Monarch butterflies have magnitite (a mineral) inside their heads and this helps them determine 'North', just like a magnet.
Measure for measure in the march of time
Measure for measure in the march of time Just as the time on a watch and a wall clock can
differ, techniques for marking time in the earth's layers can give
different results. Geologists and palaeontologists gathered last
month for the annual meeting of the Geological Society of America
to discuss the different techniques used for measuring the
Earth’s timeline. These scientists are anxious to know which
method they can trust to gauge the pace of evolution's Cambrian
explosion, for instance, or the timing of the huge volcanic
eruptions that led to mass extinctions in the past. Currently,
scientists use methods such as counting sedimentary layers in
ancient rock, much like counting tree rings, or by following the
orbital changes of the Earth over millennia. 12 NOVEMBER 1999, P. 1279
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