双语畅销书《艾伦图灵传》第4章:彼岸新星(62)
The second problem, quite different, was the 'dull and elementary' one of actuAlly doing the computation, with numbers substituted into the approximate formula, and worked out for thousands of different entries.
It so happened that the formula was rather like those which occurred in plotting the positions of the planets, because it was of the form of a sum of circular functions with different frequencies.
这个公式的形式是一系列不同频率的周期函数的总和，类似于计算天体位置。It was for this reason that Titchmarsh had contrived to have the dull repetitive work of addition, multiplication, and of looking up of entries in cosine tables done by the same punched-card methods that were used in planetary astronomy.
这就是为什么蒂施马奇要采用天文学中的打孔卡片，来做加法、乘法、查询余弦表这些重复而繁琐的工作。
But it occurred to Alan that the problem was very similar to another kind of computation which was also done on a large practical scale, that of tide prediction.
在艾伦眼中，这个问题更像一个更大规模的问题──潮汐预测。Tides could also be regarded as the sum of a number of waves of different periods: daily, monthly, yearly oscillations of rise and fall.
潮汐可以看成是大量不同周期的波浪的总和。At Liverpool there was a machine which performed the summation automatically, by generating circular motions of the right frequencies and adding them up.
在利物浦，有一台机器能自动地执行这样的求和，它产生特定频率的周期运动，并把它们叠加起来。It was a simple analogue machine; that is, it created a physical analogue of the mathematical function that had to be calculated.
这是一个简单的模拟机，它为需要计算的数学函数构造一个物理的模拟。This was a quite different idea from that of the Turing machine, which would work away on a finite, discrete, set of symbols.
这是和图灵机很不一样的想法，图灵机是基于一套有限的、离散的符号集，This tide predicting machine, like a slide rule, depended not on symbols, but on the measurement of lengths.
而这个潮汐预测机则像是一把计算尺，它与符号无关，只依赖于长度的测量。
