= Aperture synthesis
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Aperture synthesis reconstructs the sky's brightness from <complex visibilities> measured at different <interferometric baselines>. Each measurement constrains a <Fourier transform> component of the brightness, rather than supplying a little photograph. Combining many such components can distinguish sources that each individual <antenna> leaves unresolved. The remarkable economy is that changing separations and the rotation of <Earth> can provide many measurements with only a few physical <antennas>.
<Martin Ryle>'s Cambridge group made <aperture synthesis> a practical method of astronomical imaging at the Mullard Radio Astronomy Observatory. Cambridge's institutional history connects that work with the <One-Mile Telescope> and its larger successors.<Mullard Radio Astronomy Observatory at Lord’s Bridge by Cavendish Laboratory, University of Cambridge>[Cavendish Laboratory, Mullard Radio Astronomy Observatory at Lord’s Bridge, sections Foundation and early development and A centre for radio interferometry]{ref}
In his 1974 lecture Radio Telescopes of Large Resolving Power, <Martin Ryle> recalled the problem of distinguishing weak extragalactic sources and resolving their structure. He explained sequential wavefront sampling using one simultaneously observed element as a <wave phase> reference, and the saving obtained by letting <Earth> rotate the apparent baseline.<Radio Telescopes of Large Resolving Power by Martin Ryle>[Ryle (1974), Radio Telescopes of Large Resolving Power, pp. 187–192, Figures 1 and 4]{ref}
The 1974 <Nobel Prize in Physics> distinguished <Martin Ryle>'s observations and inventions, especially <aperture synthesis>, from <Antony Hewish>'s role in discovering <pulsars>. The latter is a separate astronomical discovery, with its own observational history.<The Nobel Prize in Physics 1974 by Nobel Prize Outreach>[Nobel Prize in Physics 1974, award explanation and equal prize shares]{ref}
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