Vastu Shastr is an ancient Indian technique on how to design and construct residential house after balancing five elements namely Vayu, Jal, Agni, Pruthvi, Aakash. A Vastu expert will divide land in to 81 divisions and based on this will design plan and elevation. Before going in to details of scientific principles involved, let us understand fundamentals of Fluid Mechanics and Dynamics of Machines required to understand natural phenomena of wind currents.
1. Dynamic of Machines
Fig. 1 Motion of particle, absolute frame of reference and relative frame of reference.
As shown in Fig. 1 disc rotates ccw. At time t1 a ball is thrown from point A towards point B, point A being on disc while point B outside disc. The angle between point A and B is pi radians. At time t2, the point A displaces to A’, making angle between A’ and B less than pi radians. Observer seating at point A will observe the ball deflecting towards his right side but in reality the observer at B will observe the ball has traveled on its predefined linear path. This phenomena is knows as Coriolis effect. Technically observer B is absolute frame of reference and observer A is relative frame of reference. You can verify this phenomena using merry-go-round available at Children’s park.
2. Motion of Particle on Earth
Fig. 2 Motion of particle on earth.
As shown in Fig. 2, if earth is steady and a particle is propelled towards north from the equator, it will travel in a straight line as observed from the earth surface. In reality earth itself rotates East to west (ccw if seen from north pole) and hence, as explained in Section 1 above, an observer on earth will observer that particle deflecting rightward. As shown in Fig. 3, this can be further understood after dividing earth in two halves and projecting its surface in to a disc rotating in ccw direction, where north pole will become center of the disc while equator becomes edge of disc.
Fig. 3. Development of surface of northern hemisphere of earth
3. Coriolis Effect and Wind Current
Fig. 4. Counter Clockwise direction of cyclone in northern hemisphere.
After getting heat from Sun the hot and lighter air near equator will rise above earth’s surface. Parallely cold and heavy air from north pole will try to move towards equator. This combined effect is reason behind wind current on earth. The air particles would have moved in linear trajectory if earth was steady. In reality, due to Coriolis effect as a result of combined rotational motion of earth and linear motion of air particles, as explained in Fig. 1 to 3, the air particles will deflect rightward. Sometime pressure reaches such a low that it goes below atmospheric pressure, creating low pressure region in atmosphere. This low pressure region will act as sink in which surrounding high pressure air will try to move in. This low pressure region is known as ‘Eye of Cyclone‘. As explained in Fig. 4, this is how ccw Cyclones are generated in the northern hemisphere and cw cyclones in southern hemisphere.
4. Fluid Mechanics and Vastu Shastr
Fig. 5. Vastu purush and Vastu plan.
A fundamental question was in my mind from many years why the direction of Vastu Purush is NE and why not in other direction? India is in northern hemisphere and as explained in previous sections the air will deflect rightward while blowing from south, which observer in house may feel it is coming from SW direction. This means direction of Vastu Purush resembles one of the five elements named Vayu. Some of the salient features of the Vastu are (refer Fig. 5)
Bedrooms at SW(Nairuty), S, W, NW(Vayavy).
Store room at South.
Study room at East.
Kitchen at SE(Agni).
Temple at NE(Ishan).
According to scientific understanding, considering house as relative reference frame, NW, W, SW, S, SE are upwind locations while N, NE, E, SE are downwind locations. It is preferable routine activities should be performed at the place where ample fresh air and sunlight available while activities related to fire safety should be place at downwind location. Location of bedrooms matches with scientific principles of availability of fresh wind required for human comfort and health. Organism like insects and pests flourish in the environment having insufficient air. To avoid this store room is placed in South where fresh air will be available. Availability of clear sunlight in east is the reason of having study room in east. To stop house from being burn in the situation of fire, the fire places i.e. kitchen and temple are placed at downstream of wind so that fire will always move away from house.
Vastu Shastr is science of giving comfort to residents. It is designed after scientific understanding of wind current on earth. Basic comfort requirements of human like ample sunlight and fresh air, and basic safety requirements like fire are considered in identifying the location inside the house. No doubt, Vastu Shastr is purely scientific techniques given by Indians to the world. Based on this understanding the direction of Vastu Purush should be SW direction in the southern hemisphere.