When Flash runs at speeds of light and greater, how does he not end up in space and beyond. His horizontal velocity trajectory would be so huge that gravitational force would be meaningless. So when flash hits a bump or a hill or any kind of inclining underground he would simply fly off of it into space... or my physics needs a little brushup?

  • 10
    and greater (than the speed of light) should be your first hint that the Flash and Physics arn't friends.
    – user16696
    Commented Dec 20, 2014 at 21:29
  • He wouldn't even need to hit a bump, as the earth isn't flat. At a sufficient velocity, he would simply continue going straight, away from the curvature of the earth. That said, he would presumably at this point be unable to continue accelerating, so unless he jumps to such high velocities instantaneously...
    – Doc
    Commented Dec 21, 2014 at 4:55

2 Answers 2


Your physics are sound, the Flash's not so much. A quick back of the envelope calculation shows this problem. When traveling a curved course, the acceleration needed to stay on that curve is calculated by a = v^2 / r. Input the appropriate values (a = gravity, r = the radius of Earth), you end up with the velocity of 7800 meters/second squared. Travel faster than that on Earth's surface, and you would more or less run faster than gravity would pull you down, which would put a damper on Flash's running.

However, the Flash has been known to run at the speed of light, which is significantly faster than that, and stay on Earth. How does the Flash do that? The source of his power, the Speed Force. It grants him his super speed abilities, and also provides him some basic protections. In short, it's the hand-wavey comic book physics thing that enables the Flash to do his thing.

The Speed Force enables the Flash to do physics-defying things, as it grants the Flash some supernatural control over velocity and acceleration. This is how the Flash is able to move as fast as he does, and how he's able to run fast enough that gravity should let loose its grasp.


TV-verse, gravity also affects him at accelerated speeds while he's using his powers.

This was shown (though not explicitly stated) in Arrow 3x08, The Brave and the Bold, when he was using Oliver's exercise bar. He doesn't simply drop when he moves to a lower level, he's moving downwards as fast as he moves upwards.

  • 2
    And yet he can run up the sides of buildings.
    – user1027
    Commented Dec 21, 2014 at 4:41
  • @Keen Maybe it's optional/unconscious? I haven't picked up The Flash, but I don't recall him doing so in that Arrow episode
    – Izkata
    Commented Dec 21, 2014 at 7:12
  • "gravity also affects him at accelerated speeds" Haha. Thank you for that.
    – njzk2
    Commented Apr 27, 2017 at 20:11

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