Talk:Bremermann's limit

message: :No closed computer system, however constructed, can have an internal signal flow that exceeds mc2/h bits per second (here m is the total mass of the system, c the velocity of light in vacuum, and h is Planck's constant)...the numerical value of c2/h is 1.35×1047 (bits per second per gram)
Italics are per original source, namely p172 of "Complexity and Transcomputability", Hans J. Bremerman, in The Encyclopedia of Ignorance, edited by Ronald Duncan and Miranda Weston-Smith, 1977, Pergamon Press (reprinted by Wallaby/Pocket Books/Simon & Schuster/Gulf & Western 1978), p167-174. Author cites derivations in the following articles:
* "A basic limitation of the speed of digital computers, W. W. Bledsoe, IRE Transactions on Electronic Computers, EC-10, 530, 1961
*"Part 1: Limitations on Data Processing Arising from Quantum Theory", in "Optimization Through Evolution and Recombination", H. Bremermanm, in Self Organizing Systems, edited by M. C. Yovits, G. T. Jacobi, and G. D. Goldstein, Spartan Books, 1962
*an "improved argument" in "Quantum Noise and Information", H. Bremermann, Proceedings of the Fifth Berkeley Symposium  on Mathematical Statistics and Probability, University of California Bress, 1967
*"planned for publication" article: "Evolution and Optimization", in Biomathematics Lecture Note Series, 1978, Springer-Verlag 
All those references seem noteworthy to me, though I'd like to verify the 1978 article.
Typing the string c^2/h into Google yields 1.35639293 × 1050 kg-1 s-1. If no dissent I will modify the article when I get around to it.
--munge 07:58, 25 December 2006 (UTC)
thread_title:  ~1.35×10<sup>47</sup> bit/s/g 

message: Should the phrase "double the speed of encryption" be "double the cost of encryption" or "halve the speed of encryption"?
174.22.190.248 (talk) 03:41, 2 November 2009 (UTC)
replies: text: Neither; it depends on the algorithm. Now fixed. --David-Sarah Hopwood ⚥ (talk) 23:50, 14 October 2010 (UTC)
thread_title:  Encryption speed 

message: Maybe I'm stupid, but isn't 1072 years a constant? I think this needs clarification, or maybe a link or citation. --Nyelvmark (talk) 20:54, 9 August 2011 (UTC)
thread_title:  ...without increasing the time for encryption by more than a constant factor 

message: Doesn't this explanation of cryptography assume P not equal NP? Maybe someone who knows more should add a note to this extent.  — Preceding unsigned comment added by 128.42.216.63 (talk) 19:56, 27 August 2011 (UTC)
thread_title:  Assuming... 

message: This newer (2000) article reaches a slightly higher limit of 5.4258 ×1050 operations per second for a one-kilogram, one-litre "laptop". --Roentgenium111 (talk) 15:06, 29 August 2011 (UTC)
thread_title:  Outdated? 

message: Bremermann's law relates to linear (non-parallel) computation. If the "matter" doing the computation could perform computations in parallel, then a higher value can be reached. For example, each atom in 1 kg of hydrogen computes the force on it from each and every other atom. Given there are 10^30 odd atoms, this means that there must be 10^60 computations or so, each plank time, giving a total of 10^100 odd calculations per second (so long as your question can be posed in such a way that it can be answered by the gravitational interaction of particles).  — Preceding unsigned comment added by 195.12.16.211 (talk) 14:32, 6 September 2011 (UTC)
thread_title:  Linear? 

message: The article currently uses the phrase "...create an algorithm that could never be cracked by a brute-force search."  I believe this is incorrect.  It would be very, very, very unlikely, but it is possible that a brute-force search could find the key on the first guess. --Guy Macon (talk) 22:22, 9 April 2012 (UTC)
thread_title:  Never be cracked? 

message: Since this is included in Limits to computation, please include comparisons with the processing speed of actual modern hardware, like the bits per second of the world's fastest supercomputers divided by their mass.  — Preceding unsigned comment added by 71.167.67.219 (talk) 20:45, 5 May 2013 (UTC)
thread_title:  Comparisons with actual hardware