By Sam Fox, Engage in STEM Mentor
If you can believe it, I’ve watched para-sailors (also known as para-gliders) fly off of a mountain’s edge! This brought about my curiosity of how such a sport works. Not surprisingly, there was a lot of physical science behind it.
Just like sailing on a boat, air is the ultimate force behind motion on this apparatus. It consists of an inflatable type wing that catches drafts of wind which keeps the pilot flying. But what causes these air drafts you ask?
There are many different types of air drafts but I will focus on just a few. The first is a called a thermal draft. This is when air towards the ground is heated up by the sun and expands which causes it to rise. This causes a tube of air going straight up into the sky. If you want to actually see air expand, place an under-inflated basketball into a tub of warm water for a few minutes. This excites and expands the air molecules inside the basketball and actually makes the ball more inflated for a short period of time! This experiment could work with a dented ping pong ball as well. As we know, science phenomenon repeats itself time and time again. For example, feeling the cool breeze from the ocean is the same process as these thermal drafts. A sea breeze is formed because air over the land heats up faster than air over the water. The hot air rises in a thermal draft and the cool air from the water rushes in to fill the empty space. When you’re on the ocean, you can tell it is sea breeze because the wind is generally much cooler then the temperature outside. Anyways, a para-sailor can catch these columns of air and rise up to almost 35,000 feet! To put that into perspective, Mount Everest is about 29,000 feet. Another type of draft that keeps these crazy pilots flying is called a ridge lift. This comes from wind near the ground that hits the side of a mountain, directing the wind straight up in the air. You cannot go as high with these drafts because they usually don’t go much higher than the highest peak of the mountain. They are great for just flying around at mountain level.
I find it amazing how just the sun and the shape of the land create wind drafts that allow this sport to even exist. Here are a few more photographs of this insane past time:
Which is a ridge lift and which is a thermal? (hint: one is sailing high in the air and one is sailing low relative to the photographer.)
Would you ever try this? Or, maybe you already have! Share your comments below!