Hot air balloons
Hot air balloons represent the very first invention which allowed humanity to conquer the skies. The principle involved in the creation of these items is rather simple. It is all based on Archimedes' law. This means that the balloon itself relies on the lower density of the hot air compared to the colder air outside.
Typically all hot air balloons consist of 5 main parts: the balloon itself, a cradle to hold the crew and the other equipment, a burner to heat the air in the balloon, ballast and the valve which allows the hot air from the balloon to be released. These last two items are very important as they allow a method of control towards the altitude of the balloon.
Nowadays though hot air balloons tend to contain much more gadgets. Virtually any balloon now has a GPS enabled device and some balloons even have propellers attached to better control the horizontal movement.
There is a method of control though that allows experienced hot air balloons crews to control these beautiful machines. At different altitudes the wind blows in different directions. This means that by altering the vertical coordinate they can decide which way to go. This is more or less a real art on its own and it is what makes ballooning so beautiful to begin with.
Hot air balloons though nowadays are not used exclusively for entertainment. Their more advanced cousins like helium filled balloons (a very light gas) are getting more attention from a lot of unlikely fields. Among them telecommunications seem weird enough the one to reap the most benefits, as these balloons allow the setting up of telecommunication relays at high altitude with a very low cost. It has been suggested that one day they may very well replace satellites when it comes to regional communications. A network of balloons is cheaper with an order of magnitude than a network of satellites.
Altogether hot air balloons represent an interesting alternative to flying and although this technique may seem slightly outdated they still remain the best way to experience the serenity of the open skies. As the human race is now striving for methods to reduce the consumption of fossil fuels hot air balloons and light gas balloons are now becoming an extremely attractive mean of getting some airlift without much fuel consumption. We can safely expect that new innovations will always keep this field an interesting one.