Question

What exactly is the "Icelandic low" that weathercasters talk about?

An Icelandic low is a low-pressure center that originates over Iceland and southern Greenland and dominates the wind circulation over the North Atlantic Ocean. In summer, the low weakens and often divides into two separate cells.

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How did the idea of a Christmas tree start?

Its origin is probably within winter celebrations long before the beginning of Christianity. The practice of decorating a tree, or using plants and trees that were green year-round, was important for people in winter climates. Some cultures believed evergreens would keep witches, ghosts, evil spirits, and even illness at bay. During the Middle Ages, December 24 was celebrated as the Feast of Adam and Eve, complete with a Paradise Tree, which was a fir tree hung with red apples. Today, the practice of using decorated evergreen trees as part of the Christian celebration of Christmas is a custom begun in Germany over 400 years ago that spread rapidly throughout northern Europe and, hence, became a tradition transplanted to the New World by European immigrants.

How is sea level determined? Is it the same for every sea?

Sea level is determined halfway between high tide and low tide, as measured by a tide gauge. It is a relative, rather than an absolute, measurement and varies from ocean to ocean. It even varies from coast to coast on the same ocean. Sediment deposits at the mouths of rivers, natural and manmade erosion, and engineering projects can affect relative local sea level. Continental drift and global warming also may be factors. Sea level is the standard used to determine local land elevations and geographic features. Mean sea level is the average height of all the oceans and is used to determine the relative height of geographic features worldwide. According to most estimates, mean sea level has risen about four to eight inches over the past hundred years.

Where did the dollar sign ($) for U.S. currency originate?

The American colonists used both the British pound and the Spanish dollar as monetary units. The Spanish dollar, or piece of eight, predominated, as it was the international standard during the 17th and 18th centuries. It also was the prototype for the 1785 American silver dollar. There are several theories about the origin of the dollar sign, but the Treasury Department believes that the Spanish P (for piastre, or piece of eight) gradually came to be overlaid with an S, resulting in a close equivalent of the dollar sign. The symbol was widely used before the adoption of the U.S. dollar.

Is there any source (especially a Web site) that has the daily weather records for every place on Earth for the past 100 years?

No. However, there are places that have a significant amount of weather data. You can get a good start right here at The Old Farmer's Almanac Web site, which has a weather history section at http://www.almanac.com/weather/history Find historical weather data by zip code, accessing weather archives for more than 1,300 stations across United States and Canada, going back to 1960.

When I attended a criminal investigation academy, the following question arose: If wool shrinks in water, why don't sheep shrink when it rains, since they have a coat of wool?

Sheep don't shrink because they manufacture lanolin, a greasy secretion from the sebaceous glands. The lanolin collects in the wool and prevents it from drying out and shrinking. Once the wool is sheared, it passes through several water rinses designed to remove the lanolin.

How many people were supposed to have sailed on the Mayflower?

When the ship sailed on September 16, 1620, from Plymouth, England, it was carrying 120 passengers. It set anchor November 21, not in Virginia, as planned, but near what is now Provincetown, Massachusetts.

What floor of the Empire State Building did the Army Air Force plane crash into on July 28, 1945?

The B-25 U.S. Army Air Forces bomber flew into the skyscraper's 79th floor on its north side. Piloted by Colonel Bill Smith, the plane was lost in the fog when it crashed. Fourteen people were killed and 21 were injured. The Empire State Building sustained no structural damage.

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