Radiocarbon dating a third radiocarbon revolution. Occasionally, radiocarbon dating techniques date an object of popular interest, for example the Shroud of Turin, a piece of linen cloth thought by some to bear an image of Jesus Christ after his crucifixion. Three separate laboratories dated samples of linen from the Shroud in 1988; the results pointed to 14th-century origins, raising doubts about the shroud's authenticity as an alleged 1st-century relic. Researchers have studied other radioactive isotopes created by cosmic rays to determine if they could also be used to assist in dating objects of archaeological interest; such isotopes include , , , ,
Stable-isotope probing Stable-isotope probing Stable-isotope probing (SIP) is a technique in microbial ecology for tracing fluxes of nutrients in biogeochemical cycling by microorganisms. A substrate is enriched with a heavier stable isotope that is consumed by the organisms to be studied. Biomarkers with the heavier isotope incorporated into them can be separated from biomarkers containing the more naturally abundant lighter isotope by isopycnic centrifugation. For example, CO can be used to find out which organisms are actively photosynthesizing or consuming new photosynthate. As the biomarker, DNA with C is then separated from DNA with C by centrifugation. Sequencing the DNA identifies which