How long does a pendulum need to be to swing once every 20 years?

The calculation points to 667,767 times the length between the Sun and the earth in a simplified model.

This question came out and got answered as I was proof-reading the final version of our translation on Prof. Church's article "A Pendulum Swung Too Far"  （【Church: 钟摆摆得太远】）which gives a historical account of the classical competition between rationalism and empiricism in science history and the implications on AI and NLP in the last 20 years and the coming generation.  Repeated patterns seem to reveal an arguable rule of each school taking the lead for about 20 years much like a pendulum although the last empiricist trend in NLP based on machine learning seems to run overtime and still shows no sign of swinging back.  A fascinating article we have had pleasure of reading and translating.

【立委按】这几天忙着最后校正翻译稿【Church: 钟摆摆得太远】，其中揭示了科学历史上理性主义和经验主义像钟摆一样每20年各领风骚此消彼长的历史规律。于是有问：20年一次振荡的钟摆该 多长呢？这是一个科学问题，自然有科学的答案。因此促成此篇科普小品。

每隔二十多年振荡一次的钟摆要多长

洪爷打油道：

廿年钟摆常规晃，

螺旋NLP增长。

经验难穿理性墙，

崂山道士王生样。

【置顶：立委科学网博客NLP博文一览（定期更新版）】