Forget all the speculation as to the purpose of Stonehenge. After a detailed Computational Fluid Dynamics (CFD) study it appears Stonehenge's original purpose was to generate a focused vortex.

CFD Simulation of a Vortex at StonehengeStreamline arrows colored by velocity

Coinciding with the summer solstice the heat from the sun on the longest day creates a vortex that originates from the inner ring of stones at Stonehenge and swirls upwards. At ground level it isn't obvious there is a vortex, but once you observe the air velocity above the highest stones there is a clear and powerful vortex.

Iso-Surfaces of Velocity at StonehengeCFD simulation reveals vertical extent of the vortex

There is still some uncertainty as to the purpose of such a vortex. Some say it is to aid the transition of ancient spirits to their afterlife. Others suggest that it is an ancient form of power generation long forgotten.

Ribbons Tracing a Vortex at StonehengeCFD simulation shows ribbons colored by velocity

What is certain is that the exact shape and configuration of stones is no coincidence. This is a sophisticated vortex machine.