Vastu is a logical explanation of scientific truths and facts about energy patterns in buildings. The Vastu principles are related with the properties (Natural Energies) of our Earth plane. Vastu says that the sources of energies are to be open and the flow of energies is not to be disturbed. Vastu Shastra prescribes desirable characteristics for sites and buildings based on flow of energy ("Prana" in Sanskrit). Many of the rules are attributed to cosmological considerations; the Sun's path, the rotation of the Moon above the Earth plane, magnetic fields, etc. The morning Sun is considered especially beneficial and purifying and hence the East is a treasured direction.
Vastu believes that there are essentially two types of forces, which are equal and opposite in nature. The interaction of these two forces is cosmically ordained and produces a third type of force, which is prana, needed for life to exist. One type of force is subtle and fine. The other is dark and dense. We, for understanding this subject, can call the first one as "positive" and the other as "negative". Prana is liberated by the interaction of these forces. Over the surface of the globe, these forces continuously interact, releasing prana. When a structure is built over the surface of the Earth, it comes in the way of a natural interaction. Both the forces enter the structure where the interaction continues. However, the intensity of forces that enter the structure need not be the same. Depending on various factors like levels, water bodies, door placement, etc., either the positive or the negative can have stronger presence.