On the Plains of San Agustin in New Mexico, 27 dishes each weighing 230 tons sit on railroad tracks in a giant Y with 13-mile arms, and they move. This episode explores the Karl G. Jansky Very Large Array and the technique of aperture synthesis interferometry that lets separate antennas act as one enormous instrument. We explain how measuring tiny time delays across 351 antenna pairs builds an image, why the array is reconfigured every three to four months between its A and D layouts, and what a resolution of 0.04 arcseconds actually means.

We then cover what the VLA sees at centimeter wavelengths that optical telescopes cannot: magnetic filaments at the galactic center, protoplanetary disks, synchrotron radiation from black hole jets, the faint 1989 transmission from Voyager 2 at Neptune, a SETI search of nearby galaxies, and the VLA Sky S ...