I was not even a thought in the 1970s, but I've heard it was a pretty good time to be a rock. People took you as their pets, and I'll bet Professor Lawrence Edwards had a couple Pet Rocks back in the day.
Courtesy Wikimedia Commons
You see, Edwards is an isotope geochemist, which sounds just about as awesome as it is: he studies the teeny tiny radioactive elements in rocks. These elements help Edwards date rocks. No, that doesn't mean he wines and dines them. Quite the opposite! Edwards developed a sneaky way to figure out how old they are (and let me tell you, nobody wants to be reminded of their age when they're hundreds of thousands of years old).
Edwards' method is similar to carbon-14 dating, only way better. In certain kinds of rocks, Edwards can date rocks as old as 500,000 years compared to carbon-14's measly 50,000 years. That's a whole order of magnitude older! Here's how Edwards' method works: Scientists know that half of any quantity of uranium decays into thorium every 245,500 years. Edwards uses a mass spectrometer to measure the ratio of two radioactive elements -- uranium and thorium. Then, Edwards compares the present ratio of uranium to thorium to what scientists would expect from the half-life decay and bada-bing, bada-boom! Simply genius.
Why am I getting all hyped up over some old rocks? Because they're helping us learn more about ourselves and the tenuous place we hold in this world. For example, Edwards has used his super-special method to trace the strength of monsoon seasons in China. Turns out weak monsoon seasons correlate with the fall of several historical dynasties, and strong monsoons correlate with climatic warming in Europe. Edwards calls this work,
"the best-dated climate record covering this time period."