The Earth's Spin

Posted on December 30, 2013 by Richard Hoptroff

Clink Street, London, 14th November 2013

As a watchmaker it is a delight to understand and depict daily cycle.Watches and clocks allow time to lose its cold inevitability and start to take on beauty and rhythm that we can appreciate on a human scale, not least for its flaws.

In the past, people thought that our world was governed by regular, Godly cycles.  But if God does play a hand, then nature is His workman and He leaves him to get on with it, in his own, imperfect way. So time is a bit of a mess, when you look close up.

You’d think that how long days are would be simple enough, but no.  The earth’s spin slows as tides drag on it, and speeds up as mountain snows melt.  Hence the ‘leap second’ that gets slipped in to let the sun catch up every few years.  (In theory, leap second might need to be taken out instead of put in, but that hasn't happened yet.)

Leap seconds are not predictable, so over the longer term, even an atomic watch need adjusting.  Thankfully, though, the drift is not enough to disturb a celestial navigator even on a six-month sailing voyage at sea.

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