## 5 - The notion of the black hole

### N. Lygeros

Translated from the Greek by Vicky Baklessi

Many epistemologists begin their historical introduction presenting it as the first significant idea, the birth of this abstract conception, the black hole, (abstract in the sense that it hasn’t been experimentally proven yet) that of LAPLACE. Of course this idea diversified its thinker from his intellectual era, but we mustn’t forget the almost dictatorial supremacy of the wave theory of light within which he was born. So this revolutionary spark would had been completely devoured from the dark existence of this theory if some genius with the help of experiments of its thoughts hadn’t withdrawn it from oblivion and hadn’t succeed in giving it flare capable of radiating the intellectual world. This genius was called EINSTEIN! However this essay would have been redundant if scientific stringency and accuracy didn’t have its place. In the 20th century many and various problems started resisting the classical engineering and so they placed it in criticality. Then it was verified that these would be fatal for it. In science though, catastrophe is only the first phase of creation and so from the ruins of classical engineering the two grandiose theories of 20th centuries were born: The theory of relativity and quantum theory. The contribution of EINSTEIN to both will be significant not only for the scientific level, but also to the philosophical not in a similar manner. The discovery of the dual aspect of the elements which consists matter and light, namely the conception of wave-particle, lead to the invention of many concepts in the cogitative field. Between them the new approach of the mythic quantum: the photon. The theory of general relativity processed by EINSTEIN provide us with a complete vision of our universe giving it four dimensions. So the concept of space-time appeared and then, one of its most remarkable properties, its deformation from the existence of its mass. This property of deformation is primitive, indeed, because gravity no longer appears as a distant action but as geometric property. So it becomes easier to interpret it. The geodesics of this space-time are not that of a straight lines, as in a Euclidean system, but of curves. And the light similarly as matter follows these curves. The local curvature is important to the evolution of particles that are in its neighboring space-time. The gravitation of a star can then be interpreted as a cavity where this cavity will depend on two parameters, the mass and the radius of the star. In this manner while the parameters are large, the larger the local curvature and then the larger will be its action to the neighboring space-time. While continuing this thought, let us imagine for example a cavity even deeper until its depth becomes infinite, we will have conceived the notion of the black hole.