Sure, but the point of the trial is that he needs to take a leap of faith. Within the world of the movie, I bet those tests would have failed. Plus if there's

Sure, but the point of the trial is that he needs to take a leap of faith. Within the world of the movie, I bet those tests would have failed. Plus if there's "really" an invisible bridge you could throw a pebble at, it should already be covered in dust anyway. Unless the guy who lives in the grail room comes out and sweeps it or something.