Velocity Lab, Or Why We Don't Do "Real" Labs

One of the most interesting things I noticed in the PBS series Einstein's Big Idea was how the early investigators looking into physical phenomena were able to make such precise measurements using such primitive equipment and facilities. If the re-enactments are to be believed, scientists like Antoine-Laurent Lavoisier and Emilie du Châtelet were basically conducting their research in a spare room at home. It must have taken a tremendous amount of patience to gather the data that proved, for example, the principle of conservation of matter or that the energy contained in a falling object was proportional to the square of its velocity.

In this experiment, we recreated Mme. Châtelet's demonstration by dropping marbles into cups of flour from various heights and measuring how far down into the flour they sank. Although I don't usually bother recording data -- no one is particularly interested in keeping track of what we're doing besides me -- in this case I thought we'd do it "the real way," like the classroom instructions call for. But right away we had to make changes. First, we could only find yard sticks, not meter sticks. So we cobbled together a meter stick by taping a tongue depressor onto our yard stick and marking off the extra centimeters.

(Note marble in mid-flight)

Next, the lab called for regular glass marbles, but we found that our results were rather random -- the marbles fell different depths without regard to what height they were dropped from. And sometimes they barely broke the surface of the flour. So we used some steel marbles we found, which tunneled into the flour an amount that could be measured.

Finally, the regular drink-sized paper cups called for in the lab were too shallow, and the (metal) marbles hit bottom and bounced back up. So I dug out some super-sized plastic cups that were about twice as tall as the original cups.

But in the end, our data was gibberish. We were simply too careless, and we didn't do enough trials to get a reliable answer. The whole experience reminded me of my traumatic days in high school science, where the top students (the ones who went onto med school, as it happens) routinely made up data to fit the expected results, so they'd get a good grade in the class.

(Stick marked in cm for measuring depth of marble)

In the three years since I began really focusing on science, I've been very proud of myself for getting nearly all the "labs" we do to work -- by which I mean they provide an impressive demonstration of the principle I'm hoping to illustrate. But I just think it's too much to ask for these demonstrations to provide useful data as well. We're not scientists, but we like watching cool things happen. I'm sorry to admit it, but it's true.

So if you're using this blog to find ideas for your own home or classroom science activities, take our example with a grain of salt. We're dilitantes with a capital "d," and we cannot be held responsible if your results vary.

Einstein's Big Idea

If it seems crazy to start our study of physics with relativity, then let me say that I had in fact, originally drawn up a nice teaching plan which followed a more traditional physics sequence -- motion and mechanics through December, heat and thermodynamics in January, electricity and magnetism in February -- and lightly touched on everything after classical physics in May or June. (The list of topics I made up came directly from the Physics4Kids website.) But as I began to look at the material to be covered and the possible activities we could do (some of which the kids did many years ago when a friend taught a co-op class using the book Teaching Physics with Toys), I thought about how much of this stuff I had retained from my own formal science classes in high school. The answer was, not much.

If you have been following me through our adventures with chemistry and biology, you know that I am an English major with a geeky bent who got high marks in high school science and then promptly forgot everything I “learned.” My goal is to do some interesting activities that might help my kids and I grasp some of the concepts of each science discipline with worrying about getting the “right result” or memorizing a lot of jargon. Right after I made up my traditional teaching plan, I read the essay mentioned in the post Quantum Mechanics in Middle School? And I realized that – as with biology, when we focused on microorganisms where much exciting research is being done today – what I really wanted to find out about was the new stuff being done in physics. In the few weeks that I’ve been working on putting this course together, I’ve heard several times that the theory of relativity is the basis of all modern physics. I imagine that it is the equivalent of evolutionary theory to biology – to study the subject without starting with that game-changing idea is to get a skewed picture of how the field is treated today.

All of which leads us to Einstein’s Big Idea, the PBS NOVA episode which we watched last week. I literally pulled it off the library shelf without really knowing what it was about. But as luck would have it, I think this has been an excellent entry point for our study of physics. Einstein’s Big Idea uses actors to recreate the lives of Einstein and his predecessors: Michael Faraday, Sir Humphry Davy, Antoine-Laurent Lavoisier, James Clerk Maxwell. There are also comments from living physicists and David Bodanis, author of the book E=mc2 on which the episode was based. Taking this personal approach, the show highlights something I never realized: how many women were involved in the development of modern physics. Along the names already mentioned, we meet Mme Lavoisier, who greatly helped her husband in his work; Emilie du Châtelet, math genius and companion of Voltaire; Lise Meitner, who split the atom and helped prove Einstein’s theory, but who had to leave Germany when the Nazis began persecuting Jewish scholars. And of course Mileva Maric, who gave up her own physics studies in college when she became Einstein's first wife and mother to his son. All of these women have been neglected in the popular history of science, and it was a revelation to discover their existence.

Beyond the personalities, Einstein’s Big Idea did a good job of explaining the concepts involved in a way that most teens and adults can understand, and showing how Einstein’s theory was built upon the work of others while forging a new path at the same time. I highly recommend this video to anyone who wants to begin to understand the basis of all physics today.