Archaeologists believe Egypt’s large pyramids are the work of the Old Kingdom society that rose to prominence in the Nile Valley after 3000 B. Historical analysis tells us that the Egyptians built the Giza Pyramids in a span of 85 years between 25 BC.Interest in Egyptian chronology is widespread in both popular and scholarly circles.We wanted to use science to test the accepted historical dates of several Old Kingdom monuments.

By measuring how much C14 remains in a sample of organic material, we can estimate its age within a range of dates.

Samples older than 50,000 to 60,000 years are not useful for radiocarbon testing because by then, the amount of C14 remaining is too small to be dated.

But material from the time of the pyramids lends itself well to radiocarbon dating because they fall into the 2575-1640 date range.

The earliest experiments in radiocarbon dating were done on ancient material from Egypt. Libby’s team obtained acacia wood from the 3rd Dynasty Step Pyramid of Djoser to test a hypothesis they had developed.

Libby reasoned that since the half-life of C years, the Djoser sample’s C14 concentration should be about 50% of the concentration found in living wood (for further details, see Arnold and Libby, 1949). Subsequent work with radiocarbon testing raised questions about the fluctuation of atmospheric C14 over time.

Scientists have developed calibration techniques to adjust for these fluctuations.

While alive, all plants and animals take C14 into their bodies.

The numbers of C14 atoms and non-radioactive carbon atoms remain approximately the same over time during the organism’s life.

As soon as a plant or animal dies, the carbon uptake stops.

The radioactive carbon isotope is no longer replenished; it only decays.

Scientists have calculated the rate at which C14 decays.