The weight of it all
Living in it as we do our whole lives, it's easy to forget that air is heavy stuff. All of the air that rests on top of an adult's head (an area of about 500 square centimetres or one-half square foot) weighs roughly 400 kg, or about half a tonne! Thankfully, our bodies are up to this challenge. There's enough outward force from our bodies and the air inside us to keep us from imploding. We sense the true force ofaironly when it's blowing against us in a strong wind, or when we move upward quicklyenough. As we ascend in an elevator or airplane, the air pressure around us drops quickly, and the air inside us tries to escape, causing discomfort in our ears or our stomachs. Many people claim to be able to predict weather by feeling it*in their bones'. What's likely going on is that a sharp pressure drop (which usually signals a dramatic weather change) is enough to cause the air within sensitive tissues – such as those inflamed by arthritis – to expand and trigger pain.