  Radio astronomy began with one array (Jansky's) and one paraboloid of
revolution (Reber's) as collecting areas and has now reached the point where a
large number of facilities are arrays of paraboloids, each of which would have
looked enormous to Reber in 1932. In the process, interferometry has
contributed to the counting of radio sources, establishing superluminal
velocities in AGN jets, mapping of sources from the bipolar cow shape on up to
full grey-scale and colored images, determining spectral energy distributions
requiring non-thermal emission processes, and much else. The process has not
been free of competition and controversy, at least partly because it is just a
little difficult to understand how earth-rotation, aperture-synthesis
interferometry works. Some very important results, for instance the mapping of
HI in the Milky Way to reveal spiral arms, warping, and flaring, actually came
from single moderate-sized paraboloids. The entry of China into the radio
astronomy community has given large (40-110 meter) paraboloids a new lease on
life.
