Radio Waves: Spark gaps vs general wireless radio antennas?
First, your friend wasn't quite correct to say that &quot;radio waves are only generated when an electric current is made to move violently through a conductor&quot; because, for example there is the maser that generates radio waves through molecular processes rather than from electric currents in a conductor.
However, moving current is the most usual way to generate a radio wave. Basically from Maxwell's equations we know that charge produces electric fields, and current produces magnetic fields. So a moving charge produces a changing electric field, and a changing current produces a changing magnetic field.
And a second thing we know from Maxwell's equations is that changing electric fields produce magnetic fields and changing magnetic fields produce electric fields. A self-sustaining wave produced by these processes (in the appropriate frequency band) is exactly what we call a radio or light wave.
Whether you want to call the changing currents or moving charges in the antenna that produces the radio wave &quot;violent&quot; is up to you, though.