Monthly Archives: February 2014

Bill Nye was on The Bill Maher Show tonight.He’s been very popular the past week or two, appearing in a debate on evolution and the viability of intelligent design, he spoke about climate science with Marsha Blackburn on Sunday’s Meet the Press, and now Bill Maher.

Teddy Roosevelt and party at the tree, General Sherman.

On Maher’s show Nye was asked how it is that we know the world is older than 6000 years. Or to rephrase, “How could we know if a tree is older than 6800 years old?”

It’s actually a good question.  It’s a good question that gets to the crux of what Bill Nye was engaging Ken Ham on: how do we know things?

To address that big question, let’s talk about how we would answer the smaller one about the tree and see if that gives us any insight into how we gain knowledge…

Every kid has heard that the rings in a tree stump correspond to years that that tree lived. But how do we know?

Forestry.about.com tells us that, “The new, large cells that are produced the following spring are easily distinguished from the previous year’s tree growth as a distinctive ring. A ring composed of a light part (spring growth) and a dark part (late summer/fall growth) represents each year’s growth.”

If you want to test this method for dating trees, the best place to start is to find a tree that you know was planted at a certain date. Perhaps in a housing development, something you planted yourself, something your parents planted, or better yet… get some trees to plant this year and come back in a decade or so. 

Over the course of a decade or so, cut one of your trees or use an increment borer to take a sample that includes the pith (the centermost section of the tree). Now count the rings. While you’re at it, consult some records that can tell you the weather patterns over the time that this particular tree lived. With this information, you can now cross-reference your tree ring data with weather data. If you have bores from your trees over successive years, you can line your samples up and compare. Do the older trees have more rings? Do all of your trees have numbers of rings corresponding to their known age? Do you see any weather-related patterns in your ring spacing? Do all the trees have the same weather patterns for the same years?

What I’m proposing is, you can adopt the hypothesis that trees make a ring every year and then test it just as we described above.

If you do this, you’re doing science. You can see the data yourself, see how the data supports or refutes the hypothesis you made. You don’t need any outside help, you just need time and access to some trees (and perhaps the equipment that enables you to get your data).

Now ask yourself, ‘do you believe your data? Do you think it supports your idea? What experiment would give you the best opportunity to change your mind about this?’

Now do that experiment.

And call yourself a scientist while you’re at it.

You aren’t just answering the question that started this column. You are seeing how scientific method works and getting a glimpse into the way that we learn from the world around us.