Tony Ryan: the spider is a master engineer

From the Royal Institution Christmas lecture by the Professor of Physical Chemistry, to be broadcast on Channel 4 on Boxing Day

A spider is a miniature silk factory – its tiny body can make 400 metres of silk in just a few hours. The spider's web is an incredibly complex structure that does a multitude of tasks. Each of her polymer fibres is spun to do a specific job – some for strength and flexibility, others to catch food. They all have different physical properties. Anchored fibres are load bearing. The spider makes the silk very sticky, so it acts like glue and sticks firmly to whatever structure is built on to.

If we move out to the centre, these load-bearing fibres are linked by cross-members, strands of polymer that tie the whole structure together. These have different physical properties. They're more flexible – imagine a fly, with all its forward momentum, hitting the web. If it was rigid, the strands would break and the web will collapse or the fly would bounce off. So these polymers are flexible – they're designed to absorb impact and trap the fly. The spider adjusts the composition – the make-up of the polymers – so the silk "behaves" in the right way. And it does this by altering the water content of the silk.

The spider is a master engineer, and doesn't even know it. Can you think of any structures where we use similar construction techniques to the spider? Suspension bridges. Humans use all the engineering principles you see in a spider's web and apply them to bridges. You have load-bearing lines – which take the weight. And just like the web, they're anchored to the ground. Attached to the lines are thinner cables, which are flexible – like the cross-members in the web – that support the road or rail platform.

So the engineering principles used by us are borrowed from the spider. We're even building bridges made from the same material as webs – polymers with different physical properties, so they flex and move with various weather conditions. The difference of course is that the spider can build her web in just two hours. For humans – well, it takes a little longer.