• Question: Why can we pass our fingers through a flame quickly and not get burnt by the heat?

    Asked by to Edward, Ian, Mathew, Naomi on 25 Jun 2014. This question was also asked by .
    • Photo: Ian Stephenson

      Ian Stephenson answered on 25 Jun 2014:

      It’s about energy, vs power…

      the flame is hot, and depending and the hotter it is the more energy it has. When you put something cold near it, it starts transferring energy from the flame, into the cold thing (your fingers!). The bigger the difference in temperature the faster the energy will get transferred – this is the power (how fast you use energy).

      But its not the power that’s the problem – its the total amount of energy. That depends not just on how fast its transferring, but how LONG its transferring. If you subjected to a thousand watts of energy (1000 joules per second) for only 1 thousandth of a second, thats only 1 joule of energy. On the other hand getting it with 10watts for ten seconds is 100 joules of energy.

      There are also other effects taking place, where any moisture on your skin will absorb the heat, and either evaporate (taking the energy with it), or form a protective barrier, which will protect you for a short while. There’s a myth busters episode where they dip their hands into molten metal thats supper how, but there hands are wet, which protects them (don’t try this at home!)

    • Photo: Naomi Osborne

      Naomi Osborne answered on 25 Jun 2014:

      If you pass your fingers through the bottom of a candle flame it’s not as hot as the top of it – because heat rises. This only works if you do it fast though – if you do it slow, more heat is transferred to your skin, which causes damage to your skin cells. It helps if your hands are wet, as the heat is transferred to the water before it reaches your skin.

      I wouldn’t recommend trying it though – you could get hurt!

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