How many sand grains on a beach?

Alan Whittington, University of Missouri-Columbia.
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Short (15 minute) exercise for use in small or large classes. Could also be used in a laboratory. Three parts:

  • students are asked to think about how they would calculate the number of sand grains on a beach, specifically what information is needed.
  • Example data is supplied to allow a first order answer to the question.
  • The resulting large number is put in the context of other large numbers that should be relevant to non-scientists.

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Learning Goals

- Increase student confidence in estimation and handling large numbers using scientific notation
- Practice unit conversion and use of the metric system
- Demonstrate the relevance of large numbers to non-scientists

Context for Use

Could be used in small or large classes. No equipment required - probably best to discourage the use of calculators. Should take no more than 15 minutes for all three parts, although could be longer if students are encouraged to come up with their own dimensions for the beach and the size of a sand grain.

Description and Teaching Materials

See Word document, Instructors notes with example solution (Microsoft Word 53kB Aug29 06)

References and Resources

World population clock, from Princeton University (needs java):
This one updates every second or so, which is more fun than the one available from the US Census Bureau:

US National Debt counter (needs java):
This is one of many available online, based on daily updated information from the US Treasury Department (but hosted by a private group). The US treasury has a much less exciting page, but it does claim to be accurate "to the penny: