Human civilization is quite old whereas modern science is relatively new. In early civilization human beings used to know things and happenings of nature through direct experience. The cause of happenings was sometimes attributed to some supernatural power which they perceived through different forms of God. Serious thinkers developed different philosophy of life, nature, universe and God through different schools of thoughts. Vedic science is the oldest science which rendered early scientific understanding of nature. The cause-to-effect analogy was the basis of exploring nature. The metaphysical understanding was always insisted upon the continuity of conceptual understanding. Modern science deals only with material science in macro-domain and micro-domain. Existence of matter in finer domain (micro-micro domain) has not been explored in modern science. The micro domain science provided the cause of macro phenomena where the cause was not confined to macro science only. Scientists accepted many quantum assumptions in micro domain physics and they have no answer for the cause of quantum reality. The cause of quantum reality lies in the physics of matter in micro-micro domain. The micro-micro domain particles have mass in micro-micro domain scale. Physicists ignored the matter value of micro-micro particles (photons) as the impact of photon on atomic and subatomic particles in micro domain scale is zero. The impact of micro atomic particles on celestial bodies in macro domain does not make any change of velocity of celestial bodies. In mass scale of celestial bodies the mass of atom is zero. But micro atomic particles have mass in atomic scale. Likewise light particles not having mass in atomic mass-scale have mass in photonic mass-scale (micro-micro domain scale). Therefore it is not correct to assume photons to be mass-less in all scales. The light particles having rest mass have rest existence therefore have a placement in the structure of all micro particles, structure of macro bodies and in the structure of space medium as space matter particles. Within a macro body, there exist both micro structure and micro-micro structure. The macro structure, micro structure and micro micro structure co-existing in equilibrium of individual structures also maintains equilibrium among different structures. Thus the properties of any macro system are predictable either from the study of its micro structure or from the study of its micro-micro structure. Modern science explores study of microstructure to characterize the properties of macro phenomena. On the other hand Spiritual science, homeopathic science, astrological science (which believes on existence of structure in finer domain) characterizes macro systems from micro-micro domain analysis. The language of expression of different domain-based sciences being different, the modern science does not accept the basics of other sciences. If all sciences including the modern science are translated from domain-based language to universal language then the non-acceptable barrier would disappear. 

To express all systems and all events in all domains of the universe in universal language we need to understand the basic constituents of the universe and the very basic interaction property of the basic constituents. Proper interpretation of Vedic science and modern science has made this author to identify mass & space as the only basic constituents of the universe and both are physical entities. Matter at any stage in any domain is a mass-space integral system. The basic interactions of mass and space are mass-space attraction, mass-mass repulsion and space-space repulsion. This basic interaction norm of mass and space governs the stability of matter in static and dynamic state and it is the cause of all forces of nature. The four fundamental forces of nature remain unified at the level of their cause. For a unified force of nature, the structure & dynamics of centrally organized systems in different domains are to be similar. For finding similarity between solar system and atomic system we need to understand the detail features of solar system and atomic system. The author made a serious study to understand the unity of universe through similarity of structure in different domains. These are discussed in different volumes of the series of publication.