How do we tell if a window is open?
Just throw a stone at it.
Does it make a noise?
Well, it was open.
Now let’s try another..
*Source: Where the Sidewalk ends by Shel Silverstein
Not only can you tell if the window is open or not, you have successfully got both the windows opened.
All you’ve got to do is throw a stone. All you’ve got to do is START trying.