July 5 – Happy Birthday, Andrew Douglass

nPostednon July 5, 2014

n Havenyou ever seen a tree stump with clear, countable tree rings?

nWell,ntoday’s birthday boy (born on this date in 1867) is the fellow whondidn’t just look at tree rings – he figured out that they could benused to date events and learn about long-ago weather!

nInnother words, Andrew Douglass invented dendrochronology!

nWouldnit surprise you to learn that Douglass studied tree rings whilenworking as an astronomer? You may wonder how the study of space andnthe study of tree rings relate…

n…andnthe answer is “the sunspot cycle.”

Thensunspot cycle is the change in the Sun’s activity and appearance overntime. Each cycle lasts an average of 11 years, and the cycle (or itsneffects) have been observed for years. For example, there are a lotnmore auroras when the Sun is “active” – that is, when it is busynhaving flares and ejecting material into space. Sunspots arentemporary dark spots caused by intense magnetic activity. I find itninteresting to note that sunspots look black on the sun’s surfacenbecause they are cooler than their surroundings, but they wouldnappear brighter than the moon if they could be seen separated fromnthe rest of the Sun. Sunspots occur when and where solar flares andnejections occur.

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nThensunspot cycles is more and more important to us humans. Not so muchnso we can plan our viewing of auroras (although I’d love to see onenin real life), but because solar activity can cause disruptions innour power grid and radio and satellite transmissions, and it can evenndamage the electronics in our satellites. We’re talking cell phonesnand satellite TV and GPS, folks!

nOkay,nso the Sun has cycles, and it’s important that we understand thencycles because they affect us here on Earth. What does any of thatnhave to do with tree rings?

nWell,nsunspots and solar activity affect Earth’s weather, too, because thendisturbance to Earth’s magnetosphere allows much more UV radiation tonpenetrate our atmosphere. Our weather systems are so complex, we’rennot certain exactly how the extra UV light affects weather—so wenneed a lot of data to crunch so that we can better see patterns.

nItnturns out that tree rings are affected by weather. The inner portionnof a tree’s growth ring forms early in the spring growing season,nwhen growth is rapid and therefore the wood is less dense. In thenlate summer and early fall, the wood that is produced is denser.nThat’s why each tree ring – which is basically a band of less andnthen more dense wood – represents one year of growth. When therenwas a lot of sunlight and water in a year, the ring is relativelynwide. When conditions were bad in a year, the ring is quite narrow.nSince some trees live hundreds or even thousands of years, and sincenwe have access to old wood that was used in buildings, tree ringsnprovide information about local weather conditions dating backnseveral thousand years – up to 11,000 years ago in some cases!

nTodaynwe give a shout-out to A. E. Douglass and his dendrochronology. Hisnwork helps us better understand astronomy (the study of the Sun andnother space stuff), botany (the study of trees and other plants),nmeteorology (the study of climate and weather), physics (the study ofnradiation, magnetism, and all the other physical forces in thenuniverse), and even archeology (the study of bones, tools, monuments,nand other remnants of ancient peoples) as scientists began to usentree ring dating as they studied ancient civilizations.

Becausenall things are interrelated. Even if you study just one topic, you’renbound to wander through lots of fields. Discoveries made in one areanof science are bound to impact other areas as well. I love that aboutnthe universe!

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