Yes, enough but in parting
Bitcoin hashrate can never be accurately known
Really ? Mining is online, right ? Bitcoinwisdom is online.
Why on earth can´t current hashrate be accurately known ? Well, within say 1-2%. Why the hell is hashrate flat on the last difficulty adjustment when it´s supposed to rise by 7.7% in two days ? Where is that 20+ PH/s going to come from ? And if it´s impossible to accurately know the hashrate how can the difficulty be estimated to a single digit in a number of 40 billion ?
The best way to think about Bitcoin difficulty is to view it as the maximum amount of computing power it will take to find a particular block reward. The difficulty number is what helps keep the Bitcoin block time at around ten minutes. As more hashing power is added to the network from different computers around the world, the difficulty of finding a block needs to be adjusted accordingly. If there was no mechanism for regulating the amount of hashing power it will take to mine a particular block, then it would be impossible to effectively secure the blockchain.
Difficulty History
Date Difficulty Change Hash Rate
Dec 30 2014 40,640,955,017 3.00% 290,919,288 GH/s
Dec 17 2014 39,457,671,307 -1.37% 282,449,013 GH/s
Dec 02 2014 40,007,470,271 -0.73% 286,384,627 GH/s