In your reflections you should write down your ideas about science, light, or topics we are covering in class. Below are some sample reflections written by TA's. Some of them contain conjectures that are not scientifically accurate but that demonstrate good scientific thinking all the same. You don't always have to be right to be a good scientist. What you do have to do is think logically and creatively about problems.

Don't constrain yourself to these topics or formats. Surprise us, capture our interest, teach us something! If you're at a loss for inspiration, you can read one of the articles on the science links page and discuss an issue you found there. Most of all, have fun! When you start looking at the world with a scientific eye, you'll be surprised and delighted at all the interesting phenomena you've been missing all these years.

#1.

A friend said that he read that you can shine light on the backs of your knees to help you wake up when you're adjusting to a time difference. Why the backs of your knees? I asked. Because there you have maximum blood flowing past, he replied. This seems to imply that some reaction happens between light and blood that makes you feel more awake. But I always thought that it was seeing more light that made you feel more awake. And not just any kind of light; for example, artificial lighting never seems to help me adjust to a time change--I have to be outside in the sun. I can't imagine it making any difference whether I wear shorts or jeans, i.e. whether my knees are exposed or unexposed to light.

My friend couldn't remember where he read about the knees and jet lag phenomenon, but if he finds it I would want to make sure that the study systematically eliminated a reaction between the light and the eye. From my own experience, I think it is more plausible that the reaction between light and retinal, stimulating the rods and cones of the eye, triggers something or releases some chemical that triggers the feeling of alertness. If the scientists kept the subjects in dim, artificially lit spaces while studying the effects of shining lights on the backs of the knees (they'd have to put a black cloth around the backs of the subjects' knees so that the light wouldn't get into the subjects' eyes), then maybe I'd be convinced that it was a light-blood reaction and not a light-retinal reaction. To persuade me, they'd also have to have tried the same tests with a lot of different wavelengths of light. I'll bet they'll find that the wavelengths that work the best are the ones in the visible range that are the most prevalent in natural sunlight.

#2.

The thing that most boggles my mind when I think about the things we've done in this class is the physical constants. Planck's constant, for example: where did that come from? Or the gravitational constant, or the speed of light. Why do these constants have their oh-so-particular values? In The Anthropic Cosmological Principle, Frank Tipler and John Barrow argue that humans could not have come into existence in a universe where the fundamental constants of physics were slightly different. The necessity of such a precarious balance of exact constants, each carried out to infinite necessarily precise decimal places, seems to imply something non-coincidental about our existence. In other words, a Designer, a God.

Eugene Wigner, a nobel prize winning theoretical physicist from the atomic bomb era, writes about "the unreasonable effectiveness of mathematics in the natural sciences." Why should the relationship between the diameter and circumference of a circle have anything to do with the way populations move? Yet that relationship, pi, shows up in ecosystems, economies, physics, chemistry, mathematics, the stock market . . . Is this also a coincidence?

What does the particular nature of the constants mean? What does the re-appearance of the same irrational numbers mean? Is the universe trying to tell us something? Is a Designer trying to tell us something? Some of the early Greeks actually killed themselves when they proved that irrational numbers such as pi existed. To them, the existence of irrational number was proof that the universe wasn't rational, so there was no point living in it. In September 1998, a movie written and directed by Darren Aronofsky called "Pi" came out that purported to examine the mysteries of this ubiquitous number. It ends when the main character, in his quest to unravel the secrets that he (and a group of Jewish cabalists) believes are embedded in the digits of pi, finally goes crazy and self-inflicts a lobotomy to escape his own conclusions. Me, I'm just curious.

#3

Last weekend I flew to Alaska. I had such a good time; you can check out the pictures on other parts of my web page. But that's not the point. The point is that I flew on a clear day and had a great view out of the airplane window. And I noticed something sort of funny: the clouds that were over the water seemed to stop at land. It was like that for the whole four and a half hour flight. Maybe this was just a coincidence, but I started wondering why it might happen and I came up with the following hypothesis.

