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Table of Contents
2.1: The concept of time traveling in BTTF trilogy
2.1.2: What is SPE (Self Preservation Effect)?
SPE is the idea that in time travel, the continuum works itself out to avoid paradoxes, retaining very important things such as meetings, (Doc and Marty), and memories, such as Identies and maybe even memories (which is why Dave and Marty don't end up with traded names and why Marty still remembers the Twin Pines Timeline). (Chaltab)
2.1.3: What is Ripple Effect?
When you make a change in the past, it is spread like a wave to each year into the future. When Marty changed 1955, it first change 1956, then 1957 and so on. This is called the ripple effect. When the ripple effect reach fx. 1960, all references in the future till this year are changed, but references in the years after 1960 are not changed yet, until the ripple effect reach that year. (mr.xl – Source: FAQ on the BTTF DVD box)
2.1.4: What is "space and time continuum"?
In order to have balance in the events of the universe the past have to take place at a correct time and order in such way that the future will end up correct as well. The Self Preservation Effect will keep space and time continuum intact by keeping important events happen, even if a past is altered. If a paradox are provoked to happend, the people involved may faint, like when Jennifer (from 1985) meet her older self in 2015. Marty and Doc have to avoid meeting themselves in the past and future to avoid the breakdown of the space and time continuum
Doc talks a lot of not disturbing the space and time continuum, but it's not proved if he are correct in his assumptions. The universe may or may not have a mechanism to survive even if a disturbans should occur. Actually, nobody know exactly what will happened if a paradox DID occur.
2.1.5: How are time traveling explained in the trilogy?
Back to the future trilogy are a complex time travel movie. Some events may be explained with one theory, and other events by another one. Remember that these theories beneath are only speculation. The problem is that the concept change during the trilogy. What seems logic in BTTF1 doesn't work out in BTTF2 and BTTF3. Mainly it can be divided into two concepts. Single and Parallel timeline
22.214.171.124: Single timeline
This is based on that there only excist one timeline. Whenever there is made a change, everything are changed and replaced based on what happened before, but those who travel are not effected in the same way. This theory is widely accepted by fans.
126.96.36.199: Parallel timeline
Whenever a change is made in the past or the future, the universe split thereafter. If something or someone are left behind in a wrong time period, it cannot be retrieved if the past are changed as the future would be changed. The people who are not time traveling are living their lives again, based on the change in the past. However, the SPE make sure that some important events remain the same.
This theory does have a problem to explain why Einstein still exists at the end of BTTF3. He was left behind in A1985, and by this theory he should be trapped there.
2.2: General plot questions of BTTF trilogy
2.2.1: When are Doc Brown born?
The scripts and the novel for Part I confirm that Doc is 65 in 1985, putting his year of birth somewhere between January and September 1920.
However, an episode of the animated series ("Gone Fishin'") says that Doc was 4 in 1926, making his birth year 1922 and thus would have been 63 in 1985. Most fans regard this as just a slight slip-up or choose to ignore this, and accept the 1920 date as it is in the script and novel for the *movie* which is more canon than the animated series.
Doc's age according to the novels and draft scripts, are as follows:
- November 5th-16th 1955 - 35 years old
- October 26th 1985 - 65 years old
- January 1st 1885 - 65 years old
- September 2nd 1885 - 66 years old (chances are Doc had a birthday between January and September, and he was probably a few months past his 65th birthday by October 1985!).
- October 27th 1985 (In BTTF3), circa 12pm - around 76 years old, assuming he and his family had been in the past for 10 years or so. Of course, Marty and Jennifer aside the people of 1985 Hill Valley would still think he is 65/66. (Frasier Crane – Source: BTTF1 draft script and novel)
2.2.2: When are Marty born?
It is stated that Marty is 17 years old in 1985, which would set the year of birth somewhere in 1968.