where did the tradition of flying flags at half mast come from
Half-mast The tradition of flying the flag at half-mast began in the 17th century.[3] According to some sources, the flag is lowered to make room for an "invisible flag of death" flying above.[4] However, there is disagreement about where on a flagpole a flag should be when it is at half-staff. It is often recommended that a flag at half-staff should be lowered only as much as the hoist, or width, of the flag.[5][6] British flag protocol is that a flag should be flown no less than two-thirds of the way up the flagpole, with at least the height of the flag between the top of the flag and the top of the pole.[7] It is common for the phrase to be taken literally and for a flag to be flown only half way up a flagpole,[8] although some authorities deprecate that practice.[6]