(written from a Production point of view)
Harvey P. Lynn, Jr. (1921 – 31 December 1986)  was a RAND Corporation physicist and the special scientific adviser for Star Trek's pilot episode, "The Cage". Using his own personal time, Lynn served almost a year and a half as a science consultant for the series.
Rand took exception to some of the jargon used by Gene Roddenberry, such as "laser" and "rocket", because these were devices already in existence in the 20th century. Originally, the episode was to take place in the Sirius star group, but Lynn suggested that another star system be used instead. Lynn is often credited with inventing the term "phaser".
His son, Harvey P. Lynn III, has commented in 2002 about his fathers involvement, "He graduated as an Electrical Engineer. Worked at RAND as a liaison Officer between RAND and Project Airforce. Was never starstruck and had little interest in TV, films, or science fiction. Apparently he met Mr. Roddenberry though a mutual friend and was selected for the technical consultant job more because he hit it off with Mr. Roddenberry than his technical expertise. When offered the job, he boned up on physics, astronomy, etc. He picked up surprisingly quickly on how to express the technical elements simply...ie not having to explain how a phaser works...sort of how most people know that a light switch turns on the lights but don't wonder about the mechanics. From his earnings as consultant, we bought our first color TV. I think that's in 'The Making of Star Trek'. My Dad was never really a big fan of the show...not a Trekkie in today's sense. I've retained only about 3 scripts. My family was really moved by Mr. Roddenberry sending flowers to Dad's funeral in Texas as they hadn't really been in contact for years." 
He died on New Year's Eve, 1986, one month after his eagerly looked-forward-to retirement. (Inside Star Trek: The Real Story, p 442)