Radioactive isotopes were a piece of technology developed by the Tok'ra. The isotopes were made specifically to make an individual with the isotope completely undetectable to the sensors of Anubis' mothership for approximately eight hours. Despite this advantage, they are not rendered invisible to the naked eye. In 2003, Daniel Jackson and Jonas Quinn were given the isotope as part of the plan to destroy Anubis' mothership. The isotope wore off just before the two escaped the mothership via ring transporter. (SG1: "Fallen", "Homecoming")