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? The practical lesson to be drawn from the argument is not to use words like "there" in a loose, unscientific way, without specifying whether you mean "located there" or "occupying space there." In the humoristic magazine "Annals of Improbable Research", Anders Sandberg has presented a calculation based on theories of information physics and quantum gravity, establishing an upper bound of 8.6766×10 angels. Comparing medieval superstition and modern science, George Bernard Shaw wrote in the introduction to the play "Saint Joan" that "The medieval doctors of divinity who did not pretend to settle how many angels could dance on the point