Just how old is the earth? How does one even figure it out? A guy named James Ussher decided that the best way, in 1650, was to find the actual, historical years for events noted in the Bible, using ancient history texts available at the time. The earliest event in the Bible, for which he could find some other confirmation and description, was the death of Nebuchadnezzar, King of Babylon and captor of Daniel. Then, after deciding which set of Torah books with the chronology of prophets' deaths and births, he used their ages, all the way back to Adam, from Genesis, to state that the world began on October 23, 40004 BCE. Ussher wasn't alone, but his calculations were the most famous, until the mid-20th-century.
By the twentieth century, most scientists didn't really buy that the earth was about 6,000 years old. But they had no real way of calculating how old it really is. We had rocks, many in sedimentary layers. But we couldn't use those layers to calculate age. Sedimentation could occur at almost any rate throughout the Earth's history without even giving us a clue as to what the rate was, so adding up sediment layers produced wildly conflicting numbers.
Great for tourism, not so much for math
We had rocks. We knew what elements made up rocks at differing levels and places. And we had the knowledge that certain elements are inherently unstable to the point that their nuclei actually "decay" into other elements, until the final downgrade reaches a stable element that won't change. In other words, nuclear transmutation. The most common final, stable, element is lead. Scientists spent a chunk of the early 20th century just studying the rate of transmutation, or radioactive decay, of radioactive materials, especially uranium.
So, we have rocks containing uranium decaying into lead. And we can figure out the rate of decay. But we need to know- how much lead was in uranium from the formation of the Earth? Where do we find the rocks that are clearly from the time of the Earth's formation, so we have that initial baseline? Well, we don't actually find them on Earth.
We find them in Bruce Willis movies
The earliest rocks of Earth are gone, melted down and part of the hotter sections of the planet, during the bombardment and early volcanic history of the first few hundred million years. In the early years of our star, particles of iron, oxygen, and carbon started colliding, sometimes sticking to each other. After billions of collisions, recognizable objects with significantly more mass attracted even more particles, or particle clumps. These clumps added yet more mass to each object, which eventually became the cores of our worlds. As bigger and bigger clumps of early solar system debris hit our worlds, the energy from the collisions sparked a ridiculously hot surface temp, melting down most of what was there. And subsequent additions buried it.
Early Earth. Or Mars. Something.
So, where in the solar system are rocks, surviving from the creation of the planets, with their original elements preserved? And how do we get those rocks, so we can examine the amounts of uranium and lead in them? Turns out, the very rocks we need, eventually come to us. Yep, the Asteroids between Mars and Jupiter, leftover debris circling out by the gravitational pull of our system's largest planet, sometimes fall on Earth as meteors. And we had some excellent samples from the crater at Canyon Diablo, AZ. That meteorite reached Earth about 50,000 years ago, only millenia before humanity started painting in caves. And it has a load of zircon, which contains uranium decaying into lead.
Can tell you how old the Earth is, sort of
In 1947, a Professor at the University of Chicago, Harrison Brown, hired two grad students to examine zircon from the Canyon Diablo Meteorite for both uranium and lead. George Tilton got the job of measuring the uranium, which turned out to be easy and quick. Brown gave Clair Patterson (voiced by Richard Gere) the job of measuring the lead content, which he considered so easy he told Patterson it was Duck Soup. Patterson began in 1947. It took six years.
Patterson (left) and George (right). Here, put this rock with uranium right in your hand.
Six years of working like a dog to completely eradicate all trace amounts of lead from every testing room he tried. Six years of inconstant, unreliable data on lead amounts because Patterson couldn't tell what was lead contamination of the room and equipment, and what was the lead in the zircon from the meteorite. Eventually, the project took so long, that when Harrison Brown went to Caltech, Patterson went with him. At Caltech, he boiled his equipment and tools in acid, and had to find out how to eliminate lead from every surface, every grain of air. He made the first "Clean Room", a room so sterile you can finally, accurately measure how much lead (or some other element) is truly in a substance. It took six years for Patterson to finally get the actual amount of lead in that specimen, at the Argonne National Labratory. And then, he sat down and calculated the age of the earth, knowing how much uranium and lead were really in Earth's first rocks, in 1953. He told his mother first. What a sweet boy.
Mom, looky what I can do!
