• Question: What makes things feel smooth, rough, soft, or any other texture?

    Asked by lisaloo to Claire, Kate, Matt, Rob, Sam on 17 Jun 2013.
    • Photo: Sam Geen

      Sam Geen answered on 17 Jun 2013:

      The atoms on the surface are often arranged so that they have ridges if you look at them closely with a microscope: look at this comparison of paper and aluminium:

      So this is your finger picking up these small changes, and the friction made by rubbing against them. Ice feel smooth sometimes because the surface melts as you push against it, which is why ice-skating works (although be careful – if the ice is very cold your skin can stick to it!)

    • Photo: Matthew Pankhurst

      Matthew Pankhurst answered on 17 Jun 2013:

      It’s all about the surface and how our fingertips sense that surface. A rough surface has lots of complicated high bits and low bits, which our fingertips can sense as tiny bumps as we touch it. The bumps set off signals in our fingertips which shoot up into our brain and we feel it as rough. Smooth things have a very flat surface, so our fingertips just glide across and don’t get bumped, we still feel pressure as we press our finger on it but it doesn’t get bumped. Soft things are very delicate and made up of a lot of air, so when you push against them they don’t push back. Hard things are very strong and the atoms are packed together tightly, so they put up a lot of resistance when we press against it.

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