Time's Flying

I stepped into class today with a couple of bagels from the campus bakery and took my seat. I’d have to say that today is the first day where it’s really hit me that I have to go home in only a few days. It’s hard to walk anywhere on campus without seeing a few Ben Franklin quotes, and I think one of the ones that has stuck most is, “When the well is dry we know the worth of water.” I’m realizing now that I only have a few days left here so of anything I’ll try to appreciate them more than any of the others instead of whining about it. Anyways, I was in a very receptive mood for Ryan’s lecture on radioactivity and I think I learned a lot from it.

Ryan first discussed the development of what we know about the atom and how we learned it. This stuff was mostly review for me because of my chemistry classes, but it honestly amazes me every time how scientists such as Thomson and Rutherford pieced together an accurate model of the atom while everyone else thought they were crazy at the time. It also impresses me how each of these atomic models built on the last but did not totally discard. Thomson proposed that there were positive and negative charges in the nucleus and Rutherford discovered that the nucleus is actually a dense positive center. This model was improved on by Niels Bohr where he theorized that electrons orbit the nucleus much like planets do the sun. This was later revised, but the ideas of each of these scientists were still kept in some form.

The next part of Ryan’s lecture was talking about the uses of nuclear energy and a few common misconceptions about it. One of the first things he summarized is how a nuclear reactor works. By packing together fuel rods near each other, the excess neutrons from an atom fly out and then hot another atom which produces a couple more neutrons for each one that hit it causing a chain reaction. Then, what surprises a lot of people is that this energy is simply absorbed and used to boil water. From this point on, the power is generated just as it is in any other power plant; the steam is used to drive a turbine which turns a magnet which creates a current.

One of the first misconceptions that Ryan sought to debunk is that many people think of radiation as dangerous and very negative. What many people don’t realize is that radiation also has many applications that are very beneficial to humans when controlled properly. One of the biggest areas radiation is used to benefit humans is in the medical industry. As I believe Ryan pointed out, the acronym MRI is really missing a letter; it should really be NMRI which stands for Nuclear Magnetic Resonance Imaging. MRI machines use carefully aimed radiation to get something like an X-ray of your body, but 3 dimensional and with a low dose of radiation. Furthermore, radiation can be very carefully aimed at malignant tumors in the body to kill them before they mestastethize. Although this treatment is not always successful, it can help in some cases and is certainly a good application of radiation.

The day only got better as we got further in, because the next part of our day was about string theory. We watched a brief movie on the fundamentals of string theory, and then talk to one of the leading experts in the field, Burt Ovrut. The fact that Burt truly talked to us and didn’t have a lecture prepared made his talk extremely valuable because we could easily tap his brain about any part of the subject we were interested in. The basic premise of the talk was that string theory proposes that the universe is full of tiny vibrating strings that when struck at different frequencies act as the ‘particles’ we commonly observe. I will avoid trying to dump a huge amount of information here, but the reason that string theory is so important is because it could unify all of physics as we know it. Today, physics is a shattered mess of quantum mechanics, general relativity, and a bundle of different forces. String theory is intriguing because when you work out the complex equations, there are simple solutions to these complicated problems. For example, string theory predicts only one force instead of the gravitational, electric, magnetic, strong, and weak forces as we know them today. As Bill always says, it’s only philosophy until there’s solid evidence, there is little evidence to support string theory today. However, the Large Hadron Collider in Switzerland may well find evidence for or against sting theory, and guess what college physics program helped develop some of the detectors for the LHC. That’s right, scientists at UPenn helped. It’s very exciting to be around a place where there is so much progress going on.

Traveling at the Speed of Light

Class today was very laid back. We started off the day with our speed of light lab. Since we had already set up our circuits, all that was left to do was line up our laser with a mirror across a dark hall in such a way that it bounced back and hit our second photo receptor just right (the first sensor was placed next to a beam splitter in front of the laser. Both receptors were attached to an oscilloscope so we could determine the delay between the two waves (it came out to about 8 nanoseconds). Because we knew the length that the light had to travel from the first sensor, to the mirror and back to the second sensor, we were able to measure the speed at about 3.4 x 10^8 m/s, which is not too far off the accepted value. We were given two hours to collect our data and make our calculations, but because my group finished early, we had about 30 minutes to kick back before our guest lecture.

