What is the nature of free space such that it requires antennae to be at
least 1/4 wave
before accepting radiation efficiently?

Is it that some form of electric "twist" must be appled to Free Space, and
that
the maximum "twist" occurs with 1/4 cycle of a quarter wave?

Were there to be two short antennae closely spaced, but fed 90 degrees
out of phase, wouldthat result in efficient radiation?

What if they were spaced by 1/4 wave but with the feeders completely
screened
from Free Space, or does there have to be all fractions of antnna betwen the
two extremes?