Sun is the source of creative process on earth. The entire physical world composed of atoms is influenced by the rays of the sun. That is why the sun is worshipped as a maifestation of the God. Modern man,who once disbelieved sun as God, has now started considering him as a potential source for creation on the surface of earth. The diameter of the sun is 8,65,380 miles. Powerful fumes generated by the thermonuclear reaction on the sun travel with a super sonic speed. The quantity of heat generated by the sun is expected to be about 3.7 x 1026 watts. However the planet earth receives only a fraction of the above heat. But that fraction itself is enough to keep the vegetation ,trees and food production sufficient for the existence of living organism. The water vapour,formed because of the rays of sun , turns into clouds and bring us rain.
Scientists have proved that the sun rays have many positive effects on human body. It is said that basking in the morning sun after applying any vegetable oil to the body,helps in the formation of vitamin’D’ in the body, which has a curative effect on diabetes. The rays of the sun are composed of seven colors forming a spectrum viz.,violet,indigo,blue,green,yellow,orange and red and this phenonmenon is made use of in nature cure whereby the process of reflection of rays through mirrors on human body,is adopted for curing certain diseases. So,is the immense invaluable power of the sun. That is why our ancestors had presented Surya Namaskaras as alma medica for best physique.
With the development of science of Vastu , man has started constructing houses as per the tenets and thus the positive influence of the five elements viz., earth,water,light,air and sky could be realised. House is the inseparable factor in the life of man. This has been realized and a science is evolved about it, which is called Vastu.
As per Vastu, land extending from east to west is termed as ‘Purush Sthana’ (Masculine site) and is considered as the best, because it is exposed to sun light more prominently . To ensure free and direct access to the morning sun rays,the science of Vastu forbids any type of high structures or tall trees in the eastern side of the building. Further it has been prescribed ,that the vacant space in east must be more than that of west. It is laid down that tall trees should be planted in the west,to prevent the powerful rays of the sun during the afternoons , causing harm to the human beings and for helping the process of photosynthesis.The effect will be vice versa if the trees are grown in the east. With the growing threat of Green-house effect due to the extinction of ozone layer,the tall trees in west and south have become the only phenomenon,which would come to the rescue of the residents in any house,and at the world at large.
The logic behind the principle of leaving more vacant space in north also is to ensure more quantity of sunlight to the inhabitants during Uttarayana (Northward movement of the sun). The northward movement of the sun during the period of December 21st to June20th is called Uttarayana. The southward movement of the sun during the period June21st to December 20th is called Dakshinayana.
During the Uttarayana period many diseases and ailments , that were prevalent during Dakshiyana,subside and cause less suffering. That is why the wise suggest,that for performing marriages,undertaking construction activity and for other auspicious projects,Uttarayana period proves to be congenial. Bheeshma the staumch warrior and the commander-in-chief of Great Mahabharata battle lied upon the bed of arrows awaiting for the arrival a Uttarayana,and left his last breath on Ekadashi,after teaching all the secrets of jurisprudence,ethics and philosophy to Yudhisthira,on the request of Sri Krishna. The reason behind such logic is the positive impact of the rays of the sun during the period.
In order to derive maximum benefits out of the sun rays during Uttarayana, it is suggested that there should be more vacant space in north and east rather than in south and west. Contrary to it the vacant land in south and west would prove detrimental to the interest of the structures , be it a house,industry,hut or a temple and paves way for its dilapidation.