It was good we were given that time because after a short break, I was able to give all of my attention to Ken Lande when it was time for his lecture to begin. Dr. Lande spoke to us about the energy crisis, how long our current consumption of petroleum can be sustained, and the effects waste products such as CO2 emissions are having on the environment.

Once he convinced us that an alternate source of energy was necessary, he discussed possible solutions. I was surprised at how inefficient the current sources of green energy are. For instance, in order to power the united states with exclusively solar energy, an area twice the size pf Pennsylvania would need to be covered with solar panels. Even more shocking was the amount of land that would be needed to grow crops for bio fuels to power the country: 1/6 of the area of the United States, which would not leave very much room for agriculture. We also discussed fission reactors, but after the disaster in Japan, people are hesitant to rely on something so potentially hazardous. Additionally, in order to rely on fission reactors for energy, we would need to increase the number of plants we currently have by a factor of five. Dr. Lande maintained that the most promising alternate energy source is wind turbines. Only half a million wind turbines would provide enough energy to free us from our dependence on fossil fuels, which would only cost about $200 million a year (only a fraction of what we spend on automobile gasoline).

I appreciated his lecture for its practicality in the real world, in fact he often teaches classes at Wharton school of Business because there is so much money going into alternate energy sources. No wonder too, it is arguably the most pressing issue the world faces today. Me and Brian discussed its importance and the lecture in depth as we walked to lunch.

When we returned, we were given time to do whatever it was we needed to get done. For me that was working with my Hershey Park group on making a PowerPoint for our presentation tomorrow. We wrote up an analysis, slapped a couple graphs of the data we collected, added a video and called it a day.

After class, I went with a book and read for a while by the coy pond. It was very relaxing and it allowed me to sit back and let time move a little slower for a while. With only three days left, I want to get everything I can out of the time I have.

Energy

Yesterday I talked about how building our light-speed measuring device tied together many of the concepts we’ve been learning, but today was even better because we actually operated our device and got values for the speed of light. The first thing we did was to take our laser in the hallway, remove as much light from the hall as possible, and to set our mirror a ways down the hall from our laser. The next step took a lot of fine tuning, because the laser was far away from the mirror which was small, any tiny adjustment to the angle of the laser would throw it feet away from our target, the mirror. After plenty of trial and error we got our laser beam aimed perfectly so that it the beam split in half where one beam immediately entered the oscilloscope and the other beam went down the hall bounced back and then entered the oscilloscope. In order to keep our data as clear as possible, we did several things such as re-concentrating the laser beam onto our sensor after it had hit the mirror and bounced back. Once we got the whole system set up, taking our measurements and understanding what they represented was actually relatively easy.

By reading the time difference between the wave leaving the laser and immediately hitting the oscilloscope and the one that travelled, we had a time measurement for how long the trip down and back the hallway took our light beam. We recorded this data and then measured the distance down the hall and the distance back to our sensor. As I said earlier, the technology we used was complicated, but the idea was simple because all we had to do to calculate our value for the speed of light then was to divide the distance we measured by the time it took to get our speed value which ended up at 3.4*10^8 meters per second. We measured the distance after we got our time values so that we would essentially be doing a ‘blind’ experiment so that we couldn’t change the numbers to better fit the already known value of approximately 3.0*10^8 meters/second. For two days of high school students working, I was quite impressed by how close we got to the actual value. Once again, many thanks to Bill, Ryan, Craig, and Mary for guiding but not pushing us through the experiment.

Once again I was excited to listen to another guest speaker, Dr. Ken Lande. I was particularly excited to listen to him speak because he was speaking about one of the topics I am most interested in – solving our energy problems-. I have had a passion for energy conservation since I was much younger and I changed all the bulbs in our house to compact fluorescents. Ken began his talk by painting the picture of the sad state that American energy supply is in today. Nearly as pressing as the budget deficit deadline, the world is approximately at the date of ‘peak oil’ where the most oil is being extracted per day and the extraction can only decline from here on out. Obviously this is a huge problem, because while our oil supplies are dwindling, our appetite for oil is not. Additionally, climate change has presented a huge need to immediately begin weaning ourselves off of fossil fuels.

