No Impact Man

We watched "No Impact Man" a few days ago. I was really looking forward to the movie, as I've often thought about the same exact themes in my own life.

I found the movie to be informative, entertaining, but I also fell that it fell short in a number of important ways.

The basic idea of the movie is to ask if it's possible to live in such a way that you produce as little impact as possible on the environment around you. Impact is defined in a number of ways:

• Trash
• Personal transportation (= direct pollution)
• Food transportation, electricity generation (= indirect pollution)
• Buying stuff (= consumer culture, which also leads to direct and indirect pollution)

The movie explores how much we need in order to live a happy life vs. how much we want for the sake of convenience, or because modern society has conditioned us for to want it. The protagonist and his family take some of the following steps to reduce their impact:

• Don't buy new things as much as possible.
• Instead, buy old things that someone else no longer wants.
• For instance, no new clothes, buy all clothes used.
• This reduces direct impact (no packaging trash) and indirect impact (no resources consumed to produce new items).
• This is a reaction to modern consumer culture.
• Reuse things as much as possible.
• For instance, no kleenex (use a handkerchief), no toilet paper (use textile rags that can be washed and reused).
• This is a reaction to the culture of using something once and throwing it away.
• Buy food locally.
• Locally here is defined as a 250 mile radius around NY.
• This is a reaction to the fact that modern agriculture is very oil-intensive: food is produced using fertilizer (generally, oil-derived) and transported from far away (also using oil).
• Stop using electricity.
• Live by sun-light alone, use candles at night.
• Electricity generation is very dirty, more than 50% of electricity in the world today comes from coal.
• Don't drive anywhere.
• Bike or walk.

Overall, the family manages to pull through this year long experiment and find that their life, while radically changed in many ways, was still largely happy and enjoyable. For instance, they traded TV for more quality time with friends and family; they lost weight and got into much better physical shape from eating less sugar-rich highly-processed foods and biking/walking everywhere; and so on.

What the movie did not address, unfortunately, is that such a life-style, while possible, depends on a number of unstated assumptions:

1. Time. You need lots more time to walk everywhere, cook meals from raw materials (as opposed to buying them pre-processed), and so on. In my own life, time is a scarce commodity, even though I'm keenly aware of it and try to budget it carefully.
2. Money. You have to pay the rent, pretty much no matter where you live. The movie hardly explored the fact that the wife had a high-paying job that covered their bills, and allowed the husband to basically not work for a year and stay home to conduct this experiment (with all that entails).
3. Distance. To make such a lifestyle possible, you have to be able to walk or bike reasonable distances to get food, or to go to work, etc. This is possible in NY, since it's one of the densest cities in the world. This may not be possible in a more rural, or even less dense city somewhere else.
4. Luck. Trading the fridge turned out to be very difficult because their food spoiled fast. In my opinion, the family was lucky that they didn't get sick during the second half of the movie. They probably mitigated this by buying their food daily or every other day and not storing it over any length of time. This is possible, but requires even more time investment.

Some of these issues could be addressed by living on a self-sufficient farm -- a mostly closed-loop system that provides for most of your needs, without needing to go outside it for other stuff. It's much less clear to me if an impact-free life is possible in a modern urban environment, especially one that depends on fossil fuel for energy. After all, your food must come from outside the city, and for that you basically need oil for transportation.

Even with these shortcomings, the movie was still entertaining and informative. I liked the fact that the movie took a very optimistic tone and genuinely tried to look at these problems and see what solutions might exist.

The movie also highlighted the fact that one person's actions do matter. Many people get discouraged by the fact that they might be alone in a sea of other people who don't care or are unwilling to change, so why bother? The protagonist answers, and I agree: "Being optimistic [...] is the most radical political act there is."

In terms of our own life, it prompted me to think harder about what other changes could we make to reduce our impact:

• Could we reduce single-use items (like Kleenex, shaving cream cans) in favor of multiple-use items (like handkerchiefs, shaving soap)?
• Could we go to the farmers market down the street every week instead of buying so much packaged food at grocery stores?
• Could we reduce TV/Internet use in favor of other activities?
• Could we buy more stuff used (craigslist, antique stores, etc.) instead of new?

Given where we live and where my job is located, it is unlikely that I will be able to reduce the impact of transportation, at least for the time being. But I remain optimistic.

Diodes and demodulation

As we described before, a diode lets current flow in only one direction. This is essential for demodulation: the process of extracting information from a signal. To understand demodulation we need to first understand the first and simplest kind of radio transmission -- amplitude modulation.

