Study how to investigate

hints

   visible info

        1 input & output quantity
        2 input & output frequency
        3 movement of profit
        4 where can store info
        5 energy consumptions

   invisible info

        1 visible info type
        2 invisible info type
        3 something, not happens & should happens in probability

   visible objects

        1 where energy gather,      property of objects ?
        2 where gravity happens,   property of objects ?
        3 where energy flow into,   property of objects ?
        4 where energy flow out,   property of objects ?