[ExI] for the fermi paradox fans

Robin D Hanson rhanson at gmu.edu
Sun Jun 8 00:23:14 UTC 2014

On Jun 7, 2014, at 7:26 PM, Anders Sandberg <anders at aleph.se<mailto:anders at aleph.se>> wrote:
Robin D Hanson <rhanson at gmu.edu<mailto:rhanson at gmu.edu>> , 7/6/2014 6:20 PM:
I know that people often say things like this, but I think it gets the physics wrong. The real resource is negentropy. One just stores that in a form of free energy, but how many bits one can erase later with that negentropy doesn't depend on the temperature later, at least to first order. One will want to do reversible computing later, and that isn't necessarily much more efficient at lower temperatures.

Hmm... how does this actually work? You make a lot of negentropic stuff, and when you need to erase a bit in a late era you use the negentropy to mop up the bit entropy? But the energy cost of making the negentropy/free energy stuff in the early era seems to be significant.

When you are designing reversible computing systems, you are focused on making each small part individually be nearly reversible - you have to drive it in some direction via some deviation from full reversibility, but that cost is an entropy cost - the process can work fine at lots of different temperatures. To get free energy to run this process, you use your negentropy store to create it, as one usually does in thermodynamic system design. 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.

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
703-993-2326 FAX: 703-993-2323

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