• Question: How can the time delay between lightening and thunder be used to tell how far away a storm is?

    Asked by thequestionmaker to Werner, Vicky, Nick, Madgie, Carla on 14 Nov 2013.
    • Photo: Werner Muller

      Werner Muller answered on 14 Nov 2013:

      lightening and thunder are not linked to a storm, more to the centre of lightening. The lightening is instant (travels fast) while the thunder travels with speed of sound (which is dependent also on the atmosphere conditions).
      The distance between both signals tells you how far away the lightening happened. It can move quickly so it is impossible to predict where the next lightening will strike. If there is no difference in time between lighting and sound then you are in the centre.

    • Photo: Marlene Lorgen

      Marlene Lorgen answered on 14 Nov 2013:

      Light travels at a speed of around 300,000,000 meters per second, while sound travels at around only 340 m/s. This means that when lightning flashes, we see it almost instantly, but sound takes its time to travel. If you could how many seconds there are between a flash of lightning and a crash of thunder, then multiply this number by the speed of sounds (i.e. by 340) you can roughly work out how many meters away the lightning is. So if there was a 2 second delay, the distance is 2 x 340 = 680 meters away. If there is no delay, you are in the centre of the storm, scary!

    • Photo: Nick Groves-Kirkby

      Nick Groves-Kirkby answered on 14 Nov 2013:

      You can do a simple experiment to show that sound and light travel at different speeds.

      Stand at one end of a football pitch and get friends to hit two sticks together at the other end. You’ll see the sticks hit shortly before you hear the sound they make.

      I remember doing this at school using rounders bats!

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