With the targeted application of radar technology for astronomical research, he laid the basis for the development of radio astronomy.

Hey studied physics at the University of Manchester, graduating in 1930, and obtained his master's degree in X-ray crystallography the next year as a student of Lawrence Bragg.

Realising that the direction of maximum interference seemed to follow the Sun, he checked with the Royal Observatory, Greenwich and found that a very active sunspot was traversing the solar disc.

Later, in 1944–1945, Hey used radar to track the paths of V-2 rockets approaching London at about 100 miles high, aiming to be able to predict their point of impact.

When he tried to increase the sensitivity of his radar in order to track V-2s from a greater distance, he rediscovered the cosmic radio noise that Karl Jansky and Grote Reber had found in the 1930s.

[4] From 1952 he returned to ADRDE, which later became part of the Royal Radar Establishment at Malvern, Worcestershire, where he also continued his radio astronomical observations.

At his observatory at Defford, Worcestershire, he built a variable-spacing radio interferometer, with which he briefly parallelled Martin Ryle's research at Cambridge.

Brought up in a church-going Wesleyan Methodist family, Hey became an agnostic in his teenage years, and remained so for the rest of his life.