From particles to the cosmos: the theory, simulation and inference methods physics is built on.
Numerical methods that evolve fluid flow together with the photons or neutrinos that heat, cool and push it; the hard part is transport at the speed of light across huge opacity ranges.
Combining signals from widely separated antennas samples the Fourier transform of the sky; imaging means inverting that incomplete, noisy data. It underlies radio surveys and black-hole images.