And Hypersonic Flight

Figure 6UNDISTURBED INTERPENETRATIONSimple waves, as Leonardo explained, do not transportmatter transversely, and hence sets of such wavescan interpenetrate undisturbed.the stones closes up again at once and this motionmade by the sudden opening and closing produces acertain shaking, which can be called trembling ratherthan motion. And to make what I say plainer, take heedof those straws which by their lightness stand on thewater; notwithstanding the wave made under them bythe coming of the circles, they do not leave their firstlocations. . . . (Institutde France Ms. A61r)Source: Institut de France Ms. A 61 r.Such waves then, according to Leonardo, are able to "actat a distance" without any work done.Leonardo indicates another experiment in the same direction:If we put a flame in front of the mouth of a singer,the flame will not move, but the same sound wave couldrelease energy on a glass and break the glass, by the effectof resonance known to Leonardo. As he wrote: "The blowgiven to the bell will cause a slight sound and movement inanother bell similar to itself; the same for a string of a lute,and you will see this by placing a straw upon the stringsimilar to that which has sounded" (Madrid 22v).Leonardo continued doing extensive studies of otherphenomena associated with this type of simple surface wave,which he naturally extended to sound and lightwaves. Hereare some of the main aspects of his work:Reflection. There are many quotes throughout his notebooksand especially in his book On Painting.Diffraction, also called the Young Principle (Figure 7).Color formation with a ray going through water.Such waves can be represented as sinusoidal waves travelingalong a cylinder even if the actual motion of the processis a transverse cylindrical action and a longitudinaldouble rotation of conical form (Figure 8).Leonardo then generalized such wave motion to all kindsof action in different media (Figure 9). Here we see hiscomparison of sound, magnetism, light, and olfactorywaves, with their properties of reflection. Leonardo askshimself the question, why do sound and smell go througha wall, while light waves do not? The answer is not given,Figure 7DIFFRACTION(a) Diffraction of a wave front passing through a slit,in a drawing by Leonardo. Here he is studying vocalsound. Because of his understanding of the commonbehavior of fluids, he used water for the experiment.(b) Photo of straight waves undergoing diffraction inpassing through an opening.Source: Leonardo, Anatomical Notebooks III: 12v. G.A. Williams, ElementaryPhysics, p. 286.but will be implicit in the kind of elaboration he makes later.We could express it in modern terms with the double aspectof particle (photon)-wave property of the light wave, or interms of the self-transparency of electromagnetic waves. Itis the "particle" aspect of the light that does not go throughthe wall.FUSION January-February 1986 23