In an effort to explain my absence…

…I present to you a summary of the last few months of my life.

So many chapters.

And there are more folders where those came from.

A few months ago I was offered the opportunity to write for the teacher’s edition (TE) of a high school physics textbook. I took it happily, but the tight schedules of the publishing world (on top of the website job that I also had to attend to) left little time for unpaid writing.

One thing that struck me during the project was how much writing for the TE felt like writing for this blog. A big component of teaching science (and anything else, really) is taking a concept and connecting it to observations students have already made and experiences that they have already had. This can be a direct connection, like explaining how charges move when a doorknob shocks you, or a more analogous one, like using marbles in a jar to model kinetic molecular theory. While making these connections is fairly straightforward when dealing with Newtonian mechanics and electromagnetism, it can be tricky for concepts such as quantum mechanics and relativity.

Teaching relativity is especially difficult because it deals with phenomena that directly contradict students’ everyday observations. Two primary consequences of special relativity are time dilation and length contraction: moving clocks run slower and moving meter sticks are shorter. Students resist these concepts; why shouldn’t they? After all, science is based on drawing logical conclusions from experimental data and observations of one’s environment. When was the last time a bus looked shorter when it started moving?

The answer is that the bus always gets shorter when it starts moving, but the difference in length is so small that we can’t notice it. The length of the bus contracts by a factor that depends on its speed (we’ll look at the exact equations in another post); the faster the bus moves, the more it contracts. However, unless the speed of the bus approaches the speed of light, this length contraction factor is insignificant.

While the effects of special relativity are frequently unnoticeable, they are still always present.

You know what this means, right?

Driving faster really does reduce the distance between you and your destination.

(But if you get pulled over, you didn’t hear that from me.)


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