I can fill a room but take up no space. What am I?

Light is an excellent answer to the riddle, "I can fill a room but take up no space." This is because light, a form of electromagnetic radiation, doesn't occupy physical volume in the same way a solid object or even air does. When you turn on a light, it instantly spreads throughout the entire room, illuminating every corner without displacing anything already there. You can still walk through the room, and objects within it remain in their places, unaffected by the presence of light.

Visible light is just a small part of the electromagnetic spectrum, which also includes radio waves, microwaves, X-rays, and gamma rays. All these forms of radiation travel at the incredible speed of approximately 186,000 miles per second (300,000 kilometers per second) in a vacuum, a fundamental constant of nature. While light behaves like a wave, it also exhibits particle-like properties, meaning it can be thought of as tiny packets of energy called photons.

These photons carry energy and interact with matter, which is how we perceive light and color. When light enters a room, these photons bounce off surfaces, reflecting and refracting, ultimately allowing our eyes to see the surroundings. This ability to spread and interact without physically occupying space is what makes light a perfect fit for the riddle.