Energy is all around us, a physical quantity that follows precise natural laws.
我们周围充满了能量，一种严格遵循自然规律的物理质量。
Our universe has a finite amount of it;
宇宙中的能量是有限的；
it's neither created nor destroyed but can take different forms, such as kinetic or potential energy,
能量不会产生也不会毁灭，但能以不同形式存在，如动能和势能，
with different properties and formulas to remember.
有不同的性质和公式要记。
For instance, an LED desk lamp's 6 Watt bulb transfers 6 Joules of light energy per second.
比如，一个LED灯的6瓦灯泡，每秒转移6焦耳的光能。
But let's jump back up into space to look at our planet, its systems, and their energy flow.
先让我们跳到太空去看看我们的行星、它的系统以及能量的流动。
Earth's physical systems include the atmosphere, hydrosphere, lithosphere, and biosphere.
地球的物理系统包括大气层、水圈、岩石圈和生物圈。
Energy moves in and out of these systems, and during any energy transfer between them,
能量在这些系统之间出入流动，能量在它们之间转换的时候，
some is lost to the surroundings, as heat, light, sound, vibration, or movement.
一些散失到周围环境当中，比如热、光、声、震动或移动。
Our planet's energy comes from internal and external sources.
我们星球的能量取自于地球内部和外部。
Geothermal energy from radioactive isotopes and rotational energy from the spinning of the Earth are internal sources of energy,
来自放射性同位素的地热能与透过地球旋转产生的旋转能，这两个属于内部能量来源，
while the Sun is the major external source, driving certain systems, like our weather and climate.
而太阳则是最主要的外部能源，影响了一些如天气和气候的系统。
Sunlight warms the surface and atmosphere in varying amounts,
阳光不同程度地温暖着表面与大气层，
and this causes convection, producing winds and influencing ocean currents.
这就引起了对流，引起了风并影响了海洋气流。
Infrared radiation, radiating out from the warmed surface of the Earth,
红外线辐射，从地球温暖的表面散发出来，
gets trapped by greenhouse gases and further affects the energy flow.
被温室气体笼罩住，从而进一步影响能量流动。
The Sun is also the major source of energy for organisms.
对于有机体而言，太阳也是一个主要的能源。
Plants, algae, and cyanobacteria use sunlight
植物、海藻类和蓝细菌，用阳光
to produce organic matter from carbon dioxide and water, powering the biosphere's food chains.
从二氧化碳和水中产生有机物质，为生物圈的食物链提供能量。
We release this food energy using chemical reactions, like combustion and respiration.
我们由化学反应释放食物中的能量，比如氧化和呼吸。
At each level in a food chain, some energy is stored in newly made chemical structures,
在每一个食物链的阶层，有些能量在刚形成的化学结构下被贮存起来，
but most is lost to the surroundings, as heat, like your body heat, released by your digestion of food.
但大部分散失到环境中，像是热量，透过食物的消化，身体散发的热量被释放。

Now, as plants are eaten by primary consumers, only about 10% of their total energy is passed on to the next level.
而植物是由初级消费者食用，大约只有原获得能量的百分之十会转移给下一个营养阶层。
Since energy can only flow in one direction in a food chain,
又因能量在食物链只能以同一方向流动，
from producers on to consumers and decomposers,
从生产者到消费者和分解者，
an organism that eats lower on the food chain, is more efficient than one higher up.
在食物链中食用较自己低层的生物得到的能量会比吃高层的还高。
So eating producers is the most efficient level at which an animal can get its energy,
所以食用生产者是最有效的，一只动物可以借此得到能量，
but without continual input of energy to those producers, mostly from sunlight,
若持续缺乏了输入给生产者的能量，大部分是来自太阳光，
life on Earth as we know it would cease to exist.
我们所知在地球上的生物将不复存在。
We humans, of course, spend our energy doing a lot of things besides eating.
我们人类，除了吃，当然消耗精力去做很多事情。
We travel, we build, we power all sorts of technology.
我们旅行、我们建设、我们供电给各种科技。
To do all this, we use sources like fossil fuels: coal, oil, and natural gas,
要做到这一切，必须使用像是化石燃料的来源：煤、石油和天然气，
which contain energy that plants captured from sunlight long ago and stored in the form of carbon.
其中含有的能量是植物长年从太阳光所吸取的能量，并以碳的形式贮存。
When we burn fossil fuels in power plants, we release this stored energy to generate electricity.
当化石燃料在发电厂燃烧时，它所储存的能量会释放，我们用此来发电。
To generate electricity, heat from burning fossil fuels is used to power turbines that rotate magnets,
为了发电，燃烧化石燃料产生的热能，提供涡轮机动力，旋转磁铁，
which, in turn, create magnetic field changes relative to a coil of wire, causing electrons to be induced to flow in the wire.
进而使磁场改变，造成线圈产生相对运动，电子因此感应流动于线圈中。
Modern civilization depends on our ability to keep powering that flow of electrons.
现代文明仰赖我们电量持续的供给。
Fortunately, we aren't limited to burning non-renewable fossil fuels to generate electricity.
幸运的是，我们没有限制说一定要燃烧不可再生的化石燃料来发电。
Electrons can also be induced to flow by direct interaction with light particles, which is how a solar cell operates.
电子也能通过与光子的直接互动感应流动而发电，这就是太阳能电池的运作方式。
Other renewable energy sources, such as wind, water, geothermal, and biofuels can also be used to generate electricity.
其他可再生能源，例如风、水、地热及生物燃料，都可以拿来发电。
Global demand for energy is increasing,
全球能源需求在不断增加，
but the planet has limited energy resources to access through a complex energy infrastructure.
但地球上能使用的能源有限，要透过复杂的能源基础建设才能用到。
As populations rise, alongside rates of industrialization and development,
随着人口逐增，以及工业化和发展的速度加快，
our energy decisions grow more and more important.
我们对能源的决策也越来越重视。
Access to energy impacts health, education, political power, and socioeconomic status.
能源利用的影响攸关健康、教育、政治权力和社会经济地位。
If we improve our energy efficiency, we can use our natural resources more responsibly and improve quality of life for everyone.
如果我们改善使用能源的效率，我们使用自然资源时就能更合理，并提升每个人的生活质量。