The MWA is a radio interferometer in the desert

This animation shows radio signals from the sky incident on the MWA receivers.
If the signal source is directly overhead and all antennas are tuned to receive a signal from that location, then all the tiles receive the signal at the same time. If the direction of the source or the weightings applied to the antenna are not exactly lined up, then the physical separation between tiles and elements requires the waves to travel slightly different distances to reach every tile. These small distances are seen as time delays by the system, and so the signals from all tiles require correlation in order to form a coherent image of the sky.

Credit: CAASTRO/Swinburne Astronomy Productions