The Little Things
While walking between classes today I remembered the assignment from class: instead of walking between classes in a kind of daze and ending up where I needed to be having thought about nothing for a time, I took my time to notice the little things around me. I am a fan of numbers, and so I decided to count things and over my multiple walks between classes I found some interesting information.1. There are approximately (I might have miscounted) 300 of the sidewalk tiles (slabs?) between IIT's Tech Park North building and the Engineering 1 building on the other side of campus. It never occured to me before to think about how much work went into making the street that I walked on the way it was; how many pounds of concrete; how many people working on them. According to a cursory internet search, sidewalks should be no thinner than 4 inches, and with a rough estimate of each tile being a 3 foot square (I did not measure them) that would come to 36*36*4 or 5184 cubic inches. This comes to 129600 cubic feet for all 300, a huge number for such a small part of the city. Once again, a cursory internet search revealed that a contractor normally charges $5 per square foot, or $13500 just to lay the concrete, let alone buy the supplies.
2. On this same walk I noticed another thing about the sidewalks. Since it seemed to me that they had been there awhile (obviously I had not thought about the logistics of the sidewalk being created) I started to notice the wear on the sidewalk itself. Right away I noticed that the first 4 tiles with cracks in them were all on the left side, away from the road as you walk north. I was confused by this, and made up a hypothesis quickly that the reason was there were more places for water to drain to nearer to the road, and so the ice that normally would cause a crack in the sidewalk had a harder time forming near the road. As I walked on, however, I realized that my original sample size was much to small to make a prediction off of, and that I had fallen into a trap by trying to make an explanation fit the data. By the end, I had found that there were 18 tiles cracked, and there were 10 on the right (near the road) while only 8 on the left, and 4 of those 8 were right away. As it turns out, I don't know what caused the change from all left to mostly right cracks, but my original thought was proven incorrect.
3. I don't do much walking around the campus without some kind of distraction (like other people) except for my excursions between classes. So once again, I found myself walking from the Tech Park to the Engineering 1 building, and it occurred to me to count the trees near the sidewalk. IIT is one of the greener parts of the city, and is obviously not the kind of atmosphere that most people think of when they hear 'Chicago' so I wanted to quantify just how green our campus was. It turns out that there are around 80 trees within roughly 10 feet of the sidewalk between these two buildings. I realized part-way through my walk that there were also many different kinds of trees on our campus, but I did not look further into the types, merely the numbers.
4. One more things caught my eye as I walked between these classes, and it was the only concept that did not have to do with my counting of them in some way. I spotted numerous manhole covers along my path, and I decided to do some research on the subject of these entrances to the city sewers. Manhole covers are normally around 50kg in weight, and date back to at least the Roman Empire in the 1st century AD. What I did not expect when I began researching them, however, is that the round shape of a manhole cover has much debate over its reason, sparked by an interview question Microsoft used to use: Why are manhole covers round? Originally it was meant to simply not have a single correct answer and to see how people responded to it, but now there are many solutions and they can be found, among other places, on the wikipedia page on the subject. They include:
- A round manhole cover cannot fall through its circular opening, whereas a square manhole cover may fall in if it were inserted diagonally in the hole. (A Reuleaux triangle or other curve of constant width would also serve this purpose, but round covers are much easier to manufacture. The existence of a "lip" holding up the lid means that the underlying hole is smaller than the cover, so that other shapes might suffice.)
- Round tubes are the strongest and most material-efficient shape against the compression of the earth around them, and so it is natural that the cover of a round tube assume a circular shape.
- The bearing surfaces of manhole frames and covers are machined to assure flatness and prevent them from becoming dislodged by traffic. Round castings are much easier to machine using a lathe.
- Circular covers do not need to be rotated to align with the manhole.
- A round manhole cover can be more easily moved by being rolled.
- A round manhole cover requires the least amount of metal to cover an opening wide enough for a person to get through.
It is kind amazing the kind of thing people think about that we walk by everyday without a backwards glance or a fleeting though, but there is a world around us, from the sheer immensity of the city to the intricacies of manhole cover design, that lives outside of us, running tangentially to our routines, unseen, unappreciated, but entirely necessary.
Noticing some of the things on campus is hard when you are in a rush, but I have found since then that it is actually rather therapeutic to wander around campus when I have no work to do.
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