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  • Energy is all around us,

  • a physical quantity that follows precise natural laws.

  • Our universe has a finite amount of it;

  • it's neither created nor destroyed

  • but can take different forms,

  • such as kinetic or potential energy,

  • with different properties and formulas to remember.

  • For instance,

  • an LED desk lamp's 6 Watt bulb

  • transfers 6 Joules of light energy per second.

  • But let's jump back up into space

  • to look at our planet, its systems, and their energy flow.

  • Earth's physical systems include

  • the atmosphere,

  • hydrosphere,

  • lithosphere,

  • and biosphere.

  • Energy moves in and out of these systems,

  • and during any energy transfer between them,

  • some is lost to the surroundings,

  • as heat, light, sound, vibration, or movement.

  • Our planet's energy comes from

  • internal and external sources;

  • geothermal energy from radioactive isotopes

  • and rotational energy from the spinning of the Earth

  • are internal sources of energy,

  • while the Sun is the major external source,

  • driving certain systems,

  • like our weather and climate.

  • Sunlight warms the surface and atmosphere

  • in varying amounts,

  • and this causes convection,

  • producing winds and influencing ocean currents.

  • Infrared radiation, radiating out

  • from the warmed surface of the Earth,

  • gets trapped by greenhouse gases

  • and further affects the energy flow.

  • The Sun is also the major source of energy

  • for organisms.

  • Plants, algae, and cyanobacteria

  • use sunlight to produce organic matter

  • from carbon dioxide and water,

  • powering the biosphere's food chains.

  • We release this food energy

  • using chemical reactions,

  • like combustion and respiration.

  • At each level in a food chain,

  • some energy is stored

  • in newly made chemical structures,

  • but most is lost to the surroundings,

  • as heat, like your body heat,

  • released by your digestion of food.

  • Now, as plants are eaten by primary consumers,

  • only about 10% of their total energy

  • is passed on to the next level.

  • Since energy can only flow in one direction

  • in a food chain,

  • from producers onto consumers and decomposers,

  • an organism that eats lower on the food chain,

  • is more efficient than one higher up.

  • So eating producers is the most efficient level

  • at which an animal can get its energy,

  • but without continual input of energy

  • to those producers,

  • mostly from sunlight,

  • life on Earth as we know it

  • would cease to exist.

  • We humans, of course, spend our energy

  • doing a lot of things besides eating.

  • We travel, we build, we power all sorts of technology.

  • To do all this,

  • we use sources like fossil fuels:

  • coal, oil, and natural gas,

  • which contain energy

  • that plants captured from sunlight

  • long ago

  • and stored in the form of carbon.

  • When we burn fossil fuels in power plants,

  • we release this stored energy

  • to generate electricity.

  • To generate electricity,

  • heat from burning fossil fuels

  • is used to power turbines

  • that rotate magnets,

  • which, in turn, create magnetic field changes

  • relative to a coil of wire,

  • causing electrons to be induced to flow in the wire.

  • Modern civilization depends on our ability

  • to keep powering that flow of electrons.

  • Fortunately, we aren't limited

  • to burning non-renewable fossil fuels

  • to generate electricity.

  • Electrons can also be induced to flow

  • by direct interaction with light particles,

  • which is how a solar cell operates.

  • Other renewable energy sources,

  • such as wind, water, geothermal, and biofuels

  • can also be used to generate electricity.

  • Global demand for energy is increasing,

  • but the planet has limited energy resources

  • to access through a complex energy infrastructure.

  • As populations rise,

  • alongside rates of industrialization and development,

  • our energy decisions grow more and more important.

  • Access to energy

  • impacts health, education, political power, and socioeconomic status.

  • If we improve our energy efficiency,

  • we can use our natural resources more responsibly

  • and improve quality of life for everyone.

Energy is all around us,

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B1 TED-Ed energy fossil flow sunlight electricity

【TED-Ed】A guide to the energy of the Earth - Joshua M. Sneideman

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    林筠芳 posted on 2014/08/11
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