Return of the Trivia

Apologies for the two-day hiatus...I was back in Richmond (graduating booyah) and unexpectedly had no internet access in my down time.  Although I suppose we should all be more amazed that I haven't had an internet access problem until nearly halfway through the year (ish).  Anyway, seven hours down, seven hours back, and some pyrotechnics and polyester trashbags in between.  No, it was nice.  A good wrap-up.

Okay, enough about me.  Time for a pop quiz!  Question: Why are manhole covers round?

Actually, this is a serious question made famous in a serious interview (or rather, a series of serious interviews) by the company Microsoft.  I read about it in the book Outliers (by Gladwell), but I think it stuck with me because I've been preparing a bit for interviews.  This kind of question, though strange, allegedly measures an important aspect of an individual not easily assessed by the SAT, GRE, MCAT, GPA, or any other mouthful of alphabet soup.  While those measures all do a relatively good job of reporting what we typically think of as intelligence, they don't really investigate practical intelligence, street-smarts, or creativity.  Ask someone why manholes are round, or how many uses they can think of for a blanket, and - the logic goes - discover who can hit the curveballs and who can't.

But if you're like me, you're probably a little irritated - how the heck are you supposed to know when an interviewer will tolerate insane (and probably smart-ass) remarks versus when they expect you to play by a more conventional set of rules? - and you also want to know, well, why are manhole covers round, anyway?

Firstly, not all of them are.  There are plenty of manhole covers from Rhode Island to Rome that are square, rectangular, triangular, etc. and the world carries right along.  However, Microsoft probably wants a bit more than that, so...

Geometrical reasons

• A round cover can't fall through a similarly-sized round opening, whereas another shape might be able to (a rectangle, for instance, or a square inserted diagonally).
• Spheres and circles are strong shapes and good at distributing weight and pressure.
• Circles have a large area to perimeter ratio.

Manufacturing reasons:

• Circles are easy and efficient to make.
• They also use less material.
• Round holes are simple to dig.
• So that they don't catch on car wheels and feet (etc), the cover needs to be flattened, and round or curved surfaces are easiest to lathe (...apparently).
• Circles are the traditional shape, and they can be mass-produced in standardized shapes and sizes, rather than custom-made.

Utilitarian reasons:

• People's torsos are roughly circular in cross-section.
• Circular covers will match up with a circular hole in any direction, and do not need to be maneuvered or rotated into place.
• Round things can be easily rolled if they need to be moved.

Painfully obvious reasons:

• Manholes are round, so their covers ought to be round, too.

 Wellllllllll there you have it.  Now interview away!