What causes bubbles to pop in mid air?

If a bubble is floating what causes it to just suddenly pop in mid air. Doesn't it only pop when it hits something solid?What causes bubbles to pop in mid air?
It pops because at some point it gets a hole in it. That hole can be created by lots of things (think of a pin in a balloon.) It doesn't appear that the air has a pin in it, but it sort of might. Sometimes loose atoms (oxygen, carbon-dioxide, etc.) might be adhereing to the bubble to cause it to "dry out" and one spot and pop. If enough time goes by, gravity itself might weaken the bubble enough to cause it to pop. (The moisture is heavier than air, and would sink to the bottom of the bubble, leaving the top weaker and weaker until eventually it would have a hole in it.)

Most bubbles are popped by "dust" in the air. The dust is dry, and when it touches the bubble wall, it dries it out enough to suck moisture away from the wall. Thus, the "pin" is really just one of those little dust particles you see floating by in a shaft of sunlight.

The dust particle--while small--is "something solid."
Bubbles pop because the longer they exist the liquid that makes them up sinks to the bottom of the bubble and there for the tp slowly doesn't have any and once there isn't enough on the top it pulls aparts and pops.What causes bubbles to pop in mid air?
Gravity, as bubule is in the air, gravity cause the liquid around the buble to drop below and the skin on the top get thinner and burst, if you look close on bubbles, you will learn that the liquids are dropping from the buttom,
When a bubble floats into the air, it's volume will start to increase as the pressure within it pushes its thin liquid "casing" outwards. This results in it popping in mid air.What causes bubbles to pop in mid air?
The surface tension of the bubble is lost as it dries in mid air.