does a propeller screw itself on air or is it just reaction

[Puppet]

Cold
noun

the relative absence of heat.

When you open a window and the outdoor temperature is lower than inside, the warm inside air (less dense) will escape and rise into the atmosphere until it has cooled to equal the temperature of the surrounding air. The cold outside air (more dense) will enter the window to replace the escaping warm air and subside into the room.

Why is there confusion here? And why the hell are we discussing this in the first place?

Edit: I have just reread the OP's posts. I am not entirely sure exactly what point this thread is intended to prove. Several lines appear to be incomprehensible, however this could be due to the punctuation and grammar.

Edit 2: Did he say he is an engineer?!