I’m sorry for such a convoluted question, but this has been bothering me for some time now. While the title isn’t quite accurate, I couldn’t think of a better way to phrase it - feel free to edit if you can.

In sci-fi literature, (backwards) time travel tends to take one of two forms: either (1) one’s actions were already taken into account in the timeline, leading to the trope of someone trying to prevent something from happening but causes it to happen in the end (think Doctor Who); or (2) one can actually alter the past, leading to a branching timeline (think Back to the Future).

Does Judaism address whether either of these are accurate? That is, assuming time travel is possible, can one go back in time and alter the past?

The flip side of the coin, which might open some other possibilities for answers: if I somehow receive a message from the future, can I take measures to prevent it from happening, or will it automatically happen regardless of what I do?

The main question ends here. The following are some of my thoughts on potential proofs one way or another from methods we know to be true of predicting the future.

While astrology, kishuf, necromancy, and urim v’tumim all do this to some effect or another, there is a fundamental issue with all of them that prevents them from being proofs - namely, a large portion of the message is left up to interpretation, and thus any inaccuracies might be chalked up to user error. Take the example of Paroh’s message of Ra’ah (Shemos 10:10) - while one could argue that the symbol was overturned, one could just as easily argue that it was never intended to refer to murder, and Paroh misread the stars.

Nevuah, also, isn’t a good proof: a negative prophecy can be overturned, but perhaps it was just to scare the people and never was intended to be fulfilled at all. A positive prophecy might never be overturned, but that could be just because Hashem doesn’t lie - not that it fundamentally can’t be overturned, but that He chooses not to overturn it.

While different, yedi’ah versus bechirah is very heavily related.

  • So you're not interested in self fulfilling prophecies?
    – robev
    Apr 8, 2018 at 14:44
  • @robev If you could bring a proof from one I’d be interested, but only if it can avoid the issues I raised in the question.
    – DonielF
    Apr 8, 2018 at 14:45
  • Basically, since we cannot prove one way or the other, it is not worth asking. All we can know is the way things actually happen. There is no way we can actually prove either way. Apr 8, 2018 at 14:52
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    One argument in favor of your option (1) is that one is not allowed to pray to change something in the past, (though I suppose if you do enough handwaving you make option (2) fit as well).
    – Nic
    Apr 9, 2018 at 13:36
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    @DanF Probably edited in later. Cf. Gid HaNasheh according to the Chachamim.
    – DonielF
    Apr 9, 2018 at 16:51

2 Answers 2


I am sorry to write my comments as an answer, but it might help to think of some additional ideas.

When watching a movie on a PC I asked myself: "How come, the whole movie is stored on my disc as a file, but I can only watch it sequentially?"

Same with the creation, it is one "4D" piece that unfolds before our eyes sequentially. I met this concept a lot in the Lurianic (Kabbalic) tradition (by R' Moshe Luria Z"L), for example:

  1. תהו ובהו וחושך וכו - hints on the 4 Galuyot from the moment of the Creation

  2. Abraham chased the enemies to Dan and then he suddenly weakened as his descendants are destined to sin at Dan

  3. Binyomin wept at Yossef's neck upon the destruction of the two Temples, that Ariz"l says was destined and fixed in the creation.

In this approach, the time travel is impossible and meaningless as the Creation together with its timeline is one.

Therefore the question of "הכל צפוי והרשות נתונה" is resolved on the spiritual level only - the only thing a person is given powers to control is his "intentions" not deeds ("חוץ מיראת שמים"). This is unsourced, but that's what I learned from R' Luriah.

  • I already said that I’m basing my question on the premise that time travel is possible. Therefore this isn’t an answer - the Arizal learns like the other side in the debate, while I’m following those who say it is possible for the sake of this question.
    – DonielF
    Aug 26, 2018 at 15:14
  • You asked a very unclear question as the title does not correlate with your main question and the last paragraph is also off the time travel. You might want to focus on a specific point. I answered the title and the last paragraph.
    – Al Berko
    Aug 26, 2018 at 15:52
  • Between your comment here and to my question it’s clear that you didn’t read it thoroughly enough. Assuming that time travel is possible, theoretically it would lead to one of two results: actually changing the timeline, or history already reflects your actions in the past. It’s not a tautology at all, and your answer is saying that a premise is false when, in fact, there seems to be enough Talmudic literature to support either side of the argument.
    – DonielF
    Aug 26, 2018 at 16:23
  • @DonielF "or history already reflects your actions in the past" - where did this come from? Can you give an example of it?
    – Al Berko
    Aug 26, 2018 at 16:28
  • Second paragraph in my question. It’s exactly what it sounds like - you tripped over a rock, so you went back to move it out of the way so you wouldn’t trip over it, but instead ended up putting it in exactly the position where you tripped over it.
    – DonielF
    Aug 26, 2018 at 16:36

Without getting into comparing sci-fi literature to lehavdil Judaism. Time holds a prominent place in Judaism.

