page_title: Balloon
section_title: Air pressure
hierarchical_section_title: Balloon / Physics / Air pressure
caption_attribution_description: Jacques Charles: Charlière (1783) Français&#160;: Premier voyage aérien exécuté dans un aérostat à gaz hydrogène par Jacques Charles et Marie-Noël Robert. Le 1er décembre 1783. Départ des Tuileries. English: Departure of Jacques Charles and Marie-Noel Robert’s ‘aerostatic globe’ balloon from the Jardin des Tuileries, Paris, on Dec. 1, 1783. Drawing shows Jacques Charles and Nicolas Marie-Noel Robert standing in their hydrogen-filled balloon waving flags, beginning their ascent from the Tuileries Gardens, Paris, with the former Tuileries Palace in the background. Thousands of spectators are gathered in the foreground to witness the first manned gas balloon flight. "Anonymous engraving on the same lines, with print entitled 'To the honour of Messrs. Charls and Robert'"—typed on accompanying note. Deutsch: Darstellung des Aufstiegs der Charlière mit Jacques Charles und Marie-Noël Robert von den Tuilerien in Paris am 1. Dezember 1783.
context_page_description: A balloon is a flexible bag that can be inflated with a gas, such as helium, hydrogen, nitrous oxide, oxygen, and air. For special tasks, balloons can be filled with smoke, liquid water, granular media, or light sources. Modern day balloons are made from materials such as rubber, latex, polychloroprene, or a nylon fabric, and can come in many different colors. Some early balloons were made of dried animal bladders, such as the pig bladder. Some balloons are used for decorative purposes or entertaining purposes, while others are used for practical purposes such as meteorology, medical treatment, military defense, or transportation. A balloon's properties, including its low density and low cost, have led to a wide range of applications.
  The rubber balloon was invented by Michael Faraday in 1824, during experiments with various gases. He invented them for use in the lab.
context_section_description: Once inflated with regular, atmospheric air, the air inside the balloon will have a greater air pressure than the original atmospheric air pressure.
  Air pressure, technically, is a measurement of the amount of collisions against a surface at any time. In the case of balloon, it's supposed to measure how many particles at any in any given time space collide with the wall of the balloon and bounce off. However, since this is near impossible to measure, air pressure seems to be easier described as density. The similarity comes from the idea that when there are more molecules in the same space, more of them will be heading towards a collision course with the wall.
  The first concept of air pressure within a balloon that is necessary to know is that air pressures "try" to even out. With all the bouncing against the balloon wall (both interior and exterior) there will be a certain amount of expansion/contraction. As air pressure itself is a description of the total forces against an object, each of these forces, on the outside of the balloon, causes the balloon to contract a tiny bit, while the inside forces cause the balloon to expand. With this knowledge, one would immediately assume that a balloon with high air pressure inside would expand based on the high amount of internal forces, and vice versa. This would make the inside and outside air pressures equal.
  However, balloons have a certain elasticity to them that needs to be taken into account. The act of stretching a balloon fills it with potential energy. When it is released, the potential energy is converted to kinetic energy and the balloon snaps back into its original position, though perhaps a little stretched out. When a balloon is filled with air, the balloon is being stretched. While the elasticity of the balloon causes tension that would have the balloon collapse, it is also being pushed back out by the constant bouncing of the internal air molecules. The internal air has to exert force not only to counteract the external air to keep the air pressures "even", but it also has to counteract the natural contraction of the balloon. Therefore, it requires more air pressure (or force) than the air outside the balloon wall. Because of this, when helium balloons are left and they float higher, as atmospheric pressure decreases, the air inside it exerts more pressure than outside it so the balloon pops from tension. In some cases, the helium leaks out from pores and the balloon deflates, falling down.
caption: Contemporary illustration of the first flight by Professor Jacques Charles, December 1, 1783
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