# Flying without wings

#### Forces & MotionBuoyancyAtoms & MoleculesGas Laws

##### Above: Image © sassy1902, Wikimedia Commons

How many helium balloons would it take for you to float away? What can we learn from the boy-in-balloon scare?

While watching the boy-in-balloon scare on TV last month, I remembered how much I loved helium balloons when I was younger. I used to pretend that if I just got a few more balloons, then maybe I could float up into the sky like Mary Poppins. Now, after last month's event, I’m wondering how many balloons I would have needed.

Did you know? Buoyancy is a force that works against gravity.

Of course, it’s more about the amount or volume of helium and less about the number of balloons that governs floating. The rest of this article will look at the concept of buoyancy and will investigate whether we need to be careful with how many balloons we give our younger siblings at their next birthday.

Floating is based on the law of buoyancy, which is the upward force that keeps things afloat. An item will float in the water or air when its weight is less than the weight of the water or air it displaces.

Did you know? The air we breathe is 80 per cent nitrogen. Because nitrogen atoms have more electrons, protons and neutrons than helium atoms, they are also heavier.

This issue of buoyancy is why a balloon filled with air falls to the ground (because the air inside is the same weight as the air outside) but a helium-filled balloon floats up into the air, despite the additional weight of the balloon (because helium gas is lighter than the air we breathe).

In order to lift a person off the ground, we need a lot more helium than one balloon’s worth. We need to displace enough nitrogen-heavy air with helium gas to compensate for our body-weight. There are some pretty neat calculations in the references at the end of the article that you can use to determine just how big a balloon you would need to get you off the ground.

Did you know? A 12 foot diameter balloon that holds 900 cubic feet of helium gas could lift 57 pounds.

Although last month's scare turned out to be a hoax, it’s pretty obvious that floating away with a helium balloon is possible — as long as it’s big enough!

Britannica Online Encyclopedia - Archimedes' principle http://www.britannica.com/EBchecked/topic/32827/Archimedes-principle

How Stuff Works - How Helium Balloons Work http://science.howstuffworks.com/helium.htm

Article first published on November 22, 2009.

Photo Credit: Susie B/FreeDigitalPhotos.net

#### Rebecca Spring

I am a science communication graduate. I work at an environmental organization in Toronto. In my free time, I am learning Spanish so I can travel and work in South America.