how radio waves are broadcast out of an antenna.
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I am telecommunication engineer and this topic was difficult for me to understand when I was studying. This is how I build an intuition about it.
The simplest kind of antenna is a wire, just a piece of metal. Hence it is conductive, you can have an electrical current though it. Electrical current is just movement of free electrons in the wire. For example, if you have an AC current you can imagine electrons going back and forth along the wire.
Here comes the interesting part. How this current is radiated out of the wire? It is simpler than it seems, the effect of moving charges in the antenna (electron flows) generates charges in the air around it (what is called an electromagnetic field). This charges as they move back and forth from the antenna stimulate the air around it and so on and so forth. The farther you go, the smaller this effect is (power decrease rapidly with the distance). However, if the current in the antenna is powerful enough and the antenna is cleverly design (not just a wire) you can reach interstellar distances with this method.
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