The Pull of the Moon and the Sweep of the Changing Tides

Set your tide clock on the day of the full moon.

To make the best use of your VICTORIA HOUSE METAL WORKS tide clock, you should understand a little about what causes the high and low tides. The gravitational pull of the moon is the major cause of the tides. The "lunar day" (the time it takes the moon to reappear at the same place in the sky) is 24 hours and 50 minutes and some odd seconds. Most places have two high tides and two low tides each day. So the tide clock hand rotates once every 12 hours and 25 minutes (twice each lunar day).

The tide clock stays in exact step with the moon. But, there are many other factors that can make day-to-day tides a little earlier or later than the tide clock shows. The sun affects the tides, but has less than half the influence of the moon. When the sun, moon and earth are lined up, as they are at the time of a new moon or full moon, their influences combine and the tides are higher than normal and low tide is lower than normal. When the sun and moon are at right angles, as they are at the first quarter and last quarter of the moon, the sun cancels some of the moon's effect and the range of tide is smaller than normal. At these times the sun will make the tides somewhat earlier or later than average. This is why it is so important to set your tide clock on the day of a full moon, because the moon has the dominant effect on the tides.

Regarding the more complex Pacific Coast and Gulf of Mexico tides:

There are actually two tidal cycles, a twice-daily cycle and a once-daily cycle. On a tide when the two cycles help each other, high tides will be higher and low tides lower. On the next tide, when they conflict, the tidal range will be smaller. The relative strength of these two cycles varies from week to week, and also varies from one place to another. In the United States, along the Atlantic Coast, the two daily tides have a similar range, but on the northern Pacific Coast there tends to be a large difference between the two daily tides. Farther south and in the Gulf of Mexico, the difference is so great there often appears to be just one high and one low tide per day. For this reason, our tide clocks find their greatest use on the Atlantic Coast.

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