The Whole and the Parts – Feedback Loops

Imagine you live on one of the planets around one of the stars in one of these galaxies:

collidinggalaxiesImagine further that you live in a society that has figured out the physics of Newton’s laws, and that this society has gathered enough astronomical data so that it has a pretty good idea, like you do from looking at this picture, that the two galaxies have been colliding, are colliding and will continue to collide.  Imagine further that you don’t like this prospect and that you would like to avoid or slow down the inevitable-looking future.  If the beings that live on this planet in this galaxy have a very long life expectancy, this problem might even be urgent for them.

What should they do?  What can they do?

schoolbus-emergenceIn contrast, compare the school bus and the motorcycle in this picture.  Imagine you are standing next to the motorcycle, and you see the school bus coming straight at you, is your future as doomed as that of the beings on the planet in the colliding galaxies?  I think you’d likely answer no.  If you were standing next to the motorcycle, you might continue to stretch your legs, take pictures, eat your lunch, as if the school bus was not there.  If you gave the schoolbus a second thought at all, you would assume it would simply follow the road and turn along the hairpin.  You might not even look up unless you heard screeching sounds and a horn blaring at full blast.

I think it is interesting to look at the difference between the two situations.  The school bus, just as much as the galaxies, is subject to Newton’s laws.  In fact, if the school bus driver had a heart attack at exactly the moment pictured,  the school bus would barrel towards the motorcycle at full speed and collide.   Having a live school bus driver in the school bus makes all the difference.  Yet the difference isn’t that the school bus driver can make the school bus ignore or violate Newton’s laws.  Whatever the school bus driver does to follow the road down is itself in full compliance with Newton’s laws.  And in case of school buses, we’re quite familiar with how it’s done.  The school bus driver steers, and there is a steering wheel and an entire supporting mechanism which ultimately relies on friction from the tires.  No part of this violates Newton’s laws, in fact, each part is completely depending on Newton’s laws to continue to operate as before.

A steering system is one example of a feedback loop.  Feedback loops are extremely common.  A  thermostat in the heating system of your house forms a feedback loop.  If you aim at a target and the shot goes too high, then aim your next shot a tad lower, then you’re part of a feedback loop.  If, when you’re hungry, you eat – you’re part of a feedback loop.  If, when you’re warm, you take off your down coat, you’re part of a feedback loop.  A simple feedback loop has a detection system and a reaction system.  The detection system detects that something is off too far from the desired norm.  The reaction system is something that can do something about for the future.  The reaction system is coupled to the detection system.  If you have your heating thermostat set at 68 degrees, it will detect when the room temperature drops too low, and it will turn on the furnace.  Your thermostat will also detect when the room temperature gets too high, and it will turn the furnace off again.  The thermostat will alternate between these three states: too low, too high, or within-range.
If you are a driver in a lane on the highway will be steering almost continuously to stay in the lane.  You may not notice you do this until you take your hands (and your knees) off the steering wheel and discover how soon your car veers uncomfortably towards one side.  The detection system, in this case, is typically your vision.  If you stop paying attention long enough, there is often a backup detection system – the distinctive sound you hear and the sharp vibration you feel through your whole body when your car actually traverses the lane boundary.  If the vibration markers aren’t there on that particular road, you are at the mercy of other cars honking at you.

Feedback loops are a common way to turn a collection of parts into a whole.  All living systems have feedback loops, but feedback loops are not limited to living systems.  Feedback loops can enforce boundaries, whether by design or not.  On earth, most earthly things stay on earth.  Even if you throw something upwards, it comes back down.  If you let go of a helium balloon it will float upwards, but it doesn’t keep going up forever.  The earth, including its atmosphere, is a rather self-contained collection of particles.  Once in a while, it may lose some particles, and once in a while it gains some, like a meteor or meteorite.  The total mass of the earth hasn’t changed materially in quite a while.  Feedback loops aren’t perfect, and I will look into some of their limitations in subsequent posts.  But by and large, feedback loops are a good thing to have.  Every galaxy should have some.

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1 Response to The Whole and the Parts – Feedback Loops

  1. Pingback: The Whole and the Parts - Feedback Loops with Delay « Learning and Unlearning Math

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