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I'm just wondering whether the DeLorean time machine has any restrictions on how far into the future or how far into the past it can travel.

Inspired when I was considering an earlier question of mine it struck me that the earliest we actually see the DeLorean travel to 1st of January 1885 - the time circuits may have defaulted to that date because that was the earliest date (i.e. 100 years from when it was made and 70 years from when it was in 1955) that the DeLorean could travel to. Yet, we see in the beginning of Back to the Future that Doc suggests the time machine could travel to witness the birth of Christ (the date he uses is 25 December 0000).

So, my question: is there any evidence to suggest there are any restrictions on how far into the future or past the DeLorean can travel to?

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Often Right
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    Too bad Doc Brown is intelligent enough to build a time machine but doesn't realise that the year 0000 doesn't exist... – Lightness Races in Orbit Jul 16 '15 at 09:31
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    It can only travel within it's own lifetime – Rob Jul 16 '15 at 10:56
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    @Rob What do you mean by that? – Dr R Dizzle Jul 16 '15 at 11:27
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    @Rob: That's obviously not true, unless Doc Brown is really old and first built the DeLorean in the time of the wicky wicky wild wild west – Lightness Races in Orbit Jul 16 '15 at 14:01
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    Forgive me, it is a Quantum Leap reference, I had expected some other time travel enthusiasts to get it. – Rob Jul 16 '15 at 14:14
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    @Rob Don't worry, not everyone missed it. – Kevin Jul 16 '15 at 17:27
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    As a practical limit, given the fact that the machine's spatial location (relative to the Earth, of course) doesn't change (paraphrase: "You're not thinking fourth dimensionally, Marty: the screen won't/the tracks will be there in 1885/1955!"), one would want to travel at a terrestrial location with very accurate historical maps. (The hover conversion does make aerial travel possible and prudent though, especially heading into the future.) – jscs Jul 16 '15 at 20:07
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    @LightnessRacesinOrbit To be fair, Doc Brown was probably manually compensating for the discontinuity in our calendar. – RBarryYoung Jul 16 '15 at 20:15
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    @RBarryYoung Even compensating for those discontinuities, Christ was probably born around 4 BC, and probably not in the winter. But I wouldn't expect a light-hearted movie like BTTF to try to explain that. – Kevin Krumwiede Jul 17 '15 at 22:21
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    A bit off-topic, but spatial positioning/navigation during time travel might be just as big an issue as time travel itself, unless you manage to somehow entangle your destination locations to the time machine. We're steadily moving in space and have absolutely no reference point. Earth moves around our solar system's center of gravity, solar system around the galactic one, the milky way towards Andromeda... And mostly everything away from each other. – Arc Jul 18 '15 at 04:49
  • @LightnessRacesinOrbit I have to stand up for the Doc here. He's an impressive scientist (not an historian) who just pulled an all-nighter fine tuning the most impressive invention of all time, which utilizes radioactive Plutonium to operate, and all under the threat of being found by the terrorists he ripped off. His education in "history" was just beginning. –  Jul 18 '15 at 06:54
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    @LightnessRacesinOrbit That depends on which numbering system you use. – hvd Jul 18 '15 at 12:00
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    @Archimedix The usual assumption used to hand-wave that problem away is that the time-travel mechanism is fixed relative to the largest local Center of Mass and Center of Moment (i.e., the surface of the Earth). – RBarryYoung Jul 18 '15 at 17:38
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    @KevinKrumwiede The actual year/date of Christ's birth is a matter of some speculation and varying differences of opinion, anywhere from 8 BC to 7 AD. Plus the Gregorian-to-Julian differential could add/subtract years/months depending on how it's accounted for. Again, presumably, Doc Brown knew all of that and compensated for it. (Incidentally, this is why no computers builtin time formats go back before the last Julian/Gregorian transition, there just wasn't any consistently agreed upon "current date/time") – RBarryYoung Jul 18 '15 at 17:47

5 Answers5

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Well, the controls are 4-digit year. Because Y2K wasn't realized as a problem back then :)

So, presumably, even if the Flux Capacitor could take you anytime (as per @N_Soong's answer), you couldn't configure the controls outside of 0AD-9999AD year range.

