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 More Times How Many More Times "How Many More Times" is the ninth and final track on English rock band Led Zeppelin's 1969 debut album "Led Zeppelin". The song is credited in the album liner to Jimmy Page, John Paul Jones, and John Bonham, but Robert Plant was later added to the ASCAP credits. At eight and a half minutes, "How Many More Times" is the longest song on the album. It is one of three Led Zeppelin songs on which Page used bowed guitar. In an interview he gave to "Guitar World" magazine in 1993, Page stated that the song "was