Steiner refers to the experiments of Young and Fresnel and others in connection with this matter, saying that it was Fresnel's work which shook the corpuscular theory. But before getting further to their work, we take note of his Figures 12 and 13 with particular reference to the portion of the screen upon which the two reflected beams of light overlap. There is a lattice-work image upon the screen within this area. How is it explained?

Now let us try to grasp what happens in reality in this experiment. Suppose that this [stream that hits mirror 1] is the one stream of light. It is thrown by reflection across here, but now the other stream of light [directed toward mirror 2] arrives here and encounters it—the phenomenon is undeniable. The two disturb each other. The one wants to rush on; the other gets in the way and, in consequence, extinguishes the light coming from the other side. In rushing through it extinguishes the light. Here therefore on the screen [where the two reflected streams overlap on the screen] we do not get a lighting-up but in reality darkness is reflected across here. So we here get an element of darkness (Figure 13). But now all this is not at rest—it is in constant movement. What has here been disturbed goes on. Here, so to speak, a hole has arisen in the light. The light rushed through; a hole was made, appearing dark. And as an outcome of this "hole," the next body-of-light will go through all the more easily and alongside the darkness you will have a patch of light so much the lighter. The next thing to happen, one step further on, is that once more a little cylinder of light from above impinges on a light place, again extinguishes the latter, and so evokes another element of darkness. And as the darkness in its turn has thus moved on another step, here once again the light is able to get through more easily. We get the pattern of a lattice, moving on from step to step. Turn by turn, the light from above can get through and extinguishes the other, producing darkness once again, and this moves on from step to step. . . . When one light rushes into another the light is canceled-turned to darkness. . . . The velocity of light-nay, altogether what arises here by way of differences in velocity of light-is not of great significance. What I am trying to make clear is what here arises within the light itself by means of this apparatus, so that a lattice-work is reflected—light, dark, light, dark, and so on.

Steiner explains how the physicists solve this problem with their theory of transverse waves perpendicular to the direction the light is moving. "When the train of waves arrives here [where the paths of light reflected from the two mirrors overlap on the screen in Figure 13], it may well be that the one infinitesimal particle with its perpendicular vibrations happens to be vibrating downward at the very moment when the other is vibrating upward. Then they will cancel each other out and darkness will arise at this place. Or if the two are vibrating upward at the same moment, light will arise. Thus they explain, by the vibrations of infinitesimal particles, what we were explaining just now by the light itself. I was saying that here we get alternations of light patches and dark. The so-called wave-theory of light explains them on the assumption that light is a wave movement in the ether. If the infinitesimal particles are vibrating so as to reinforce each other, a lighter patch will arise; if contrary to one another, we get a darker patch."⁴⁰

You see from this example that our fundamental way of thought requires us so to explain the phenomena that they themselves are the eventual explanation. They must contain their own explanation. Please set great store by this. Mere spun-out theories and theorizings are to be rejected. Of course the waves might conceivably be there, and it might be that the one swings upward when the other downward so that they cancel each other out. But they have all been invented! What is there, however, without question is this lattice. It is to the light itself that we must look if we desire a genuine and not a spurious explanation.⁴¹

Steiner also demonstrated phenomena in conflict with the wave-theory explanation of interference. He performed an experiment which he then illustrated in Figures 14, 15 and 16. In Figure 14 the light from a white incandescent solid body passes through a downward pointing prism (wider part at top) so that the light is displaced upward with the blue colors on top and red on bottom. In Figure 15 the light from the solid body is

But then the remarkable thing comes about when we combine the two experiments as in Figure 16. What happens then is very like what Steiner was showing us in Fresnel's experiment (Figure 13).

FIGURE 16

In the resulting spectrum you might expect the yellow to appear extra strong, since it is there to begin with and now the yellow of the sodium flame is added to it. But this is not what happens. On the contrary, the yellow of the sodium flame extinguishes the other yellow and you get a dark place where it was. Precisely where you would expect a lighter part you get a darker. Why is it so? It simply depends on the intensity of force that is brought to bear. If the sodium light arising here were selfless enough simply to let the kindred yellow light go through it, it would have to extinguish itself in so doing. This it does not do; it puts itself in the way at the very place where the yellow should be coming through. It is simply there, and though it is yellow itself, its effect is not to intensify but to extinguish. As a real active force, it puts itself in the way, even as any indifferent obstacle might do; it gets in the way. This yellow part of the spectrum is extinguished and a black strip is brought about instead. From this you see again that we need only bear in mind what is actually there. The flowing light itself gives us the explanation.