Define "polar vortex"
I heard a lot about the "polar vortex" when the weather got cold Monday and Tuesday. Can you tell me what that is?
The "polar vortex" is a huge, dense and extremely cold cyclone that typically sits near or over one or both of the North and South poles in the winter. Occasionally these polar vortexes push far beyond their usual boundaries, dropping heavy winds and bitterly cold temperatures into heavily populated areas.
This was one of those times, and it brought the lowest temperatures in about 20 years to the northern and central United States. Some examples: Wind-chills in parts of Montana, North Dakota and the upper Midwest reached about 60 degrees below zero. Chicago recorded a minus-42 degrees around 11 a.m. Monday.
Dr. Jeff Masters, founder of the Weather Underground, had this scientific explanation in a blog post on www.wunderground.com:
"In the winter, the 24-hour darkness over the snow and ice-covered polar regions allows a huge dome of cold air to form. This cold air increases the difference in temperature between the pole and the equator, and leads to an intensification of the strong upper-level winds of the jet stream.
"The strong jet stream winds act to isolate the polar regions from intrusions of warmer air, creating a 'polar vortex' of frigid counter-clockwise swirling air over the Arctic. The chaotic flow of the air in the polar vortex sometimes allows a large dip (a sharp trough of low pressure) to form in the jet stream over North America, allowing the Arctic air that had been steadily cooling in the northern reaches of Canada in areas with 24-hour darkness to spill southwards deep into the United States." Fortunately, things soon got back to normal.
The CDC and that urine
A recent article about the harmful ingredients in antibacterial soap states that the Centers for Disease Control and Prevention found the chemicals in the urine of three-fourths of Americans. How was the CDC able to collect and analyze hundreds of million of urine samples from the American population?
CDC scientists tested the urine of 2,517 people ages 6 and older who participated in the National Health and Nutrition Examination Survey (NHANES) in 2003-2004, according to the CDC's fact sheet on triclosan, a chemical with antibacterial properties. "Triclosan was detected in the urine of nearly 75 (percent) of the people tested," according to the CDC.
The Food and Drug Administration is requiring soap manufacturers to determine if triclosan (liquid soaps) and triclocarban (bar soaps) are safe. Studies in animals have shown that the chemicals "can disrupt the normal development of the reproductive system and metabolism," the New York Times reported.
Note: Last Sunday we misstated Texas' population. It is roughly 26 million.
Compiled from Times and wire reports. To submit a question, email email@example.com.