Class today woke me right up (despite my late start) with a fascinating lab. We measured the distance between two balanced wires, hung tiny weights from them then ran opposite current through them until they balance again. Because we knew the length of the wires, the magnetic force needed to lift the weights, and the current we were able to calculate the constant for the permeability of free space, which is a very cool concept. Basically, what it implies is that a vacuum allows magnetic fields to emanate at a rate that is neither zero or infinity, meaning nothingness has properties of its own in a sense. As a follow up, we learned that the inverse of the square root of the sum of the permeability constant multiplied by the permittivity constant (involving electric charges rather than magnetic fields) is equal to the speed of light. This proves that light is an electromagnetic wave.

Next we sat through a lecture about general relativity, the concept that acceleration is equivalent to gravity within a single reference frame and that massive objects bent space, making euclidean geometry no longer applicable, which is what accounts for the planet's orbital motions and even, when studied further, mercury's irregular path. This lecture was fairly interesting, but honestly completely over shadowed by the presentation that followed.

Today's guest lecture was the most entertaining, excited and easily accessible speaker we have had so far. By a lot. He did not have power point slides that he simply read out loud. He drew on the chalk board, walked around, had us stand up and participate in his demonstrations in an incredibly engaging way. His name was Vijay Balasubramanian and his "lecture" (although it seemed like way too much fun to be called that) was about the physics of neuroscience. In the past he has done research in particles, cosmology, and string theory but today he talked mostly about the field he is currently doing work in, which is essentially how the brain works, and more specifically (which is what separates his field from biology) systems neuroscience:

*why*it works the way it does.He started the talk with a drawing of a neuron, a description of their structure and how dendrites and axons receive and transmit electrical signals. He then used volunteers to build a human neural circuit that displayed how the connections between the cells allow highly specialized cells to work together to do a broad variety of things. He lined up six students and gave them each a job (for example, if you see a white piece of paper, poke the person behind you or if you get poked raise your hand, etc.).

He also discussed with us the miraculous efficiency with which our brains operate. For example, only 10 watts is used to power it (as opposed to a standard 80 watt computer) and in one cubic millimeter of tissue, 4 kilometers of "wiring" can be found. He also mentioned that the rate at which signals are fired is only about 4 Hz, which is shockingly slow compared to a computer, but he discussed the drawbacks of having it go any faster: requiring more energy, a larger head, and not reaping proportionate benefits (as shown by the law of diminishing returns which basically states that double the information results in less than double the usefulness). It was really, really cool. So cool in fact that I cut my lunch time about half an our short to listen to him discuss how he got interested in his field and what more there is to discover in it (apparently a lot). He suggested we read the article in this months Scientific America about the limits of intelligence, in which he is quoted three times. I intend to do just that.

After lunch we went back to work collecting our single photon diffraction data and we've got a very nice looking graph to show for it now. We also started preparing for the presentation we are going to give next week. It should be cool telling our classmates the results of our lab and about how we proved particle/wave duality, but I am even more excited to hear what all the other groups have learned and maybe run across some Non Newtonian fluids.

After class, seven of us from my floor and Brian and Alex's floor signed out and looked around center city. We wandered for a while, grabbed some dinner at a sandwich shop and ate it next to a fountain that we were actually encouraged to dip our feet in. It was a great day and I'm really glad we finally got out to see the city.

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