Click HERE to Send E-mail to Deep-Six
Return to the Deep-Six Home Page
George D Campbell III
March 24, 2017
Hot air does not rise. Neither do helium balloons or rockets. Fill a balloon with hot air and put in a hot room and it will just rest on the floor. It has no power to rise. The Quarterback throws the ball producing the winning touchdown. He is lifted up to the shoulders of teammates. He did not rise to that position. He was grabbed and lifted. He was pushed up to be seen by the admiring throngs. Many times you hear hot air rises, it does not. It gets pushed up by something else. Sorry to bust your bubble.
Let's experiment. Plug in a hot plate and make it warm. Carefully hold a plastic bag over it. It should puff out. It should go up if it is let go. Refrain from shouting, "It is rising!" In fact it is getting pushed up. It is the result of the force created by the cooler air surrounding the hot plate.
Air is made up of nitrogen and oxygen. Nitrogen molecules make up 78% and almost all the rest is oxygen. The molecules are moving back and forth. They are vibrating. Heat causes that vibration. They molecules can be made to slow down by removing heat from them. If they are cooled down enough they will stop moving entirely. When all the heat is gone you are 459.67 degrees F below zero. Yikes! Because they don't move at this never-reached temperature they are able get close to each other. That would make the density of the air very high because the spaces between the nitrogen and oxygen molecules would be tiny. Add some heat and they would move apart. The more added heat means more vibration and thus the more space between each molecule. It would be the same if you had a crowd of people standing shoulder to shoulder as still as mice. Make them dance and the size of the crowd would grow but the number of people would stay the same. The density of the crowd would go down as they dance more violently.
By putting air over a hot plate the molecules vibrate faster, the spaces grow bigger, the density drops, and the package becomes lighter. The air around the package is colder and denser. Just as heavy water in an aquarium sinks under a light air bubble pushing the bubble to the surface, the denser cool air pushes the warmer up. The warmer air cannot rise without this force. A hot air balloon works the same way. It does not rise!
On to rain and snow: When air is made to go up the weather typically gets dicey. If air comes down things tend to clear up. The sun is shining on a large muddy field and the ground gets hot. The air over the field gets hot and lighter. The cooler air in the forest surrounding the field is denser and sinks under the air in the field pushing it up. The cooler air gets hot over the field and more forest air repeats the process. To add to the upward push the earth's air upstairs has less pressure. The upward moving air expands and gets even lighter. At the same time the temperature drops as the altitude increases. (When you are at 30,000 feet on your way to the Caribbean for a dive in 87 degree water, the air outside is -55 degrees.) So, the field air is expanding on its upward journey. That cools it down. The water in the air cools and changes from an invisible gas over the field to a visible liquid droplet. We just made a cloud and a lot of heat is released to the air making the upward movement intensify. The cloud might be a small puffy cumulus cloud or it could become a violent cumulonimbus rain cloud with thunder and lightning.
Let’s fast forward to bigger things: The earth is rotating from the west toward the east. It is approximately 25,000 miles around at the equator. In one day an Equatorian would have to travel that distance in 24 hours. People in northern Brazil living on the Equator are moving at 1,000 miles per hour and they don't even feel it. New York City is about one-half way between the Equator the North Pole. The distance around that smaller part of the globe is 12,000 miles. A New Yorker is traveling around 500 miles per hour. So are the buildings, streets, and Grant’s Tomb. If they had a way to keep an eye on the Brazilian traveling twice as fast they would still remain opposite each other. If a resident of northern Brazil was instantly moved to NY they would zoom toward the east at 500 miles per hour
If a cannon ball was shot from the equator to NY it would quickly move ahead of the slower NY ball. Looking at the shot from space the cannon ball would curve to the right as it traveled north. By reversing the shot the NY ball traveling at 500 mph and fired toward the equator would curve to the right as well as it lagged behind the 1000 mph ball at the equator. Cannon balls are like big nitrogen and oxygen molecules. A package of air traveling from south to north would be deflected to the east. Things in the southern hemisphere behave in an opposite way. The faster equator is in the north so a package of air traveling from north to south would be deflected to the east making it a left hand turn.
The same thing happens in a sink as tiny as it is. Open the drain in a sink in the northern hemisphere and the water rapidly moves toward the hole. The water molecules in the south part of the sink (closer to the Equator) from the drain down are moving from fast to slow and are curving ahead of those nearer the drain, a turn to the right. The molecules coming from the north of the drain and are moving from slower to faster and make a right hand turn (looking from the north side of the sink). Right from the south, right from the north and a counterclockwise whirlpool forms at the drain. My late aunt traveled extensively and tested sinks in many locations. She found the sink whirlpools to be CCW north of the equator and CW south. That was the case most of the time. One time she was vacationing on the Equator and found the sink’s behavior to be erratic.
Now we are on to something: The drain in the sink is the plowed field. The cool air flows from the forest on the north, east, south, and west to the hotter, lighter air over the field. The winds from the north and south are flowing to and from the Equator. Those winds are deflected and cause the counterclockwise spin over the field as the air flows in and up. That CCW flow could be as gentle as a summer breeze or as violent as a tornado or hurricane. CCW is the storm’s spin in the northern hemisphere and CW in the southern. As the air flows toward the center and is pushed up the weather turns quite foul.
There you have it: As air is pushed up the conditions deteriorate. Clouds, fog, rain, snow, sleet, freezing rain, hail (a 4” hailstone requires an upward wind of 100 miles per hour), tornadoes, and hurricanes need moisture within the air going aloft. The next time you are out on a sunny day and see those puffy cumulus clouds here and there remember the air under, in and above the clouds is headed upward while the air where the sky is blue has air falling toward the earth. Falling air makes for clear weather.
Click HERE to Send E-mail to Deep-Six
Deep-Six Home Page