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It's easy to appreciate the power of the sun
在这样炎热的夏日，站在德州湾海边
on a nice hot summer's day like here on the Texas Gulf Coast.
不难体会太阳的威力
And you can feel the power of the sun on your skin,
皮肤能清楚感受到太阳的热力
sunscreens is on.
我擦了防晒乳液
But man the sun is just you know
但太阳实在…
the actual physics of what's going on inside the sun,
太阳内部的物理作用
the power of the sun,
太阳的力量
the energy that the sun is releasing
和释放的威力
is almost beyond comprehension.
几乎超出我们的理解范围
But it is only almost beyond comprehension.
但只是“几乎”超出我们的理解范围
And you can measure its power output with some simple apparatus.
我们可以用简单的装置测量太阳的能量输出
One of the earliest experiments to try and measure
最早尝试测量太阳威力的人之一
the actual power of the sun was by astronomer William Herschel
是19世纪的天文学家
in the 19th century,
威廉赫歇耳
where he had the brilliant idea of
他的想法很高明
just watching a piece of ice melt
就是观察一块冰块融化
to see how long it would take and therefore
记录所需的时间
from the properties of the ice work out
再根据冰块的特质
how much sunlight was coming to the ground.
计算地面的日照量
As a demonstration of the sun's power
用这个实验来展现太阳的力量
it doesn't look that impressive.
看起来似乎没啥了不起
But Hershel realized that he could use
但赫歇耳发现
the time it takes to melt one bit of ice to
他可以用冰块融化所需的时间
calculate the sun's total power output.
计算太阳能量输出的总量
So here we see the ice is almost completely melted
过了29分钟…将近半小时后
in roughly 29 minutes almost half an hour.
冰块几乎完全融化
But Herschel was able to use this experiment
但是赫歇耳得以使用这个实验
and the time that it took to,
和冰块融化所需的时间
to melt the ice to work out some basic properties of the sun.
推算出太阳的某些基本特性
Here's how Herschel's thinking worked.
赫歇耳的立论依据如下：
In the time it takes to melt a slab of ice on Earth
在融化地面冰块所需的时间内
the sun is radiating heat in all directions
太阳朝四面八方释放热力
enough to melt a complete shell of ice around it
足以融化包围太阳的冰层
a diameter of 300 million kilometres.
冰层直径为三亿公里
A shell half a centimetre thick
厚度0.5厘米的冰层
and 300 million kilometres across contains a lot of ice.
直径三亿公里，含有大量的冰
Enough to make an ice cube bigger than the Earth.
足以形成比地球还大的冰块
To melt that much ice in just 30 minutes
要在30分钟内融化这么多冰
would take an energy input of a billion billion billion watts.
所需的能量输出，高达10的27次方瓦特
It's a rough, but surprisingly accurate experiment
这个实验看似粗糙，但却出奇地精准
modern satellite readings confirm the figures to within a few percent.
现代卫星读数证实了，其误差不超过几个百分点
It's an almost unimaginable amount of energy.
此能量大得几近难以想像
If we could harness the sun's power output
要是能够充分利用太阳能
for a single second it would satisfy the world's energy
只要短短一秒就足以满足世界
demands for the next million years.
未来一百万年间的能源需求
But it's one thing to know how much power the sun is producing.
但推算太阳产生的能量多少是一回事
It's something else to know how it is doing it.
厘清其制造过程又是另一回事
Until the middle of the 20th century no-one had any idea
在20世纪中期之前，没有人明白
what made the sun work.
太阳的运作原理
For scientists in Hershel's time it was a mystery.
对赫歇耳时代的科学家而言，这是个不解之谜
Well one of the issues was of course what powered the sun.
议题之一当然是，太阳的动力来源
And - um - some very clever people actually
有些颇有才智的人士甚至觉得
considered the fact that the sun might be powered by burning coal.
太阳的动力可能来自燃煤
I mean it seems ludicrous but why not coal.
这种说法听起来荒谬，但又有何不可呢？
That was an important source of energy on the earth.
毕竟在19世纪的那段时间
Er in that part of the 19th century
煤炭是地球的重要能量来源
If the sun was made entirely of coal,
但若太阳由煤炭组成
there would be one unfortunate consequence.
会产生一个不幸的后果
It would burn itself out in just a few thousand years.
它会在几千年后燃烧殆尽
