garden hose, glass beads and dirt from your garden or you can use the efflux from the Brahmaputra River — both demonstrate the same features.
The remarkable images from the Huygens probe landing on Titan in 2005 show startlingly familiar landscapes derived from methane. These are another example of the universality of the laws of erosion and sedimentation.
Seismic stratigraphy, which begat sequence stratigraphy, established the principles of interpretation that can be applied to ground penetrating radar. In the seismic game we work in milliseconds/hundreds of metres, and in GPR interpretation we work in microseconds/metres, but the rules are the same.
Similarly, in seismic practice we normally measure the thickness and derive the physical properties of rock laid down over millions of years. In GPR, we measure the thickness and physical properties of materials like municipal solid waste or other traces of human activity laid down over periods from decades to centuries.
So there you have it. We geoscientists are different from other, more normal people because we use our imaginations to extend a few basic time/space/material independent principles to a wide range of issues, problems and opportunities. In the process, we develop new skills and technologies that work to society’s benefit.
Think about it: there are about 4,500 geoscientists and technologists (OK, maybe 5,000) that keep 35 million Canadians warm and their houses lit, across the second largest landmass in the world. Oh yes, and they keep a lot of Canadians gainfully employed as well.
Not bad for a group of people obses-sed with time and in love with rocks.