While the first part of Ken’s talk was quite frankly depressing because of the seemingly unsolvable crisis of fossil fuels, Ken soon shifted his talk to possible solutions to our energy need. The main possibilities for our energy supply as Ken sees it are photovoltaic panels, solar thermal concentrators, wind turbines, bio-fuels, wind, and nuclear power. I suppose I am biased towards solar energy because I live in California where we have tons of intense sunlight, but Ken presented his best idea as a blend of wind power and nuclear power. He presented a very well-developed argument because we already have the technology to make millions of wind turbines, and wind is also a close second to fossil fuels such as coal economically. While it’s a painful reality to face, it’s important to realize that all change in the world is driven by economics, so the fact that wind is comparable in price to fossil fuels makes it very appealing compared to solar which costs nearly 3 times as much as coal. Additionally, Ken argued for nuclear power because although it isn’t renewable, we have a massive amount of energy that we can harvest from uranium and plutonium. Although nuclear power is currently frowned on because of the meltdowns in Japan, there are much safer reactor designs that are possible, and either way nuclear energy is a must because the problems of climate change and literally running out of fossil fuels will force alternatives. Additionally, Ken pointed out that for the number of deaths associated with mining for fossil fuels compared to those from nuclear meltdowns, nuclear is safer. In a sense, the stigma associated with nuclear power vs. coal is like that of airplanes vs. car crashes. Although the deaths due to car travel per mile are literally orders of magnitude higher than those for plane travel per mile, people make a bigger deal out of plane crashes because they are so conditioned to accept car crashes but plane crashes happen rarely and are therefore a big deal. I don’t mean in any way to say that nuclear meltdowns are a small matter, but based on the safety statistics and energy demand, it is a good alternative.

I was very impressed by Ken’s lecture and the thoughtful questions that my fellow students asked. I have been interested in this field for a long time, and today only wet my appetite more.

Speed of Light Confirmed

We got it working! Our contraption that we had hoped would measure the speed of light actually worked this morning. Well, I shouldn’t say that WE got it working. Apparently the same problems that were occurring with our apparatus were also present in several other groups. Because of this, Bill and the TAs stayed after class several hours yesterday to diagnose and fix the problems with our machines. Apparently the problem was with the scanning range of our oscilloscopes. This was a relief because it meant that we did not cause the problem. Once we did the final checks on our circuits and oscilloscope, we moved our cart with our apparatus on top into the hall. We had to place the laser and light-receiving diode at one end of the hall and put a mirror far enough away so that we could get a decent measurement. We placed our mirror about fifteen meters away from the laser. Once we had everything aligned correctly, which actually took a while because the laser was so small and the mirror was so far away, we began taking our measurements. We measured the wavelength of the laser at two points: one about two centimeters away from the tip of the laser and the other at the diode when the light was bounced back by the mirror. The oscilloscope showed us both wavelengths on different channels so we could find two peaks in the wavelengths and measure the time between the peaks. Our first time was about two-hundred nanoseconds, which means that is how long it took for the light to go from the laser to the diode. We divided the distance traveled by the light by the time it took for the light to travel that distance, because velocity is distance divided by time, and our answer was not what we were looking for. Our results actually told us that the laser was travelling at twice the speed of light. After much trial and error, we asked Ryan what we could have possibly done wrong and he told us that there was too much noise in our data. He helped us get a stronger focus on the wavelengths of the oscilloscope and once he did that, the rest was easy. We found two peaks, measured the time, and came to the correct result, 3*10^8 . Well, we actually got 3.06*10^8, but the difference is negligible. Ryan actually did not believe us when we told him that our measurements were not that close to the actual result. Apparently other groups were getting results around 3.20*10^8 or 2.8*10^8, which is understandable because there are several errors that could occur. We did it though. We measured the speed of light.

Believe it or not, that's a tape measure...a deadly tape measure...

