balancing act

ScientistjenlucThings have been a bit quiet at the cocktail party this past week, I know. That’s partly because I wrote another "Random Walks" column for 3 Quarks Daily over the weekend, about shock-rocker Alice Cooper and his connection to medieval mystery plays — you know, something wholesome for the Easter holiday that the entire family can enjoy. Another reason is that my entire life has been subsumed by packing: packing for various trips, and packing up my home, not to mention sifting through the accumulated detritus of my life in DC deciding what to discard and what to transport with me to sunny La-La Land. (It’s frankly tempting to just ditch everything and start over from scratch, except I’ve grown quite fond of certain items that might prove difficult to replace.) Tonight I’m packing for a two-day "Communicating Science" workshop in Lincoln, Nebraska — where, no doubt, the dreaded "framing" topic will come up — after which I fly directly to Jacksonville, Florida, for the APS April meeting. So expect lots of blogging from Friday through Tuesday about all kinds of nifty science-type stuff.

In the meantime, commenter Jongleur has chastised me for not mentioning British physicist C.V. Boys in the bubbles post. Mea culpa, although, you know, these posts aren’t meant to be exhaustive. I realize their sheer length might suggest otherwise, but it’s still just a blog, folks. Nonetheless, Charles Vernon Boys is one of those scientists who made a quieter mark on physics than some of his peers, and it’s nice to bring him out of history’s shadows on occasion. He was the son of an Anglican vicar who earned a degree in mining and metallurgy while teaching himself advanced mathematics.

Jongleur mentioned Boys because, in the late 19th century, he gave a series of public lectures on the properties of soap films at the London Institution. (Michael Faraday started the whole public lecture tradition in 1826.) Those lectures became the classic book, Soap Bubbles: Their Colours and the Forces Which Mould Them. In Boys’ day it was the epitome of scientific popularization, and no wonder, since it was filled with creative, crowd-pleasing tidbits like explaining "wine tears" — the pattern that forms when wine climbs up the glass and falls back down, making it seem as if the glass is "weeping."

He also demonstrated the use of capillary action to raise or lower liquid levels in a tube, how to build water bombs out of paper folded into a small origami box, and explained how it might, indeed, have been possible for men to go to sea in a sieve, per the nonsense lyric by Edward Lear: "They went to sea in a sieve, they did,/ In a sieve they went to sea:/ In spite of all their friends could say,/ On a winter’s morn, on a stormy day,/ In a sieve they went to sea." It’s all a matter of getting the right surface characteristics for the sieve wire and mesh size so that surface tension could prevent water from entering the holes. Jen-Luc Piquant also directs our attention to a modern-day C.V. Boys, Maarten Rutgers, a soft condensed matter physicist at Ohio State University, who is known for inventing his own apparatus to construct gigantic soap bubble films in science museums around the country — like this four-story flowing soap film he made for the Carnegie Science Center in Pittsburgh. Four

Boys wasn’t just about bubbles, however. He was, first and foremost, an ingenious experimentalist who liked to invent handy measurement devices. For instance, while still a student at the Royal School of Mines, he invented a
mechanical device for plotting the integral of a function (see "The
Calculus Diaries" series of posts in the sidebar for my own preliminary
foray into integrals).

He also played around with torsion balances and conducted experiments to more accurately measure the gravitational constant (a.k.a., "Big G"). There’s a long history of such experiments, dating back to Sir Isaac Newton. In his Principia, published in 1687, Newton asserted that on level ground, a "plumb bob" would hang vertically because it was attracted to the Earth’s center. However, if there was a large mass nearby, like a mountain, the bob would be pulled slightly off its vertical path because of extra attraction toward the mountain.

In the summer of 1774, Nevil Maskelyne, Astronomer Royal, spent four months in the Scottish highlands testing Newton’s assertion on Mount Schiehallion. (It should be noted that he wasn’t happy about it, but apparently no one else could be persuaded to go to Scotland, even for the sake of science.) And it worked! The little plumb bob was indeed attracted to the mountain. After Maskelyne presented his results to the Royal Society on July 6, 1775, the mathematician Charles Hutton used the data to determine the mean density of the Earth. Hutton was within 20% of the current accepted value.

Physicists have been attempting to measure "Big G" more accurately ever since. They got a big boost with the invention of the torsion balance in the late 18th century, a device intended to measure very small forces. (Whether it was invented by Charles Coulomb or the Reverend John Mitchell is the subject of occasional rancorous debate.) It’s simplicity itself in concept: the torsion balance is little more than a horizontal beam with small lead balls at each end. The beam is suspended from its center by a thin torsion wire. If you place a large lead ball near each of the smaller balls (in the same horizontal plane), the resulting gravitational attraction will twist the torsion wire in the same direction. And the angle of the twist can be measured to determine the amount of force acting upon it.

Henry Cavendish was the first to use the torsion balance to measure Big G and determine the mean density of the Earth in 1798. But that’s no reason not to keep repeating the experiments with ever-more-sensitive equipment and conditions! The Earth could go on a crash diet at any time! So 100 years later, Boys improved on the torsion balance used by Cavendish by (a) making it smaller, and (b) replacing the copper torsion wire with quartz fiber (different materials have different levels of elasticity and therefore react differently to the twisting motion).

With these improvements, Boys was able to measure Big G to about 1 part in 1000, a singular improvement, but he struggled to improve it further because the results were marred by all the external vibration. His experiment was housed in an underground tunnel, and what with students traipsing about and coal deliveries and the like, it was tough to weed out all the "noise." Eventually he moved the experiment to Oxford, which was a bit quieter, but there was still a lot of traffic on the cobblestone streets. Boys found it best to do the work on Sunday mornings, and while he did get a slightly better measurement, it took four years, during which he took no holidays, and he abandoned further work, claiming exhaustion.

As recently as 2000, physicists were still trying to more accurately measure Big G — and getting conflicting answers.  As we saw with the case of Maskelyne and Hutton, one
of the "applications" of knowing the gravitational constant is that it
enables scientists to determine exactly how much the earth "weighs."
Doing so is no mean feat, since gravity is so much weaker than the
other fundamental forces. As Boys discovered in his London and Oxford experiments, the apparatus must be
completely isolated and performed in a vacuum, although almost nothing
can completely shield it from minute outside gravitational influences.
(In fact, during one such experiment at the University of California,
Irvine, the experiment showed tiny "wriggles" in the data which turned
out to be caused by the sprinkler system just outside the physics lab

And that’s today’s foray into the annals of physics history. Charles Vernon Boys: not just about the bubbles.  Someone’s got to carry on the tradition of Boys and Maskelyne the Reluctant and carry out the tedious dirty work of physics. It’s nice to have them remembered now and then.

3 thoughts on “balancing act”

  1. A small and irrelevant addition to your discussion, which did include mines and metallurgy: back during the Sixties, the occasional comment about the M&M building at the University of Minnesota was “Achtung! Minen und Metallurgen”.

  2. And another Minnesota connection:
    Maartin Rutgers was a U of M undergrad, one of the first students I taught as a wet behind the ears assistant professor. He had workded for Dan Dahlberg (of Physics Force fame – see, a Communicating Science connection as well) in magnetism, but then went over to the dark side and soft condensed matter. (I keed, I keed – I’ve done more than my share of experiments on rice and peas [] to cast stones (or sand) at anyone else.
    Say Hey to D for me.

  3. Thankyou for such an extensive account of Boys and his work. I will be shamed into silence from now on, though there was in truth no malice nor pejoration intended in my earlier comment, for which chastisement is too strong a word.

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