# Want to facilitate the flow of pedestrians or particles through an opening? Add an obstacle.

Grain being emptied from a silo, people leaving a room, and cars entering a construction zone all have something in common: they tend to spontaneously clog.

How and why these clogs develop is important to a wide range of applications – from industrial processing to a building’s fire safety. Recent results from a team of researchers at the Universidad de Navarra in Spain shed new light on what factors do and don’t contribute to clogging and, hence, how to prevent it. In particular, they’ve shown that an obstacle at the right distance from the exit decreases the probability of a clog by 99 percent.

Every time I bake cookies, I wonder if I’m making the most of the space on the cookie sheet. I finally decided to stop wondering and figure it out.

Experimental methods

My investigation involved circular cookies of two different sizes:

They were arranged on cookie sheets of two different sizes:

Now, the most common way to arrange cookies is in equally spaced rows and columns. This is called a square lattice; when you draw a line from the center of a cookie to each of its four “nearest neighbors,” you end up with a pattern of squares.

Another option is, instead of putting the cookies in row two directly under the cookies in row one, to arrange them in the “gaps” between the cookies on the first row. If you do this, you get a triangular lattice, also called a hexagonal lattice; when you draw a line from the center of a cookie to each of its six “nearest neighbors,” you get a pattern of triangles.

As you can see, the cookies are more densely packed when they’re in a triangular lattice, even though they’re the same distance away from the cookies closest to them. If you work out the geometry problem, it turns out that cookies arranged in a triangular lattice take up 86.6 percent as much space as cookies in a square lattice. In other words, you can fit 15 percent more cookies into the same amount of area.

Well, problem solved! Triangular lattice it is.

But wait! What if your cookie sheet isn’t wide enough for an offset second row? Is the triangular lattice still the way to go? Is it still worth it to get the rows closer together, when it means every other row is a cookie short?

To find the answer to these questions, I first tested the four different set-ups in my kitchen (small cookies on a small cookie sheet, small cookies on a large cookie sheet, large cookies on a small cookie sheet, and large cookies on a large cookie sheet). Then I used equations and graphs to generalize the answers.

# There’s a lot of cool science out there . . .

. . . and I want to do my own, small part to help it become a bigger part of people’s lives and conversations.

How do I intend to do that? Right now, I’m envisioning mainly trying to help disseminate and explain interesting new research — besides the handful of Science and Nature articles that get widespread press every year.

And I’ll probably also share the whimsical science/math calculations I occasionally do for my own entertainment, in hopes that they may entertain others as well. (These include such pressing questions such as, “Is arranging the cookie dough balls in a triangular lattice ALWAYS more efficient than using a square lattice? Or can the size of the cookie sheet change that?” and “When jumping off a 12-foot platform into a lake, should one try to do two back flips on the way down, or just one?”)

Other than that, I think this is one of those situations where there are many possible outcomes, and you just have to do the experiment and see how it goes!