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The Sunflower Spiral and the Fibonacci Metric Henry Segerman http://www.segerman.org Department of Mathematics and Statistics The University of Melbourne July 28 th 2010 1 1 1 2 1 2 2 1 2 2 2 3 1 2 2 2 3 2 3 3 1 2 2 2 3 2 3 3 2 3 3 3 4 1 2 2 2 3 2 3 3 2 3 3 3 4 2 3 3 3 4 3 4 4 1 2 2 2 3 2 3 3 2 3 3 3 4 2 3 3 3 4 3 4 4 2 3 3 3 4 3 4 4 3 4 4 4 5 1 2 2 2 3 2 3 3 2 3 3 3 4 2 3 3 3 4 3 4 4 2 3 3 3 4 3 4 4 3 4 4 4 5 2 3 3 3 4 3 4 4 3 4 4 4 5 3 4 4 4 5 4 5 5 1

The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

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Page 1: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

The Sunflower Spiral and the Fibonacci Metric

Henry Segermanhttp://www.segerman.org

Department of Mathematics and StatisticsThe University of Melbourne

July 28th 2010

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Page 2: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

The Sunflower SpiralLet S(n) = (r(n), θ(n)) = (

√n, 2πϕn), where

ϕ =√

5−12 = Φ− 1 ≈ 0.618, and Φ =

√5+12 is the golden ratio.

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2¼'

Page 3: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

The Sunflower SpiralLet S(n) = (r(n), θ(n)) = (

√n, 2πϕn), where

ϕ =√

5−12 = Φ− 1 ≈ 0.618, and Φ =

√5+12 is the golden ratio.

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Page 4: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

The Sunflower SpiralLet S(n) = (r(n), θ(n)) = (

√n, 2πϕn), where

ϕ =√

5−12 = Φ− 1 ≈ 0.618, and Φ =

√5+12 is the golden ratio.

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Page 5: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

The Sunflower SpiralLet S(n) = (r(n), θ(n)) = (

√n, 2πϕn), where

ϕ =√

5−12 = Φ− 1 ≈ 0.618, and Φ =

√5+12 is the golden ratio.

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Page 6: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

The Sunflower SpiralLet S(n) = (r(n), θ(n)) = (

√n, 2πϕn), where

ϕ =√

5−12 = Φ− 1 ≈ 0.618, and Φ =

√5+12 is the golden ratio.

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Page 7: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

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Page 8: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

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Page 9: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

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Page 10: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

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Page 11: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

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Page 12: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

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Page 13: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

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Page 14: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

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Page 15: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

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Page 16: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

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Page 17: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

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Page 18: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

This sequence of points models many patterns in nature, inparticular the florets on a sunflower head.

Photo credit: http://www.flickr.com/photos/lucapost/694780262/

Page 19: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Fibonacci Metric

Let M : N→ N be a function, M(n) is the minimal number ofFibonacci numbers Fi needed in order to sum to n.

1 = 1 M(1) = 12 = 2 M(2) = 13 = 3 M(3) = 14 = 3 + 1 M(4) = 25 = 5 M(5) = 16 = 5 + 1 M(6) = 27 = 5 + 2 M(7) = 28 = 8 M(8) = 19 = 8 + 1 M(9) = 2

10 = 8 + 2 M(10) = 211 = 8 + 3 M(11) = 212 = 8 + 3 + 1 M(12) = 3

Page 20: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

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Page 21: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

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Page 22: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Page 23: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Where do the patterns come from?

1. Radial spokes2. Circular tree rings

For the spoke at θ = 0:

Fk = Φk−(1−Φ)k√5

⇓Fk − ϕFk+1 = (−ϕ)k+1

⇓θ(Fk+1) = 2πϕFk+1

= 2π(Fk − (−ϕ)k+1)

(−ϕ)k+1 is small, and so for large k , θ(Fk+1) is almost a multipleof 2π.

Thus the Fibonacci numbers themselves are near θ = 0.

Page 24: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Where do the patterns come from?

1. Radial spokes2. Circular tree rings

For the spoke at θ = 0:

Fk = Φk−(1−Φ)k√5

⇓Fk − ϕFk+1 = (−ϕ)k+1

⇓θ(Fk+1) = 2πϕFk+1

= 2π(Fk − (−ϕ)k+1)

(−ϕ)k+1 is small, and so for large k , θ(Fk+1) is almost a multipleof 2π.

Thus the Fibonacci numbers themselves are near θ = 0.

Page 25: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Where do the patterns come from?

1. Radial spokes2. Circular tree rings

For the spoke at θ = 0:

Fk = Φk−(1−Φ)k√5

⇓Fk − ϕFk+1 = (−ϕ)k+1

⇓θ(Fk+1) = 2πϕFk+1

= 2π(Fk − (−ϕ)k+1)

(−ϕ)k+1 is small, and so for large k , θ(Fk+1) is almost a multipleof 2π.

Thus the Fibonacci numbers themselves are near θ = 0.

Page 26: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Where do the patterns come from?

Sums of Fibonacci numbers haveangles the sum of the angles of theFibonacci numbers, so sums of asmall number of large Fibonaccinumbers are also near θ = 0. Thismakes up other points of the θ = 0spoke.

Other spokes are rotations of theθ = 0 spoke, formed by adding asmall number to all of the numbersin the θ = 0 spoke.

For the tree rings: Just after a large number m with small M(m),there will be many numbers n for which the minimal M(n) isachieved using m and some small number of additional Fibonaccinumbers, because n −m is small.

Page 27: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Where do the patterns come from?

Sums of Fibonacci numbers haveangles the sum of the angles of theFibonacci numbers, so sums of asmall number of large Fibonaccinumbers are also near θ = 0. Thismakes up other points of the θ = 0spoke.

Other spokes are rotations of theθ = 0 spoke, formed by adding asmall number to all of the numbersin the θ = 0 spoke.

For the tree rings: Just after a large number m with small M(m),there will be many numbers n for which the minimal M(n) isachieved using m and some small number of additional Fibonaccinumbers, because n −m is small.

Page 28: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Where do the patterns come from?

Sums of Fibonacci numbers haveangles the sum of the angles of theFibonacci numbers, so sums of asmall number of large Fibonaccinumbers are also near θ = 0. Thismakes up other points of the θ = 0spoke.

Other spokes are rotations of theθ = 0 spoke, formed by adding asmall number to all of the numbersin the θ = 0 spoke.

For the tree rings: Just after a large number m with small M(m),there will be many numbers n for which the minimal M(n) isachieved using m and some small number of additional Fibonaccinumbers, because n −m is small.

Page 29: The Sunflower Spiral and the Fibonacci Metricmath.okstate.edu/people/segerman/talks/sunflower_spiral_talk.pdf · 1 2 3 4 5 6 7 9 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Thanks!