Bitcoin : Could somebody ELI5 why this double spend happened & would (not) happen again?
In an article from Coindesk from 2013 ([https://www.coindesk.com/today-is-d-day-for-bitcoin-miner-upgrades/](https://www.coindesk.com/today-is-d-day-for-bitcoin-miner-upgrades/)):
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*”A block that had a larger number of total transaction inputs than previously seen was mined and broadcasted. Bitcoin 0.8 nodes were able to handle this, but some pre-0.8 Bitcoin nodes rejected it, causing an unexpected hard fork of the chain. The pre-0.8 incompatible chain at that point had around 60% of the hash power ensuring the split did not automatically resolve.*
*”In order to restore a canonical chain as soon as possible, BTCGuild and Slush downgraded their Bitcoin 0.8 nodes to 0.7 so their pools would also reject the larger block. This placed majority hashpower on the chain without the larger block. During this time there was at least one large double spend. However, it was done by someone experimenting to see if it was possible and was not intended to be malicious.”*
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I think I understand why it happened in the first place: the nodes running that “pre-0.8 incompatible chain” hade 60% of the hash power. And that second chain emerged because the previous chain couldn’t handle the larger block size. Right?
But how did it happen that the hashingpower was unevenly distributed?
And how is it possible in the first place that one block gets more transactions than specified? I thought that each block holds always a pre-determined number of transactions?
How could a similar scenario occur today?
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Would be great if somebody could ELI5 these things (and/or point to materials where I can learn to understand it myself) – thanks!
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