Geology of the National Parks

Optional Enrichment Article


Babies, Big Ben, and the Age of the Earth

In this course, we will deal with a number of ideas—the age of the Earth, the occurrence of evolution, the prospect of global warming, and others—about which there are heated public debates in the US. These debates have persisted in the US, and in some other places, long after scientists reached consensus and moved on, using the science to help people. These debates have persisted here long after most people in many other countries accepted the scientific results, and began helping the scientists use the information to help people. Why is this? Are scientists and people in some other countries just stupid, ignoring common sense? Are many regular people in the US just stupid? Are US politicians cynically exploiting subjects for personal gain? You will get many different answers to these questions from different people!

Here, we’d like to give you something to think about. The discussion here in no way proves that scientists are right about the age of the Earth, or evolution, or global warming—we’ll discuss the evidence about these later in the course. But, the discussion here may help you to think about thinking about these issues, and to examine your own ideas on the topics. So…

Have you ever visited an old European city and tried to drive through the downtown? Or have you watched from the sidewalk, or in a movie, while others tried to drive the winding streets of Rome or London? People who have done so quickly form opinions about the experience, and those opinions are very seldom, “Wow, what an efficiently designed road system, ideal for moving traffic.” Far more common is “Wow, what a mess!” And yet, although almost everyone knows that the roads are a mess in the downtowns of major old cities, those roads are still there. Why?

The answer is fairly simple. The roads were built when the city was tiny, centuries or even millennia ago, to serve that proto-city. Then, as the city grew, it grew around those roads. Buildings went up, and museums and castles and theaters and sewers and all the other stuff of a city. Would you move Big Ben, or tear down the Louvre and start over, to straighten out a winding road? When faced with that choice, people usually keep the old roads. Careful checking will show you that people actually have put a lot of effort into improving the roads over time, moving things, tunneling under or bridging over, adding subways to take off some of the strain, patching and fixing and repairing, spending billions of dollars (or Euros, or pounds, or whatever), but always starting from the existing system rather than starting over.

There is a useful analogy here in considering how humans learn things, and in particular how we learn science. I (this is Dr. Alley writing) have had the joy of watching closely as our two daughters grew from babies to toddlers (and on to remarkable young women), and there is a good chance that you have either closely observed growing babies, or will. Scientists watch babies, too, and are learning a lot about learning.

By the time a baby is a year old, he or she knows an amazing amount about the world. The baby knows that some things are inanimate and others animate—rattles don’t walk away, but parents do. Many things are predictable for a baby—a rattle released in midair always falls down, not up, unless grabbed by a mother or father or other living thing. A rattle placed properly on the railing of a crib will stay there.

In gaining this knowledge, the baby is putting down “roads” in the brain, wiring in information that later will be called “common sense”. When artificial-intelligence researchers have tried to get computers to do human jobs, perhaps the biggest difficulty has been that the computers lack this “common sense”—teaching the computer all the things that a baby learns proves to be quite difficult, because the baby learns so much.

Notice, however, that this “common sense” is often not really correct. For example, babies do not start off with a modern view of the shape of the Earth and the physics of gravity. Whatever a baby does think, a “round, round world”, with people and rattles pulled toward the center by the warping of space-time by mass that causes gravity, is not in the original common-sense picture.

Careful studies show that, when children are finally told about gravity on the spherical Earth, they initially resist the idea. They may deny it, or they may try to modify it to fit with their “common sense”. (If asked to draw the world, they may add a flat spot or divot just where they live in an otherwise spherical Earth, or they may draw people living inside a sphere.) Often, it takes until age nine or so before children really say that they accept the idea that they are held to a spherical Earth by gravity, and they draw pictures properly illustrating the idea.

Furthermore, studies find that children show this sort of resistance to most or all new ideas that conflict with the “naïve physics” or “naïve psychology” formed in the cradle. Like a city preserving its old roads, a child preserves the initial ideas—perhaps adding or patching, building new paths in the “suburbs” of the mind or building “subways” that take the new idea around the old one, but getting rid of the old idea only when absolutely necessary.

Now, almost all children eventually come to accept the spherical Earth. (There actually are a few people out there who still argue against the spherical Earth, just not very many.) But, typically all of the authority figures in a child’s life agree in telling the child that the Earth is spherical—teachers, parents, preachers, TV, books, and more—with almost no disagreement. (And yes, even young children have a ranking of reliability of information sources, picking which “authority figures” to believe more.) Yet with all of the authority figures agreeing, years may still be needed to convince a child to replace the old “road” in the brain with a new one (and that old road might even still be in there somewhere).

What about, say, the age of the Earth? The scientific evidence indicates that the Earth formed about 4.6 billion years ago. But 4.6 billion years is not “common sense” to most people—we don’t imagine such large numbers very well. If you ask a very young child how old the Earth is, you are almost guaranteed to get an answer that is not “4.6 billion years”.

In many parts of the world, all of the authority figures in a child’s life agree in telling a child that the Earth actually is 4.6 billion years old—teachers and parents and preachers and politicians and more—and almost all children in those places eventually come to believe that the Earth is 4.6 billion years old. But in some places, including the USA, many authority figures do not agree on this. Some preachers, some parents, some politicians, and even a few teachers express doubt about this scientific idea, and some may be actively hostile to it, claiming a very different answer. When faced with a scientific idea that runs against the “common sense” developed at a young age, and with a split opinion among authority figures, a typical child will keep the old “road” through the “city” of their mind. And that child is likely to grow up into a parent, or preacher, or politician who disagrees with the science.

As noted above, this does not in any way prove that science is right and young-Earth politicians are wrong, or that young-Earth politicians are right and scientists are wrong. We’ll address those questions later, after looking at how the Earth works. But, lots of evidence (and common sense!) shows that people do arrive at ideas much as described here, and you can go watch babies, visit other places, and convince yourself. (You might also look at the article listed at the end of this text for a little more information; some of the ideas and examples given here were taken from that article, which provides additional insights.) So, when you visit Paris or Madrid, please safely enjoy walking the narrow, winding streets. Then, on the plane home, ask yourself what the “roads” look like in the mind of the person in the seat next to yours—or in your seat.


Childhood Origins of Adult Resistance to Science
Paul Bloom and Deena Skolnick Weisberg
Science, 2007, v. 316, p. 996-997