code: function (t, dt) {
      if (!dt) return;
  
      var i;
      var callbacks = this.callbacks;
  
      for (i = 0; i < this.callbacks.beforeStep.length; i++) {
        this.callbacks.beforeStep[i].beforeStep(t, dt);
      }
  
      this.driver.step(Math.min(dt / 1000, this.data.maxInterval));
  
      for (i = 0; i < callbacks.step.length; i++) {
        callbacks.step[i].step(t, dt);
      }
  
      for (i = 0; i < callbacks.afterStep.length; i++) {
        callbacks.afterStep[i].afterStep(t, dt);
      }
    }
docs: Updates the physics world on each tick of the A-Frame scene. It would be
  entirely possible to separate the two – updating physics more or less
  frequently than the scene – if greater precision or performance were
  necessary.
  @param  {number} t
  @param  {number} dt