At what speed do photons travel?

Photons, which are the fundamental particles of light, travel at a constant speed known as the speed of light in a vacuum. This speed is approximately 299,792 kilometers per second (or about 186,282 miles per second). This property of photons is a cornerstone of modern physics and underpins theories such as special relativity, which explores the implications of the constancy of the speed of light for all observers regardless of their relative motion.

In contrast, the other options suggest speeds that are either slower than the speed of light or related to other physical phenomena. The speed of sound, for example, is much slower than the speed of light, varying based on the medium through which it travels, such as air, water, or solids. Therefore, recognizing that photons travel at the speed of light is crucial as it distinguishes their behavior from other wave phenomena, thus reinforcing our understanding of electromagnetic radiation and its interaction with matter.