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THE MOON

What is syzygy?

Syzygy occurs when the Moon and Sun are aligned, an event that happens twice monthly. The effect on Earth is that the gravitational pull of these two space bodies is strengthened, increasing the elevation of high tides and decreasing low tides.

What is the difference between a lunar eclipse and a solar eclipse?

A solar eclipse occurs when the Moon passes between the Earth and the Sun, while a lunar eclipse happens when the

Earth is between the Moon and the Sun. In a solar eclipse, the Moon casts a shadow on the Earth's surface, while the opposite is true of a lunar eclipse.

A total solar eclipse as seen from Baja California on July 11, 1991. (NASA)

A total solar eclipse as seen from Baja California on July 11, 1991. (NASA)

What is a blue moon?

"Once in a blue moon" is an expression referring to an event that does not happen very often. A blue moon happens about once every 2.7 years when the Moon is full twice during the same calendar month. The exact origin of the phrase is not certain, but it seems to be about 400 years old and comes from English roots. To say that the Moon was blue would be to express that something was absurd or unlikely. Thus, the phrase did not mean that the Moon was literally blue.

Sometimes, however, the Moon has been known to take on a bluish hue, especially when there is a lot of ash or dust in the atmosphere, such as after a large forest fire or volcanic eruption.

What are tides?

Tides are the consequence of any two objects that exert gravitational pull on one another over a long period of time. Basically, each object gently pulls the other object into an egg-like shape, because the gravitational acceleration on one side of the object is larger than on the other side. On Earth, the most observable evidence of this gravitational effect is the changing tides we witness.

How do tides work?

Two cycles of high and low tides occur each day, roughly 13 hours apart. High tides occur both where the water is closest to the Moon, and where it is farthest away. At the points in between, there are low tides.

Does the air have tides?

Strangely enough, yes. Just as with water, the atmosphere can be affected by the Moon's tug on the Earth, so that air pressure can change in air masses daily. The changes are very small, though—about one or two millibars—and these changes are mostly seen only in equatorial zones.

How often do ocean tides occur on Earth?

During a 26-hour period, each point on Earth's surface moves through a series of two high tides and two low tides—first high, then low, then high again, then low again. The length of the cycle is the sum of Earth's period of rotation, or the length of its day (24 hours), and the Moon's eastward orbital movement around Earth (two hours).

Do lakes have tides?

Compared to oceans and seas, lakes generally do not contain enough water to have noticeable tides due to the gravitational effects of the Moon on the Earth. They do have tides, though, and large lakes, such as Lake Superior in North America, are big enough to have observable tides. Lake Superior's waters fluctuate about three inches.

Can tides influence weather?

Many scientists believe that tides have a small influence on the weather. Tides can have some effect upon ocean currents, for example, which, in turn, influence weather patterns. It is also known that the Moon's tug on our planet can actually cause measurable changes in topology (the Earth's crust actually moving up and down). This can, in turn, encourage earthquakes or volcano eruptions, and the latter definitely affects our weather. Tides, it can be said, may also be relevant to weather because, when strong onshore winds coincide with high tides, coastal flooding is made worse than would otherwise occur at low tides.

 
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