Wednesday, July 20, 2011

Networks of Neurons

Today was full of learning and adventure from the start. I woke up and got breakfast with the usual suspects, Alex and Fred. Feeling well-fueled, we made our way to class and excitedly took our seats. I was excited for today’s lecture, because I knew that Craig was going to talk about a topic that I am quite interested in – general relativity-. Craig’s talk was very good and I enjoyed the content a lot.
Craig began to talk about the idea of general relativity which basically says that physics is just a form of geometry. While we all think oh geometry, I did that back in the freshman year of high school; Craig began to talk about Non-Euclidian geometry which is geometry on curved surfaces. In straight space, the degrees in a triangle add to 180, but in curved space, the angles can add to more or less than 180. The next thing that Craig talked about was defining what mass is. Mass can be thought of as a measure of how much matter there is, but also as a measure of inertia. While it might seem obvious, Craig stressed that an object in motion and a stationary object have the same mass. Craig then moved on to state Einstein’s Equivalence Principle which states that without an outside reference frame, it is impossible to tell the difference between gravity and acceleration.
The next topic that Craig discussed was the bending of light by gravity. Einstein predicted that light should be bent by the mass of the Sun as it passes through its gravitational field. When the experimental measurements were taken, it became clear that Newton’s Law of gravitation was not in fact a Law, and that Einstein was right. While I was confused at first why light photons, which are mass less, would be bent by gravity, Craig reminded us of Einstein’s famous equation E=mc2. Another cool thing that Craig talked about was the irregularity of Mercury’s orbit. It was interesting because he presented the idea of gravitational waves that ripple through space-time at the speed of light. While we tend to think of gravity as instantaneous, gravity also takes time to make its way through space. The new way of thinking I have about gravity now is that an object with mass bends the space around it and that other masses simply follow the paths of least resistance and approach the massive object.
Following Craig’s lecture, we were fortunate to have another guest lecturer from the UPenn faculty visit us, Dr. Vijay Balasubramanian. Vijay was one of the best speakers I have ever heard, because regardless of the fact that he has 30 more years of education than me, he presented his ideas perfectly. Vijay began his discussion by discussing how the brain works. What I found very interesting was his way of thinking about how individual neurons know nothing by themselves but that together they make up our personalities and complex emotions. Vijay continued to explain how the mind overcomes being imperfect by having redundant processes check each other and in a way ‘vote’ to decide with great accuracy what is true. An example of this is a bundle of photoreceptors that are hit by photons of light. While a ton of photons might hit them at the same time and lead to confusion, the photons cleverly figure out what happened by deciding what the majority experienced. One of the things that amazes me most is how imperfect humans are and yet we are still able to outperform machines that are superior to us statically.
All of us wonder how much smarter we can become. Vijay addressed this question from a very realistic standpoint. The most important statistic of the day that he told us is that the brain is 2% of the body’s mass yet it consumes 20% of the body’s resources. Thus doubling our brainpower would require that we eat a ton more, in which case we would spend more time food gathering and less thinking. Additionally, nature imposes limits on how smart we can get, because even if you double your mental faculties you would still not be able to think twice as fast as before. While we can’t be sure without seeing how our brains evolve over the next several millennia, Vijay seemed fairly confident that our brains are quite optimized. Hearing this from a man that was quoted three times in the latest Scientific American article on neurology was quite convincing.

What an amazing day.

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