How tall is a tree?

Every Friday we go to the forest, this is in addition to our time in our outside classroom.  Sometimes the children have specific science activities to do and sometimes they are presented with a challenge.

This week's challenge was how tall is a tree, or indeed how can one measure the height of a tree.
I had a basket containing tape measures, yard and meter sticks, string and yarn, protractors and set squares,  and safety goggles for the children to use if they needed.

Well, as usual my class went at the task with gusto and I enjoyed watching the various ways they solved the challenge.

So how did they do it?

Find a small tree and measure it with a measuring tape or stick.

Find a dead tree and measure along its length with a tape measure.

Find a thin, bendy tree, pull it down from the top, attach a tape measure to it and let it spring back up.

Measure a tree that is leaning over.  - I added a question for this group - did you measure the height of the tree or the length?  They realized they had in fact measured the length and redid it measuring the height.

Get a group of students together, one person climb the tree, the other hand them a measuring stick, and yet another hold the tree trunk steady.

Find a really long tree branch, use it to measure a tall tree and then measure the branch.

Eyeball a tree, think it is about three times the height of a student - so estimating about 12 feet tall.

The idea of measuring shadows came up and caused a lot of discussion.  The conclusion grade was, that measuring with a shadow would not work because shadows change in length throughout the day. They also noticed that at the time their shadows were longer than them so it wouldn't be an accurate measurement.  One student actually got down on the ground to see if that would make his shadow match his height, but noticed it didn't.  - I did wonder that after this experiment whether they would take it further, noticing just how long their shadow was compared to them, then using that same ratio with a tree, but they decided shadows were not going to work, so moved on to a different idea.

What I liked the best about this challenge was the range of ideas the children came up with.  It worked whatever their ideas were, it worked for all kinds of thinkers. They stayed focused, they measured many trees, they worked in teams, they understood the importance of safety, shared ideas with each other, discussed tough questions and also had a lot of fun.