The audio example is good and easy to demonstrate. A lot of positive feedback appears to be in the timing. If the input is out of synch with the action being affected it becomes a dampening effect, if it is in synch, however it quickly ramps up. Like compound interest, something anyone with a mortgage, school loans, or a credit card can appreciate.
My favorite simple example is a swing. With very little input you wind up far higher in the air than you could ever jump using all your energy, via the positive feedback mechanism of times weight shifts. You can even demonstrate this in front of an audience with a piece of sting and a weight. Waves are also good, like sound they can amplify themselves or cancel each other out, again, easily demonstrable, but heavy and messy. Anyone who has moved anything heavier than they can lift knows about positive feedback from rocking the object to get it moving. People might relate to the compound interest and swing examples pretty well, because they are something most people have experience with. Neahga On Fri, Jul 6, 2012 at 12:33 PM, Lou Gross <[email protected]> wrote: > Folks, > Dawn Stover asked for methods to explain positive feedback (for > issues such as climate change) to a general audience. For many years > I have used the most common "feedback" that general audiences > are aware of - from live audio systems. Music is ubiquitous and part of > everyday experience for our students and much of the public, and > as a concert audio engineer I am well aware how essentially everyone > has experienced "feedback". So I have a whole portion of my > general audience talks on mathematics related to biology - a > typical title is "Drugs, Sex and Rock n' Roll: Biology and Mathematics > in Everyday Experience" - devoted to first demonstrating audio > feedback (it's a simple preparation to do this in any venue I've ever > talked in - just hold your mic near a speaker), and then explaining > verbally, symbolically and graphically why it arises. > > I encourage those interested in providing an intuitive explanation > for positive feedback in climate systems to use audio examples and > let me know how it has worked for you. There are hosts of other examples > of positive feedback in biological systems (onset of contractions > in childbirth, blood clotting, lactation, action potential in nerves, > evolutionary arms races) and of course homeostatic mechanisms are > examples of negative feedback. All this goes back to Norbert Weiner's > classic work in cybernetics. > > Cheers, > Lou > > -- > Louis J. Gross > James R. Cox and Alvin and Sally Beaman Distinguished > Professor of Ecology and Evolutionary Biology > and Mathematics > Director, National Institute for Mathematical and Biological > Synthesis (NIMBioS.org) > Director, The Institute for Environmental Modeling > University of Tennessee - Knoxville > Past-President, UTK Faculty Senate > Past-President, Society for Mathematical Biology (www.smb.org) > [email protected] > http://www.tiem.utk.edu/~gross/ > http://NIMBioS.org/ >
