Improved techniques now date the earliest stone structures at Stonehenge to about 2600 B. Sir Joseph Norman Lockyer, who co-discovered helium and founded the journal, Nature, wrote in 1901 that the Heel Stone section of Stonehenge "had been originally aligned with the summer solstice" and calculated that it was built in 1800 B. Further investigations have suggested that Stonehenge was an astronomical observatory, a place of worship and healing or perhaps a cemetery.Whatever its exact history, origins or age, thousands each year flock to Stonehenge to welcome the sun on the summer solstice.
He remained a lifelong proponent of nuclear bombs, offering advice summarized in a glowing 1955 profile in Time magazine as "Let's build them as big as we can, and build all we can.
The dating process is always designed to try to extract the carbon from a sample which is most representative of the original organism.
In general it is always better to date a properly identified single entity (such as a cereal grain or an identified bone) rather than a mixture of unidentified organic remains.
First tested and calibrated with material found in 4,000-year-old Egyptian tombs, carbon-dating has been used on progressively older and older relics, and has become an extremely important tool for anthropologists, archaeologists, geologists, and other earth scientists.
Carbon-14 dating is now believed to be accurate for finding the age of materials up to 70,000 years old, with a margin of error of about ten percent.
Radiocarbon dating is especially good for determining the age of sites occupied within the last 26,000 years or so (but has the potential for sites over 50,000), can be used on carbon-based materials (organic or inorganic), and can be accurate to within ±30-50 years.