ON THE APPARENT MAGNITUDE

in the high and pure ether. This indeed does not seem difficult for the mind to grasp, nor is it denied by anyone, since it is proven by eyewitness observation original: "αὐτοψίᾳ" (autopsia), meaning seeing for oneself or direct personal observation itself. There is certainly no one who has not observed the same thing in the Moon, especially when it shines with a full orb. Indeed, either immediately at its rising, or just before its setting, it is found to be more vast than when it shines brightly in the high sky. I had added that the Sun near the horizon casts a larger shadow than when it walks high in the sky. I could have asserted this also using the example of the Moon, since this fact is established for me by certain experiments.

I see, however, that this is what caused the difficulty. For if the shadow is larger while the Sun rests on the horizon, the Sun ought therefore to appear smaller; yet this contradicts the observation explained earlier In classical optics, a larger light source usually creates a smaller, more tapered shadow. Gassendi is addressing the contradiction where the Sun looks bigger but its shadow also seems broader.. Perhaps I did not explain clearly enough the reasoning I conceived in my mind when I saw the shadow growing larger near the horizon, contrary to all expectation? I fear this is so. For this reason, the whole matter must be discussed a bit more fully, so that it may become more clearly known.

II. Therefore, when I say first of all that a larger shadow is cast, I do not mean a longer one. It is certain that a longer shadow is created by a low Sun over the level of the horizon, and a shorter one when the Sun is high. I mean rather a thicker shadow, whether in terms of width or as viewed in the transverse diameter The "transverse diameter" refers to the width of the shadow measured across, rather than its length along the ground.. This is surely distinguished and compared with a smaller (or if you prefer, a narrower) shadow at the same distance from the opaque object that creates the shadow. To explain the matter graphically,