Moon Phases and the Predicted Heights of HighTide at Hampton Harbor, NH, for the Month of November, 2015.

Project #1587 on iSENSEProject.org

According to our textbook, Astronomy, "tides are caused mainly by differences in how much the moon’s gravity pulls on different parts of Earth.  At any one time there are two places with high tides and two places with low tides on Earth. As Earth rotates, one high tide stays on the side of Earth facing the moon. The second high tide stays on the opposite side of Earth.” (Pearson)

There are four times during the month that the sun’s gravitational pull has an impact on the height of the tides.  

According to the National Oceanic and Atmospheric Administration (NOAA), “During full or new moons—which occur when the Earth, sun, and moon are nearly in alignment—average tidal ranges are slightly larger. This occurs twice each month. The moon appears new (dark) when it is directly between the Earth and the sun. The moon appears full when the Earth is between the moon and the sun. In both cases, the gravitational pull of the sun is ‘added’ to the gravitational pull of the moon on Earth, causing the oceans to bulge a bit more than usual. This means that high tides are a little higher and low tides are a little lower than average.

These are called spring tides, a common historical term that has nothing to do with the season of spring. Rather, the term is derived from the concept of the tide ‘springing forth.’ Spring tides occur twice each lunar month all year long, without regard to the season.

Seven days after a spring tide, the sun and moon are at right angles to each other. When this happens, the bulge of the ocean caused by the sun partially cancels out the bulge of the ocean caused by the moon. This produces moderate tides known as neap tides, meaning that high tides are a little lower and low tides are a little higher than average. Neap tides occur during the first and third quarter moon, when the moon appears ‘half full.’ “  (noaa.gov)

According to Nasa, "technically, each phase, just like the one called a New Moon, when the Moon is exactly between Earth and the Sun, lasts only a brief instant. But to our eyes, a New Moon can last for a few days."  (nasa.gov)

In addition to the sun’s effect on the height of the tides, The shape of the path the moon travels around the Earth can have an effect as well.   “The Moon's orbit periodically grows rounder and then more oval; it is never a perfect circle.  The point at which it is nearest Earth each month is called its perigee (this varies throughout the year).” (almanac.com)  A decrease in distance between the Earth and the moon increases the gravitational pull between the two, thus increasing the height of the tides at perigee.  Moon perigee will occur on November 23. (nasa.gov)

Guiding Questions:

1. Describe the pattern created by the predicted heights of high tide during the month of November.

2. During which two moon phases will the heights of the tides be the highest?

3. Perigee will occur on November 23.  How will that affect the height of the tide around that time?  How is this shown on the graph?

www.pearsonsuccessnet.com

http://oceanservice.noaa.gov/facts/springtide.html

http://spaceplace.nasa.gov/review/dr-marc-earth/moon-phases.html

http://eclipse.gsfc.nasa.gov/SKYCAL/SKYCAL.html?cal2015#skycal

http://www.almanac.com/content/perigee-and-apogee

http://nh.usharbors.com/monthly-tides/New%20Hampshire/Hampton%20Harbor