Bill helps us with our oscilloscope

After our lab, we were given a lecture by Penn professor Dr. Ken Lande. Dr. Lande focuses his research in experimental astrophysics and the investigation of fusion energy. His lecture was one of the most interesting yet. He discussed the energy crisis and the different options we have in fighting it. According to Dr. Lande, our options for alternative energies include photo-voltaic solar light converters, solar thermal concentrators, wind turbines, bio-fuels, and nuclear power. The most viable solution of these choices at the moment is the implementation of wind turbines. This is because they are cheap to produce and construct (relative to the other choices) and they are the most efficient form of capturing natural energy. I was very interested to hear about what Dr. Lande said about the best form of alternative energy was because I had to debate that very topic three years ago in Forensics. He also discussed the use of nuclear power, primarily fission reactors. The US has only one-hundred and two fission reactors that we use for twenty percent of our energy needs. France has many more reactors and supplies 70% of its energy needs using fission. It is astonishing how politics can get in the way of what could possibly end one of the most significant issues of the century, certainly of my lifetime. I asked Dr. Lande about the use of IFRs (Integral Fast Reactors) and whether they were more or less safe and about their efficiency after the lecture. He told me that this style of fission reactor was incredibly efficient and was proven to be safe, but because of the political climate and decisions made around the ‘70s the project was put on hold indefinitely (thank you SO much former President Carter). I enjoyed Dr. Lande’s lecture very much and it was clear that Bill had been saving one of the best for last.

Dr. Lande presents a possible solution to the crisis

After our guest lecture and lunch, Brian, Julia, Mike, and I met back at DRL to begin our PowerPoint presentation on the Sooperdooperlooper, the roller coaster we had to analyze during our time at Hershey Park. We did not finish the PowerPoint at the labs because Mike had to commute back home and we preferred to finish at the dorms. We decided to include some history on the ride and a detailed description of what riders experienced while on the coaster. In addition to these, we had to type up descriptions of the physics behind the ride, which is the real meat of the presentation. We conclude our presentation with our graph data on the different accelerations of the carts as well as the altitude throughout the ride. Following our graphs, we will show the video we took of the ride, even though the protective bar on the cart obscures most of the view. Due to the low quality of our video, we also included a link to the YouTube video that shows the ride from a first-person point of view. The video is much better than ours and I think it will be a great way to conclude the presentation. I have a lot of confidence in our presentation as well as the data we will be presenting.

After putting the finishing touches on our PowerPoint, I headed down to a large field near the DRL to play in what was supposed to be the staff vs student ultimate Frisbee game. This wasn’t exactly how it played out because there were only three RCs. It was still a great game, regardless, and I definitely had a lot of fun. I even got to know a couple of the RCs better that I had not had the opportunity to meet previously. I also surprised myself in this game because I was a lot more useful to the team than I usually am. Usually I just hang around the other team’s goal, unnoticed by the other team for the first few goals of the game, and wait for my teammates to get the Frisbee. I can usually get a few goals this way because I am relatively open and already near the goal while everybody on the other team has to run back to play defense. Instead, I was much more mobile in this game. Although throwing was still my Achilles heel, I was playing more offensively by intercepting and blocking throws, in addition to my usual strategy. It was a great game concluding game of ultimate Frisbee and I will miss playing such a fun game with my Penn peers.

The rest of the night was basically just spent lounging around the dorm. Fred, Onur, Alison, Brian, and I were all quite tired from our intense game of Frisbee so we did not feel like doing much of anything. We all sat around in my dorm listening to music, sharing our favorite videos on YouTube, and playing a game called QWOP. In this game, you control an Olympic runner and you have to control his thighs and calves using the Q, W, O, and P buttons in order to make him run. It is nearly impossible to control the runner, but it is incredibly entertaining to watch. We also ordered Insomnia Cookies and had them delivered to the dorm. It was quite the evening, even though we didn’t do much of anything. We just enjoyed each other’s company.

Three days remain.

Oooooobleck!

Maximizing the amount of sleep I get lately has been one of my top goals. Last night I got plenty of sleep and felt energetic and ready to head to class. I grabbed a quick breakfast to eat on my way/in class and then walked over to our class with Alex because Julia had already left. Alex and I were a little early today, so I had time to say hello to my friend Mikael before class began. Today was unique because Bill tied together many of the ideas we have been studying in the last few weeks into one large goal for the next couple of days – measuring the speed of light-.

To be a bit more specific, over the last several weeks, we have studied mechanics, optics, learned to use oscilloscopes and many other neat things. These topics are being united in a way because measuring the speed of light we will need to use our knowledge that we gained here to put together a device that is essentially a laser that sends out a beam of light that we split, reflect, and carefully time how long the pulse takes to return to our oscilloscope which we learned how to use last week.

