Everybody should read your post...

Very erudite of you, Capt. And you didn't lose your temper. And you didn't call
me names. Your a good example for how newsgroup discussion should be done.

Cheers,
Ellen



"Capt. Scumbalino" wrote in message ...
| Ellen MacArthur wrote:
|
| Thanks for the explanation. So what's the difference between the
| rule of 12ths and the rule of thirds. In the rule of thirds the first
| two hours it goes down 1/4 which is the same as your 3/12th. The
| second two hours it goes down 1/2 which is the same as your 6/12th
| and the third two hours it goes down 1/4 which is the same as your
| 3/12th. See I got it right in spite of myself.
|
| It's based on the pretty-much universal fact that the time for the tide to
| change from high to low water, and vice-versa, is pretty close to six hours.
| Since we humans deal with time in chunks of one hour, the question we ask
| is: "how much does the tide change in one hour?". Since the smallest
| fraction is one twelfth, just before and just after slack water, it's
| natural to refer to the tidal change during other hours in terms of the same
| denominator. One twelfth in the first hour leads us to express the change
| during the second as two twelfths, etc.
|
| Also, the larger the time slot, the greater the granularity. Imagine you're
| waiting for the tide to rise enough to clear a sandbar. The rule of thirds
| would have you waiting in chunks of two hours before you sail. The rule of
| 12ths would keep you at anchor for chunks of one hour. Of course, plot the
| heights on a graph over time, and you can pinpoint your departure time
| (rather, the time at which you can safely cross the sandbar) much more
| finely.
|
| Whilst your 'rule of thirds' (which, incidentally, isn't exclusive to
| photography, but is a general principle used in many forms of visual art)
| may be mathematically correct at its junctures, it doesn't fit with how
| people think of time (ie, we think in days of 24 hours, not days of 12
| bi-hours).
|
|
| --
| Capt Scumbalino
|
|
|