• Question: Hello! (btw @Kate is a legend!) Why did the universe have such low entropy in the past, resulting in the distinction between past and future and the second law of thermodynamics?

    Asked by Xx_Shrek_Is_Life_xX to Joe, Jos, Kate, Lisa, Pierre on 18 Nov 2014.
    • Photo: Kate Dobson

      Kate Dobson answered on 18 Nov 2014:


      I’m not going to be able to anser this question without looking it up, which I will if none of the others know the answer, but thank you for the compliment Xx_Shrek_Is_Life_xX!

    • Photo: Joe Reed

      Joe Reed answered on 19 Nov 2014:


      Entropy is a measure of disorder, and always increases(2nd law). You can see this as things going from a less likely to a more likely state.
      Imagine your room, there are lots more ways that it can be ‘messy’ than it can be ‘tidy’, so if you move one item in your room, it is likely to become more messy than more tidy.
      So, very crudely, low entropy = low probability = tidy, high entropy = higher probability = messy.

      If time were to reverse, the equations that describe different processes would still apply and work, but it would violate this second law. This gives the ‘asymmetry of time’ i.e. time moves forward.

      Hope this explains it, its complicated.

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