Dear Tom,
The first day of winter is Dec. 21, the shortest day of the year. Days start lengthening after that and the Earth also gets closer to the sun. So why does Chicago continue to get colder almost to February?
Bob Thurston
Dear Bob,
The sun is 2.8 million miles closer to Earth in early January than it is at its most distant point in early July. However, the effect of that "closeness" is overwhelmed by the effect of the tilt of our planet's axis relative to the sun. That tilt situates the Northern Hemisphere away from the sun's most direct rays, thereby reducing the amount of solar energy available for heating.
Other cooling factors such as round-the-clock darkness and widespread snow cover in the polar north prove far more important in determining temperature than closeness to the sun, and cold air continues to expand its dominance well into January.
The first day of winter is Dec. 21, the shortest day of the year. Days start lengthening after that and the Earth also gets closer to the sun. So why does Chicago continue to get colder almost to February?
Bob Thurston
Dear Bob,
The sun is 2.8 million miles closer to Earth in early January than it is at its most distant point in early July. However, the effect of that "closeness" is overwhelmed by the effect of the tilt of our planet's axis relative to the sun. That tilt situates the Northern Hemisphere away from the sun's most direct rays, thereby reducing the amount of solar energy available for heating.
Other cooling factors such as round-the-clock darkness and widespread snow cover in the polar north prove far more important in determining temperature than closeness to the sun, and cold air continues to expand its dominance well into January.
Tom,
Can TV stations "stream" their live broadcasts over the web, or does that process require a higher speed than currently available?
Bett and I are in Blaine Washington. We've just enjoyed 4 days w/o precip, but the more usual is returning today. Return to IL next week.
Msny thanks.
Wayne