• Question: Could you measure the age of water if it was pure water?

    Asked by to Ben, Emily, Hattie, Jemma, Veronica on 23 Jun 2014. This question was also asked by .
    • Photo: Ben Butler

      Ben Butler answered on 23 Jun 2014:

      Hi muizzasif2000,

      That has to be my favourite question in the water zone so far!

      Even if the water was perfectly pure, scientists can actually still do some clever analysis to try and estimate how old it is. Scientists often use isotopes to work out how old something is. These isotopes are just atoms of the same element that weigh slightly different amounts because they have different numbers of neutrons.

      To age pure water, scientists can look at the different isotopes of hydrogen. There are three types of hydrogen:
      1. Hydrogen with a mass of 1
      2 Hydrogen with a mass of 2 called Deuterium
      3 Hydrogen with a mass of 3 called Trititum

      Scientists can measure the amount of Tritium in the water and use the concentration to calculate how many years old it is.

    • Photo: Emily Hayward

      Emily Hayward answered on 23 Jun 2014:

      Hi Muizzasif2000,

      what a great question! Scientists can guess the age of water by the type of hydrogen in it as there are 3 types with different masses, however its very much of a guess when they work it out. There are some things in science which are easy to get answers to, and other things which are a huge challenge – this is one of the areas its a huge challenge, like finding a cure to cancer. We can guess but cant be sure. Maybe one day we can discover a very accurate way to tell how old water is!

    • Photo: Jemma Rowlandson

      Jemma Rowlandson answered on 23 Jun 2014:

      Hi!

      Ben and Emily have pretty much covered everything. I’d just add that the atoms we use to measure the age of something not only have to isotopes (same number of protons and electrons but a different number of neutrons), but they also have to be radioactive.

      Radioactive atoms are not very stable and they break-down randomly into non-radioactive atoms. Every radioactive atom tends to break-down in a similar amount of time though. Scientists know how long it takes for half of the radioactive atoms to break down into non-radioactive ones, and this is what we measure.

      This means some of your pure water would have to be made with tritium, not hydrogen. Tritium is radioactive but hydrogen and deuterium (as Ben said, one of hydrogen’s isotopes) are not, so they can’t be measured. Scientists measure how radioactive the tritium-water is still, and from that they can work out how old the water is.

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