I just read this from here:
http://cfcp.uchicago.edu/education/explorers/2002summer-YERKES/pdfs-sum02/background.pdf

A radio transmitter whose job it is to move electric charges
rhythmically up and down its antenna sets the signal that is to be
propagated in motion. These waves that are propagated carry
signals that are received by antennae on your radio or television set.
(note: antennas are used both to transmit or and receive signals)
The movement of the electric charges produces a changing electric field--
a structure in space that pushes on electric charges--and a changing
magnetic field--a structure in space that pushes on magnetic poles.
Because the electric field changes with time, it creates the magnetic field
and because the magnetic field changes with time, it creates the electric
field. The two travel off across space as a pair, endlessly recreating one
another in an electromagnetic wave that will continue to the ends of the
universe. However, when this wave encounters the antenna of your radio,
its electric field begins to push electric charges up and down on that
antenna. Your radio senses this motion of electric charges and thus
detects the passing radio wave.

This is the part I'm having trouble with:

A radio transmitter whose job it is to move electric charges
rhythmically up and down its antenna sets the signal that is to be
propagated in motion.

How does it "move" charges up and down the antenna if there isn't a
closed circuit?


However, when this wave encounters the antenna of your radio,
its electric field begins to push electric charges up and down on that
antenna. Your radio senses this motion of electric charges and thus
detects the passing radio wave.

This makes a little more sense, but I'm still having trouble with this part.
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