What's the little bubble in the window?

Question

I fly alot, prolly like once a month. I always try to get a window seat. Well, every time I'v been on a plane I see a little tiny cyclinder (like 1/2 cenitmeter long, 1mm wide) inside the window, on the bottom, about 2 inches up. It's been in every plane I have been on. What is it? I also nopticed frost makes a Perfect cicrle around it about 1cm away. It's so weird. If you don't know what i am talking about, next time go on plane, look inside the window on the bottom, you ill see it.

Answer 1

I believe that it is to equalize pressure.Since the windows are double paned they would burst from the changes in air pressure as the aircraft climbs and descends.The cabin is pressurized but has bleeder valves to maintain a certain pressure altitude for the comfort of the passengers.Hope that helps.