How do we know the age of the Earth?

• Rubio's saying Earth's age is one of 'great mysteries' upset pundits, scientists
• Scientists generally concur planet is 4.5 billion years old
• Scientist Clair Cameron Patterson credited with first establishing the age

Football is fun for bickering, but for really wrecking family dinners over the Thanksgiving holidays, try tackling the week's political argument over the age of the Earth.

The fun kicked off when GQ Magazine quoted political hot property Sen. Marco Rubio, R-Fla., saying in an interview that our planet's age was "one of the great mysteries." Acknowledging the many believers in the biblical account of creation, Rubio said, "Whether the Earth was created in seven days, or seven actual eras, I'm not sure we'll ever be able to answer that."

But Rubio's answer upset pundits and geophysicists. The actual age of our planet had been provided some time ago by a scientist whose contributions were ignored in the opinion-page fights that followed. The scientist was Caltech geophysicist, Clair Cameron Patterson, the forgotten man in the week's most discussed debate, besides Thursday's Lions vs. Texans NFL refereeing debacle, of course.

No one mentioned Patterson as consternation ensued from both the right and left. Dueling New York Times columnists Ross Douthat and Paul Krugman critiqued the answer from the 41-year-old politician, who is widely seen as a possible 2016 presidential election contender (yep, they are already arguing about that). Slate's Dan Engber came along on Tuesday and noted that in 2008, then-senator Barack Obama also didn't directly answer 4.5 billion years when asked a similar sort of question.

Lost amid the political back-and-forth is the answer to the question of how we know the age of our planet. And that is a shame, because the scientist who figured it out, Patterson, also provided the planet more than just its birth date. He saved many of us alive today from the scourge of lead poisoning.

"He was a fearless guy," says Caltech geologist John Eiler, who spoke from the lab where Patterson made many of his discoveries. "Wherever the science took him, he would follow."

In 1956, Patterson published a study in the journal Geochimica et Cosmochimica Acta, that reported lead ratios found in one of the Canyon Diablo meteorites. These iron meteorites are the leftover pieces of a big one that created Meteor Crater in Arizona about 50,000 years ago. Most important, they were also leftovers from the formation of the solar system, which before the publication of his papers was known only to be billions of years ago. As Patterson explained in an interview in the year that he died, the Canyon Diablo meteorites didn't contain any uranium, a metal that radioactively decays into lead at well-established rates taking hundreds of millions of years. Other rocks contained both lead and uranium, screwing up earlier age estimates.

So, by reporting the ratio of lead types found in these pristine meteorites and comparing them to lead ratios found in the other rocks on the Earth and other meteorites, Patterson could calculate the age of the solar system, when the Earth formed, to be 4.55 billion years old, give or take 70 million years. "Except for a few minor disagreements, this paper is probably a concrete expression of the attitudes of most investigators in the field," Patterson noted in the study.

The estimate, now refined and narrowed by other investigations, has stood for five decades, Eiler says, "and has only gotten more solid over time."

Arguments over the Earth's age this week dismayed geochemists such as Francis Albarede of France's École Normale Supérieure in Lyon, a fellow of the American Geophysical Union and an expert on the geology of planets. "I understand we have to be sensitive to people's feelings, but in all honesty there is no serious scientist who wouldn't acknowledge all the evidence that the Earth is about 4.5 billion years old," Albarede says. "There is no excuse for teaching kids anything else."

What's remarkable about Patterson isn't that he found the age of the Earth, but that he didn't care about it all that much, greatly crediting the work of the scientists who came before him for the discovery, Eiler says. "He led the fight against lead in paint and lead in gasoline in science for decades, and his chief interest was in environmental chemistry," Eiler says. "You can do it, but it's pretty hard to buy leaded gas nowadays."

The ability to detect faint traces of lead in billion-year-old rocks allowed Patterson to also realize that the Industrial Age was awash in lead. In 1965, he reported that lead from gasoline, solder, paint and pesticides meant that lead levels were 100 times higher than normal in the bloodstreams of most Americans, a result that led to congressional hearings and disagreements with scientists employed by the petroleum industry. Looking at 1,600-year-old Peruvian mummies led him to report in a 1975 New England Journal of Medicine study that modern people suffered lead levels thousands of times greater than in the past, levels close to being poisonous, with debilitating effects on the brain, kidneys and almost every other organ.

The fight led to the removal of lead from many modern-day products. And in the decades since his discoveries, lead has only come to seem more dangerous, according to the Agency for Toxic Substances and Disease Registry, with even small exposure to lead affecting children's test scores and lead dust linked to violence.

"Patterson is a pretty clear example of the link between basic science that seems unrelated to everyday life, the age of the Earth, and science that makes a crucial difference every moment in our everyday lives," Eiler says. "There really isn't a difference between the skills, the methods and the thinking that led him to both discoveries. That's the story of science."

And that's something that everyone can agree on over the holidays, before we get back to arguing about football.