Why is this the answer?

The answer is light because this clever riddle is all about that bright, speedy energy that lets you see everything around you. Imagine you walk into a room that is completely dark. When you flip the light switch, light rushes out from the bulb and quickly spreads everywhere, filling the whole space instantly. It travels extremely fast, much quicker than anything else, and it doesn't leave any dark corners behind. It fills the room from wall to wall, floor to ceiling, making the whole area visible. The second part of the riddle asks what "takes up no space." This is where light shows how truly special it is. When a room is filled with physical things, like a big table, a tall bookcase, or a box of toys, those objects take up space. They are solid, and you cannot put anything else where they are. But light is not a solid object. It is a special kind of energy that travels in waves. These waves are so tiny and gentle that they can travel right through the air and around all the things in the room, like the furniture, your toys, and even you. Because light is energy and not a physical object, it never needs its own spot. It can fill up the room without pushing anything out of the way. It shares the space with everything else, and that is why you can walk right through a sunbeam without bumping into it. This makes light the perfect answer: it completely fills a room so you can see, but it is so light and airy that it takes up no space at all. It is a wonderful puzzle that makes you think about this invisible part of our world.