The Eratosthenes Experiment
How big around is Earth? Step outside and measure it next
Friday ... in collaboration with dozens of schools, from the UK
to Greece to China, and other latitudes in between!
At their respective noontimes on the equinox, 21 March,
students the world over will measure the length of shadows cast
by sticks, then consult observations made by others at the same
latitude. By sharing these data, invoking the properties of
right triangles, and applying proportional reasoning to angular
distances, students will obtain a good measurement of our
planet's size — a feat first documented by the Greek
astronomer Eratosthenes in 240 B.C.
Create a free account with the OpenScienceResources Project to
download a lesson plan:
The Eratosthenes Experiment is organized in the framework of
the European Commission's Open Discovery Space project. Similar
past initiatives, also featured in these pages through the
years, have sometimes called this "the Noon Day Measurement."
PoW taking place: math problem-solving moment of the week
"We had SO MANY submissions this week — I enjoyed reading
them all, and seeing lots of different strategies. Some were
very popular and others, completely unique. The highlighted
solutions below represent a wide range of strategies."
- Max, commenting on the Pre-Algebra PoW's Latest Solution
Crazy 8s Math Club
Bedtime Math, whose second book appeared in these pages two
weeks ago, announced Tuesday the national launch of an
"over-the-top after-school club designed to get kids fired up
Having already piloted with more than a thousand children at
40 schools, libraries, and other accredited after-school
enrichment programs, Crazy 8s clubs gather with an adult coach
weekly for hands-on "mischief-making" activities such as
Bouncy Dice Explosion and Toilet Paper Olympics.
Bedtime Math provides almost all needed materials and
instructions. For full details about costs, set-up, and other
frequently asked questions, download this FAQ:
Early interest has already outpaced the number of coaches
available. Sign up here to join the fun:
Now taking place: math education conversation of the day
"This deserves to be in the editorial section of the NY Times!"
- Dina, posted to the secondary (grades 9-12) discussion group
of the Association of Math Teachers of New York State
Division and Multiplication of Whole Numbers MOOC-Ed
How do children move beyond the notion that "multiplication is
repeated addition" (MIRA)?
What mathematical distinctions do students make when reasoning
with multiple contexts for multiplication and division?
TurnOnCCMath will soon take up these and other questions with
its next free, Massive Open Online Course for Educators
"Division and Multiplication of Whole Numbers: Bridging to
Fraction Understanding" will explore how students begin to
recognize contextual problems and model with multiplication and
division problems, properties, and number facts. Along the way,
the MOOC-Ed will identify "where some of the key misconceptions
Open to elementary and middle grades educators seeking to
understand student multiplicative reasoning, this free MOOC-Ed
runs through early May. Even though it begins this coming
Monday, 17 March, registration for this self-directed course
will stay open through Monday, 31 March:
We last featured TurnOnCCMath in June, upon the launch of its
first MOOC-Ed, "The Equipartitioning Learning Trajectory: A K-5
Foundation for Rational Number Reasoning." The team from North
Carolina State University offers these courses at no cost as
part of research and professional development funding provided
by the National Science Foundation (NSF), the William and Flora
Hewlett Foundation, the Oak Foundation, the Joseph D. Moore
Endowment, and the Friday Institute.