The goal of radio is, ultimately, to transmit sound over very long distances. A band is playing in New York and I would like to hear it in San Francisco. One way to do this is to build a sound amplifier so loud that the sound waves themselves travel directly from the origin to my ear. This is obviously impractical: it would be intolerably loud at the origin and barely audible at the destination; furthermore, you could not have multiple radio stations broadcasting at the same time, they would all clobber each other in a cacophony of noise.

Another way to do this is:

• Convert the sound wave (anywhere from 1 Hz - 10 kHz) to another equivalent wave (measured in hundreds of kHz or even MHz).
• The equivalent wave, or modulated wave, contains the original sound wave information but in a different representation.
• The carrier wave is not audible to the human ear since it is in a totally different frequency spectrum.
• Sound waves travel by making the air vibrate. The amount of energy required to make air vibrate over long distances is enormous (think loud rock concert).
• Higher frequency waves are electromagnetic waves. They can travel much longer distances using much less energy.
• Once the modulated wave arrives at my radio's antenna, the radio translates this modulated wave back into a sound wave that I can hear. This is called demodulation, and it is made possible by diodes.

 Let's first see what a modulated wave looks like (courtesy of yourdictionary.com):

The carrier wave is basically the radio station frequency. When you tune into KFRC, you tell the radio to look for sound information embedded in carrier frequency 1550 kHz.

The modulating wave is the sound. This is what is embedded into the carrier frequency and, ultimately, the "information" we want to hear.

The modulated wave is the combined wave that travels from the radio tower to my radio. Visually, it roughly looks like a combination between the carrier wave and the modulating wave, which should hopefully agree with your intuition and some of the descriptions above.

Now, we wish to turn this modulated wave into sound. To understand how that works we need to first understand how a loudspeaker works, as shown on this diagram (courtesy of soundonmind.com):

• The magnet provides a fixed, constant magnetic field.
• The signal input provides the sound wave we wish to ultimately hear.
• When the signal input goes into the voice coil, the voice coil becomes an electromagnet.
• The voice coil's magnetic field "pushes against" the magnet's field, based on the strength of the signal input.
• The voice coil is attached to the diaphragm, which is basically a piece of cardboard.
• When the voice coil moves, the diaphragm moves, and pushes air to varying extents, generating a sound wave we can hear.
• If you've ever touched a loudspeaker that was playing music, you can actually feel the movement of the diaphragm with your fingers.

Let's step back and look at the complete picture:

• We have a modulated wave that contains the sound information embedded in a carrier wave. This modulated wave has very high frequency, measured in hundreds or thousands of kHz, so it is not audible by the human ear.
• We have a loudspeaker that can convert a wave into sound by vibrating a piece of cardboard.

What would happen if we feed the modulated wave directly into the loudspeaker? Think about it for a minute before reading on.

The answer is: absolutely nothing:

• The modulated wave has very high frequency, which means that the "peaks" and "throughs" come in rapid succession one after the other.
• When a "peak" arrives at the voice coil, it starts to move the voice coil out; this takes a bit of time, as the voice coil has to physically move in order to push the diaphragm and make a sound wave.
• However, a "through" quickly follows the "peak" and starts to pull the voice coil back in the opposite direction.
• The "peaks" and the "throughs" effectively cancel each other out as far as the diaphragm is concerned and no sound comes out the speaker.

What would happen if we feed the modulated wave through a diode first, and then feed the output from the diode to the speaker? A diode lets current flow in only one direction, so the modulated wave would basically be cut in "half":

Now, if we feed the demodulated wave into the speaker:

• The first peak will start to push the voice coil out.
• There is no through following this peak, simply an empty space, or "absence of signal".
• How is absence of signal different from a through?
• A through is a negative signal -- it starts to pull the voice coil in the opposite direction.
• Absence of signal is no signal -- the voice coil is left where it is will at most react based on its own inertia or the elasticity of the diagram.
• The next peak will start to push the voice coil further out.
• As you can see, the voice coil (and the attached diagram) react only to the peaks, in other words they both move according to a wave that follows the top of the peaks.

The wave that follows the top of the peaks is our original sound wave! Look back at the first diagram to see it, or just trace the peaks above with your finger.

The coil and diaphragm end up vibrating the air in accordance to the original sound wave, therefore producing sound we can hear. The diode demodulates the modulated wave back into sound we can hear.