Trees give us a unique glimpse into our past. An examination of tree rings can show us what the climate was like in a given year. Was it a wet winter? Were there hurricanes in the summer? Did a forest fire ravage the area?

An ancient tree in New Zealand is the first to provide evidence of the near reversal of the Earth's magnetic field over 41,000 years ago.

Over the past 83 million years there have been 183 magnetic pole reversals, a process that takes about 7,000 years to complete.