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    Actually a brilliant point I hadn't thought of! +1 – Often Right Jul 16 '15 at 02:29
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    @N_Soong - yeah, you and that slacker, Doc Brown, both. – DVK-on-Ahch-To Jul 16 '15 at 02:29
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    Looking at the controls, which only allow for minutes, hours, days, months, and years, I wonder how the DeLorean chooses what point, within a given minute, it should appear. – Wad Cheber Jul 16 '15 at 02:33
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    @WadCheber - (1) Random; (2) 000ms; (3) Same as departure ms – DVK-on-Ahch-To Jul 16 '15 at 02:44
  • @DVK It could use other permutations of the data to allow for traveling to other times. For instance, the first digit in the year control could turn to a letter or other symbol, indicating the millennium. Or, if the PM and AM lights are lit, it could mean that a year outside the "0000-9999 CE" range has been selected. – Wad Cheber Jul 16 '15 at 02:46
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    It could also be that travel is only accurate within a minute. – Chris B. Behrens Jul 16 '15 at 04:40
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    Bearing in mind that we see the stop watches are in sync to the second when Doc sends Einstein to the future, I think it's fair to say that it chooses the same second from which you were coming from. – Often Right Jul 16 '15 at 04:45
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    Having a 4-digit year you won't be hit by Y2K! – mgarciaisaia Jul 16 '15 at 05:24
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    @mga I was referring to the concept ; not # of digits – DVK-on-Ahch-To Jul 16 '15 at 05:27
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    I do wonder if you'd be able to utilise a 4-digit display to represent BC as negative, giving a max input range of -999 to 9999. Of course, this really is splitting hairs. – BiscuitBaker Jul 16 '15 at 08:36
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    @BiscuitBaker: that’s what came into my mind too. Then I thought, “ok, what happens when you select the year zero?” Or well, how does it handle the transitions between Gregorian, Julian and Roman calendar? – Holger Jul 16 '15 at 09:09
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    When exactly was 0AD? – Lightness Races in Orbit Jul 16 '15 at 09:31
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    @LightnessRacesinOrbit 1 year after 9999AD – WernerCD Jul 16 '15 at 13:17
  • Enter the date in hex. – Andrew Lewis Jul 16 '15 at 14:58
  • @Holger - it's a bloody computer. It doesn't know about Roman and Gregorian calendars, and it's unlikley Doc Brown programmed those in. – DVK-on-Ahch-To Jul 16 '15 at 14:59
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    @DVK: that would be strange as Doc Brown is very likely to enter the dates using the Gregorian calendar, unless we assume that he adheres to the Orthodox Russian Church. Given how much you have to care about when only implementing that single calendar in a time machine (leap years, exception to leap years, daylight saving time, leap seconds), he must have been aware of these other calendars. But maybe he handwaved these issues and the machine is indeed not supposed to travel to a date earlier than 1885 anyway… – Holger Jul 16 '15 at 15:16
  • @DVK If Doc Brown didn't programme in the Julian calendar, then he's going to be turning up eleven days late for anything he wants to see (in the UK or its colonies, including the North American ones) that's earlier than 1752. Seems like that would be a mistake.

    Of course, if he did programme in the Julian calendar, it would be really interesting to set the controls for 10 September 1752 (a date which did not exist, since we went straight from 2 September Julian to 14 September Gregorian) and see where you ended up.

     – Mike Scott Jul 17 '15 at 06:23
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    What then if he travels to December 31 9999 / 23:59 and spends a few minutes there? – kR105 Jul 18 '15 at 23:29
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    @kR105 If the destination control is independent from the current date/time display controls, probably the date/time display will show something like "Err" like '80s calculators, but you can still set the destination to any date on the 0AD-9999AD year range. – mg30rg Jul 20 '15 at 14:54
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In the Universal Studios theme park attraction, Back to the Future: The Ride (now closed), we see that the DeLorean is capable of travelling to the time of an Ice Age and the Cretaceous Period.

