# Accretion Design

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Accretion is a process in which the size of something gradually increases by steady addition of smaller parts. In accretion particles move around until they encounter another stationary particle to connect to. As particles connect, large irregular shaped clusters are formed. In diffusion-limited aggregation, a particle undergoes Brownian motion until it makes contact with a free-floating cluster of particles. This is what underlies various natural phenomena, including crystalization.

This accretion simulation was inspired by the description of the accretion process in the book Computer Simulations with Mathematica: Explorations in Complex Physical and Biological Systems, by Richard Gaylord and Paul Wellin.

• Science

## Explorations

• Use the "Circle" worksheet provided with the simulation and run it. Observe how the particles form clusters.
• Create your own accretion experiment:
• Create a new worksheet if working in AgentSheets or clear the worksheet if working in the accretion applet
• Fill it with the black Background agents using the "Draw Rectangle" tool.
• Place a stationary particle (the one with the rounded edges) somewhere in the worksheet.
• Manually place blue Particles anywhere in the worksheet or add a red Starter agent and use the "Hand" tool to click on it to get a random distribution of particles on the black background.
• Run your newly created worksheet and observe the particles forming new clusters.

## Computational Thinking Patterns

• Generate: Particles are generated randomly on background when the Hand tool is applied to the Starter agent (red dot in corner of Circle worksheet).

## Standards

• Creativity and Innovation:
• use models and simulations to explore complex systems and issues
• Science and Technology Standards
• Understandings about science and technology
• Abilities of technological design
• Content Standards: Physical Science
• particle motion (Motion and Forces)
• Science as Inquiry Standards
• Understanding about scientific inquiry
• Abilities necessary to do scientific inquiry

## Sample Accretion Lesson Plans

• PLEASE CONTRIBUTE YOUR LESSON PLAN!

## Acknowledgements

The Accretion simulation was built by Alexander Repenning.

The book recommendation above is linked to Amazon.com to allow you to get more information about the book including reviews and to be able to directly order it.