Monday, July 25, 2011

Man-made Quicksand in the Rain

Even though it had only been three days, while I was walking to class it felt like it had been a very long time since I had last been in the DRL (David Rittenhouse Labs). Today’s class was challenging, to say the least. We began class with Bill explaining how exactly we are going to measure the speed of light. In order to measure the speed of light, we will split a pulsed laser beam right at the tip of a laser pointer. Half of it will signal one channel on our oscilloscope. The other half of the beam will travel the length of the room and will be returned by a mirror. A lens will focus the returning beam on a photodiode that is connected to the second channel on our oscilloscope. The separation between Channel 1 pulse and the Channel 2 pulse indicates the time taken by light for the round trip. That doesn’t sound too complicated, right? In practice, however, it is pretty confusing. In order to get all of the apparatuses set up, a series of circuits have to be made, certain wires have to be connected in just the right places, and all of the pieces have to come together and work in unison so an accurate measurement can be obtained.

As Bill went through the procedure in his lecture, it seemed easy enough to follow, but this was not the case when we had to assemble everything. Progress was slow. We managed to get the laser working, but after that we were having trouble making our circuits. Thankfully Ryan, one of the TAs, was able to point us in the right direction and we were able to get everything connected so that it should have worked. However, it did not work for some reason. We spent the rest of our time in the lab making adjustments to the oscilloscope and our circuits, but to no avail. Before we could find the correct arrangement, it was time for our guest lecture. We will have to figure out our problem(s) tomorrow in class. Thankfully we get two days to do this lab.

Our guest lecturer was Dr. Phil Nelson, who is a part of Penn’s Nano-Bio Interface Center, and the Institute for Medicine and Engineering. His lecture was about light and its erratic behavior. The lecture was actually half bio-physics, half optics. He began by combining different colors of light and splitting white light into a rainbow by using a prism, but as the lecture continued he began talking about how our eyes and brain perceive colors. He explained that color is of vital importance our survival because it is a major factor in how we identify things in our environment. He also said that our eyes omit a lot of information and that they only pick up certain spectral colors. What I found the most interesting was his discussion of photons. He told us that photons arrive at random, no matter how hard we try to make a steady light. Their average rate corresponds to what we think of as brightness. In class, we have mostly been referring to light as a wave. We have acknowledged that it was also a particle, but this was the first time that we had every really analyzed light in that respect.

Phil Nelson discussing the interaction of different spectras of light

After lunch, we returned to the labs for the most fun part of the day. The ooblek group was finally going to get to show off what they have been learning for the past week by preparing small pools of the mixture. They prepared four tubs of the muck and, when it was all ready, they had people run across it. Most of the class ran across, save about eight or so people, and it was very fun to watch. I didn’t run because I was taking pictures and videos for almost the entire time, but it was fun nonetheless. Some decided to just run across, while others just walked across to see what it would be like to try to get out of quicksand, which is basically what ooblek is. We spent the entire second half of class outside the DRL playing in ooblek and it was one of our best sessions in class thus far.


Brian helps Bill mix the ooblek

After class, Onur, Brian, Julia, and I returned to the dorm and began our PowerPoint presentation on Newton’s Law of Cooling. It was actually easier than I had anticipated. We already knew everything we needed to know about the law, so we just had to organize our thoughts, data, and pictures. We finished preparing the presentation in about an hour. Now we just have to decide who will be covering which part(s) of the presentation and rehearse our information. I am confident that we will be able to do this with little difficulty.

A quick dinner was next on our agenda. Onur, Fred, Brian, and I headed over to the commons, while Julia went to go play squash with Abheek. When Onur and I exited the commons (Brian and Fred left dinner early to go to the gym), we discovered that it was raining. This was different rain than what we have been getting though. This rain actually fell for a good hour, maybe more! I am unsure of the exact time, but I do know that it was very refreshing and it got rid of the humidity in the air. It was actually such a welcome occurrence that Onur, Abheek, Julia, and I hung out in the middle of quad for the duration of the rain. It reminded Abheek of his home in London, just as much as it reminded me of rain back home in the Bay Area. It was a nice change, especially after that massive heat wave last week.

The rest of our evening was spent lounging in our dorm. Fred and Onur hung out for a while and we watched funny YouTube videos while we listened to music over Onur’s speakers. We are all well aware that our time together is getting shorter. Fred even began packing up clothes that he didn’t think he was going to wear in the next four days. It is sad to think about the fact that our family will be disbanding so soon, but our strong friendships and memories of the fun times that we have had over the past three weeks will make it easier to deal with. I look forward to the next few days, both because of class and the last few nights with friends. Tomorrow is another day, and I’m ready to face it, even if it means dealing with that confounded contraption we are using to measure the speed of light. On that note, good evening.

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