The Cretaceous Period was somewhere in the range of 144 to 66 million years ago, and there have been several Ice Ages that the DeLorean could have travelled to, from one just over 2.5 million years ago, to one over 2 billion years ago. Obviously, these are far outside the 0AD - 9999AD restrictions that @DVK puts forward in their answer.

To me, this shows us that even if there is an upper limit on the time travelling abilities of the DeLorean, we are unlikely to meet them in every day use, with even the most extreme examples of time travel into the distant past been handled just fine by the DeLorean.

However, I'm unsure of how canon this answer is. This question and answer would imply that Back to the Future: The Ride it is part of an alternate universe or a "What-If" type situation, but I don't think that the ride contradicts anything from the film trilogy at any point, and it seems safe to assume that the DeLorean would be capable of traveling to these times in the film trilogy.

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Dr R Dizzle
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Probably not.

Consider all the times we see the DeLorean time travel. Whether it be 1 minute into the future, or 70 years into the past, the DeLorean continues to require the same amount of energy: 1.21 jigawatts (for the Doc). As there is a consistent amount of energy required for these vastly different timespans, there probably is not any constraints on how far into the future or past the DeLorean can travel. The only restrictions would be ensuring that the DeLorean was still in an environment where it had access to the energy it needed for the flux capacitator, and the capacity to speed to 88 miles per hour.

EDIT As pointed out by Grimm The Opiner, a jigawatt (or gigawatt - I like the former because of Doc) is not a unit of energy. Just to explain my answer in light of this the script describes it in the following way:

DOC: Lightning will strike the clocktower sending one point twenty-one gigawatts into the flux-capacitor

(Source)

which, to the layperson like myself, sounds as though Doc is describing an amount of energy! If the amount of energy was consistent, which from the way it was presented is suggested to be the case, then my argument still stands. See @DVK's answer though; it raises a very good point!