To be honest, actually walking into the lab and seeing the dozens of wires and pieces of equipment that we had to hook together I felt like we wouldn’t be able to actually create the device that we needed to. With some excellent teamwork we actually managed to put together several of the circuits before we asked for help. Our teachers all have a nice approach to helping us where they try to steer us in the right direction and only interfering if we’re totally stuck. Today, Mary helped us several times when the wiring diagrams got a little overwhelming or we otherwise got stuck. I was very grateful for her help as well as Bill and Ryan’s and sooner than we expected we had constructed our light-speed measuring apparatus.

Next up, we were lucky to get to hear from another one of Penn’s faculty, Dr. Phil Nelson. Something that I’ve found great about the UPenn faculty we’ve gotten to listen to is that while they are very well educated and deeply into very specific research, they have all been excellent speakers as well. Phil spoke today about light and color. The first thing that he did was demonstrate how our eyes combine colors to make other colors. He showed us a pure yellow slide (which he proved was only yellow by shining it through a prism) and then showed us how he could overlap a red slide and a green slide to create an identical looking yellow. However, the mixed yellow could be separated back out into red and green. Then Phil began to throw some questions at us, why do our brains combine these colors instead of sorting them out? Can electronics make superior vision? And what are the applications of this knowledge?

Phil began to answer his first question by speaking about a man named Thomas Young. Young made many very accurate predictions about color and our eyes almost 200 years before his hypotheses could be confirmed. Perhaps the most consequential hypothesis that Young made is that the response of the photoreceptors in our eyes to light is equal to the Intensity times the Sensitivity. Thus our photoreceptors must sacrifice some clarity in order to be sensitive to a wider range of colors. For evolutionary reasons, humans have evolved to have three different types of photoreceptor cells that each specialize in decoding what we call red, green, and blue light. Because these photoreceptors are tuned to these colors, our brains must guess when something is in between these colors and that is where the red and green look yellow. Our brains see that the red and green photorecetors are reporting the same amount of light and ‘average it’ to yellow. Phil then talked about the many applications of this knowledge. Perhaps the most obvious is that LCD and Plasma screens each use different combinations of red, green, and blue light to make every color they display. The other applications are countless, and once again I was impressed by how articulate and relevant Phil was.

In the afternoon, it was time for my group to present what we have been working on for the last several days. As a brief synopsis, we have been experimenting (playing) with a mixture of cornstarch and water called oobleck. Oobleck is classified as a non-Newtonian fluid because it behaves as a fluid when you move something slowly through it, but it behaves as a solid when you quickly try to move through it. This has some interesting results, because you can slowly sink your hand into it and it’ll get wet and covered in oobleck, but if you punch it as hard as you can you’ll probably end up breaking your knuckles. Today, my group displayed these properties by making four huge tubs of oobleck and then having the entire class run across the surface. Watching them do this was a bit of a cruel natural selection process because the faster students made it out unscathed while those who hesitated sank in and then had to struggle to get out.

Overall, today was a lot of fun because I worked hard with my group in the morning and overcame obstacles, I enjoyed hearing another incredible lecture, and I had fun making a mess in the afternoon.

Oh, and my favorite thing that Bill said today was about how earning a PhD is beneficial, “By learning everything about something, you learn something about everything.” I don’t know if my educational interests will take me in the direction of a PhD, but I thought that quote really summed the idea of a PhD up nicely.

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.

Run!

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.

Physicists Are Not Afraid to Get Their Hands Dirty

I am continually forced to rethink my definition of "most exciting class ever" with Bill's physics course. You'd think roller coasters would prove hard to beat, but literally every class brings something new to get excited about. Today, it was more than something; it was everything. Even just the set up for the lab we are going to perform tomorrow to measure the speed of light got my blood pumping.

Admittedly, the first hour of class was incredibly hard to follow. Despite Bill's exceptional ability to eloquently explain complicated topics, describing how to build a circuit with a light-sensing diode or a laser controlled by a transistor and connected to function generator is no easy task.

Consequently, it wasn't until we broke up into our new lab groups and got to fiddle with the wires and the circuit boards that the diagrams we were given (on the left) started making any kind of sense.

At first it was confusing and slightly frustrating, especially because Bill specifically told us that he had it all set up last night so everything was working perfectly, but disassembled it just so we would have to put it back together. Once we transformed the diagrams and mess of wires and banana plugs into the mechanisms we would be using to perform our experiment, I understood why he did it. Even before the experiment began, I already felt a sense of pride and ownership regarding the data we are going to collect with the gadgets that we built ourselves. Not only that, but we have a much deeper understanding of how our tools work and therefore what the numbers that come up actually mean.
Each week it seems we delve even deeper into the realm of what experimental physics actually feels like. In this further step, not only are we collecting our own data, but we are building our own tools with which to do it and it feels amazing. If this ends up being what I do for a living, I will have no objections.

