Reading a book about thermodynamics and Maxwell trying to find a hole in 2nd law of thermodynamics. I understand the demon action of separating molecules but Rolf Landuers’s limit theory is a little confusing.
If anybody can explain it LI5 I would be greatly appreciative. Thanks.
In: 6
In a computer, the 0’s and 1’s are encoded physically somehow – maybe a certain place in a memory chip has some extra electrons, if it’s storing a 1.
But there are lots of physical states that might represent a 1. Maybe it has 19 extra electrons, maybe 21, maybe the the atoms there are jiggling *just so*, or *slightly different*.. the computer doesn’t care, these all represent “1”.
Right now, we don’t know if the bit is a 0 or 1, so there are a lot of possible physical states: all those that represent a 0, and all those that represent a 1.
If the computer erases that bit, setting it to 0, that seems like it should make the number of possible physical states go down – since all those that represent a 1 are now ruled out. But that would mean the thermodynamic entropy went down, which isn’t possible! (At least, not if the computer is a closed system).
What must have happened is there are now *more* states than before that could represent a 0, since (thermodynamic) entropy can’t decrease. Almost always, if a closed system suddenly has more possible physical states, that means the temperature when up. So erasing that bit must have added some heat into the system, and that energy had to come from somewhere: it must have cost energy to erase that bit.
Landauer’s theory says that there’s a minimum amount of energy that erasing data will cost, and we can’t erase data more cheaply than that.
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