Ok, but...isn't there.....yes.

That works. I had to make a tiny Post-It flowchart of my own, comparing the Delorean situation with Marty's, but it works.

But it all balances on a very thin thread, and that's the part that gives me selective amnesia. As many times as I've discussed this, it eludes me. For some reason, it just doesn't work. I think my brother and I's prime example had something to do with Biff.

Oh, and a really cool exploration of time travel and its effects on the subsequent timeline in a book is Orson Scott Card's Pastwatch: The Redemption of Christopher Columbus. The central conceit of the book will blow your mind.

The Biff problem is in Part II.

Old Biff goes back in time to 1955 and alters the timeline. Now, in 1985, Biff is wealthy, Hill Valley is Vegas on PCP and George McFly is dead.

Having accomplished this, Old Biff gets back in the Delorean and goes back to 2015...but he should go back to a radically different 2015, and Marty and Doc would NOT be able to get back in the Delorean and fix things. Because the entire timeline "changed around them" as Doc explains to Marty in reference to his girlfriend being dumped unceremoniously on the porch in 1985.

The 2015 that Old Biff returns to is a timeline in which Marty was sent overseas to boarding school and Doc Brown was put in an asylum (and likely didn't even invent the time-machine...causing a paradox).

I saw a movie a few months ago which had a flashback sequence to the 80s, and a hilarious visual gag with one character using what must have been a 15 lb. "cutting edge" mobile phone.

That was a big joke in American Psycho as well, along with Nouvelle Cuisine.

The scary part about seeing the original Terminator? Between the scenes with Linda Hamilton and her roommate, and the disco scene, it looks like someone's trying to DO an "80's" scene, when, in fact, it's just an 80's scene. Yes, the fashions were just as bad in the 80's as the 70's, folks, just a different style of bad.

I saw a movie a few months ago which had a flashback sequence to the 80s, and a hilarious visual gag with one character using what must have been a 15 lb. "cutting edge" mobile phone.

X-Files did this too, to a good effect.

On the other hand, Star Trek: TOS, with its cheesy sets that never looked convincing, and its velour outfits with bellbottoms, manages to get a number of things right, not the least of which being small devices with flipping lids that you can use to speak to someone who is very far away from you....

t takes out flippy cell phone and wishes it made a little chirpy sound when he flipped it open

The 2015 that Old Biff returns to is a timeline in which Marty was sent overseas to boarding school and Doc Brown was put in an asylum (and likely didn't even invent the time-machine...causing a paradox).

That's it!!

Yes, the fashions were just as bad in the 80's as the 70's, folks, just a different style of bad.

The 90s will be that bad too, in a second or so. It's like a time lag -- the clothes of X years ago look eminently mockable. More than X is retro, and less than X is familiar but unstylish.

Or so I was told.

I think there's some instant nostalgia that's happening these days that's mucking with the value of X. But for a while it was pretty constant.

The 2015 that Old Biff returns to is a timeline in which Marty was sent overseas to boarding school and Doc Brown was put in an asylum (and likely didn't even invent the time-machine...causing a paradox).

Ah, but you do notice in the movies a certain lag between the causal event and the subsequent change. I don't remember how soon after (old) Biff got back to his present that Doc and Marty left, but could it be seen that the "chronal" changes didn't catch up to the future by the time they had left for the past (85)?

takes out flippy cell phone and wishes it made a little chirpy sound when he flipped it open

I would be very surprised if there weren't a way to make your cell phone make the little chirpy noise.