Upon opening my newspaper one morning last month, I found a front-page photograph that put a big smile on my face. Science students at Springdale’s Lakeside Junior High were shown chalking 460 meters of sidewalk with figures representing 4.6 billion years of Earth’s history, with each meter symbolizing 10 million years. It’s hard to think of any project better geared than this one to fi ll a yawning gap in American education. Scientists know a lot about Earth’s long history, but we don’t teach this vital and inspiring information in many history and science courses. We need to know our roots.
Rather than beginning with ancient Egypt 5,000 years ago or agriculture 10,000 years ago, public school and college world history courses should begin when humans split oft from the other great apes 7 million years ago or, better yet, with the origin of our planet 4.6 billion years ago. Science education should also tell this story with supporting evidence.
A web search yields a wide variety of geological time scale projects. One of the largest stretches from Los Angeles to New York City, 4,500 miles, with each mile representing a millionyears. It was of course only “minds on” and not “hands on” like the Lakeside project. The oldest rocks, 4 billion years old, occur around Flagstaft, Ariz. Life began shortly thereafter, but the Cambrian explosion of multicellular life doesn’t occur until Pittsburgh, a mere 550 million years ago.
Dinosaurs appear in Philadelphia 245 million years ago and die in Trenton, N.J., 65 million years ago. The earliest humans appear seven miles out from New York, modern homo sapiens at 350 yards out, the Egyptian civilization at 25 feet out and the 21st century at 0.8 inches out.
The project works in the classroom with one millimeter representing one million years on a 4.6-meter timeline. But at this scale, modern humans are barely noticeable, appearing in the last 0.2 millimeter. A longer timeline of 46 meters might be feasible in a school hallway. Modern humans then get two millimeters.
It’s essential to emphasize the evidence. The distinguishing feature ofour age is science, and its distinguishing feature is we learn through evidence and reason. Scientifi c knowledge comes not from ancient manuscripts, tradition, authority, beliefs or your daddy’s opinion.
Here’s some evidence.
Astronomers know, from studying star-forming regions in our galaxy and computer simulations, our solar system was born from a gas cloud that collapsed gravitationally. Radioactive dating of ancient meteorites shows Earth emerged4.6 billion years ago. Life began 3.8 billion years ago as shown by the earliest chemical evidence. Radioactive dating provides these ages. Because all life on Earth is related chemically, it probably originated from a single source. Numerous origin-of-life experiments, beginning from early-Earth ingredients, show how the building blocks of life can form by “chemical evolution.”
Life comprised only single-celled organisms until a billion years ago. Animportant event leading to multicellular organisms was the formation of atmospheric oxygen that provided the metabolic energy to allow organisms to proliferate during the Cambrian explosion.
Fossil remains tell us dinosaurs and mammals appeared at about the same time, 225 million years ago. An asteroid impact 66 million years ago made nearly all dinosaurs (except birds) extinct, as we know from the crater found on the Gulf of Mexico seabed.
A thin layer of iridium, common in asteroids, has been identified at some 100 locations around the world at a depth corresponding to 66 million years ago.
Fossils show tree-living mammals including lemurs and monkeys evolved 75 million years ago.
Apes “split oft” from the monkeys 25 million years ago. About 7 million years ago a new type of ape evolved that came down from the trees to stand on two feet. There have been more than 20 two-footed species similar to us forming a clear evolutionary line to modern homo sapiens. Several of these species endured far longer than the 200,000 years we have so far survived.
Whether we will prosper for millennia in the future is up to us to decide. If we can learn to use our spectacular achievements in science and technology wisely, then our prospects are good. If we cannot base our conclusions on evidence and reason, then the outlook is for collapse of our species by violence, global warming or any number of other humancaused disasters.
If you teach science or history, I urge you to consider a geological time scale project for your class.
ART HOBSON IS A PROFESSOR EMERITUS OF PHYSICS AT THE UNIVERSITY OF ARKANSAS.
Opinion, Pages 11 on 01/12/2014