Download Energy and the Earth

Energy and the Earth
Solar energy, or energy from the Sun, drives most of the natural processes within the atmosphere and
hydrosphere. When solar energy reaches Earth, it interacts with Earth’s air, water, and land in several
different ways. The graph below shows what happens to the solar energy that reaches Earth.
Much of the solar energy absorbed by Earth is heat energy. Heat energy is transferred throughout Earth’s
atmosphere, hydrosphere, and lithosphere through radiation, conduction, and convection.
Radiation
the transfer of heat through electromagnetic waves
Conduction the transfer of heat through direct physical contact
Convection
the transfer of heat by circulation or the movement of a liquid or gas
Convection causes both Earth’s atmosphere and the ocean to move in large currents. Warm water or air is
less dense than cool water or air. The warm water or air rises. Cool water or air sinks to take its place. In
this way, both the atmosphere and ocean constantly circulate.
The circulation of the atmosphere drives the water cycle. A diagram of the water cycle:
During the water cycle, warm air containing evaporated water rises. As it rises, it cools and the water vapor
condenses and forms clouds. Precipitation may result from these clouds.
When a great deal of heat energy from the Sun warms the ocean’s surface, a large amount of water
evaporates. In addition, a large pocket of air over the warm water is heated. Large, heavy rain clouds form
as the air rises and cools. Eventually, severe weather, such as hurricanes, can form from this process.
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Heat Transfer in the Earth's System
The three mechanisms by which heat is transferred through the Earth’s system are radiation, conduction, and
convection.
Radiation is energy transmitted as rays or waves in the form of particles. Radiation does not require a material medium
through which to travel, which means it can travel through empty space. However, radiation can also travel through a
material medium (solid, liquid, or gas). The Sun heats the Earth by radiation.
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Solar heat warms the Earth’s atmosphere by varying amounts. As a result, the air is warmed at different rates
and is set in motion, creating the weather.
Conduction is the transfer of heat between objects in contact with each other as a result of molecular action. Conduction
occurs within and between all states of matter.
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A source of heat speeds up the particles in one part of a solid. These particles strike others and speed them up,
allowing heat to spread through the material and out into adjacent materials. For example, particles in a warm
coffee mug transfer heat to each other as well as to a person's hand by conduction.
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A material’s conductivity is a measure of the rate at which heat flows through it. Heat flows easily through
materials with a high conductivity, like metal. This is why pots and pans for cooking are made of metal.
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The molecules and atoms that compose matter are constantly in motion. When these molecules and
atoms collide, energy may be transferred from one object to another.
Heating causes molecules to move faster, thereby increasing the kinetic energy of the atoms within elements
and the kinetic energy of molecules or ions that make up compounds. This increased movement also increases
the likelihood of molecules colliding and the likelihood of the transfer of energy.
Conduction is heat transfer that occurs
when particles are in contact with each other.
For example, if a hot saucepan is placed on a bench, heat will flow from the hot surface of the saucepan to the
colder bench. This heat flow from a hot object to a cold object will continue until the objects reach the same
temperature.
Conduction occurs more readily in solids than in
liquids and more readily in liquids than gases. This is because the particles in a solid are arranged closer
together than the particles in a liquid, and the particles in a liquid are arranged closer together than the
particles in a gas. These closer arrangements allow molecules to more easily bump into each other to transfer
energy.
Convection is the transfer, or flow, of heat in currents. Convection commonly occurs in liquids and gases, but it can also
occur in some solids, such as the Earth's mantle.
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As a liquid or gas is heated, the hotter parts expand and become less dense. The hot fluid rises and mixes with
the cooler parts, spreading heat. At the same time, cooler parts are sinking and mixing with hotter parts to take
on heat.
Wind action results from air being warmed at different rates and the atmosphere moving in an effort to balance
temperature and pressure. Storms occur when high and low pressure areas collide.
The ocean affects climate because it efficiently stores the Sun’s heat. It heats up and cools down more slowly
than land
Photosynthesis
Photosynthesis is the process through which plants make their own food using sunlight and carbon
dioxide.
