Archer's paradox

As understanding was gained about the arrow flexing around and out of the way of the bow as it is shot (as first filmed by Clarence Hickman)[2][3] and then experiencing oscillating back-and-forth bending as it travels toward the target,[4] this dynamic flexing has incorrectly become a common usage of the term.

This misuse sometimes causes misunderstanding on the part of those only familiar with modern target bows, which often have risers with an eccentrically cutout "arrow window"; being "centre shot", these bows do not exhibit any paradoxical behaviour as the arrow is always pointing visually along its line of flight.

[9] Additionally, if an archer shoots several arrows with different dynamic spines, as they clear the bow they will be deflected on launch by different amounts and so will strike in different places.

[20][21] The American Society for Testing and Materials (ASTM) F2031-05 ("Standard Test Method for Measurement of Arrow Shaft Static Spine (Stiffness)") hangs an 880-gram (1.94 lb) weight from the center of a 28-inch (0.71 m) suspended section of the arrow shaft.

[22] The (obsolete) British Grand National Archery Society (GNAS) system used a 1.5-pound (0.68 kg) weight and a variable length with the arrow supported just behind the head and just in front of the nock.