Why do we change the clocks? On the night before Sunday 25 October, the clocks in Norway go back one hour, from 03:00 to 02:00, and winter time begins. People say we "gain an hour". But where does that hour come from? Nobody can change the sun.
What happens when the clocks go back?
A day is the time it takes the Earth to spin once. That takes about 24 hours, whatever we do with our clocks. A clock is something else: an agreement between people, so that school starts at the same moment for everyone.
In spring we move the agreement forward one hour. That is summer time, and it puts more summer light into the evening, when people are awake. In autumn we move it back. Why the evenings have been getting dark so fast this autumn is explained in Why do evenings get darker after summer?
We do not get a single extra hour of light. We only move the numbers.
In Oslo, the sun rises at about quarter past eight on Saturday 24 October and at about twenty past seven on Monday 26 October. But it sets at about quarter to six on Saturday and about twenty to five on Monday. The daylight is the same length. It has only moved on the clock.
Why is this worth learning?
The clock change shows them the difference between the time nature keeps and the time people agreed on. It fits the Norwegian curriculum in maths and natural science. Many children also feel the change in their bodies for a few days, because the body has its own clock that follows the light. More on that in Why is it so hard to get up after the holidays? Every autumn experiment is collected in our autumn laboratory.
Try it at home: a light diary
Suitable for: 5–12 years
You need paper, pencils, crayons, a clock and a window.
- Pick two fixed times, for example 07:45 and 17:00.
- Draw a table with one row per day from 19 October to 1 November.
- At both times, look out and colour the box: dark blue for dark, purple for dusk, yellow for light.
- On the night of 25 October, change a clock that does not change itself.
- Keep the diary going for another week.
- Look at the whole table. Where is the jump?
What happens if you ask someone in another Norwegian city to fill in the same table?
Questions to wonder about
- What does a cat or dog notice when the clocks change, but breakfast arrives an hour later than its body expects?
- If there were no clocks in the whole world, how would you know when to get up?
- Bergen and Oslo share the same clock, yet the sun rises more than twenty minutes later in Bergen. Why?
Every child is made of good atoms, and every child can discover that time has two clocks: one the Earth keeps, and one we made together.
Explore free content at goodatoms.com.