The Science of Olive Crystals

Lucky readers, today is science day! I'm about to share with you a marvel that not even I knew existed. But before I share with you the marvels of physical science, here are some paltry observations on social sciences.

-People's behavior is largely ruled by cost benefit.
-When one has a digital camera and the cost of photography is virtually nothing, one will take silly photos.
-When one has a blog and the cost is nothing, one will post said photos.

And now the story...


So I was shopping in the Italian Market area of South Philly. The market is a fine place, despite being a little stinky in the summer. Regardless, as I entered one shop I saw 8 large vats with different kinds of olives for sale. While perusing the olives, I noticed the most remarkable thing. The olives in one of the vats had actually self-assembled into a crystal structure! In case it was not immediately obvious from the photo, each olive is surrounded by exactly six other olives. (I have drawn in a pair of hexagons around two olives as a demonstration.) What you see is a 2D crystal lattice. I confess ignorance as to what it is called in 2D, but a similar 3D configuration is referred to as a hexagonal close packed crystal or a cubic centered face crystal. This packing (in addition to being visually pleasing) is also the most efficient way to pack spheres into a volume.

How, you ask, do stupid olives know to assemble themselves into such a fine struture? Well, they interact by virtue of whatever forces are applied to them. In this case the dominant forces are bouyancy, and I'm going to guess surface tension. If the olives are allowed to reach equilibrium, they will progress towards the lowest energy state available. To form the structure we see, there must be some attractive force between olives or overall force that drives them to the center (I'm guessing there is some sort of meniscus in the vat due to surface tension). The force is probably so slight you couldn't detect it by touch, but it is enough to cause a random correction of olives to order themselves and form an extremely precise structure. The olives do it because it is energetically convenient for them, given the nature of their forces and their environment.

I took a photo and posted it, because it was fiscally convenient for me, given the nature of my interests and my environment.

And yet consider: These olives only self-assemble in a vat and would never on a plate. Because it was easy for me, I have shared this with you, but I would never have blogged this photo from film.

This is the way the universe works: Often enough, it's not about the olives, it's about miniscule forces and the environment...