Imagine you have a question or an idea, and you want to find out if it's true or not. The null hypothesis is like the opposite of your idea. It says that there is no relationship or no difference between the things you're interested in.

For example, let's say you want to know if eating fruits helps you grow taller. Your idea is that eating fruits does make you taller. The null hypothesis would be that eating fruits has no effect on your height, meaning it doesn't make you taller.

Scientists use null hypotheses to test their ideas in experiments. They collect data and analyze it to see if it supports their idea or if it supports the null hypothesis. If the data provides strong evidence against the null hypothesis, it means there might be something to their idea. But if the data doesn't show any clear difference or relationship, then the null hypothesis might be more likely to be true.

So, the null hypothesis helps scientists compare their ideas to the possibility that there is no effect or relationship between the things they're studying.