Cocktail Party Physics

Cocktail Party Physics

Physics With a Twist

Guest Post: How Old is the Earth? Who Knows?


I've been away for the past two weeks at a truly fantastic conference -- more on that in a future post -- but promptly came down with a bad cold once we got home. Sigh. It's hard to blog coherently with a stuffy nose, scratchy throat, and woozy brain. Fortunately, my pal Jim Kakalios, a physics professor at the University of Minnesota and all-around mensch, has come through with a guest blog post, inspired by recent comments on the campaign trail by would-be presidential candidate Rick Perry.

It's especially timely in light of the just-concluded GOP candidates debate, in which the anti-science theme was particularly pronounced. I think anyone with a genuine love and respect for science and all the benefits to society it brings -- regardless of political ideology -- should be concerned by this ever-more-pronounced streak in the Grand Old Party. But here -- I'll let Jim explain how we know what we know when it comes to science, and why it's so important for a civilized society to value fact-based, curiosity-driven scientific inquiry. Take it away, Jim!

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Texas Governor Rick Perry, a candidate for the Republican nomination for President, was recently asked on the campaign trail how old he thought the Earth was. He responded “I’m not sure anyone knows really completely know how old it is.” While technically true – scientific measurements are continually being refined, allowing for more accurate determinations of the Earth’s age – it was an evasive response.

I suppose one cannot fault Gov. Perry for trying to weasel out of a direct answer – he is a politician after all. As a scientist, in order to get a more productive response, I would have phrased the question slightly differently.

I would have asked Gov. Perry: “Which do you think is closer to the true age of the Earth – 4.5 billion years or six thousand years?” And I have a follow up.

If he responded that the Earth’s age is closer to 4.5 billion years, I would then ask – why do you think so?

If he cites the overwhelming consensus of the scientific community on this age, then I wonder why he does not find equally convincing similar agreement among scientists on climate change or the theory of evolution. A paper last year in the Proceedings of the National Academy of Science found that over 97 percent of climate scientists surveyed agree that global warming is a real phenomenon and that man made causes contribute to this warming. This is not a sign of collusion – trust me, there is nothing scientists love more than showing that their colleagues are wrong. If all but a small handful of scientists agree with a particular conclusion, it is because that is what the evidence indicates. Why agree with a scientifically derived age of the Earth, and ignore the scientific evidence for climate change?

If he replied that six thousand years is closer to the true age of the Earth, I would then ask – what about cell phones?

The scientifically determined age of the Earth is not just pulled out of a hat. It is based upon measurements of the concentration of unstable uranium and thorium nuclei in rocks and meteors, employing a technique similar to Carbon-14 dating. Extracting a time since the rock’s formation from these measurements requires an understanding of quantum mechanics, the field of physics that describes the behavior of atoms and nuclei. There has been continual improvement, since the development of the first atomic bomb in 1945, in our understanding of the mechanics of radioactive decay of nuclei, with a corresponding decrease in the uncertainty of the age of the Earth, derived from such measurements.

Additionally, quantum mechanics, when combined with statistical mechanics, provides the foundation for solid-state and semiconductor physics. Modern quantum mechanics was developed in the mid-1920’s, and the transistor and laser followed approximately a generation later. There would be no computer hard drives, magnetic resonance imaging, light emitting diodes, cell phones, laptop computers or iPods without quantum mechanics.

It is of course every American’s right to dismiss the conclusions of any body of science they wish. But intellectual consistency would then suggest that one would mis-trust any electronic device that makes use of this science. At least the Amish walk the walk, and don’t just talk the talk.

Why does it matter whether Gov. Perry, or any candidate for elected office, from either party, thinks the Earth is billions or thousands of years old? Because science is not a collection of facts, but rather a process for how we can obtain reliable information about the natural world. I would bet cash money that most scientists whose field does not directly involve radioactive dating of meteors are not familiar with the isotope decay curves from which the age of the Earth is determined. But the process, by which evidence is obtained and then tested, challenged and ultimately accepted as correct, gives one confidence that when those who devote their research to such topics conclude that the Earth is 4.5 billion years old, the result can be trusted.

The scientific process has extended our lifespans, eradicated diseases, fed billions and as pointed out on an episode of the CBS comedy The Big Bang Theory last year, only sixty years after the Wright brothers flew at Kitty Hawk, enabled men to walk on the moon. As citizens and voters we should discover whether our candidates believe that science is just another opinion, and then on Election Day, we can share our opinion of them.

James Kakalios is the Taylor Distinguished Professor in the School of Physics and Astronomy at the University of Minnesota, and the author of The Physics of Superheroes and The Amazing Story of Quantum Mechanics (Gotham, 2010).

The views expressed are those of the author and are not necessarily those of Scientific American.

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