Earth is a huge magnet with two poles. North Pole and South Pole. It has also been proved that that the human body is a magnetisable object with a large percentage of iron in the blood.
As all know , opposite poles of a magnet attract each other and same magnetic poles repel each other ..
The Vastu principles of placing the head in South direction while sleeping is based on Earth's magnetic property.
Sleeping with the head towards the South enables one sleeping with the head towards the South enables one to go with the Nature and draw maximum positive energise from the cosmos to keep fit and healthy