The A-scope (1939) — radar's first display
The earliest radars showed a horizontal line on a CRT — time/range on the X axis, return strength on the Y axis. A blip on the line meant a target at that range. The A-scope was simple but gave no bearing information. Operators had to manually rotate the antenna and watch the blip rise and fall to find the direction of maximum return.
The PPI (1944) — the modern radar look
The Plan Position Indicator put the radar at the centre of the screen and painted returns at their actual map position. The antenna rotated; the trace rotated with it; the long-persistence phosphor — P7 yellow-green — kept the previous sweep visible for several seconds while the new one painted over it. That afterglow IS the look of radar.
P7 phosphor was chosen because its decay time happened to match typical antenna rotation rates (4-15 RPM). A coincidence of materials chemistry, not aesthetics, made radar green.
B-scope, E-scope, RHI
The B-scope plotted azimuth on X and range on Y — used by air-intercept radars where the pilot wants to know 'is the target left or right.' The RHI (Range-Height Indicator) plotted range on X and altitude on Y — used by height-finder radars. Each scope evolved to answer a specific operator question.
Modern screens, ancient symbols
Today every radar is digital. The display could look like anything. But air traffic controllers, ship pilots and military operators still see a green PPI with white symbology because the visual language has been refined over four generations of operators and it works. Arcade radar games inherited the look not for nostalgia but because it is genuinely the clearest way to show 'sweep + contacts + history' on a single screen.