Often Right
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  • Nice reasoning! – Matthew Lock Jul 16 '15 at 06:04
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    Firstly, it's actually the unit gigawatts. Secondly, I don't think this reasoning really holds up. The curve of energy could be a function one that doesn't vary much for small time frames (where "small" would be a couple hundred years) but starts increasing dramatically as you get to larger time ranges, like say tens of thousands or millions. For comparison, think about how the difference between Newtonian mechanics and relativity is negligible at normal scales but drastic at speeds near c. Without experimental verification, even Doc couldn't say with too much certainty what it would require. – jpmc26 Jul 16 '15 at 06:21
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    @jpmc26 - nup in the BTTF universe it's definitely jigawatts. You make an interesting point about the energy requirements, but I think that my reasoning is in line with the information presented in canon; I just feel your argument is just a bit too extreme without much evidence supported by canon. – Often Right Jul 16 '15 at 06:24
  • @N_Soong My argument is more, "No canon information given. Applying a little reasoning suggests we can't extrapolate that much. Therefore unknown." – jpmc26 Jul 16 '15 at 06:26
  • @jpmc26 and I use the word 'probably' for that very reason ;) – Often Right Jul 16 '15 at 06:27
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    @N_Soong it's gigawatts, but pronounced differently than most of us would pronounce it today. http://www.myfluxcapacitor.com/gigawatt-jigawatt – rob Jul 16 '15 at 06:57
  • "gigawatts" is a measure of power not energy. Second "jigawatts" is a frequently used pronunciation of "gigawatts" in engineering circles – teambob Jul 16 '15 at 08:04
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    Your argument falls down because jiggawatts isn't a unit of energy. Forget the 'jigga', a 'watt' is a unit of power - the rate at which energy is used (or more correctly, transformed). 1 watt of power is 1 joule per second. So, the 1.21 jiggawatts is the rate at which energy is supplied to the 'time drive' - not how much energy will actually be used. The amount of energy used (in joules) would be the power (1.21 jiggawatts) multiplied by the time in seconds the power is expended for. And as we're never shown the machine in transit through time we don't know how long the trip lasts. – Grimm The Opiner Jul 16 '15 at 08:05
  • @GrimmTheOpiner fair points made; I'm no physicist so please accept these rookie mistakes! – Often Right Jul 16 '15 at 08:54
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    @GrimmTheOpiner The way they word it in the film is: "lightning will strike the clock tower sending one point twenty one gigawatts into the flux capacitor" - you can see how the layperson would get the idea that it is delivering a certain amount of energy! – Often Right Jul 16 '15 at 09:24
  • @GrimmTheOpiner The trip lasts anywhere between -70 and 30 years. That would mean that when going from 1955 to 1885, the DeLorean uses [1.21 gigawatts * (31556940 * -70) =] negative 2672872818000 megajoules. This science is guaranteed to be 101% correct. – Dr R Dizzle Jul 16 '15 at 14:03
  • @DrRDizzle I'm fairly certain you realise that's not true. If the time experienced inside the machine was the same as the time that passed outside, then when Marty McFly first went back he would have arrived in the past as one of his grandfather's sperm. :-) – Grimm The Opiner Jul 16 '15 at 14:09
  • @GrimmTheOpiner *How dare you, my logic is infallible!* – Dr R Dizzle Jul 16 '15 at 14:16
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    @DrRDizzle Ah, so the time travelled and Marty's personal time are experienced cumulatively - in the case of going back they sum to zero. Of course, the unfortunate effect of that is that when the DeLorean goes forward in time Marty ages by twice the amount of time travelled. – Grimm The Opiner Jul 16 '15 at 15:13
  • @GrimmTheOpiner Which explains why his son (and several members of his family) look exactly like him in Back to the Future II - they took on his excess age. – Dr R Dizzle Jul 16 '15 at 15:35
  • according to Arizona state university, a lightning is usually ~10^12 watts, which is 1000GW, much more than Doc's lightning. Also, they last for ~30us, for a total energy of 3.10^7J (or 8.3 KWh, the equivalent of 4 hours of your big oven). Doc's lightning is much less energetic, about 10Wh only, or the equivalent of your same oven for ~20 seconds. It is likely that it is possible to reproduce that amount of energy with a big capacitor. – njzk2 Jul 16 '15 at 19:57
  • @njzk2 if that's the case then it seems to me to suggest that the actual time required to consume the energy is somehow less than the time it takes for lightning to expend it's energy. It's not guarantee that the energy is spent the same way, but it does seem plausible. – Wayne Werner Jul 17 '15 at 12:17
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If you consider the early 1990's cartoon TV series canon, this gives additional hints that there is no hard limit.

Season 1 Episode 3 "Forward to the Past":

To test a new invention called the Sonic Garbage Molecular Redistributor, without Marty, Doc and the boys head back to prehistoric times before 3,000,000 years so that they will not endanger anyone.

The series takes place after the events of the third movie. So strictly speaking, this would have to be either the steam train time machine or the DeLorean Mk2, which means they would be able to perform outside any hypothetical limits of the original DeLorean. There is however no indication in the series that there were any improvements made to the Flux Capacitor between the different models.

JMFB
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    Went back 3 million years to avoid endangering anyone? ... I think those writers heard of the Butterfly Effect a little too late. – jpmc26 Jul 16 '15 at 22:49
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It depends if there was relative or absolute mode with respect to those 4 digits otherwise one merely makes the jump in 9999 ( or -9998 ) years, resets rinse and repeat. The other consideration is that it is only a time travelliing machine not a T.A.R.D.I.S ( which seems to highly favour London ) and so there must be a travellable suface for it to accellerate ( or decelerate from ) 88mph. It cant be a primeval swamp or a post-nuke blast crater

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