Curious Kids: why is spider silk so easy to break when it’s supposedly stronger than steel?

Curious Kids is a series by The Conversation, which gives children of all ages the chance to have their questions about the world answered by experts. All questions are welcome: you or an adult can send them — along with your name, age and town or city where you live — to curiouskids@theconversation.com. We won’t be able to answer every question, but we’ll do our best. How is spider silk so easy to break when it’s stronger than steel? — George, aged ten, Hethersett, UK.