Just like every other organism, plants need food to survive. However, plants do not eat food like humans do. Plants and
other organisms with chlorophyll make their own food through the process of photosynthesis. Chlorophyll is a green
pigment that absorbs light energy. Look at the figure below to see how plants with chlorophyll get food from
photosynthesis.
A plant's roots absorb water, and the plant’s leaves and stems absorb carbon dioxide through tiny openings called
stomata. When light energy touches a plant cell with chlorophyll, the energy causes the water to break down into
hydrogen and oxygen. The hydrogen combines with the carbon dioxide to make a sugar that the plant can use as food.
The oxygen is released into the air. The following equation is often used to represent the net photosynthesis reaction.
Climate
The Earth's major external source of energy is the Sun. The Earth is constantly receiving solar energy, and this
energy drives weather and climate.
The solar energy received by the Earth explains why ocean currents, winds, and seasons occur, and why different
areas of the Earth experience different climates. Solar energy also provides the energy that plants use to produce
food via photosynthesis.
WATER CYCLE
The solar energy received by the Earth drives the water cycle because it provides the energy for water to
evaporate. The water vapor then condenses to form clouds. This is followed by precipitation, when the water falls
back to Earth.
UNEVEN HEATING
Different areas of the Earth receive different amounts of sunlight. The equator receives the most sunlight because
the Sun is closer to being directly overhead year-round than it is at any other place on the Earth. This increases
the amount of heat energy received and explains why areas near the equator have tropical climates. The poles
receive the least sunlight, which is why they have cold climates.
OCEAN CURRENTS
The uneven heating of the Earth's surface also creates energy flow. Winds and currents flow from warm areas to
cold areas, which mean that they travel from the equator toward the poles.
LAND AND SEA BREEZES
In coastal areas during the day, the land heats up more than the ocean. This uneven heating causes wind to blow
from the ocean to the land during the day, as the warm air over the land rises, and the cooler ocean air moves in
to take its place. These winds are called sea breezes.
In the evening, the land cools faster than the ocean. This causes wind to blow from the land to the ocean, as the
warmer ocean air rises and the air over the land moves out to take its place. These winds are called land breezes.
SEASONS
The Earth's seasons occur because of the tilt of the Earth's axis. When either the Northern Hemisphere or the
Southern Hemisphere is tilted towards the Sun, it is receiving the most solar radiation and is experiencing summer.
When it is tilted away from the Sun, it is receiving the least amount of radiation and is experiencing winter.
COASTAL VS. INLAND
Oceans also have a major effect on climate. Water has a high heat capacity, which means that it absorbs energy
without changing temperature much. This means that ocean temperature remains within a small range throughout
the year, even when the amount of solar energy received is changing. This explains why inland areas have variable
climates, while coastal regions have climates with less variation—because the water along coastlines helps to
regulate temperature.
The Ocean and Earth's Climate
Earth’s climate would be very different without its oceans. First, there would be virtually no rainfall without the ocean.
This is because the majority of water vapor in the atmosphere was directly evaporated from the ocean. In addition, with
no oceans, Earth’s average surface temperature would be far higher than Earth’s current average surface temperature,
which is 15°C.
The reason Earth’s temperature would be so much higher without the ocean is because land and water do not absorb and
release heat at the same rate. If you transferred an equal amount of heat energy to 1 kg of water and 1 kg of land, the
two materials’ temperatures would not increase by the same amount because they have different specific heats. The
specific heat of water is higher than that of land.
Specific heat is the amount of energy it takes to increase a material’s temperature by 1°C.
The ocean also helps to transport heat from tropical regions towards higher latitudes. Near the equator, the ocean
absorbs a greater amount of heat energy from the Sun than do other parts of the ocean. Surface currents carry this heat
energy away from the equator toward the poles.
As the warm water reaches cooler areas, the heat energy is released back into the atmosphere. This process helps
distribute heat around the globe. Thus, ocean circulation is an important regulator of the world’s climates.