The water is colder that the land. The general freezing-ness of the Pacific Ocean is legendary. I think it has to do with the fact that water takes longer to warm up from the sun (chemists would say it has a "higher specific heat") than land does. So maybe when the low clouds over the water hit the warmer air over the land, the warmer air causes them to dissipate. This might be the same reason why the fog rolls in over San Francisco bay but doesn't make it very far inland.

#4

My parents once decided replace all of the light bulbs in our house with those new energy saving flourescent tube light bulbs. We had one in a lamp in the living room that made the house seem haunted. We would turn the lamp off and leave the room only to return later and find the TV on. The whole family always denied turning the TV on, and eventually we figured out the lamp was at fault. Since the TV took a few seconds to turn on, you could give it a signal and leave the room before you realized you had turned on the TV. But why would the lamp have anything to do with the TV? I know that TV remote controls send an infrared signal that is picked up by the TV. So it must have been that the lamp was emitting an infrared pulse of some sort when it was turned off.

The remote control has many different commands (power, channels, volume), so it must send different signals for the different commands. How does it achieve all those commands? Maybe the signals vary in frequency, or length, or perhaps each signal is actually a series of pulses, like a code. I don't think the commands would be distunguished by frequency because remote controls are battery powered, so that's DC current. If you want a frequency, you need something in the circuit to make an oscillation. And if you need multiple frequencies, then you would probably need multiple oscillators. It seems like it might be easier (and cheaper?) to distiguish by length or code. If the remote control sends signals of different lengths, this would mean that the lamp is emitting an IR pulse for the same length of time as the pulse that means "power on" to the TV. This is a coincidence, but it is definitely possible. But it seems unlikely that remote controls would work that way. It seems like you'd have to have a pretty large margin for error to account for dying batteries or slight component difference. With all of the different commmands you have to send to TVs these days, some pulses would get pretty long. If the remote control uses a code of pulses, then most likely, the signal that means "power on" is a single pulse. It would be hard to imagine a light bulb emitting an exact series of pulses that corresponded to one of the TV codes unless the code was very simple, like a single pulse. So probably what was happening was that the light bulb was emitting a single pulse that corresponded with the signal meaning "power on" for the TV. Of course, that's all hypothesis, and you'd have to test what was really being emitted from the light bulb and the remote control to find what the similarities really were.

#5

Scientists think they are closer to discovering all that "missing mass" in the universe, or so claims this news article I just read. As I understand it, the "missing mass" problem can be summarized as follows:

* Scientists can do indirect calculations of the mass of the universe. For example, if you measure how fast the outer edges of a galaxy are spinning relative to its center, you can get a rough idea of how much mass should present. You can also look at how two galaxies interact.

* Scientists can do a more direct calculation of the mass of the universe by estimating the mass of the light-emitting objects that they see. They can also extrapolate the mass of giant dust clouds or black holes by watching the way light bends.

* The two numbers don't add up.

So, it seems like there should be a lot of "dark matter" out there that doesn't emit light, but accounts for all those gravitational effects. The above article suggests that a lot of the dark matter may be in the form of subatomic particles that have been dubbed WIMPs ("Weakly Interacting Massive Particles"). Of course, no one has found one of these particles yet, supposedly because it's very difficult to get them to interact with other particles.

This theory seems fishy to me. On the one hand, we are looking for matter that has a strong influence on our galaxy and universe. On the other hand, we apparently can't find any of it because it so rarely interacts with anything. It seems like it should be a little easier to locate these particles if they truly account for 90% of dark matter, like the article suggests.

Personally, I think that all that dark matter is in the form of golf balls. Think about it! Imagine a universe filled with golf balls (not too close together, but all spaced out). Now, golf balls don't glow, so we wouldn't see any of them. If they weren't packed really tightly together, they couldn't attract each other and form a star or anything either. Also, golf balls, with a diameter of about an inch and a half, are too large to defract light the way tiny particles of dust do. And they aren't dense enough to bend light the way a black hole does. There are probably a lot of them out there, and we'll never get to see them.

Well, it seems just as likely to me as these WIMPs.