As noted in this answer, Barry can run through time when he hits mach 2. Until recently, this was considered his top speed.

In the episode Trajectory (S02E16), Barry is told that he needs to run mach 3.3 to be able to run through the air.

Barry, to make that jump, you'll need to go Mach 3.3, but only for a second.

Barry successfully makes the jump, and does not travel through time.

Using standard, non common-core math, 3.3 > 2.0.

Given that Barry now has a new top speed, which he will undoubtedly have to use to fight villains and save people, how does he run faster than mach 2, and keep from running through time when he doesn't want to, or looking at it another way, what else besides speed is required to travel through time?

Of note, Trajectory was able to run faster than Barry, and Zoom is able to supposedly run 10 times Barry's speed previous to this episode, and also does not appear to accidentally run through time.

(I prefer an answer from the Arrowverse, but I'll accept an answer from the comics if this is sufficiently explained there.)

  • Is this not off topic because of the future works policy? Apr 15, 2016 at 19:57

2 Answers 2


To be fair, it is never stated that the ONLY thing needed to jump through time is speed but that ONE of the things needed is speed.

So far, as far as I'm aware we've seen several ways that Barry has traveled back in time and in all of them there has been a combination of Barry running over match 2 AND something else happening (energy wave, particle acelerator, tsunami wave).

In universe there is enough evidence that only running fast is not enough, there are other factos that can be diverse and that are not completely understood (and which can vary from more controlled to uncontrolled). So Barry does nothing to avoid moving through time as simply going fast does not trigger a time jump.

Out of universe of course they use the time travel feature (or parallel dimension travel) whenever they need it but always in combination with some additional "event" happening.

  • 2
    This is correct. If going over Mach 2 is all that was required, many fighter jets would be doing so any time they got up to speed.
    – Jeff
    Apr 13, 2016 at 14:53
  • Well, no, because fighter jets don't have access to the Speed Force, which is presumably a major component to being able to travel through time.
    – phantom42
    Apr 13, 2016 at 15:31
  • 2
    @phantom42 Note that Jeff said "If going over Mach 2 is all that was required", reinforcing the point of Jorge's answer.
    – TylerH
    Apr 14, 2016 at 15:51
  • My read on this, after watching the show several times, is that it does require intent. He needs to hit his 88 MPH and then engage his internal flux capacitor to travel through time. Unlike the Delorean, it's an internal switch, so he can still flip it by accident when in the wrong state of mind.
    – FuzzyBoots
    Nov 9, 2022 at 13:36

In the animated movie,the Flashpoint Paradox, Barry goes into the past and saves his Mother from being killed and thereby creating a time ripple which affects the past as well as the future from that very moment in time...

Now,he is helped by Thomas Wayne to once again become the Flash and undo the things that have led upto here....

Barry wants to travel in time but cannot because the Speed Force present is being used up by another speedster The Reverse Flash. They also confront each other and is told by the Reverse Flash that he will not relinquish the necessary amount of Speed Force to make him jump in time...

Drawing analogy,we have Speed Force concept in The Flash(Tv Series) too but it is still not so clear as to what and why it is so important. The answer to your question may lie in the future episodes with more focus being put on the Speed Force...

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