Hobbies And Interests
Spring Tides
Spring tides are the highest and lowest tides. The word "spring" does not refer to the season of the year. It means the springing effect of the tide. Spring tides occur when the moon and the sun are aligned, so that the gravitational pull from both bodies is combined. This happens twice every lunar cycle, when the moon is full and when it is new.
Neap Tides
When there is the least difference between the high and low tides, this is called a neap tide. "Neap" comes from Greek and means "scanty." These occur when the moon is in its quarter phases, and it is at right angles to the earth in relation to the sun. The sun and the moon exert a competing gravitational pull on the earth, cancelling out some of their effect.
Perigee and Apogee
The moon's distance from the earth varies by approximately 31,000 miles as it progresses through its cycle. The period when it is closest to the earth is called its perigee and the period when it is farthest away is called its apogee. When a perigee occurs during a new or full moon, the spring tide ranges will be more extreme. When an apogee occurs during the moon's quarter phases, the neap tide ranges will be further reduced.
Perihelion and Aphelion
On approximately January 2 each year, the earth is at the point in its orbit when it is at its closest to the sun. This is called its perihelion. At this time, the effect of the sun on the tides is at its strongest. The aphelion occurs when the earth is farthest from the sun, so the sun's effect is at its weakest. This occurs on approximately July 2 every year.