So, what do you do, if you've already solved a long-standing scientific problem for the world at the age of 31? Well, if you're the world's best expert in measuring lead in trace amounts, that pretty much what you do. Everywhere. Funded by petroleum companies trying to understand the content of lead in their products, Patterson quickly found his sponsors were creating a public heath disaster.
Lead has been around since about Roman times. It's not easy to get, usually nowhere near the surface. It must be mined. The Romans found it cheap, and easy to work with (it's a very soft metal). They lined their baths and cooking pots with it, made water supply pipes with it, and even used it as a sweetener. They, like us, were well aware it is highly poisonous. Which is why only slaves actually handled it or got to ingest it. Lead, once ingested, seems a lot like zinc and iron to our cells, which bond with it and try to use it as a nutrient. But, lead can't give our cells the benefits of zinc and iron, and if we miss these two nutrients, problems follow. In addition, lead blocks neurotransmitters, interfering with memory and learning. Lead poisoning causes a wide variety of symptoms and problems, but we tend to associate it with two things: causing mental disabilities in people who ate paint chips, and petroleum workers exposed to tetraehtyllead, once used as lead in gasoline to stop the knocking sound in the engine. In 1924, 17 workers at tetraethyl plants in New Jersey died, but not before going insane, dying horribly and sometimes by jumping out a window.
In response, the ethyl industry hired Robert Kehoe to tell the public that everything was okay. They just needed some darn good self-regulations in the industry to protect workers. Which, of course, they would do. The public was just fine.
And it worked, until Clair Patterson came along. Like Scooby and the Gang, Patterson wanted to know just how much lead in the natural world was actually naturally occurring, and how much was human-related. So how do you figure that out? Lead, in the mid-20th-century, was fucking everywhere- in shoe soles, light bulbs, paint, bullets, even food cans. Patterson found that it was the level of lead content that had changed. By measuring lead content in deep ocean water compared to surface water, he found huge differences. If lead was naturally occurring, it would have been more evenly mixed, leading him to think that lead amounts in air and water were a recent change. Okay. But, how recent?
The answer was near both planet's poles. Specifically, in Arctic Ice. Nature's Clean Room, Arctic Ice and rocks have been amazingly untouched. Which makes them perfect for finding out how much lead is naturally occurring on our planet. So, he had to go to, literally, to both ends of the Earth, spending 10 hour days digging shafts. Through ice and rock. His cores, which produced rocks from before the Industrial Revolution, showed that the concentration of lead in rocks was much, much smaller before the Industrial Revolution. And the change wasn't from uranium decaying, as he could calculate how much that decay would contribute extra lead today. Patterson found that Kehoe's information, or conclusions, were both wrong. The world was being mass poisoned.
I love my job, I love my job....
His sponsors tried to fund him doing any other research, on any other topic. He refused, and became a crank. Starting in the mid-60s, he repeatedly published his findings and data on just how much lead the Industrial Revolution, and lead in car exhausts spewed into our atmosphere, affecting how much lead we breathe in and poison ourselves with. And Kehoe repeatedly attacked his credentials, and work. Patterson wasn't alone, but he may as well have been. Even while the public worried about lead poisoning, the experts employed by people using lead in everything told the public that everything was fine.
Until 1966. Patterson's work was starting to raise alarms with government health experts, who had to listen to doctors telling them there was a fucking lead poisoning problem. So, Senator Edward Muskie, Chair of the Senate Subcommittee on Air and Water Pollution, held hearings. The Surgeon General also testified, but the real conflict were the testimonies of Kehoe and Patterson. The hearing had been, oddly, scheduled for a time when Patterson was supposed to be in Antarctica, but he got there on the fifth day of hearings to tell Muskie, the sub-committee, and America that his data indicated that the industries were dumping more lead into our air, water and soil then we could handle in our bodies. Kehoe vehemently denied this, insisting that there was no such evidence, even with Patterson presenting it.
Robert Kehoe, claiming the research funded by the polluters is totally legit
It was the beginning of the end for lead in commercial products or gasoline. Patterson's work laid the foundation for getting lead not just out of our air, water and land, but also out of ourselves. In 1978, Patterson received the recognition he deserved, and National Research Council appointment. And his legacy is the good news that lead levels in people have gone down significantly.
What someone says may depend on where his or her paycheck comes from, shielding bad news from the public for a while. But Nature cannot be fooled. And, if we can understand nature, we can avoid being fooled, too.
I just wanted to show this goofy picture of Tyson.
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