File:The Future Physics of Planet Earth (40217810733).jpg

Designed by Danny Hillis, this solid metal prototype cam just arrived from the Long Now Foundation. She has a lovely, lithe and sinuous shape that emerges from the precise encoding of a fundamental future for Earth’s next 10,000 years.

In the design of a clock that will run for 10,000 years, the Long Now Foundation decided to use the passage of the sun as a feedback loop on the precision of the mechanical mechanism. Every year, the timing of the sun varies with the seasons; the solar clock repeats an annual pattern as the Earth, with its tilted axis of rotation, circles the Sun. But over thousands of years, it changes in two major ways:

1) the Earth’s rotation slows by 1.8 msec/day, and this adds up to a 16 hour error over 10,000 years.

2) the axis of rotation itself wobbles over a 26,000 cycle. In 8,000 years, we will have a new North Star — Deneb instead of Polaris.

So, the cam encodes both, the steady lengthening of the day and the cyclical shift of Earth’s axial angle.

Here is a <a href="http://blog.longnow.org/02018/12/05/the-equation-of-time-cam-keeping-good-time-for-10000-years" rel="noreferrer nofollow">writeup</a> with more details and diagrams of the curves: