Lessons · Time and the sky
Counting down to frost
A paper chain with one link for every day until the first frost. Break one off each morning, and on the morning the grass crunches, count what is left.
When
August to October
Outside
About 30 minutes
What it teaches
Counting down, subtraction as distance, and what an average actually promises.
What is going on
An average first-frost date is not a forecast and not a promise. It is the day by which, in about half of past years, it had already frosted — so being a week out in either direction is the normal case, not a failure of the number. Where it gets interesting is that frost is local to a degree almost nothing else is. On a still clear night the ground radiates heat away and the air right above it chills and, being heavy, runs downhill like water and pools in the low ground. A garden at the bottom of a slope can frost while one three hundred metres up the hill does not, on the same night, in the same weather. If you live in a valley, the map is wrong about you, and finding that out is a real piece of science a family can do.
What to look for
- Where the frost sits first — the low corner of the garden, the hollow, the field beside the river
- Whether the cars frosted and the ground did not, or the other way round
- Clear still nights against cloudy windy ones. Cloud is a blanket and wind stirs the cold layer away
- What survived it. Kale and parsnip get sweeter; basil is gone by breakfast
First, outside
What to do
What to take
- Strips of paper
- Glue or tape
- Your town's average first-frost date, which this site will tell you
- 1
Look up the first-frost date for where you live and work out how many days away it is.
- 2
Make that many paper links and hang the chain somewhere everyone walks past.
- 3
Break one link off every morning, out loud, with the number said.
- 4
When the first real frost comes, stop. Count the links left over — or count how many days past zero you went.
Out loud
What to say to each of them
All three at once, off the same bucket of acorns. Read down the column that matches the child in front of you.
2
Point and name
- “Break one. Just one. Now it's gone.”
- “Cold. Touch the window — cold. Now touch your cup — warm.”
- “Is the chain long or short today?”
Subitising — seeing that a group is two without counting it — and the idea that a number word belongs to a thing you are touching.
4
Count and compare
- “How many links are left? Count them.”
- “There were twenty yesterday. How many now?”
- “Will it be frosty tomorrow? What would we look for in the morning?”
One-to-one correspondence: one number word per object, the last word you said is how many there were. Then more, fewer, and the same.
6
Tally and figure
- “Thirty-one days is four weeks and how many days?”
- “The frost came eight days early. So was the average wrong, or is an average not a promise?”
- “Next spring we'll do it backwards — counting up to the last frost, when it's safe to plant.”
Grouping as a way of counting past what fingers hold, and subtraction as the distance between two numbers rather than a taking-away.
When it is not working
What going wrong looks like
Most of what looks like failing is a child standing at a known place on a known ladder. Knowing which place changes what you do next, and it is usually not more practice.
About 2
Wants to break the whole chain at once. Hang it out of reach and bring it down each morning.
About 4
Counts the remaining links from the wrong end, or recounts from one every day. Recounting is not wasted — it is practice — but number the links and they will start reading instead of counting.
About 6
Treats the average as a deadline and calls it wrong when the frost comes late. Ask how many years would have to be late before the number itself was wrong. That question is the whole of statistics, at six.
How you know it landed
They ask whether it frosted last night before anyone tells them, and go and look at the grass to find out.
Rungs of the ladder this builds
Then, five minutes on screen
The same idea, drilled
Reading a number off a group of marks, which is the chain in shorthand.
Why this order
The walk first, the game after. Reversed, the walk becomes the price of the game, and a child who has learned that outside is what you do before the screen has learned the wrong thing very efficiently.
If they want more
Keep the number the frost actually came on. Do it three years running and you have your own frost record for your own garden, which beats any map.
When you have done it
Ticking it keeps it off the next season plan, and nothing else.
We look, we count and we put it back. Nothing goes in a mouth — not a berry, not a mushroom, not a leaf. That is the whole rule, and it is the same rule every time.
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