Carbon dating def
He found an irregular slab from a bristlecone pine that spanned the years 3050 BCE to 2700 BCE.
The tree ring sequence adjacent to the slab's bark matched the sequence near Methuselah's core. He found a piece that contained 600 rings; another contained 150 rings.
By sampling the rocks and separating certain minerals (such as quartz or pyroxene) and calculating the amount of these minerals (as a ratio to other, stable, minerals), we can work out how long the rock has been exposed on the earth’s surface.
Cosmogenic nuclides are rare nuclides that form in surface rocks because of bombardment by high-energy cosmic rays.
Samples from the tree were able to generate calibration points back to that date. It is narrow or broad, depending upon whether the weather during that year was dry or wet, and whether the tree was exposed to various stressors.
Bristlecone pines grow so slowly that its rings are paper thin; their width has to be studied under a microscope.
It is particularly useful in Antarctica, because of a number of factors: Cosmogenic nuclide dating is effective over short to long timescales (1,000-10,000,000 years), depending on which isotope you are dating.
They've plotted rings from shipwreck timbers and roof beams, and wood from the Mediterranean, Russia, and China.