The Megalithic Empire was not an empire as we perceive it. They had no central authority but did have a common bond: maritime trade. They were the first true trading guild, an extended family if you will, that traded amongst their different clans as well as other cultures especially Egypt. They possessed intimate knowledge of astronomy, navigation and construction, which they jealously guarded, that enabled them to dominate for a very long period of time. They were members of a fractious group that sometimes fought amongst themselves yet still managed to dominate the sea.
Some of their group occupied the coastal regions of Northern Europe, others would eventually become the Classic Greeks, but the most dominant were those who inhabited the coastal cities.
They had harbours in Norway, Sweden, and The Baltic Coast, Denmark, Holland, Belgium, France and Spain before any of these countries ever existed. In the Bronze Age their most prized possession was Britain from where they controlled the most precious resource of their time: TIN.
They dominated the sea and sailing for over two thousand years and with the skills they possessed they set out from their Atlantic shores and crossed the Atlantic Ocean to the Americas. Their knowledge enabled them to establish precise celestially fixed waypoints built in wood then stone to fix local time from a known prime meridian. And all of this was done before there was need for a written language.
Their sea captains and navigators possessed the knowledge of a spherical world and its division into degrees. They also had an instrument of sheer simplicity with which they could accurately determine latitude and longitude. They were superior astronomers who had charted the heavens and could steer by star, sun, compass, dead reckoning and accurate maps. They had a Time Zone reference datum to calculate global position and an accurate clock that still exist today.
The evidence is all there but only a few have had the foresight to piece it all together from the many clues they left. Almost all of them in stone. The most critical was discovered inside the Great Pyramid by Bill Grundy in 1878 and sent to Piazza Smith who recorded and sketched the items in his diary.