Solving the World’s Problems the Traveling Salesman’s Way

April 29, 2011 at 11:17 pm Leave a comment

A recurring problem for me over the past decade and more has been figuring out how to deal with the aftermath of a conversation about environmental problems. It seems like every time I sit down with a group of students (feel free to replace ‘students’ with co-workers, family, friends, neighbors or what-have-you) and we slowly we work our way through the complexities of an environmental problem, most of the participants end up feeling overwhelmed, powerless, discouraged, and extremely pessimistic. It seems a like, wherever hope for the future is concerned, a modest amount of knowledge can be a very damaging thing.

What to do?

One strategy that I have hit on is to draw a comparison with another daunting problem: the so-called Traveling Salesman Problem. This problem is easy to understand, ubiquitous, and every bit as daunting as any environmental problem, but I can easily show my students that we happily, even confidently, work on problems like this every day even though we have no idea whether we are coming up with the “best” solution.

The Traveling Salesman Problem goes like this: A salesman is responsible for sales in a group of cities. He is required to visit every city at least once in each sales trip, but to save time and money, he would like to visit each city exactly once and he would like to take the shortest trip possible overall. The problem is easily solved by “brute force” when the number of cities is small, you just write out every possible sequence of visits and figure out how much time/distance is involved in each. The best answer wins. However, once the number of cities gets into the double-digits, even the brute force approach fails (unless you program it into a computer).

Environmental problems are a lot like this. To get from where we currently are (distribution of population + distribution of wealth and natural resources + systems for extracting and distributing energy + decision-making systems + stakeholders + …) to where we would like to be, a lot of changes need to be made. And time is in short supply. So once we stop to think about how to get from “here and now” to “there and then,” the mind reels.

But, and this is the key thing, we face problems like the Traveling Salesman Problem all the time. For example, every day I write out the things that need/want to be done that day (my to-do list) and then decide throughout the day which items to work on. I usually don’t worry about having the best solution, and I know that I usually won’t accomplish everything on my list, but I don’t give up. I just do the best I can.

It turns out that you don’t have to be a big brain human to figure this out. Scientists have discovered that very simple and totally mindless entities, like the immune system’s white blood cells, can solve T.S.-type problems very efficiently (Science News, May 7, “Cells take on traveling salesman problem”). The blood cells’ job is to hunt down and engulf foreign invaders, e.g., pathogenic bacteria, by the shortest route possible. How do they accomplish this without pencil-and-paper, high-speed digital computers, or a “full and complete awareness of the problem’s scope and complexity”? Easy. They employ a strategy (“follow your [chemical] nose”) that gives almost perfect results in small systems (just a few pathogens) and pretty good results in complicated ones (lots of pathogens).

Not every solution has to be the best one. Really thorny problems can be dealt with. What other option is there? -Alan

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Entry filed under: In the News.

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