Numbers are useful for counting and measuring things. We use them all the time, even when we’re not thinking about maths. For example, I use them every day, for telling the time, cooking, exercising and driving my car.
Normally when we count, we start at zero and count upwards in whole numbers: one, two, three, and so on… But what happens if we count down from a bigger number – do we have to stop when we get back to zero?
This question was asked on a cold Winter’s day. The water in the bird bath had frozen and I used hot water from the kettle to thaw it so the birds could drink. When I explained to my 6-year-old that water freezes at zero degrees Celsius, she wondered if that was the coldest that things can get. But it isn’t – in fact some things can get much, much, much colder!
So what happens when things get hot or cold and how do we measure temperature?