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Inspired by this question which the author states is not a question of issur/heter. Assuming time travel is possible (to the future or past) is there any reason it should be assur?

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Time travel to the future is very easy. I do it all the time. –  Ariel Jan 7 '13 at 20:41
Dr Midos did it! –  Gershon Gold Jan 7 '13 at 20:54
@DoubleAA l'fi ashiras da'as wikipedia dos is nisht kein pashut en.wikipedia.org/wiki/Time_travel#Experiments_carried_out –  user2110 Jan 7 '13 at 21:15
@GershonGold Actually, it was Shnooky Shapiro who did it. And at the end, it was a dream, because, as Dr. Middos said, only Hashem is capable of existing beyond time. –  josh waxman Jan 8 '13 at 1:45
Another interesting ramification of this is whether or not you can pasken like somebody before they existed. If you went back to the 15th century, could you still hold like the Mishna Berurah? –  Shimon bM May 27 '14 at 21:31

3 Answers 3

Granting that time travel would ever be conceivable, I would make the following comments:

Initially a reason should be provided to suggest that something is assur. Coincidentally however, I have thought of a comparable precedent which demonstrates how it is permissible to travel through time.

Whenever we move, we inevitably alter time imperceptibly because of time dilation, according to the theory of relativity. And there is no halacha issue with movement, so it follows that there is no halacha issue of altering time. Perhaps according to the same logic, altering your position in time in the backward direction would not be a problem.

However, another issue can be at play. If one travels gradually backward in a machine of sorts and passes through the time of Shabbat or Yom Tov, it would seem that the familiar issues with operating machinery on these days would apply, even though one would be moving backward in time. If one could somehow skip from one moment to another though, he/she may be able to circumvent this problem.

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+1 ....never considered that gradual travel through Shabbos might be an issue, good thought –  Shokhet May 27 '14 at 18:33
+1 for cleverness –  yEz May 27 '14 at 19:04
I think that the imperceptibility of time dilation is a non-issue and would have no bearing on halacha. Travelling backwards in time may be done (theoretically) in jumps, rather than travelling back through time which wouldn't cause a problem in terms of shabbat. Just an addition. –  bondonk May 27 '14 at 20:20

The Talmud in Tractate Menachot (29b) says Moshe Rabeinu was transported in time to Rabbi Akiva's torah class and couldn't follow it.


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Isn't that more a case of seeing the future, rather than traveling to it (and more importantly for our case traveling back afterwards)? –  Yishai May 27 '14 at 18:34
@Yishai it says he actually sat in the class and was seated at the 8th row. –  ray May 27 '14 at 18:45
that is a hyper-literal interpretation. That could be his perspective in the vision (and this would probably imply the back row - in other words it is more a statement of his not being a high level student relative to the class). –  Yishai May 27 '14 at 18:50
@Yishai how do you know it was just a vision on not as the plain meaning. –  ray May 27 '14 at 21:17
I don't "know". As I said, your reading is a hyper-literal interpretation. –  Yishai May 27 '14 at 22:16

The mishna in Chagigah (2:1) mentions some things which man cannot delve into:

וכל המסתכל בארבעה דברים, ראוי לו כאילו לא בא לעולם--מה למעלה, מה למטה, מה לפנים, מה לאחור. וכל שלא חס על כבוד קונו, ראוי לו כאילו לא בא לעולם.

" Whoever looks at four things, it would have been better for him if he had never come into the world: 1) what is above [the sky], 2) what is below [the earth], 3) what was before [the Creation] and 4) what will be after [in the end of days]. And whoever takes no account of the honor of his Maker [see the following section in the Gemara], it would have been better for him if he had never come into the world."

These appear to refer to Hashem's realm of space ('above' and 'below') and time ('before' and 'after'). There are those things which are inherently incomprehensible to us. Although this isn't directly related to time travel, it Bartenura writes how it related to unknowable epochs:

מה לפנים? קודם שנברא העולם. מה לאחור? בסוף העולם לאחרית הימים.

According to the Bartenura knowledge of 'pre-Earth' as well as 'acharit hayamim' (a specific point in time in the future) would be problematic.

The Kehati gives further explanation:

ולכן אסור לו לחקור בהם, כי עלול הוא לבוא לידי טעויות ולידי מבוכה בענייני האמונה

Having said all this, this is in reference to learning about these topics. Perhaps this idea can be extrapolated by a kal v'chomer.

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