Could aliens communicate using radio waves?

Yes — aliens could plausibly communicate using radio waves. Radio is one of the best-known candidate methods for long-distance communication because radio waves are electromagnetic radiation, so they can travel through the vacuum of space at the speed of light.

Why radio waves make sense for interstellar communication:

• They travel at light speed in vacuum.
• Longer radio wavelengths are less affected by dust and gas than visible light.
• They can be generated and detected with technologies we already know how to build.
• SETI and similar efforts have long used radio telescopes to look for artificial, non-random signals from space.
• Some researchers have suggested listening in the “water hole,” a relatively quiet radio band around 1.42–1.66 GHz.

Important caveat: this is scientifically plausible, but we have not yet detected any confirmed extraterrestrial radio message. Over interstellar distances, signals get very faint and delayed, so any exchange would likely be one-way in practice unless the civilizations were relatively close and both actively transmitting. Exact detectability depends on distance, transmitter power, beam direction, and noise, so results can change as observations improve.