Decimal Glass

Time sure does drag slowly sometimes, but do you know whether your internal clock is running slow or fast? See if your brain is a good time keeper and whether you can make a sand glass or egg timer to measure 86 seconds. Why 86 seconds? We’ll explain in a decimal minute!

Try this activity by yourself or with some friends.

What you'll need

A maroon coloured table cloth with a hammer, plastic cup, nail, grey plastic funnel, glass jar of sand with a green and yellow lid, yellow stop watch and glass pitcher of apricot coloured water siting on it.

You’ll need one of each of the following things for each person:

  • one jar of fine sand or jug of coloured water
  • one empty plastic container or bottle
  • one small nail
  • one small hammer (or something to hit the nail)
  • one plastic funnel
  • one stopwatch (optional) to check your time at the end

What to do

  1. A maroon coloured table cloth with a hammer, plastic cup, nail, grey plastic funnel, glass jar of sand with a green and yellow lid, yellow stop watch and glass pitcher of apricot coloured water siting on it. Carefully use the nail and hammer to poke a hole into the bottom of the container. The hole should be large enough to let the sand or water run through.
  2. A maroon coloured table cloth with a hammer, plastic cup, nail, grey plastic funnel, glass jar of sand with a green and yellow lid, yellow stop watch and glass pitcher of apricot coloured water siting on it. Now, place your finger over the hole to stop sand or water falling out.
  3. A maroon coloured table cloth with a hammer, plastic cup, nail, grey plastic funnel, glass jar of sand with a green and yellow lid, yellow stop watch and glass pitcher of apricot coloured water siting on it. Place the funnel into the plastic food container. Pour in an amount of sand or water that you think would take 86 seconds to flow through the funnel. You can only use your brain to work out the 86 seconds. You are NOT ALLOWED to use your wristwatch, stopwatch, mobile phone or other time keeping device! Not even a grandfather clock!
  4. A maroon coloured table cloth with a hammer, plastic cup, nail, grey plastic funnel, glass jar of sand with a green and yellow lid, yellow stop watch and glass pitcher of apricot coloured water siting on it. Once everyone has made and tested their sand glass, set them off at the same time (release your finger!) and see if everyone measured out the same amount of sand. You’re allowed to use a stopwatch now to check whose sandglass came closest to 86 seconds.

Why 86 seconds? Well, maybe you have a three minute egg-timer at home that runs on traditional time, based on the numbers 12 and 60.

Decimal time is based on the number 10—a bit like how measurements such as length in metres or mass in grams are based on the number 10. One decimal minute is 86 seconds in regular time.

What's next?

When you visit the Measure Island exhibition be sure to check out an exhibit called Worth the Wait. Can you hold its button down for exactly 15 seconds?