After the lab setup, guest speaker Phil Nelson spoke about the physics of human and superhuman color vision. He began with a puzzling paradox about yellow light. First he showed us pure yellow light, visible in a spectrum created by shining white light through a prism. Next he showed us a square of yellow light made by a projector. When he diffracted this yellow light with the prism, he did not get yellow light, instead he got red and green. The question that he posed was why our eyes were unable to distinguish between the two (true yellow light versus the red/green mixture).

To explain this phenomenon, he described to us the way our eyes perceive color. Specifically, that the photo receptors in our eyes are capable of distinguishing between blue, green and red wavelengths. These can be expressed as curves showing how many photons of each particular color are sensed. The reason we are unable to distinguish true yellow from the mixture now becomes clear: our eyes can only measure the relative presence of green and red light. Therefore, because yellow neighbors both green and red on the spectrum, true yellow light contains traces of wavelengths from both red and green and so is indistinguishable to our tri-color sensitive eyes.

He went on to suggest that if we create a machine with the ability to detect more than three discrete wavelengths, it proves useful in a number of fields. Spectral karyotyping, for instance, uses such machines to detect subtle differences in stain colors of chromosomes, allowing scientists to conduct studies regarding genetic mutation, cancerous cells, and the genetic history of evolution. Superhuman color detection also allows scientists to maps the connectomes of mouse brains. When Nelson mentioned this, it really got my attention because I had seen the images he had displayed before on a podcast - the very podcast that got me interested in neuroscience in the first place. I was not aware when I watched it however, how interdisciplinary the sciences that were used in developing the method were. In fact, it is remarkable how often the guest lectures tie into my prior knowledge, and also to each other. I am slowly realizing as the weeks progress that it is very difficult to find scientific research that is independent from a network of other fields, which to me is what makes science truly spectacular.

We took a long break for lunch today so that the Non-Newtonian Fluids group could set up their "demonstration". Really, it was more like two hours of the entire class playing with the vats of "oobleck" that they brewed up. The stuff is surprisingly entertaining. We ran our fingers through it, slowly at first sow that it flowed like a liquid, then quickly so it ripped like a solid. If you moved fast enough, you could form it into a ball, but once you stopped applying pressure and just let it sit in your hand, it would melt away and slide through your fingers. Needless to say, it wasn't long before we were all covered with the corn-starch/water mixture. To demonstrate the unique principle of more applied force creating a larger resists to that force, we punched it and slapped it and threw stuff at it, and then we started to get really creative. Bill dropped a bowling ball into one of the vats and the effect was counter intuitive (as non-Newtonian fluids often are). Instead of the six pound ball creating a splash in the tub of liquid, it almost bounced off the surface before slowly sinking in.

Of course, the next step was to line the three containers up and have people run across it. The different techniques that people used to stay on the surface varied greatly. Some students hopped from tub to tub like hopscotch. This worked for some people, but when I tried it I found that the time between jumps was so long that I started to sink in as I prepared for the next jump. The easier thing to do was to continuously stomp on it, as if you were smashing grapes while running across. A surprising amount of students chose to walk through it to see what it felt like. The trick to walking is to move as slowly as possible, because as hard as it is to get something to move quickly into the mixture, it proved even more difficult to yank a foot out.
Bill wrapped the day up nicely with a demonstration of how a pro does it:

When the excitement was over, I returned to the quad and rested for a while before going out to famous cheese steak restaurant Pat's King of Steak, for Emily, the Texan on our floor's birthday. I have to say I was disappointed with the quality of food they served there. For such a famous place, the sandwiches were just not tasty. I much preferred the random little shop we found in our first couple days in the city. But we ate cake, sang happy birthday, and got to see more of the city it was an altogether pleasant experience.

As we walked off the bus, we were surprised to see it had started raining in the time it took us to make the trip home. Instead of retreating into the dorms, I took of my sneakers and played some Frisbee in the wet grass. Even though I got soaked, the air was warm enough that I didn't freeze to death like I would have back at home.

Once I got myself dried off and cozy, I relaxed in my room for the rest of the night.