It is the thing that, in a sense, dominates a Jews life. It decided when one must recite a prayer (Krias Shema), it directs man to abstain from labor (Shabbos), and it demands when one must preform other ritual duties (Korban Pesach, Korban Bein Ha’arbayim, etc.)

Yet we also find that man (more specifically the Rabbis), in a sense, have a mastery over time. For example, the Mitzvah to Sanctify the New Moon, known as Kiddush Hachodesh. Two witnesses are brought in, and through their testimony of the seeing the new moon, the Beis Din declares the new month, which then sets off a myriad of obligations.

There is a fascinating Midrash in the Yakut Shimoni that attests to this idea, that Man plays a powerful part, almost on par with G-d himself, in the control of time:

מתכנסים מלאכי השרת אצל הקב"ה ואומרים לפניו: "רבונו של עולם, אימתי ראש השנה?" והוא אומר: "ולי אתם שואלים? אני ואתם נשאל לבית דין של מטה!"

גזרו בית דין של מטה ואמרו "היום ראש השנה", אומר הקב"ה למלאכים: "העמידו בימה, והעמידו סנגורים והעמידו ספיקטורים [מקטרגים], מפני שגזרו בית דין של מטה ואמרו היום ראש השנה!". נשתהו העדים לבוא, או נמלכו בית דין לעברה למחר [החליטו לדחות את קידוש החודש למחר] - הקב"ה אומר למלאכי השרת: "העבירו בימה, ויעבירו סנגורים ויעבירו ספיקטורים, שגזרו בית דין של מטה ואמרו, ראש השנה למחר". (ילקוט שמעוני בא קצ, קצא

The angels gathered together with the Holy One, blessed be He, and said to Him: "Master of the world, when is the New Year?" G-d responded : " Why do you ask me? Rather, let us ask the Lower Court (the Human Court)

The Beis Din declared: "Today is Rosh Hashanah,"

G-d said to the angels: "Put up a stage, and put up defense attorneys, and set up accusers, because they decreed a court of heaven and said today Rosh Hashana!"

However, the witnesses failed to come, or the Beis Din decided to push Rosh Hashana off till tomorrow.

The Almighty said to the ministering angels: "remove the stage, remove defenders and Remove spikers, for the Court has ruled that Rosh Hashana is tomorrow."

We see that time, and the obligations that stem from it are placed in the hands of man, and thus make it, in a sense malleable. For how can time, being that Rosh Hashana is the literal date and beginning of the world (yes, this aspect is subject to a tannaic dispute, but the point nonetheless stands), be subject to the decisions of the Beis Din. There are further examples of this that we find throughout halacha (the status of a girl physical maturity etc. the bringing of the Korban Ha’omer).

These are but a few examples, but i hope to add more.

Regarding time travel in general, we find the Gemara in Taanis (23a)

  • 1
    While the last bit about that time travel is possible doesn’t exactly address the question - that’s better suited for the question I linked in the OP. The first bit absolutely addresses it, and I’ll have to think about that a bit.
    – DonielF
    Apr 8, 2018 at 14:57
  • @DonielF duly noted. I'll take it out till I flesh it out more. Because it does answer your question. Apr 8, 2018 at 15:35
  • I don't understand how this is related to the idea of Time? We're free to set our milestones, but how does that change the time?
    – Al Berko
    Aug 26, 2018 at 12:32
  • @AlBerko the fact that we can set dates and markers, and thus moving the day that we commemorate the day of creation, it is as if we have power over time itself Aug 26, 2018 at 12:52
  • If I celebrate my birthdays - what power over my birth do I have? Rosh Chodesh has nothing to do with the passing of time - whether we Mekadshim or not - it passes, the Moon does not stop and waits.
    – Al Berko
    Aug 26, 2018 at 16:31

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