private void calculateGravity(BlackHole bh) {
        double dx = x - bh.getX();
        double dy = y - bh.getY();
        double distance = Math.sqrt(dx * dx + dy * dy);
        if (distance != 0) {
            gravity = (FRAME_WIDTH * 1.0 / 20) / distance;
        }
        //System.out.println("dist: " + distance + " grav: " + gravity);
    }