Monday, August 1, 2011

Z-Fields, Lorentz Force, and Maxwell's Equations (the other Maxwell)

When I came to South Africa the last thing I expected to be studying was the Earth's magnetic field! Not only am I designing my very first research project, and conducting it on sharks, but I am altering the geomagnetic field! "Nope, I don't want North to be on this side of the tank. Let's put it over there instead." How cool is that?!

Here is the really interesting part: it has been proven that pelagic sharks, such as scalloped hammerheads, utilize the earths magnetic field and magnetic anomalies, such as sea mounts, to navigate across oceans. Much in the same way that whales, sea turtles, and pigeons migrate. But we do not yet understand the biological process by which sharks have this "internal magnetic compass". Sharks have a sense organ called the Ampullae of Lorenzini which allows them to perceive electrical currents in their environment. This is utilized in detecting prey and some believe that it is linked to magnetoreception as well. I would be extremely interested in finding out exactly how these amazing animals detect the geomagnetic field, but that is a little beyond my current ability. So, we decided to answer a slightly simpler question. Do demersal sharks, such as the species found here in Walker Bay, have the ability to detect changes in magnetic fields and do they respond to these changes in a way that can be observed in behavior.

The first step was to do some research into previous studies of magnetoreception and design an experiment that we could conduct here in the SASC Lab. After gathering all the background information, we consulted with the South African National Space Agency Magnetic Observatory here in Hermanus. We met with two of their best engineers, Elda and Dannie, several times to discuss coil placement, voltage amounts, field homogeneity, and structural design. Along the way, we discussed the physics of magnetic fields and how to apply mathematical equations to understand them. Most of this flew over us poor shark biologist's heads! A favorite moment came when Dannie said: "Its okay - this isn't rocket science." To which we cried out: "But you ARE rocket scientists!!"
Despite feeling that a degree in mathematics would be a requirement for this adventure, we continued to push on. As with everything in Africa, it has taken a LOT of time. We were fortunate to receive the copper wire as a donation from the Copper Development Association of Africa, but had to wait a while for it to be delivered to us.
Once Danie and Elda had applied the tank measurements to a simulation computer program, we could look at the graph to see the distribution of the field throughout the tank. Another meeting, and more tweaking of the experimental design took place to make sure that we get the field as close to "perfect" as possible.
Then it was time to start building the frames for the coils, so us interns were off to the hardware store! YAY!!!
Over this weekend we were able to assemble the frames, thanks to the wonderful SASC connections, at one of the local Abalone farms that had a full workshop. Complete with power tools :)
This morning, Cindy, Edna, and myself have been dancing with copper wires trying to braid them into a manageable coil that we can thread through plastic tubing. Talk about a team-building exercise!
And now we are patiently waiting on the final coil dimensions for our friends at SANSA and hoping for a nice day of shark catching. 

Finding magnetic North

Ahh, the lovely hum of a table saw!

Trying to look like I actually know what I'm doing.
Braiding copper wire isn't as easy as it sounds!

Determining the best method for building

Waiting for the wood glue to dry.

A very special thank you to:
Danie Gouws and Elda Saunderson at the South African National Space Agency for all their wonderful help, endless encouragement, and fabulous advice.
Cindy Zuluaga and Edna Santana, SASC Interns/evil scientists, for being beautiful. AND for helping me fulfill my crazy whims.
Rowan Yearsley (and the Aquafarm workshop) for selflessly donating his valuable time and intellect, all for a few pieces of wood.
Meaghen McCord and Tamzyn Zweig for allowing me to explore my ideas, guiding me when I needed it most, and for being fabulous every single day!
The two coolest ladies in South Africa!!!

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