Tuesday, July 26, 2011

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.


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.