Once in awhile, you’ll learn a tidbit of science and say to yourself: “D’oh! It makes perfect sense! Why didn’t I think of that?” Such is the most important clue telling us Earth’s exact age.
One of war’s legacies is the technology of weaponry. Sonar is the method of bouncing sound waves off underwater entities to determine their distance from the sound’s source. In WW2, the technology became the best way to locate innovative German weaponry: submarines. Sonar quickly advanced to a technology far better at mapping ocean floors than anything previously. After the war, scientists sailed the seas with sonar devices.
Plate tectonics had been something of an arcane theory before the mid-20th century. What sonar-sporting scientists learned about ocean floors after WW2 supported the theory. In the 1950s and following decades, plate tectonics became accepted science. Put simply, the theory states that Earth’s surface is made up of hard, crusty pieces—plates—that float on the liquid rock below them. The plates move around, bang into each other, spread apart from each other, creep from north to sound and back again.
When plates collide, one is forced over the other. Rock from the bottom plate is recycled into Earth’s mantle. Over billions of years, little to no of Earth’s original crust remains on its surface. And how would geologists know where to look for it? These facts made determining Earth’s true age very difficult indeed.
Astrophysicists explain how the universe formed. They discovered how our solar system was created—the inner rocky planets, the outer gaseous planets, and among them, asteroids and meteoroids. Our solar system formed in a continuous chain of events.
Since the beginning of human history, we have observed rocks falling from the sky. When these meteorites fall in a place like the sandy void of the Sahara Desert, they easily stand out. We are reasonably sure they are in fact meteorites.
And here’s the “D’oh!” moment. Let’s assume those meteorites formed at the same time as Earth. If we know their age, we also know Earth’s age. Of course. Meteorites are solid pieces of evidence that tell us Earth is 4.567 billion years old.
Elizabeth G Fagan is a writer and artist who resides in southeastern Wisconsin—a place she calls Lake Michigan’s Left Coast. She started writing and taking photographs while attending The Hammonasset School, a private arts high school in Connecticut. Fagan has a BA in English from Grinnell College (Grinnell, Iowa) and the University of Illinois, Chicago (UIC). She has an MA in Linguistics from UIC; she specialized in teaching English as a second language (ESL). She returned to college when she earned an associate degree in Web Development from DePaul University (Chicago).
Fagan is passionate about the natural world and its creatures. She highly recommends the work of Chicago-based nature photographer Mark Swanson.
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