[LEAPSECS] Time on time

Hal Murray hmurray at megapathdsl.net
Wed Nov 30 13:45:21 EST 2011

> Speaking of time, what sort of time is the Long Now clock keeping, anyway?

> Solar, atomic, or something else entirely?

Solar. It's all mechanical. No electronics.

>From http://en.wikipedia.org/wiki/Clock_of_the_Long_Now

> Hillis concluded that no single source of timing could meet the

> requirements. As a compromise the clock will use an unreliable but accurate

> timer to adjust an inaccurate but reliable timer, creating a phase-locked

> loop.

> In the current design, a slow mechanical oscillator, based on a torsional

> pendulum, keeps time inaccurately, but reliably. At noon the light from the

> Sun, a timer that is accurate but (due to weather) unreliable, is

> concentrated on a segment of metal through a lens. The metal buckles and the

> buckling force resets the clock to noon. The combination can, in principle,

> provide both reliability and long-term accuracy.

These are my opinions, not necessarily my employer's. I hate spam.

More information about the LEAPSECS mailing list