Big Bombs and Pretty Colors

This morning we had to be in Physics half an hour earlier (8:30) to have enough time for the abnormally long presentations, but luckily Bill brought in donuts and bagels from Dunkin' Donuts so that we could have breakfast there. Then Mary gave a presentation about nuclear energy. The strong nuclear force acts over very very short distances and holds atomic nuclei together, but if you hit a nucleus with a neutron, it deforms the nucleus enough that the electromagnetic force can take over and tear the nucleus apart. This process is called fission, and results in huge release of energy. It was discovered in the 1930s when scientists were competing to create more massive elements, and instead discovered how to create more massive explosions. Another type of nuclear reaction is fusion, which is when nuclei are combined, and it is what fuels stars. However, it needs very high temperatures and pressures, so it only happens naturally in extreme environments like the centers of stars.

Mary also talked about radioactive decay and different types of radiation. Alpha radiation is high energy helium nuclei, but because the nuclei are so massive and positively charged, it is very easily stopped--even by a piece of paper or your skin. Beta radiation is high energy electrons and is moderately strong, but can still be stopped by tin foil or a thin piece of wood. Gamma radiation, however, is high energy photons, which have no mass and no charge, so it's nearly impossible to stop. Unless you're very far away, it takes 10 cm of lead to stop gamma radiation. Mary then showed us videos of atomic bombs and radioactive plates that people didn't previously know were dangerous.

Then Bill talked about the future of science. He talked about bombs and WW2, and concluded that bad situations can lead to very important advances in science, and that if we hadn't created atomic bombs many more lives would have been lost. He drew parallels to today, when the US is shying away from genetic research, but he says that even if we ban it it will continue in other countries, and if that happens then we will not be world leaders in science anymore. 

Close-up of a computer screen

After Bill concluded his talk, we had a guest speaker, Phil Nelson, talk about vision and color. He talked about how science is about experiencing things and drawing conclusions yourself, not letting other people tell you their conclusions, so he demonstrated everything he told us. He showed us that the white light from sunlight is actually a mixture of all the colors, not an absence of color. However, he also showed that you can create white light with just a mix of red, green, and blue, and it looks the same as if you had all the colors. Why is this? Color has always fascinated humans because it's useful for object separation and recognition, and even emotional signaling--but why do our eyes discard so much information, like what makes up white light?

Graphs of what colors our eyes can sense

Phil explained that it is because our eyes only have three color sensors--blue, green, and red--so since, for example, normal yellow light triggers equal numbers of red and green sensors, an equal amount of red and green light looks the same to our eyes. This can be useful because computer screens can create every color with just different intensities of red, blue, and green pixels. However, if we could make computers that had "superhuman" eyes, with sensors tuned to every color, they would be able to differentiate many more combinations, which could be applied to things like detecting DNA defects with karyotyping.

A roller coaster at Hershey Park

After lunch Mary talked about what we'd be doing tomorrow in Hershey Park, and explained more about what was expected of our group presentations (for Wednesday morning). We chose what rides our groups would be collecting data on, and Mary played "I'm sexy and I know it" while Brian modeled the incredibly fashionable vests and fanny packs we could carry our accelerometers in. Then we played around with the accelerometers to make sure we knew how to use them. 

After class, I worked with my group for about two hours to create our presentation on Resistor-Capacitor Circuits and work out what we were going to say. We also analyzed our data and fit exponential equations to our graphs. We have it mostly worked out, but if we're going to fit it and the Hershey Park presentation into ten minutes, we're going to need to go a lot faster or make it much more concise.