If you double the radius of the balloon, the volume increases by a factor of 8 (because volume is proportional to the cube of the radius). So what happens to the material on the outside of the balloon? You want to keep everything fair, so let’s say you double the thickness of the material for your large balloon. This material only covers the surface area of the balloon, increasing its area by a factor of four. Including the double thickness, the mass of the material in the larger balloon is also eight times that of the smaller balloon.
But at some point, you don’t need to keep making the balloon skin thicker and thicker. You can get very strong materials (e.g. rubber) that are only 1 millimeter thick. This means that if you increase the radius of the balloon by a factor of 10, the volume will increase by 1,000, but the mass of the shell will probably only increase by 100. Volume is important because it provides buoyancy.
Now let’s go in the opposite direction. Let’s make an ant balloon. If you reduce the radius of a regular party balloon by a factor of 100 (actually it should be smaller than that), you will also need to reduce the thickness of the shell by a factor of 100. These balloons are already quite thin. If you reduce it too much, you won’t have a structure that can hold the balloon. If you increase the thickness a little, the mass will become too heavy and it will not float. Sorry, we don’t have parade balloons for ants.
The bigger the balloon, the more difficult it is.
yay! There is a huge balloon and it floats around. What could be better than this? Oh, sure, it would take a lot of people (and a few cars) to hold it down, but it’s still a giant balloon. But wait. There are still problems with the giant balloon. Making it bigger may help it float, but it introduces another problem.
The first problem is the wind. Sure, the wind on a small handheld balloon is a nuisance. But what happens if we increase the size of the balloon? This force pushing on the balloon is proportional to its cross-sectional area. Doubling the radius of the balloon quadruples this area and quadruples the aerodynamic forces.
(Tag Translation) Science
