Old Article: "On the Fracture of Pencil Points"

I got my first taste of solid mechanics (and fracture mechanics) as a kid when attempting to use 'Number 2' pencils, on which I gave up rather quickly. Once they break once, they will soon break again. I switched to "mechanical pencils" (I like the .07 size) when I was very young.

Here is an old article on pencil-tip fracture (by Henry Petroski). The picture below, which comes from an even earlier article, sets up the the geometry of a pencil tip.

(I was thinking about this because a 'Number 2' pencil showed up in The Grimm Legacy, which I am currently reading.)

Bumps in a Carpet

Here is my latest post for the Improbable Research blog. You'll notice that I was discussing work by a few of my Oxford colleagues.

Flaccid Mechanics: A Systematic Study of Penis Sizes

Scholars from King's College and other UK institutions have just published a new study with the scintillating title of Am I normal? A systematic review and construction of nomograms for flaccid and erect penis length and circumference in up to 15521 men.

The first sentence of the paper's introduction sums things up rather nicely: "The measurement of penis size may be important either in the assessment of men complaining of a small penis or for academic interest."

My first thought about the article was: But did they also measure elastic constants (to determine stiffness, under the assumption that the object is elastic) and other Lamé parameters?

My second thought was: Up to 15521 men? Where is the uncertainty? Despite the odd article title, this item turns out to have a simple explanation: there were multiple studies and that is the number of men involved in the largest one.

In the authors' own words, their objective was "To systematically review and create nomograms of flaccid and erect penile size measurements." Among other things, their methods included a simulation of 20000 observations of penis size from a normal distribution, though it may also have been interesting to consider a heavy-tailed distribution in case of extreme events.

(Tip of the cap to IFLS.)

Update (3/10/15): Here is the modified version of this entry that I wrote for the Improbable Research blog.

Update (3/10/15): Here is a snarky comment that I wish I had thought of earlier: Remember that "soft matter" is an important subject in condensed-matter physics.

The Physics of Ants

Apparently, a collection of fire ants can act either as a fluid or as a solid. Check out the video in the New York Times article to which I just linked. It's way cool.

(Tip of the cap to whoever posts for APS Physics on Facebook.)

Update (12/21/13): As Jimmy Lin points out, you can also make some really cool sculptures by pouring molten aluminum down anthills. Seeing this makes me want data from Anthill Art to complement our study of a rabbit warren in this paper. Notice that the depicted fire ant colonies have a much more complicated network structure than the carpenter ant colonies.

Frozen Snickers

I often froze Snickers as a child.

Snickers are much better frozen than consumed any other way. Plus, they get exceptionally hard when they are frozen. (I think that freezing Snickers bars was probably also my first true introduction to elastic moduli.)

Fun Fact: Frozen Snickers also make excellent ammunition to discourage people from applying shaving cream or toilet paper to one's front yard. (As a child, I always kept a stash around Halloween in case I needed them. Then I ate them on the days that followed.)

By the way, the reason I thought about this is that I put my Dutch waffles in the fridge to cool them down because it's been hot and humid here lately. The caramel was hardening in a way that reminded me a bit of frozen Snickers, though it wasn't as extreme today because I put them in the refrigerator rather than the freezer.

P.S. Get off my lawn!

The Physics of Ponytails

Leave it to Ray Goldstein and company to investigate the physics of ponytails. This BBC News article covers research in an article published today in Physical Review Letters. Among other things, the authors of the article define a new dimensionless quantity that they coined the "Rapunzel number". Oh dear...