There is a curious illusion with reference to the moon's apparent diameter referred to by Proctor.[81] If, when the moon is absent in the winter months, we ask a person whether the moon's diameter is greater or less than the distance between the stars δ and ε, and ε and ζ Orionis, the three well-known stars in the "belt of Orion," the answer will probably be that the moon's apparent diameter is about equal to each of these distances. But in reality the apparent distance between δ and ε Orionis (or between ε and ζ, which is about the same) is more than double the moon's apparent diameter. This seems at first sight a startling statement; but its truth is, of course, beyond all doubt and is not open to argument. Proctor points out that if a person estimates the moon as a foot in diameter, as its apparent diameter is about half a degree, this would imply that the observer estimates the circumference of the star sphere as about 720 feet (360° × 2), and hence the radius (or the moon's distance from the earth) about 115 feet. But in reality all such estimates have no scientific (that is, accurate) meaning. Some of the ancients, such as Aristotle, Cicero, and Heraclitus, seem to have estimated the moon's apparent diameter at about a foot.[82] This shows that even great minds may make serious mistakes. It has been stated by some writer that the moon as seen with the highest powers of the great Yerkes telescope (40 inches aperture) appears "just as it would be seen with the naked eye if it were suspended 60 miles over our heads." But this statement is quite erroneous. The moon as seen with the naked eye or with a telescope shows us nearly a whole hemisphere of its surface. But if the eye were placed only 60 miles from the moon's surface, we should see only a small portion of its surface. In fact, it is a curious paradox that the nearer the eye is to a sphere the less we see of its surface! The truth of this will be evident from the fact that on a level plain an eye placed at a height, say 5 feet, sees a very small portion indeed of the earth's surface, and the higher we ascend the more of the surface we see. I find that at a distance of 60 miles from the moon's surface we should only see a small portion of its visible hemisphere (about 1/90th). The lunar features would also appear under a different aspect. The view would be more of a landscape than that seen in any telescope. This view of the matter is not new. It has been previously pointed out, especially by M. Flammarion and Mr. Whitmell, but its truth is not, I think, generally recognized. Prof. Newcomb doubts whether with any telescope the moon has ever been seen so well as it would be if brought within 500 miles of the earth.