Tree Rings

Here's how the tree ring dating, known to scientists as dendrochronology (from the Greek roots Dendron = tree, and Chronos = time), works. If you cut a tree down today, it's straight forward to count the rings inwards, starting from the tree's outside (corresponding to this year's growth ring), and thereby to state that the 177th ring from the outermost one towards the center was laid down in the year 2005 minus 177, or 1828. However, the width of tree growth rings vary from year to year, depending on the rain or drought conditions in each year. Hence the sequence of the rings in a tree cross-section is like a message in Morse code formerly used for sending telegraph messages; dot-dot-dash-dot-dash in the Morse code, wide-wide-narrow-wide-narrow in the tree ring sequence. Actually, the tree ring sequence is even more diagnostic and richer in information than the Morse code because trees actually contain rings spanning many different widths, rather than the Morse code choice between dot and dash.