Friday, August 22, 2008

Doing Science in History Class

First I learned that lightning is seen before the thunder is heard because light travels much faster than sound. But I was really fascinated when I learned that the distance between the lightning and the observer could be measured by the time between the lightning and the thunder -- five seconds correspond to about a mile. I was fascinated because I figured that by making such measurements and plotting them on a graph, one could track the movement of an approaching thunderstorm, and could estimate the time of its arrival. The graph would look something like this:

The vertical scale would measure the lightning-to-thunder delay in seconds (inferring distance), and the horizontal scale would record the time of each measurement. As the storm approaches, the distance would decrease, so the graph would show a downward trend. If all the lightning came from the exact center of the storm, and the storm came toward me with constant speed, the graph would show a straight line. But, of course, the lightning strikes would be scattered throughout the storm cell, so the plotted measurements would also be scattered. However, by estimating a straight line through the center of the plotted points, the path of the center of the storm could be estimated.

I wanted to try this idea the next time that I heard the thunder of an approaching storm. To be prepared to record measurements immediately, I prepared a blank chart and kept it inside one of my textbooks so that I would be prepared whether at school or at home.

The opportunity came when I was in History class. The sky outside was darkening, and soon I began to hear thunder in the distance. I pulled out my chart, and started counting the seconds between lightning and thunder while trying to listen to the teacher -- or at least try to look like I was listening. But now and then I would glance toward the clock and my head would dip as I recorded another measurement.

As the storm approached, the measurements became more frequent, and I became more absorbed in my science project. At some point, I suddenly realized that the history teacher had stopped talking, and when I looked toward the front of the classroom, the teacher was not there.

Then I heard the teacher's voice right behind me, asking "what are you doing?" As I turned to look over my shoulder, I saw that she was looking over my shoulder with a puzzled look, trying to figure out what my chart was all about.

It was too late to hide my chart. I might as well explain what I was doing, I thought, especially since she seemed a bit curious. I hoped that I might get by with just a warning. As I explained my chart, the teacher asked me to speak up so all of the class could hear. I ended by pleading that I really didn't plan to do this during history class, but since that was when the storm came, I didn't have any other choice.

To my surprise, the teacher told me to continue my experiment! Furthermore, she said that when I had enough data to predict when the rain would start, to raise my hand and announce my prediction, announcing this to the rest of the class.

With a sense of relief, I returned to my counting and recording in earnest, no longer worried about hiding my activity. At some point, I had enough points plotted to be able to hold a transparent straight-edge over the graph and estimate a best-fit straight line. The point where this line intersected the bottom edge of the graph (representing zero distance) indicated the arrival time of the storm.

I raised my hand, and the teacher interrupted her lecture. "Two minutes after the hour" I declared, hoping that I wouldn't be embarrassed by a big error. I continued with more data recording, hoping to confirm this estimate as I completed the experiment.

When the rain started, it didn't creep up gradually with an uncertain start time. It suddenly crashed against the tall windows along the entire left side of the classroom, as though some giant had thrown a huge bucketful of water against the windows. Everyone was startled and first looked to the left at the rain suddenly pouring down the windows, than all heads turned in unison to the right, toward the clock. It was two minutes after the hour! exactly! and cheering erupted spontaneously. I was surprised by the accuracy of the prediction, but felt completely exonerated.

I did the same experiment later, at other opportunities, and learned that there was generally a difference between the arrival of the average center of the lightning and the arrival of the leading edge of the rain. Also, if the storm passes by one side of the observer, the graph would tend to be curved rather than follow a straight line. As I looked back at my first experiment, I realized that I was lucky that a number of errors happened to cancel, resulting in an unusually accurate prediction.

Wednesday, August 13, 2008

Fluorescence -- Getting Pumped Up

At the close of the Sunday message, I was praying (as I often do) that the message would bless and empower all those that heard it. As I prayed, the Holy Spirit (our prayer Assistant) gave me an analogy that I want to pass on.

I prayed that the power of the message would "fluoresce" in the hearts of the listeners, confident that God would understand what I meant by this.

When a material fluoresces, light falling on the material absorbs the energy of the light, and shortly afterward the energy is released as light of another frequency. The process actually involves individual particles: A photon of light strikes an atom or molecule and "pumps" (yes, that's the technical term) it to a higher energy level. Shortly afterward, the atom or molecule "relaxes" back to a lower energy level, releasing the energy difference in the form of another photon with a different frequency (different color of light). Some energy is typically left behind as heat.

(In a fluorescent light bulb, ultraviolet light generated by the electrified gas in the tube pumps up atoms in the chemicals coating the inside of the tube, which then pass on most of the energy as visible light. The remaining energy becomes heat.)

When a message from God's Word, the Bible, is absorbed by an individual Christian listener, the power of the message "pumps" him up. When the Christian applies the message in his life, the power of the message is released into the situation where the message is applied. The application in this situation may not be recognizably of the same form as the original message (not the same 'color'), but the power is nonetheless passed on. And some good of the message is left behind in the Christian's heart (as 'warmth', at least).

Thinking about it further, I think there is a difference between the physics of fluorescence and the application of the Word. Fluorescence is limited by the law of Conservation of Energy (total energy is never increased nor diminished). But when the Holy Spirit helps us to apply His Word, it works like the loaves and fishes -- blessing is multiplied as it is dispersed.

Monday, August 04, 2008

My Summer Projects

I have taken pictures while doing a series of projects over the last two months, and put them into an album on PicasaWeb, with captions. The link below goes to this album.

After we had new siding put on the house, it became apparent that the fiberglass wall on the west side of the house looked bad by comparison. But we liked the fact that the fiberglass, which is translucent, lets light into the shop/storage area, which has no windows. So we decided to hide the fiberglass wall with a trellis, and hide the air conditioner as well.

We had a string of potted herbs and flowers along that wall, and I had been thinking of making a raised bed for planting herbs. Over the last two years, I have been developing soil from compost for this raised bed, in another area. So we decided to put a raised bed for herbs and flowers below and in front of the trellis. We could also plant clematis in the bed to climb on the trellis.

The raised bed would require that the walkway of stones (small stones and round stepping stones) would need to be moved further away from the house. Over the years, debris falling on the stones has turned into soil, making it difficult to stop weeds from growing. So we might as well sift out the soil and wash the stones while moving them. Around the corner (south), the dirty stone problem was even worse, due to a bird feeder at the back of the house. So the stone cleaning operation would include that area, also. The soil from the stones could also be used for the raised bed.

We also have had a problem with grass along-side the stones growing in among the stones, causing the stone/grass boundary to migrate. So we would also add plastic edging (mostly underground wall) at the stone/grass boundary to prevent the migration.

When making a list of the required lumber for the raised bed and the frame to support the trellis, I realized that I would need to rent a truck to transport the lumber. I also wanted to build two shelf units to better organize the shop/storage area, so I added the lumber for the shelves to the list to save an extra truck rental.

So the trellis idea led to the raised bed, which led to stone cleaning; and the trellis and raised bed led to getting started on the storage shelves. I made detailed measurements and plans for all these projects, but absolutely no schedule. But once I got started, I wanted to keep going as much as possible.

Yes, I'm retired. But retirement isn't doing nothing. It's having no schedule.

Summer Projects Photo Album