Answer: Light.
Flip a switch and light fills every corner of a room — instantly. But it weighs nothing and occupies no physical space.
If you said “air” — air actually has mass and takes up space. If you said “sound” — close, but sound doesn’t “fill” a room visually. Light is the only thing that completely transforms a space while being physically… nothing.
Your score: __/15
Next: ➡️ Brain Teaser #13
