Marty: “He’s my son.”
[Doc slaps Marty]
Doc Brown: “I said I want the truth!”
Marty: “He’s my brother…”
[slap]
Marty: “He’s my son…”
[slap]
etc. etc.

Traditionally, of course, we’d expect their kids to have TWO heads and play the banjo. But you’ve got to figure that zero heads is also a possibility.

Lorraine exhibits what Doc describes as Florence Nightingale Syndrome. In the timeline that led to old 1985, she fell obsessively in love with George McFly aftur nursing him back from being hit by a car. George with Lorraine by his side is content with his life, even though he’s a loser, and so he continues in his dysfunctional relationship with Biff.

When Mary interferes, George is eventually forced to stand up for himself and win Lorraine’s affections away from Marty, which leads to the new 1985 timeline in which George follows his dreams and becomes a sucessful SF author. This is actually the THIRD timeline.

When Marty intervenes the first time (before contacting Doc in 1955), this puts the world on a course for a middle timeline. In this timeline, George does not kiss at the prom. Without Lorraine’s codependent love and support, George eventually snaps from the emptiness of his life under Biff’s heel, and goes not into SF, but the lucrative field of mad science. George’s intellect applied to creating monstrosities instead of best-selling novels, he makes groundbreaking strides in the field of headless engineering. With a Nobel prize under his belt, he woos Lorraine, has three kids, and starts running his demented experiments on them. This is the 1985 that mlawski describes.

Seeing the outcome of the current timeline in the picture, Marty and Doc panic and intervene a second time, changing the timeline to the new 1985 that we see at the end of the movie.

As for Marty’s hand disappearing, what would people have thought when Marty’s head just suddenly disappears and his lifeless corpse falls off stage, almost ensuring that nobody gets lucky that night. Then they are scarred for life and unable to have kids causing Hill Valley to become a ghost town where noone can live.

Because Doc is responsible for the tragedy, he turns into a psycotic killer who dresses up like Marty when he stabs young teenagers who are ‘having a good time’

Huge ACK, man!
BTTF (1) ist still the only movie I can imagine playing directly again after watching it. I often catch myself muttering the dialogues…depending on the playing version in english or in my native german (well, according to the german dubbed version).

I am puzzled as to why there are so many tacit assumptions about the nature of time travel though- BTTF is clearly shooting for some kind of many histories model, and within each history Chuck Berry, McFly, a combination or something entirely different might engender something we presume we recognise.

Likewise the headless brother photo.

Metatextually it is obviously SCIENCE! that makes the head disappear and the hand disappear, but it is easy to imagine that as has been pointed out it was the identity of the brother not his existence that had altered… Or even that the photo had to be altered using airbrushing (bit early for Photoshop outside of movie and CIA circles in 1985) and somehow Marty ended up with a bodged version in that parallel world for some reason…

As for his fading hand- he triggered a massive short circuit with the uberamp and uberspeakers, he injured it in the future, he stuck it out of car windows, inexpertly punched people with it and tried to be a gunslinger with it- played with steam with it, had skateboarding accidents with it- out of so many possible ways to lose a hand, in a high risk mission through time and so many parallel worlds… It’s a miracle he didn’t start the film with a stump… :)

OR DOES IT?