Download - Based upon:
Based upon:
Kelly, Kevin. 1989. Simple words about the new science of complexity: A talk with George Cowan. Whole Earth Review 63 (Summer 1989): 94-97.
WAYS OF LOOKING AT THE WORLD
• Humans tend to perceive things either holistically (as irreducible wholes) or reductionistically (as collections of simpler components)
• Both views have their merits• However, we must also consider the
INTERACTIONS between the components
SYSTEMS THEORY
SYSTEMS
• ‘systēma’ (Gr.) – “organised whole”• a set of interacting or interdependent
components forming an integrated whole
• many types and scales of systems, from subatomic particle interactions in matter, through metabolic systems in cells, up to star systems in the universe
SYSTEMS
• Ludwig von Bertalanffy (1901-1972)
• was frustrated by reductionist thinking
• sought a unifying theory that would cover philosophy, psychology, physics, and chemistry
General Systems Theory
• one general organising theory to unite many different areas
• central tenet: all systems, however different, have similar underlying organising principles
• General Systems Theory extends from very simple nonliving systems (e.g., thermostats) to complex living systems (e.g., organisms, societies, institutions & cultures)
SYSTEMS
open systems:• exchange matter and energy with
their surroundings-> most systems are open (living organisms, heat engines, etc.)closed systems: • exchange energy, but not matter, with
their surroundings (e.g., computer programs, planet Earth)
ALL SYSTEMS HAVE…
Structure: components that are directly or indirectly related to each other
Behavior: processes that transform inputs into outputs (material, energy or data);
ALL SYSTEMS HAVE…
Interconnectivity: their parts and processes are connected by structural and /or behavioral relationships
Boundaries: natural or defined limits which determine which parts are inside the system and which parts are outside
A PROBLEM ARISES!
Mid-1980s Desktop PC1977 Apple II Desktop
• ATTEMPTS TO DESCRIBE COMPLEX SYSTEMS IN TERMS OF THEIR
SUBSYSTEMS, SHOWING HOW THE PROPERTIES OF THE SUBSYSTEMS ARISE
FROM THE INTERACTION OF THE SUBSYSTEM “PARTS”
“EMERGENT PHENOMENA”
“EMERGENT PROPERTIES”
e.g.,• Interaction of wind with the surface of
the ocean results in WAVES • interaction of lunar gravity with the
surface of the ocean results in TIDES
• Interaction of water with the surface of the sand results in RIPPLES
• Interaction of win with the surface of the sand results in DUNES and RIPPLES
Computer simulation:
THE FORMATION OF SAND RIPPLES BYWATER WAVES IN A UNIFORM CURRENT The model contains: • topography• grain size distribution• grain volume• compaction• acoustic impedance
Unpublished mathematical model, 2005Dr. Peter Staelens (Brugge, Belgium)www: www.dotocean.eucontact: [email protected]
AN EARLY EXAMPLE (1990s) FORETELLING CURRENT SYSTEMS:
Example: Seattle Traffic Flow Map
• http://www.wsdot.wa.gov/traffic/seattle
IMPLICATIONS:
Metastable ecosystem:Freshwater marsh (e.g., Cataraqui Marsh near Kingston, ON)
• Appears very stable and unchanging• Little evidence of growth or renewal
except for seasonal change from summer green to winter brown
• Actually one of the most productive ecosystems on the planet ->
• Rapid cycles of growth, senescence, decomposition -> high energy flowsand quick cycling of materials
Wetlandnutrientcycling
and storage(yellow box)
Wetlandecosystem
components(boxes)
Wetlandecosystemprocesses(arrows)
From Hossleret al. 2011
:
E.g. Audio feedback –
Microphone picks up sound ->Amplifier makes it louder ->Speaker broadcasts it ->
Microphone picks up sound -> Amplifier makes it louder -> Speaker broadcasts it -> Microphone picks up sound -> Amplifier makes it louder -> Speaker broadcasts it ->
SHRIEK!!!SHRIEK!!!SHRIEK!!!SHRIEK!!!
E.g. Positive feedback in a natural system: Greenhouse gases in the atmosphere and climate change
UNCHECKED POSITIVE FEEDBACK LOOPS
MAY TEND TO
DESTROY
THE SYSTEM THATTHEY ARE A PART OF
• The heater kicks on, heating up a room• Heat, the output of the heater, serves as input to the thermostat.• At a certain critical temperature,
the thermostat tells the heater that the room is warm enough.
• The heater, receiving this feedback through an electrical connection, shuts itself off.
• After a while, the thermostat notices that the room has cooled to a specific temperature, and notifies the heater.
• The heater kicks on again.• The information traveling from the heater to the thermostat and back again
is a negative feedback loop.
:
Thermostat Heater
E.g. HEATER AND THERMOSTAT
E.g. Negative feedback in a natural system: Cycles in lynx and hare populations
NEGATIVE FEEDBACK LOOPS
MAY TEND TO
STABILIZE
THE SYSTEM THATTHEY ARE A PART OF
INTERACTIONS BETWEEN NEGATIVE AND POSITIVE
FEEDBACK LOOPS IN A SYSTEMCAN RESULT IN
DYNAMIC EQULIBRIUM