"This is heavy" was an expression used frequently by Marty McFly to mean a situation that was very ponderous or serious.
Since this was a slang of the 1960s which passed into the 1980s, its meaning was not clear while in 1955; when Dr. Emmett Brown overheard it, he wondered at first what weight had to do with the problem. Later, he wanted to know if there was a problem with the Earth's gravitational pull in the future.
After Doc first demonstrated how the time machine worked, Marty used a similar phrase, "This is heavy-duty", which he restated as "This is great."
Behind the scenes
- This expression was used in the trilogy a total of eight times. In Part I, Marty said it on two occasions. In Part II, young Marty said it on three occasions, while 2015 Marty said it once. In Part III, Marty only said it once, and Doc used the expression for the final time in a humorous reversal of roles.
- The use of the word "heavy" as slang for serious dates from the hippie culture of the late 1960s , as is the case with "far out!". A contemporary example was on the Beatles' 1969 album, Abbey Road, with John Lennon's lyric "She's so heavy...". Marty McFly, born in 1968, appears to have learned the expression from his parents; in one of the first drafts for a sequel to Back to the Future, Lorraine McFly is seen, in 1967, as a follower of the hippie movement.
- Tom Dalzell, Flappers 2 Rappers: American Youth Slang, Merriam-Webster, 1996