Thursday, July 15, 2010

Luminescence Dating

It's way late, but I'm finally posting my report and photos from our last session of the season!

Dr. Regina DeWitt was our guest, and she showed us how luminescence dating works. (See my previous post)

I sang a new song called "Grain of Sand" which explains the process from the sand's point of view. Just to set the mood, and to let our eyes adjust, I sang it in the dark.

Then we all headed into the closet. That's right! See what kind of shenanigans you've been missing? 

There's a large closet in the back of the room. It was the only available space we could make dark enough to see the demonstration Dr. DeWitt had prepared.

So everyone crowded into the closet, and that's when we realized that Dr. DeWitt's hot plate wasn't working and needed to be plugged into a different outlet. I had to scramble around in the dark to figure that one out. Turns out the outlet was near the top of the wall! 

Meanwhile it was getting pretty dicey with all those warm bodies crowded into a small dark space! But we got past it.

Dr. DeWitt heated up some dosimeters on the hot plate. They look like little white pills in the light. In the dark, as they warmed up, we could see them start to glow a nice pale green.

They work the same way as the sand grains Dr. DeWitt uses to date archeological digs. The dosimeter accumulates radiation damage, which basically means electrons are knocked loose and get trapped in flaws in the crystalline structure. (She had irradiated them ahead of time.)

When heated, the trapped electrons gain enough energy to escape and travel back to where they belong. Moving electrons emit light, and that's where the glow comes from.

Once we were all out of the closet, we had plenty to think and talk about. It was a pretty lively group. I'm thinking of starting every BTDS in the closet!

Dr. DeWitt brought a geiger counter in order to show us that many common things are slightly radioactive, such as bananas and nuts.

The kids had fun both during and after the presentation, testing different objects for radioactivity.

Watch for an announcement soon about our planning meeting for the next season of BTDS! If you are a researcher in or near Stillwater, OK, we'd love to have you as our guest scientist. Please write!

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