Radiometric dating--the process of determining the age of rocks from the decay of their radioactive elements--has been in widespread use for over half a century.

There are over forty such techniques, each using a different radioactive element or a different way of measuring them.

Based on pottery and architectural signifiers, the heavily fortified structure — and the rest of the Spring Citadel protecting Jerusalem’s precious water source — were dated to Canaanite construction (Middle Bronze II period).

1700 BCE — and contradict a presumed biblical linkage to the site.

Downhill from the Temple Mount of Jerusalem, the Gihon Spring guard tower was discovered in 2004 by archaeologists Ronny Reich and Eli Shukron.

A form of radiometric dating used to determine the age of organic remains in ancient objects, such as archaeological specimens, on the basis of the half-life of carbon-14 and a comparison between the ratio of carbon-12 to carbon-14 in a sample of the remains to the known ratio in living organisms. A technique for measuring the age of organic remains based on the rate of decay of carbon 14.

The carbon 14 present in an organism at the time of its death decays at a steady rate, and so the age of the remains can be calculated from the amount of carbon 14 that is left. The cells of all living things contain carbon atoms that they take in from their environment.

Carbon 14 is continually being created in the Earth's atmosphere by the interaction of nitrogen and gamma rays from outer space.

Since atmospheric carbon 14 arises at about the same rate that the atom decays, the Earth's levels of carbon 14 have remained constant.

Beside a slab of trilobites, in a quiet corner of Britain's Oxford University Museum of Natural History, lies a collection of ochre-tinted human bones known as the Red Lady of Paviland.

In 1823, palaeontologist William Buckland painstakingly removed the fossils from a cave in Wales, and discovered ivory rods, shell beads and other ornaments in the vicinity.

“This is the largest fortress found in all of Israel to date between the Canaanite cities…

and it seems that it is essentially the largest fortress found in Israel until the days of King Herod,” states the website.

So by measuring carbon 14 levels in an organism that died long ago, researchers can figure out when it died.