If refraction is a true phenomenon then it should be imperfect and only occure sometimes. Like the mirage should look very blurred and scattered. It shouldn't be possible for refraction to occure 24/7, would you agree with those two claims? However refraction seems to produce a perfect mirage as if you are on a plane with no curve. And assuming you don't have too much fog/rain/smoke... you can always use binoculars or a telescope to see objects that should be behind the earth curve. How do I know this? It happens to me all the time when I see approaching vessels when I am driving a commercial ship. Don't take my word for it, try it yourself. You just need height of the observer (above the water), and distance to the object. Then you can calculate how many feet of curvature should be blocking the object.