Cosmos Recap: How Calculating The Age Of The Earth Saved Us From Lead Poisoning

Seven weeks into the Great Cosmos Reboot -- the halfway point, yay! -- and Neil deGrasse Tyson is still insisting that science is real. What is with this guy? This week's episode, "The Clean Room," starts off with some pretty blatant science-based hatemongering toward creationists, if by "hatemongering" you mean "explaining why they're wrong." After a brief animated teaser about how Clair "Pat" Patterson's research into the true age of the Earth eventually led him to start seeing the potential for sickness all around him, Tyson says that to really understand Patterson' work, you need to start at the beginning -- of the Solar System, that is. Thankfully, there will be some parts where he summarizes.

The problem with sussing out the actual age of our planet is that it had a pretty violent past, what with all the collisions with other orbiting bodies, the molten surface being bombarded by constant new arrivals of asteroids, and so on: Nothing solid remains from those melty crashy times. "So, with all its birth and early childhood records erased, how could we ever hope to know with any certainty the true age of our world?" And then we get the famous story of Archbishop James Ussher of Ireland, who managed to calculate all the "begats" between the time of Creation and the death of Nebuchadnezzar in 562 BC, and figured that God created the Earth on Saturday, October 22, 4004 BC, around 6 PM.

Because he is a godless heathen, Tyson does not accept this perfectly reasonable scientific method, however, so he jaunts off to the rim of the Grand Canyon, where he would have us believe layers of sediment accumulated and have been eroded for "millions of years," even though he was plainly not even there to see it. And then, just to be a smartass, he goes all Rock-Magneto on the layers of sandstone, using CGI to show us what they'd look like if they weren't compressed by those alleged millions of years of pressure. So if you want to estimate the age of the Earth, just figure out how long each layer of rock took to form, and count up the layers like tree rings, right? Sadly, no, since sediment accumulated at different rates all over the world; usually very slowly, perhaps a foot of sediment per thousand years, but "when there's a rare catastrophic flood, it can happen much faster — as much as a foot in just a few days."

And that, dear readers, is Tyson's only nod to young-earth creationists, who insist that the entire Grand Canyon was formed during the single year of the Great Flood, while Noah was floating around. But it's not really much of a nod, as creationist geology is clearly disproven by the Grand Canyon itself. But it was nice of Tyson to keep them in mind. Adding up layers from different regions around the world also gives you wildly different estimates of the age, and of course, doesn't even take you down to a "first" layer, since the Earth's earliest surfaces are all gone anyway.

So how do you figure out the Earth's real age? Simple! Go find some leftovers from the formation of the solar system, like maybe a nice meteorite: a lump of space debris from that formed around the same time as Earth, got bonked out of the asteroid belt, and ended up here. Nice shot of Meteor Crater in Arizona, which is where a big ol' meteorite plunked down some 50,000 years ago. All you have to do is figure out how much of the trace uranium in a meteorite has decayed into lead — and if you think we're going to summarize radiometric dating here, you are quite the optimist. Go read the wiki, which we would only crib from anyway, or better yet, go read P.Z. Myers's "Dear Emma B." column, which pretty much should be the last thing anyone has to say to the "Were you there?" crowd — but won't be.

And now, on to the narrative that's the real meat of the episode, Clair Patterson's work on detecting minute amounts of lead — the leftovers from the decay of uranium — in grains of zircon. Simple! Only one problem: while the zircon had a consistent amount of uranium in it, the lead content in the same samples varied wildly, which suggested that the samples were contaminated by lead in the environment. And after two years of attempting to clean his lab, the samples were still full of lead. Animated Clair Patterson, voiced by Richard Gere, exclaims in frustration, "Duck soup my ass!" which would look pretty awesome on a t-shirt. Finally, Patterson ended up at Caltech, where he could build a clean room from the ground up — no outside air gets in, purification systems keep contaminants out, and hurrah — suddenly it's easy, using a mass spectrometer, to count uranium and lead atoms in samples from meteorites, calculate the decay, and zowie — the Earth is 4.5 billion years old. There's a lovely sequence showing Patterson mentally thanking all the scientists whose work led to the discovery — and then driving to tell his mom first.

After a commercial break, we're suddenly off to ancient Rome, to learn about the Romans' experience with lead. Even though they knew lead was poisonous, they mined the stuff like crazy, lined their aqueducts and cooking pots and baths with it, and even used it to make bitter wine more palatable. Hey, it was poisonous, but it was useful. Gosh, Neil, are you making a point here? JUST MAYBE.

We get a CGI visualization of what lead does inside the body — bonding to cells like normal metals, but leaving cells unable to function correctly. And worse, it's a neurotoxin, interfering with the brain's neurotransmitters. Nasty, nasty stuff. So naturally enough, the very next sequence looks at how the makers of lead-based paint marketed their product to families with children in the 1920s. Next, the exciting story of tetraethyl lead, which made a dandy anti-knock compound for cars, with the tiny drawback that sometimes the people who worked with the stuff would go insane and die. (Animation shows a worker plunging out a window, and yes, there is a Wilhelm Scream. ) Happily, the Ethyl Corporation and General Motors found a legitimate scientist, Robert Kehoe, a Cincinnati doctor, to write reassuring papers arguing that lead was a naturally occurring trace element, and that it was nothing to worry about.

Enter Clair Patterson, part two: as a bona fide expert on lead, he received funding from the American Petroleum Institute to measure lead concentrations in the oceans, and he got another puzzling result: there was relatively little lead in samples from the deepest parts of the ocean, but concentrations near the surface were hundreds of times greater. Time to do some science — so I paused the DVR and said to Kid Zoom, "Well, there's only one explanation for that…" to which he shot back, "My god. Lead learned to float." He's going to go a long way, I think.

And so, considering how long it takes water at the surface to reach the sea floor, Patterson concluded that the source had to be lead in gasoline, because lead had only been in the atmosphere for a few decades by then. He published his results in Nature, and within three days, Patterson started getting pushback from the oil industry. They pulled his funding, but luckily — in another bit where Tyson all but nudges you with an elbow — funding from government sources replaced it, and Patterson was able to continue his research, including testing Arctic ice from centuries ago, before the industrial revolution started spreading lead in the environment.

And despite pushback from industry — there's a nice recreation of Senate hearings where Patterson went up against Kehoe — government was finally convinced of the threat of lead, and leaded gasoline and other products were eventually banned by the mid-1980s. And now, nobody likes lead. However, Tyson warns, even today, when "scientists sound the alarm on other environmental dangers, vested interests still hire their own scientists to confuse the issue. But in the end, nature will not be fooled." And there we end, anticipating an upcoming episode on global warming, which is merely a liberal plot by scientists who want to take away your four-wheel drive truck and make you drive a Prius because they hate freedom.