What is the Speed Force, and why is it the wildest concept in comics?

The answer

The Speed Force, introduced by writer Mark Waid in The Flash #91 (1994), was created to solve an absurd physics problem: at the Flash's speeds, friction should incinerate his body, sonic booms should deafen him, and g-forces should liquefy his organs. Waid's solution was an extra-dimensional energy field that generates a protective aura around all speedsters, shielding them from extreme physics. The concept expanded wildly over decades - the Speed Force now has its own counterparts including the Still Force (inertia), Sage Force (intellect), Strength Force (physicality), and the Negative Speed Force created by Reverse-Flash. It exists as a literal plane of reality that speedsters can physically enter, and it powers every speedster in the DC Universe simultaneously.