The idea of leaving the body has run from Egyptian tombs to the Theosophists to modern sleep research. Here is where astral projection comes from, what people report, what science has found, and what remains open.
Remote viewing was studied at SRI in the 1970s, became a secret Cold War program, and ended in 1995 when evaluators said it had produced no usable intelligence. Here is how it is supposed to work, what the tests found and what is still argued over.
