Compass has a half-life of only about 12 years, so a compass that contains 120 mCi of tritium when new will contain only 60 when it is 12 years old, 30 when it is 24 years old, and so on. Consequently, the illumination of the display will fade. Mariners' compasses can have two or more magnets permanently attached to a compass card, which moves freely on a pivot. A "lubber line", which can be a marking on the compass bowl or a small fixed needle, indicates the ship's heading on the compass card. Traditionally the card is divided into thirty-two points
How many angels can dance on the head of a pin? Suite Part II: Let It Grow", a song from the 1973 Grateful Dead album Wake of the Flood, includes the line "As well to count the angels dancing on a pin." In the comic book "The Crow" by James O'Barr, the main character asks this question to one of his victims before killing them, answering himself, "Depends on the tune". The song "Velodrome" from Minnesota rapper Dessa's 2018 album Chime, references this question in the first verse asking, "Aquinas, call on me/ How many angels on the/ Head of your pin?" How many angels can dance on the head of