I think about it more and harder always and constantly. It’s sickness. A TIME SICKNESS.

If I remember correctly, Later Than 2015 Doc came back to 1985 to convince Marty to go 2015. So 2015 Marty wouldn’t remember it because it hasn’t happened yet. If 1985 Marty decided of his own accord to go to 2015, then 2015 Marty would remember it. But since Marty’s trip to 2015 was triggered by an event after 2015, he can’t remember it since it didn’t happen that way origially.

Time travel is such a wonderous, fascinating subject that you have to be doing something pretty wrong to fail to melt underwear with it.

I don’t feel like the actions in BTTF have immediate consequences. In the first movie Marty causes his parents not to meet, but he does not disappear immediately. In fact, his older brother didn’t even disappear immediately in the picture. Change happens in a ripple effect through the space-time continuum. There is still a chance that Mary’s parents will get together, so the future (Marty and the picture) is reflecting the odds of this still occurring. I feel this applies in Part 2, when they travel to the future. Doc and Marty and Jennifer travel to the most probable future scenario; one where the most likely outcome will be that after jumping ahead in time, Marty and Jennifer will eventually return back to their original time and live out the rest of their lives. (Conversely, the scenario that Einstein was going to return to his original time of origin after his one-minute time jump was non existent, so he does not meet his one-minute future self. Same thing with Doc, there’s probably not a 2015 Doc walking around, because the chances that Doc would ever return to and live out in his original time was non-existent. He would never meet his older self in 2015 because he never planned to return to 1985 and life out until 2015, and the space-time continuum reflected that.) If Marty and Jennifer never returned to 1985 it could have cause a paradox, or at the very least they would’ve seen the 2015 world change around them eventually. Wouldn’t Old Marty remember that he travelled to 2015 when he was 17yo? Yeah, maybe, but maybe he also forgot the exact date. Even without the event of Part 2, 47yo Marty would still remember that Doc had travelled 30 years to the future, and should be arriving in Lyon Estates any day now. That doesn’t mean he wouldn’t go about his normal day, or maybe even forget the exact date and time.

ANYWAY, the true point I wanted to make here is that, in my younger years I would use the above rationale of the paradoxes in BTTF as my go-to “think about baseball” substitute to prolong horizontal activities.

Old Biff disappears because in the Alternate 2015 that he created, he is no longer alive. This is a question actually answered by Gale and Zemeckis. They theorize that Biff was killed before 2015 because of his fame and wealth, possibly be Lorraine.

I always assumed the “it’s your kids” line was a ruse and the elaborate over-planning a smokescreen for something else going on in Doc’s head that maybe he didn’t want to explain to Marty. Like maybe the whole thing was a science experiment to explore the effects of people crossing their own future timelines… There’s also the question of the closed timelike curve here: did 1985 Doc maybe just do all of it because of what he remembered and wrote down about the second visit from Marty to 1955 Doc and the letter from 1885 Doc?

Panty-demovers?

“when old Biff returns the DeLorean, he is is his normal time stream.”

There’s a deleted scene that I consider canon where old Biff returns to 2015 and then vanishes. He’s absorbed by the time stream because of his alterations to the past. You could extrapolate from this that the entire 2015 timeline would collapse in on itself if Marty and Doc had lingered too long.

Real retail version supposedly still coming “this year” http://time.com/3662868/nike-back-to-the-future-shoes/

I don’t know about the proper “power lace” version of the shoes, but Nike auctioned off a number of them a couple years ago & put the proceeds to charity (specifically for Parkinson’s research, if I recall)

They were huge, and colorful, and we’re going for way more than any pair of shoes should (without power laces)

I haven’t been keeping tabs on power lace development, so that could be this years big reveal.

They are definitely coming out. No idea if it’s this year or not, though

Alterations to the past cause immediate and observable consequences to objects only if that object is out of its normal time stream. Marty in 2015 is in his time stream, so he doesn’t change when Marty from 1985 leaves 1985. Note that the horrible future where Biff rules Hill Valley is an alternate timeline, not a change to Biff. This is shown because when old Biff returns the DeLorean, he is is his normal time stream.

IOW, you’re just not thinking fourth-dimentionally.

There WAS a lot of umlauts on stuff

Maybe 2015 Marty is just So Awesome that he’s all like “Yeah, today my younger self us coming to meet myself. Imma totally pretend like I don’t remember thus happening when I was my younger self bahaga its gonna be hilarious for all those dudes trying to figure out how the timelines work”

I feel like this line from Doc is him FINALLY understanding how time and causality work. Like, he just didn’t get it for 3 movies. He nearly destroyed the universe because he was too dumb to say, “It’s your kids Marty! Something has to be done about your kids! So in about 15 years, make sure your kid isn’t pressured by Griff to… you should be writing this down. You know like all the letters? The one you sent me that saved my life and the one I sent you from 1885. That’s good enough! We don’t actually have to travel into the future and make a change that will be pointlessly undone by every choice you make for the next 15 years. You get this right, Marty?”

Linear causality time travel doesn’t allow for “what your’re probably going to do.” These aren’t bullshit Bill and Ted rules here.

Those shoes ARE coming out this year. Aren’t they? I remember reading about them and watching a video.

You were at ShpielbÖrg’s house.

BTTF uses a linear causality time travel principal. All of their actions in the past (such as preventing Marty’s parents from dating) have immediate and observable consequences in the future (Marty and his siblings ceasing to exists). These are the rules they’ve established for the films (despite the fact that they ignore them whenever convenient). Using these rules, one can NEVER visit their own future AND see their future self. They stopped existing in that timeline as soon as they left it and were never around to age into their older self. Just because WE know that Marty eventually goes home to 1985 doesn’t mean the timeline knows that.

Even if they could bend the rules and have an older Marty (perhaps this is young Marty’s 40th or 50th times through this series of events, so the timeline assumes at least one version of him will return and age), older Marty would be all, “Oh right, this is the day I come to the future and meet myself.”

Doc comes back and gets him somehow in part 3.

The 2015 that 1985 Marty went to wasn’t HIS 2015. His 2015 is the one where hoverboards are produced by Lexus, and Nike is the biggest party pooper ever.

Indeed – the only reason that a 1985 Marty going forward into the future would result in 2015 stopping existing would be if ’85 Marty never returned to the “present”. (Although, as Frank says, ’15 Marty should remember all this).

Time to go and watch 12 Monkeys again….

In retrospect, I dont think it actually was Spielbergs house, since I never left Sweden and I dont think he lives here.