The Bitcoin blockchain has recorded a very slow mining time: almost two hours for the verification of a single block. Such a slow time for mining a single Bitcoin block has occurred very rarely in the past.
Bitcoin: a slow blockchain. What happened?
The block at height 597.273 was a real odyssey for the miners. It took 119 minutes for this block to be verified, despite the recent record hashrate.
Interestingly enough, the next block, number 597.274, was verified in only 1 minute.
Bitcoin was created with the intention of maintaining a mining difficulty such that the verification of a single block takes place approximately every 10 minutes. Up to now, it has always been maintained within the set time, recording only small, insignificant variations.
The time of ten minutes per block is maintained thanks to the automatic adjustment of the mining difficulty. It is adjusted every two weeks according to the performance of the network.
Some miners may also try to optimise their work by relying on probabilistic analysis.
Possible reasons for the slowness
The explanations behind such a slow time may vary, but the most likely is that of a simple statistical anomaly.
Some believe that there has been a failure to reach consensus in the network, while others believe that there may have been a momentary fork. This last hypothesis has been discarded because there is no evidence of such an event.
Antoine Le Calvez, through a Twitter post, pointed out that such an event happened only 10 times in the ten-year history of Bitcoin. The last time it happened was in May 2014, so more than 5 years ago.
The recorded anomaly follows the news of a few days ago concerning the sudden 30% drop in the total hashing power of the Bitcoin network.
Moreover, according to some data, the Bitcoin network has lost about 1400 nodes in the last three months.