Loopsidaisy
Programming is fun
A loop is a structure where the start adjoins the beginning. We can make a loop out of string by tying the one end of the string to the other. Interesting to kittens perhaps. But a loop within a loop makes a lasso which is a tool adequate to capture horses or cattle. These are physical loops. Feedback loops are more abstract (though still physical) sorts of loops. We've all heard feedback loops (say when amateurs set up the audio at a demonstration) - all of a sudden the speakers start screeching with a steadily increasing pitch. A system that formerly accurately amplified the volume of an input sound now uses any input sound to produce the same screech. And it's easy to understand what's happening. The sound from the speakers is input for the microphone which drives the sound from the speakers. This is a loop. The frequency of the screech of an audio feedback loop is determined by how fast a sound can hit the mike and drive the speaker to make a sound to hit the mike. That is the frequency of the screech shows the time for one cycle of the loop to play out. This gives the potential for extremely sensitive measurements - a potential exploited by electron tunnelling microscopes that can both detect and move individual atoms.
It's not hard to see evolution as a feedback loop of sorts. Each generation is the product of the preceding one and produces the succeeding one. But evolution is a strange sort of feedback loop - not all of the products of the loop feed back in and influence it. So when conditions are stable a certain sort of equilibrium is attained. And when conditions change then there new elements get incorporated in the loop. Loops are used a lot in computer programming. Here's a simple one:
for x = 1 to 10
print x,
next x
as you might guess, the output is 1 2 3 4 5 6 7 8 9 10
This is much easier than writing
print 1,
print 2,
print 3,
. . . . .
especially if the limit was 100 or 1000 or . . . . .
Here's another way to write a loop: z=z+1. Each time you run that statement z gets increased by 1.
Pretty cool huh? Well - fundamental but boring.
How about if we complicate it a bit?
z = z times z + 1
In this case z gets large very quickly - it zooms off to infinity - still pretty boring.
If you add a further twist; make z into a complex number (I won't go into that now) but you get loops that produce the sort of image over by the hill
Cycles are loops and are very common in nature. The planets orbit the sun SORTA returning to the same place each year. When you add the tilt of the earth's axis to the loop the seasons emerge. And the seasons drive the great currents in the air and water.
Chemistry makes possible another sort of loop - self-catalyzing reactions. Wikipedia tells us: (@ http://en.wikipedia.org/wiki/Autocatalysis) {start quote) A single chemical reaction is said to have undergone autocatalysis, or be autocatalytic, if the reaction product itself is the catalyst for that reaction. A set of chemical reactions can be said to be "collectively autocatalytic" if a number of those reactions produce, as reaction products, catalysts for enough of the other reactions that the entire set of chemical reactions is self-sustaining given an input of energy and food molecules (end quote)
This little animation gives a sense of the sort of pattern these reactions can produce:
http://en.wikipedia.org/wiki/File:The_Belousov-Zhabotinsky_Reaction.gif
What loops enable are complex systems that can be self balancing. From this emerges systems that are stable (in equilibrium) but also dynamic and able to respond to changing conditions. A key thing to notice that this responsiveness is a global property of the whole system.
These complex loopy systems can be very complex as we see with living things where loops are involved from the molecular level of cell mechanics to the global level of climate and the seasons.
The ability of animals to behave according to conditions involves an abstract sort of loop - a stimulus/response loop. Stimulus/response loops can be very simple as when a frog snaps up a fly with a flick of it's tongue or very complicated as when Elaine makes a piece of virtual medical equipment.
What are the philosophical implications of loops? Contemplation of systems of loops can give a sense of how the weird mix of order and chaos that we observe in reality is possible. Many people feel that scientific thinking is sterile and lacking in wonder. For me the contemplation of such a simple idea as loops shows how wrong they are.
What do you think?
I present regular philosophy discussions in a virtual reality called Second Life.
I set a topic and people come as avatars and sit around a virtual table to discuss it.
Each week I write a short essay to set the topic.
I show a selection of them here.