it doesn't work that way. look at the faq
Gladly. Are you able to point out which part of the FAQ is relevant to a flaw in my assumptions?
I want to clarify some potential counterobjections:
"But there would be a longer period of high difficulty, so it all balances out."
Yes, but the strong computer is turned off during this time. With all else being equal, the strong computer would be off more often than on. This saves electricity, and makes the planet greener, so perhaps this is a good thing.
"The total mining output is lower than if you mine all the time."
Yes, the total mining output is lower ... but being able to turn off during high difficulty periods means the *efficiency* of mining is higher.
"The total difficulty would still increase even if the strong computer turns off, because new computers are joining the network so rapidly as to still increase ."
Yes, but the point is that the difficulty would have increased even more had the strong computer been on, so there is still a benefit. The strong computer is able to hash without the system being able to account for its computing power.
"Other people would take advantage of it, too."
Either other people would, or they would not. Let's assume that there is another strong computer network (let's call it Strong#2)
a) Suppose Strong#2 does not take advantage of it; it acts as normal. Well, that's already the scenario I'm proposing here.
b) Suppose Strong#2 takes advantage of it. Then they would collectively behave just like a big network of "Strong#1+2" computers, and we'd get an even more emphasized effect. So the strong computer(s) would be able to save even more on electricity.
c) Suppose acts to do the opposite of what the first strong computer network does. (I'm not sure why anyone would do this, but let's assume for the moment that they choose to do so.) Strong#2 hashes during the time that Strong#1 is resting. This means Strong#2 would have to spend more time hashing at a difficulty level that has been increased by Strong#1 the previous 2016 blocks. At the end of the 2016, the relative difficulty drops because Strong#1 hadn't contributed --but according to this plan Strong#2 would then turn off, allowing Strong#1 a higher chance of finding the hash first. (Yes, of course Strong#2 itself will raise the difficulty, but it was going to do that in any case.)
"You need to have greater than 50% of the computing power of the total network." (Yes, someone actually voiced this objection in IRC.)
No, you don't.
Overall, it seems to me that it would actually be to everyone's advantage to cooperate in manipulating the system this way, in terms of bitcoin mined per kilojoule of electricity spent. Basically, you are rationing out the computing power of the network, in effect countering the arms race effect of everyone trying to compute more and more.
Am I missing anything?