Download Preview of Period 13: The Energy Balance of the Earth

Preview of Period 13:
The Energy Balance of the Earth
13.1 Sensitive and Non-Sensitive Systems
What laws determine the motion of objects?
Why can we predict the motion of some
objects, but not others?
13.2 Probability and Sensitive Systems
How is the sensitivity of a system related to
the probability of a particular outcome?
13.3 Unpredictability in Our Environment
What causes winds to blow?
Is weather a sensitive or a non-sensitive system?
Do you think that the Earth’s environment is a
sensitive or a non-sensitive system?
13-1
Motion and Newton’s Laws
Why can we predict the motion of the cart?
The cart’s motion follows Newton’s Laws
1. An object remains at rest or moves at
constant speed in a straight line unless a
net force acts on it.
2. If forces act on an object, and if the
forces do not balance one another, the
object experiences a net force and
accelerates. Force = Mass x acceleration
3. If one object exerts a force on a second
object, the second object exerts an equal
and opposite force on the first object.
4.
Near the Earth, the force of gravity is
Force = Mass x g where g = 9.8 m/s2
13-2
Deterministic Systems
• A system is a sequence of events and a set of
rules that define the events and any relation
between these events.
• In a deterministic system, there is a welldefined relation between successive events.
• Each successive event may be determined
from previous events.
• All systems in nature are deterministic.
• If we know all of the equations that govern
the behavior of any system, the subsequent
behavior of that system can be determined by
previous events.
13-3
Sensitive Systems
♦ Some deterministic systems are inherently
sensitive to the initial conditions of the event,
such as the initial position or velocity of an
object.
♦ In sensitive systems, small changes to initial
conditions can result in large differences in
outcomes.
♦ Two similar sensitive systems that start off
with very similar initial conditions can behave
very differently after a short time.
♦ This is known as the butterfly effect.
13-4
Predictable and Unpredictable Systems
What is the difference between a system that is
predictable and one that is not predictable?
♦ A predictable system is one that is not
greatly affected by (is not sensitive to)
the choice of the system’s initial
conditions.
♦ An unpredictable system’s behavior is
sensitive to its initial conditions.
♦ The outcomes of a non-sensitive system
are predictable. But the outcomes of a
sensitive system are not predictable
13-4a
The Water Cycle
• Water from the soil, rivers, lakes, and
oceans is evaporated by the sun’s energy
into water vapor.
• When water vapor in the atmosphere cools
sufficiently, it condenses to form clouds.
• Precipitation from clouds brings the water
back to the ground.
13-5
Why Do Winds Blow?
Global wind patterns are produced by
1)
the spinning of the Earth, which produces
the Coriolis effect and
2)
the uneven heating of the Earth’s surface,
which causes convection currents.
♦ Heated air at the equator rises to higher
latitudes.
♦ Cooler air from higher latitudes flows
toward the equator.
♦ This convection mixes warm equatorial air
with cooler high latitude air.
13-6
What Causes Land and Sea Breezes?
♦ During the day, the land heats up more
quickly than the water.
♦ Air above the land is heated and rises, creating
a region of low pressure above the shore.
♦ Air above the water moves inland toward the
region of low pressure. This circulation
creates convection currents.
♦ At night, the land cools off more quickly than
the water. Warm air above the water rises,
creating a region of low pressure above the
water.
♦ Air from the land moves seaward toward the
region of low pressure.
♦ The night time breeze moves in the opposite
direction (out to sea) as the day time breeze.
13-6a
Computer Simulations and Probabilities
How could a simulation program such as
Balance of the Planet be used to develop a
series of probable outcomes?
♦ A computer program is run many times with
slightly different initial conditions.
♦ If the results form clusters, you can turn
those clusters into probabilities.
♦ Example: If a simulation gives a particular
result 10% of the time, then that result has
a 10% probability of occurring, according to
this simulation.
Note: The outcome of a sensitive system
(sometimes called a chaotic system) is too
uncertain to discuss in other than
probabilities, such as a 40% predicted
chance of rain tomorrow.
13-7
Period 13 Summary
13.1: Energy Balance of the Earth: The total
energy in from the Sun must equal the total
energy radiated out to prevent the Earth
from heating up.
13.2 Water Cycle: Water from oceans and
lakes evaporates when the Sun’s energy
warms the water.
Water vapor rises, is cooled, and condenses,
forming clouds. When clouds become
saturated, precipitation falls as rain or snow.
Precipitation eventually runs back into lakes
and oceans and the cycle repeats.
Winds: Heated air at the equator rises to
higher latitudes. Cooler air from higher
latitudes flows toward the equator, causing
convection currents.
The spinning of the Earth (Coriolis effect)
also produces global wind patterns.
Land and sea breezes occur because land
surfaces heat up and cool off more quickly
than water surfaces, causing convection.
13.3
Biomass: Energy sources derived from
plant and animals. Examples: alcohol
used as fuel, and fossil fuels (coal, gas, oil).
Period 13 Summary, continued
13.4
A system is a sequence of events and a
set of rules that define the possible events
and any relation between events.
In a deterministic system, there is a welldefined relation between successive
events. Each successive event may be
determined from previous events.
Some deterministic systems are sensitive
to the initial conditions of the event.
In sensitive systems, small changes to
initial conditions can result in large
differences in outcomes. (butterfly effect)
The outcome of a sensitive system is too
uncertain to discuss in other than probabilities.
13.5 Computer simulations can be used to
develop a series of probable outcomes.
A program is run many times with slightly
different initial conditions. If the results
form clusters, you can turn those clusters
into probabilities.
Example: If a simulation gives a particular
result 10% of the time, then that result has
a 10% probability of occurring, according
to the simulation.
Period 13 Review Questions
R.1 What is the energy balance of the earth?
What could happen if this balance is upset?
R.2 What is the water cycle? How does solar
energy play a role in the water cycle?
R.3 What is biomass?
What are some
advantages of using biomass as fuel?
R.4 What could happen to the outcome of a
sensitive system that experiences small
changes in its initial conditions?
R.5 In what circumstances are computer
simulations useful? What are some of the
limitations of computer simulations?