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Comment by olegkikin | Hacker News Reader

I think you are wrong, blocks will not be mined 3 times slower just because the global hashrate dropped by 70%.

Think of it as a race, many participants are running the distance with slightly different speeds. You randomly remove 70% of the runners, and your new top runner will be likely just a tiny bit behind the previous top runner, if at all.

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No, it's not a race to a finish line, it's a race to find a random number that when placed in the block header hashes to a value that is less than the difficulty. The difficulty is adjusted as desdiv said above based on the network performance in the previous period. When network hashrate increases significantly, the next difficulty adjustment happens sooner and if the hashrate dropped dramatically then it would happen slower.

The better analogy would be a race to turn over stones looking for the one with the secret on the back but the number of stones was adjusted for the previous number of searchers and now with fewer searchers it will take longer for any of them to find it.

It's not a race, it's a scavenger hunt. If you remove half of the searchers you'll take twice as long.

I don't think your runner analogy holds up, as the difficulty change essentially effects the global work required (lower chance of finding a suitable random value). It's more like measuring the total distance run by all runners - reaching the same total distance with less runners would take significantly longer.

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