Reflections on Mylar, Helium, and the Atmosphere, Part 2

The Mylar balloon I wrote about in my last post (July 13) reminded me of the rare helium balloons in my childhood.  I grew up in Cleveland, and once each summer, my family went to an amusement park called Euclid Beach.  It was the absolute most magical of all possible family jaunts.

         To a young child, the rides seemed hatched directly out of imagination.  Holding on for dear life in shallow, shiny chrome cars, we jerked up and down and side to side in wild, unpredictable zigzags.  Or we rose higher and higher in stately silver rocket ships, sailing in serene circles far above the ground.  Or, bathed in celestially bright light, we rode merry-go-round horses up and down and round and round to a hurdy-gurdy that took complete possession of our senses.

         All nourishment rules were suspended.  We chewed on Euclid Beach taffy, ten times more delicious than the saltwater stuff relatives sent from the East Coast.  We consumed cotton candy, popcorn balls, and ice cream.  Last of all, before we left, came a helium balloon for each child.

         As we drove back home, we were still full of the excitement we had experienced all day long.  But back in our workaday, ordinary house, the one bit of magic that remained, to prove it hadn’t all been a dream, was that balloon up on the ceiling, defying gravity.

         Maybe it was my child’s eye view, but I seem to recall those helium balloons staying up for days.  Or maybe the helium was purer, and they really did stay up longer.

         As an adult, I love the way helium balloons illustrate that we live at the bottom of an ocean of air.  Just as a beach ball floats on water because the air it’s full of is less dense than water, so a helium balloon floats on air because the helium it’s full of is less dense than air.  The reason is that helium atoms weigh much less than the nitrogen and oxygen molecules that make up most of our atmosphere.        

         Reflecting on this, I was startled when I realized that if we filled a balloon with helium on the moon, it would just drop to the ground!  No atmosphere on the moon for a helium balloon to float on.

         But that tendency of helium to rise to the top of the atmosphere here on earth means that once it gets loose, helium is always leaving.  Eventually, we may run out of helium, a disappointing thought.  More on this next time.