In A World of Systems

Meet Marcel, Cynthia, and Kiki.

Or rather, meet Marcel's circulatory

system, Cynthia's nervous system, and

Kiki's digestive system.

Not only are these three made of

systems, but they're also part of

systems, like the family system that

connects them together.

Tonight, Marcel and Cynthia are

preparing to host their good friend Alex

for dinner.

Cynthia worked all afternoon in the

garden, and her basket is full of

freshly picked vegetables.

Now they need to get ready.

Cynthia goes upstairs to take a shower,

and Marcel heads to the kitchen to cook.

Cynthia is still thinking about those

tasty peas she just harvested.

She's certainly not thinking about

systems.

Little does she know that she's about to

enter one right now.

A shower is a convenient way to clean

up, but it's also a system.

We can think of a system as a set of

parts that are connected to one another

and organized to achieve a certain goal.

In this case, the goal is to bring

heated water upstairs for Cynthia and

Marcel to use. But watch what happens

when Cynthia goes to start her shower.

Cynthia herself is a part of the shower

system, and her feedback will help her

get the temperature just right.

Eventually, every time Cynthia adjusts

the shower handle,

she brings the temperature closer to

where she wants it.

While Cynthia is finally happy in the

shower,

here's a way of looking at the system.

Water is flowing from the shower head at

a certain temperature.

Cynthia knows what temperature is ideal

for her, and the nerve endings in her

hand

perceive a gap between the current

temperature and her desired temperature,

which makes her turn the handle to

adjust the temperature of the water

closer to the level she wants.

Altogether, these actions feed back into

each other in a loop that can be

repeated until the desired temperature

is reached.

Here's the same feedback loop presented

in a different way.

A feedback loop that is self-correcting

is called a balancing feedback loop.

But why does it take so long to get the

temperature right?

Well, that delay is part of the system,

too.

The shower system continues from the

bathroom upstairs

all the way down to the water tank and

the heater in the basement.

And it takes time for the heated water

to travel through the pipes.

Because delays are important forces in

systems, we better add one to our

feedback loop. Voilà! We place it here

to indicate that it takes time for the

temperature adjustment to result in a

change in the water temperature. In this

shower system, we also mentioned the

water tank and the heater.

The water in the tank is a good example

of a stock.

A quantity that can grow over time as a

result of an inflow

and can decrease over time as a result

of an outflow.

So, the stock of water in the tank

receives an inflow of cold water and

releases an outflow of heated water for

Cynthia to use.

Marcel in the kitchen is also drawing

from the stock of hot water as he washes

some dishes.

The shower system is just one part of

the house's larger water system.

But systems extend far beyond water or

the house. At that very moment, Marcel

gets a call from Alex.

He's on his way, but stuck in traffic.

Something is causing a major backup on

the roads.

Alex has driven this route a hundred

times without delay. So, what's going

on?

Well, there's been an accident on the

highway that's slowing everything down.

Normally cars would be flowing through

the highway smoothly, but today they're

at a standstill.

Cars keep entering the traffic jam from

the back, but no one can move until the

accident is cleared up.

The outflow in this system is all

blocked. And it looks like Alex might

just have to wait it out.

Unfortunately, it seems that no one is

very patient at this time of day trying

to get home for dinner.

Someone in a car nearby honks his horn.

Now that no one is moving, a social

system has been added to the traffic

system, and Alex is on edge.

The woman behind him keeps trying to

nudge her car up even though there isn't

any extra room.

Alex is getting more and more tense.

And so are the drivers around him.

The whole thing is quickly escalating

into quite a mess.

Why is everybody getting angrier?

Well, just like Cynthia responding to

the temperature of her shower, the

people in this traffic system are

responding to one another in a feedback

loop.

But rather than bringing the system into

balance, they're driving it further and

further to the extreme.

As Alex's anger increases,

his expressions of anger make other

drivers around him angrier.

And when angrier, their expressions of

anger escalate into a frenzy of gestures

and offensive words that make Alex

angrier.

Here's the same feedback loop presented

in a different way.

This type of feedback loop is called

reinforcing

because it gains strength at each cycle.

But back in the traffic jam, something

is happening.

Luckily, just as things are threatening

to get out of hand,

a traffic sign lights up with details

about the delay.

Now that he knows what's going on and

has some information to plan with,

Alex starts to relax.

He imagines new additions to the

transportation system to speed things up

and avoid traffic.

A well-trained raptor to the rescue.

Or a more feasible light rail could do

the trick.

How pleasant it would be to step on a

train and be able to bypass the highway

entirely.

And finally, the traffic starts moving

again. Phew. Surely that transportation

system was complicated enough for one

night, right? Well, not exactly. Back at

the house, Marcel proudly shows Cynthia

the fish he picked out at the fish

market earlier today.

But purchasing a fish is only one very

small part of the fishery system that

Marcel is now a part of.

This seemingly simple entrée,

where did it come from?

Marcel's fish started out in the ocean

as part of a school of fish.

The school is itself a system and, like

the shower and the traffic system,

it has flows. New fish flow into the

school as fish reproduce.

And fish flow out because of fishing,

predators, and because of natural

deaths. If the outflows match to the

inflow of new fish, the fish population

would stay fairly stable.

That would be a healthy fishery. But as

it turns out, Marcel isn't the only one

who enjoys a nice fish fillet now and

then.

Demand for fish is high.

Fishing is increasing. And the stock of

fish is shrinking.

There are rules in place to try to

protect the fish schools.

Fishermen can only fish for a certain

part of the year.

The fish they take must be a certain

minimum size.

And any individual can harvest only so

many fish.

But the people who made those rules had

only imperfect information on how many

fish are left.

And they may have been thinking more of

today's economic returns

than the long-term health of the fish

stocks.

The system has been set up to deplete

itself.

In a system designed to maintain a

healthy stock of fish in the long-term,

wouldn't Marcel have been able to afford

that fish he bought?

Would there be that species of fish for

sale at all?

Of course, none of these complexities

are on Marcel's mind as he sets the

table. He's just happy that the fish is

ready and looking tasty.

Cynthia feels refreshed from her shower

and Alex finally pulls into the driveway

to join them.

They all sit down to enjoy a nice meal

together. While they're lost in the

evening's delicious food and pleasant

company,

it's easier to see the systems that made

it all possible.

The house's water system,

the neighborhood's transportation

system,

the nation's fishery system, and many,

many more.

Including the system of friendship that

binds these three together.