Inadvertently, the human page turner, that fallible and sometimes reviled third party onstage, has been absent from most of Haywoodâs recent performances, a consequence of the wireless age. The advantages are obvious: The iPad is portable, discreet, always well-rested.
He measured the half-life of Carbon-14 to be about 5,568 years. However after about 50,000 years there is so little Carbon-14 left in the specimen that it is very hard, almost impossible, to calculate its age. (Van Der Merwe) Libby ran many tests on items where the age was known, or estimated by other means.
Prior to about 450,000 years before present time (BP) atmospheric CO2 levels were always at or below 260 ppmv and reached lowest values, approaching 170 ppmv, between 660,000 and 670,000 years ago. The highest pre-industrial value recorded in 800,000 years of ice-core record was 298.6 ppmv, around 330,000 years ago.