Looking to the Trees: A Young Naturalist and the Fibonacci Sequence

Science is, at its heart, the act of following a trail of questions.  Answer one question, and it will lead to ten more.  Luckily, we can often use the answer to one question to fuel the exploration of the next.  One of the 2011 American Museum of Natural History Young Naturalist Award winners, 13-year-old Aidan, found just this when he took a keen observation about tree branching patterns and used it to design and test a more efficient solar panel array.

Aidan noticed that the spiraling pattern of tree branches was eerily similar among several tree species.  He asked the questions:  is there really a pattern, and what kind of pattern is it?  To find the answer, Aidan took measurements on fallen tree branches and found that he was following in the footsteps of the 18th century naturalist Charles Bonnet.  Bonnet had also observed the tree branching pattern and linked it to the Fibonacci sequence, a series of numbers starting with zero and one where each number in the series is the sum of the prior two numbers (ie, 0, 1, 1, 2, 3, 5, 8, etc.)

Not just satisfied by being right, Aidan (like a true scientist) asked another question:  what was the purpose behind this pattern?  Since leaves are a tree's way of collecting solar energy, it made sense to ask whether or not the Fibonacci-inspired pattern somehow made the leaves more efficient at this task.

To test this hypothesis, Aidan did an experiment:  he made artificial "trees" in the form of solar panel arrays.  One array he constructed so the panels were all at the same angle and facing the same direction (the way solar panels are conventionally constructed).  The other array had the panels in an elm tree's spiralling Fibonacci pattern.  Aidan then placed these two arrays in the his backyard and measured their energy output over a few months.

His results?

I compared my results on graphs, and they were interesting! The Fibonacci tree design performed better than the flat-panel model. The tree design made 20% more electricity and collected 2 1/2 more hours of sunlight during the day. But the most interesting results were in December, when the Sun was at its lowest point in the sky. The tree design made 50% more electricity, and the collection time of sunlight was up to 50% longer!

Furthermore, the tree design was able to maintain its output even during the winter solstice, when there was the least amount of light and the Earth's axis was tilted the farthest away from the sun.  As Aidan points out in his write-up, his results suggest that trees have evolved to use this pattern because it is more efficient, especially under challenging collection conditions, and that solar panel makers might do well to emulate trees when they're designing collection arrays.

Seeing a young investigator go through the entire scientific method like this warms my science-loving heart.  This is exactly the type of thing that I wish more science education programs would encourage and aid.  

Hats off to you, Aidan and the rest of the Young Naturalist awardees.  Great job!

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