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.