There are probably hundreds of myths and legends about Stonehenge. Various people have attributed the building of this great megalith to the Danes, Romans, Saxons, Greeks, Atlantes, Egyptians, Phoenicians Celts, King Aurelius Ambrosius's, Merlin, and even Aliens.
One of the most popular beliefs was that Stonehenge was built by the Druids. These high priests of the Celts, constructed it for sacrificial ceremonies. It was John Aubrey, who first linked Stonehenge to the Druids. Additionally, Dr. William Stukeley, another Stonehenge antiquary, also claimed the Druids were Stonehenge's builders. Stukeley studied Stonehenge a century later than Aubrey and became so involved in the study of the Druid religion that he himself became one. Through his work he was very instrumental in popularizing the theory that Stonehenge was built by Druids.
Stonehenge was created using a trabeated system. It is a system in which there is a horizontal structure supported by two pillar-like structures. In this particular system, this order was repeated over and over again in a circular fashion.
It was designed using simple geometric principles, see the link
At Stonehenge human remains were found as well as tools used to help constructing the henge.
To stiffen the floor frame.
The interstate highway system was designed to be used as military runways.
It was not used as a barometer.
used for a clock
Pagans.
the most common angle used in constructing building is 90 degree.
limestone
Stonehenge has not been used for thousands of years so no one knows the answer to this.
Stonehenge has no official ceremonial use today, other than a tourist attraction.
clay
sightseeing and tourism.