Many years ago I lived in Southern California. While the weather was foreign to my Montana experience, what really impressed me was the pollution - thick, stinking photochemical smog and soot. At least once a week you had to clean a brownish film from the windows and wondered what your lungs looked like. Visibility was frequently well under a mile and the nearby San Gabriels were mostly hidden from view.
I only make it back to the area every five years or so, but each time I've noticed the traffic is worse and the air is cleaner. On the last visit I was on the beach in Venice with a spectacular view of the mountains. Regulation of emissions that drive photochemical smog has been the game changer and there has been amazing progress. This begs the question of what the air was like in earlier times - when did it get bad?
One reads accounts of terrible smogs in industrial areas in the 19th century. The efficiency of early internal combustion engines was terrible. Early steam engines converted less than one percent of the energy in the coal they burned into useful work. Home and office heating was done with wood or coal at similar low efficiencies with fireplaces in the low single digits until Ben Franklin and Count Rumford came up with designs that were efficiencies in the 10 to 15 percent range. Inefficient combustion of coal and wood creates a lot of unburned and partly burned byproducts. Not exactly a lung friendly period if you lived in a city or industrial area.
By 1850 the industrial revolution was beginning to bring major change in Europe and the US, but it was just starting to ramp. We didn't have electricity or petroleum. Transportation was primitive and agriculture accounted for an enormous amount of human and animal labor. At the same time work we were getting from our dominant energy sources of wood and coal was at the cost of great inefficiency. Looking into the numbers leads to a startling conclusion - the average American only uses three times as much energy now as in 1850, but we get much more work out of it.1
The answer to the question "how has the average American's energy use changed over time?" is not as obvious as one might think and leads to a host of new questions. Unfortunately many people stop looking at seemingly simple questions as they get older. For whatever reason they aren't asking the basic questions that they might ask when their age was closer to their shoe size.
As an undergraduate I took a seminar class devoted asking simple questions. In many ways this is all physics is, but the approach was to consider the every day world and start with the questions a ten year old might ask. Once the question was asked the trick was to build several simple hypotheses and finally to analyze them with whatever tools we had. Some questions turned out to be very deep and others were simple. All were interesting. Many were part of folklore - folklore that was wrong. Each session was devoted to diving into two or three questions with a few more assigned as homeworks.
One of the first homeworks was "why are trees tall?"
A great question. I remember doing a simple calculations on the popular explanation which lead to the obviously wrong answer that a tree could only grow to a height of about thirty feet. There were ways to patch this, but all of them were wrong. That lead to thinking about negative pressure in liquids. I asked a biology student who didn't understand the physics, but gave an important clue - enough for me to propose a model that might work and worthy of test. As it happens it turns out to be what is observed.
This is a great way to teach science assuming the student has enough background to pose and work through a variety of models. It turns out how many scientists work when they're playing with an idea. Ten bad approaches and then one that might have a bit of merit. It helps you form the right questions - those that require observation and experimentation and those that might lead to something deeper.
Great, but how do you teach science to those who are interested in other paths? A bit of science literacy is important in modern society, but unfortunately education often breaks down. I've been puzzling this for the past few years. One of the people who has been helping me think through these issues sent a video that illustrates a nice path. It happens to be the tree height problem and uses effective story telling to get the core points across. Watch it and see what you think. Although it lacks the depth an engineering or science student requires, it does a great job at getting the core idea across and gives a sense of the play of science.2
Story telling, particularly cinematic or visually beautiful story telling, can be very powerful. The trick is a compelling and accurate enough story for the audience. Very difficult in practice.
1 There are limits. The best steam engines have improved in efficiency by an order of magnitude since 1850, but we're near theoretical limits. Improvements have to come from other areas.
2 There are several difficult problems to solve - the most difficult is how much is enough and still correct? I, and many scientists, tend to drill in. Rather than talking about the assumption that water can only be drawn up about 30 feet, my natural inclination would be to show why. There is also the issue of creating a compelling story. I've been fascinated with Horace Dediu's Airshow approach for talks to small groups. The thinking and discipline that goes into it may well lead to the necessary constraints for general audiences.
Just a sketch without measurements this time -- oven dried tomatoes. Tomatoes this time of year are mostly awful, but you can use great canned tomatoes for many dishes and turn cherry or plum tomatoes into something great by oven drying them. I cut them in half and arrange them cut side up on a baking sheet, add some sliced garlic clove, sprinkle on a bit of sea salt and thyme springs and drizzle on a good extra virgin olive oil. Finally the sheet goes into a 300°F oven for about an hour and fifteen minutes until the tomatoes are shrunken and the garlic turns golden brown. Discard the thyme sprigs before serving. This is really good on pasta!
(if you must have measurements I used a quart of cherry tomatoes, 4 thinly sliced garlic cloves, about 5 springs of fresh thyme and a fair amount of olive oil (probably a quarter cup)