Have you ever looked at a hot air balloon off in the distance and wondered how it works? What keeps those big, beautiful balloons up in the air? How do you steer them? How do you land it? How do you ride in one? Well, it all comes down to one simple law of physics: warmer air rises in cooler air. Why is this? Because hot air is lighter than cool air and as a result, it has less mass per unit of volume. For example, a cubic foot of air weighs roughly 28 grams. When you heat the air by 100 degrees F, it weighs 7 grams less. How does this impact hot air balloon flight? Each cubic foot of air contained in a hot air balloon can lift about 7 grams. That's right - only 7 grams; not very much. So, the way we compensate for this is by making the hot air balloon very large, or enough to lift 1,000 pounds. How do you keep the balloon rising? By reheating the air with a "burner" positioned under the open balloon envelope. The pilot reheats the cooling air in the balloon by firing the burner.

So what type of fuel do pilots use while hot air ballooning? Propane, which is stored in compressed liquid form, in the balloon basket. Hers how hot air balloon rides work:

* In order to draw the liquid out, the intake hose goes to the bottom of the cylinder.

* It flows fairly fast through the hoses because the propane is highly compressed.

* When the pilot starts up the burner, the propane flows out in liquid form and is ignited by a pilot light.

* As the flame is burning, it heats up all of the metal in the surrounding tubing area.

* When the tubing gets hot, it heats the propane flowing through it, changing the propane from a liquid to a gas.

* How does this help? It makes for a more powerful flame and more efficient fuel consumption.

Why doesn't the hot air escape from the hole at the bottom of the hot air balloon? because buoyancy keeps it moving up. You've probably seen hot air balloon pilots fire the burners. If they do this a lot, the balloon will continue to rise. Of course, since air becomes thin at high altitudes, the buoyant force eventually gets too weak to lift the balloon.

So, how does a pilot maneuver this air craft? It does take some skill, but the controls are fairly simple. To lift the hot air balloon during the ride, the pilot moves a control that opens up the propane valve. The flow of gas increases as they turn it, so the flame grows correspondingly in size. How does the pilot increase the vertical speed? By blasting a larger flame which heats the air faster.

So, that's really it. Only two main things to remember: heating to make the balloon rise and venting to make it sink. How do hot air balloon pilots they get the balloon from place to place? They actually can maneuver horizontally by changing their vertical position, because wind blows in different directions at different altitudes. Based on where exactly they want to go, a pilot ascends and descends to the appropriate level, and rides with the wind.

Hot air ballooning is one of life's simple pleasures!