what can fill a room but takes up no space

This riddle can be interpreted in more than one way, depending on the perspective. From a literal point of view, the answer would be light, as it can fill a room and take up no space. However, another possible interpretation could be that the answer is a silent listener or a quiet presence that can be heard but does not take up physical space. For example, in a busy restaurant, one might say that a quiet and unobtrusive server is filling the room with good service without taking up any physical space. Alternatively, in a big city, one could say that the city itself is filling the streets with life and activity, yet it takes up no physical space. This riddle is therefore open to interpretation and can be understood in a number of different ways.