• Question: is it possible to walk on water if it is how

    Asked by charliet to Alastair, Emma, Hywel, Keith on 24 Jun 2010 in Categories: .
    • Photo: Alastair Sloan

      Alastair Sloan answered on 23 Jun 2010:

      No it’s not possible as the surface tension on the water is not enough to support our weight – not unless we run very quickly over the surface. The so-called ‘jesus lizards’ weigh around 200g and run at 1.5 metres per sec over water. If we wanted to do that then, saying the average male adult human weight around 12 stone, we would have to run at about 60-70 metres per sec!! That is 250 kilometres per hour!

    • Photo: Emma Carter

      Emma Carter answered on 23 Jun 2010:

      Yes! Some insects can walk on water because they are so light, the surface tension of the water can support them. Unfortunately for us, we’re a bit heavy for that trick.

    • Photo: Keith Brain

      Keith Brain answered on 23 Jun 2010:

      Here are some ideas:

      – Freeze the surface and iceskate;
      – make some “hoverboots” – like hovercrafts, but smaller;
      – shrink yourself to the size of an insect and use the surface tension, like a “Pond Skater” (insect) – OK, this one isn’t very realistic …!
      – increase the surface tension of the water, so that you can walk on it without shrinking … not sure how to do this, though … (Random aside: I wonder what the surface tension of tritiated water it …)
      – add an enormous amount of salt (NaCl) to water, or another “salt” with even higher solubility – this will increase the density of the water so that you “float” higher. This happens in some very salty places like the “Dead Sea”. If the density is high enough, I wonder if you can walk? Probably not, but it might be fun to try!

    • Photo: Hywel Vaughan

      Hywel Vaughan answered on 24 Jun 2010:

      Not for humans I’m afraid Charlie, however you can walk on custard!
      Custard is what’s called a negative thixotropic material – uncooked custard powder mixed with water in the right proportions becomes more viscous when under pressure, meaning that as long as you impact it quickly, you can walk on it!