Monday, October 31, 2016

Stepping Up

This is a ladder leading to an elevated playhouse for kids visiting Brookside Gardens in Maryland. The ladder reveals a frequency distribution of foot placement wear. On most steps we see more wear in the middle of the ladder rung and less wear towards the left and right edges. This leaves a bell-shaped pattern of use.

But a rung near the bottom has a bi-modal pattern, showing the wear resulting from both left and right feet. This doesn't persist on higher rungs. There the wear seems more central. So why not on the lower rung as well? Perhaps central steps on higher rungs feel safer. A care that is not that needed closer to the ground.

Monday, October 24, 2016

Guitar Fret Wear?

Here is an image from imgur of the fret board on a 1956 Fender Stratocaster guitar showing the frequency distribution of playing wear (thanks Scott). But many on Reddit disagree, calling it faked. Not being a guitar player, I can't judge. What do you think?

Monday, October 17, 2016

Fair, Minimal Symmetry Dice

Mathematician Henry Segerman demonstrates his 3D printed skewed or squished six-sided dice. He states "they work like ordinary dice". He exploits 3D symmetries to produce these isohedral dice with "just enough symmetry to be fair". Check out his video above and links to his extra footage.

Tuesday, October 11, 2016

Menu Basket Queue

This is a view of a basket of menus at a restaurant in Chincoteague, Virginia. Notice the pattern of marks left as groups of menus scratch the wall when they are returned to the basket. As customers are seated at the restaurant, they are given menus that are removed from the right hand side of the basket. After ordering, the menus are returned to the basket and placed to the right of the remaining menus. When a single is menu returned, it nicks the wall at a location that depends on how many menus are currently in the hands of customers. If few menus are out with the customers, more remain in the basket and the wall marks of this returning menu will be further to the right. If many menus are out with customers, say just before the lunch rush, this returning menu will make a mark on the wall further to the left.

But it is not often that a single menu is returned alone. It is much more likely that a group of menus will be returned to the basket in a bunch. The size of the bunch that is returned is random depending on the size of the party seated. Each of the menus in the bunch makes a mark on the wall as they are returned to the basket. What we see is a steady state distribution of the number of seated customers, with menus in hand, waiting for their order to be taken.

Monday, October 3, 2016

Manhattan Metric 2

In the previous post we saw use of the program Galton that maps out on city streets how far you can travel in 10 or 20 minutes. Displayed on a rectangular array of streets and avenues, square or rectangular regions develop, as walking is constrained to follow the paths of the gridded streets.

The image above is a Google Earth view of the parking lot of an office building in Maryland. Commuters have parked their cars to enter a building just off the image at the lower left. They must follow perpendicular paths and walk between the cars and/or along the lanes to enter the building. But to minimize the distance of the walk, most have parked along lines of equal distance from the bottom left according to the Manhattan or city block metric. A few stragglers don't fit this pattern, perhaps wanting to protect their cars from door dings or just get a little extra exercise. But the prominent pattern in the image above is one quadrant of the rectangular 'circle' of the city block metric.

 This line graphic from Taxicab Geometry.


Monday, September 26, 2016

Manhattan Metric

Urbica is a design firm specializing in urban data analysis. They have developed a program called Galton that graphs, for a few select cities, how far you could walk in 10 minutes (in dark blue) or 20 minutes (in lighter blue). The map of Manhattan above shows those regions for a walk originating at Broadway and 42st Street. As you walk NYC you are, for the most part, constrained to travel the grid of avenues and streets. Of course, you cannot travel as the crow flies. If you could, these regions would be concentric circles with a perimeter an equal (Euclidean) distance from your start. But walking the streets, your distance is measured by the city block metric (also known as the taxicab metric or more appropriate here the Manhattan metric). This measures distances constrained along perpendicular avenues and streets. Plotting points of equal distance with this metric from would result in the roughly rectangular (or diamond-shaped) regions shown above. Since the streets and avenues are not equally spaced and obstacles can block our travel, we don't see perfect square or rectangular regions. By the Manhattan metric, circles become squares.
Via Maps Mania.

Next week, we will see directly the results of minimizing the distance traveled in such constrained walking.

Monday, September 19, 2016

Wow, It's Hot

From xkcd, a timeline of the earth's temperature from 20,000 BCE to the present, best seen here.
When people say "the climate has changed before" these are the kind of changes they're talking about.
Since the last ice age glaciation, at no time has the climate changed faster than in the last few generations!