[ExI] for the fermi paradox fans

[Robin D Hanson]

On Jun 8, 2014, at 1:47 PM, Anders Sandberg <anders at aleph.se<mailto:anders at aleph.se>> wrote:
And when have to do error correction and to erase bits, you primarily focus on moving bits reversibly from your system into the negentropy store. The resource that you fundamentally have in your storage is negentropy. It can be stored in different ways and converted between those ways, but the way to count it is as negentropy.

Yes, but making one bit of negentropy, doesn't that cost kTln(2)? (where T is the *current* temperature)

Energy is conserved, so you don't actually ever have to spend it. What you usually have as a limited resource to spend is *free energy, which is a form of negentropy. If you are careful, you can always use that resource to erase the same number of bits in a wide range of environments, including a wide range of temperatures.

The origin of the bit = kTln(2) equation is that temperature is defined as the inverse of the derivative of system entropy with system energy. So literally you can reduce the entropy of a system by one bit by taking away energy according to that formula. But that is raw energy, not free energy, so that doesn't actually cost you anything in negentropy terms, if you do it reversibly.


Robin Hanson  http://hanson.gmu.edu
Res. Assoc., Future of Humanity Inst., Oxford Univ.
Assoc. Professor, George Mason University
Chief Scientist, Consensus Point
MSN 1D3, Carow Hall, Fairfax VA 22030
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