Back to the Future: Does physics of Marty's time travel add up?

Today is 21 October 2015 – the date Marty McFly and Doc Brown travel to in Back to the Future Part II. Can we reconcile the films with reality?

This amazing new physics theory made me believe time travel is possible

time travel - Why was Marty present in his jump to 2015 in Back to the Future 2? - Science Fiction & Fantasy Stack Exchange

Back To The Future: All 8 Timelines In The Movies Explained

Back to the Future: The Complete Trilogy (DVD) [2020] – Back to the Future™

9 Rules for Writing Time Travel – Kimberly Van Ginkel

The Time-Travel Paradoxes

What's the real-life science behind time travel?

Time Travel – T.E. Mark – Writer

Time Travel Anthropology

How The Flux Capacitor Works In Back To The Future

Back to the Future (creative franchise): What are some of your favourite BTTF time related oddities/changes that occur through the film? - Quora