Bitcoin: More than an hour to confirm a block

Today it took more than an hour to confirm block 759.054 on Bitcoin’s blockchain.

In fact, the previous block was mined at 7:09 UTC, while block 759,054 was mined at 8:34 UTC.

For one hour and 25 minutes, Bitcoin’s blockchain stood at block 759,053, waiting for the next block to be mined.

Mining 759,055, on the other hand, only took 5 minutes.

Anomaly in the confirmation time of a Bitcoin block

To understand the reasons for this apparent problem, it is necessary to know how Bitcoin’s block time calculation works.

After all, nowhere in the Bitcoin protocol does it say that there must be about 10 minutes between each block. The average block time of 10 minutes is just a result of the relationship between difficulty and hashrate.

Today, for example, the average blocking time is about 10 and a half minutes, and yesterday it was exactly 10 minutes. So the hour and 25 minutes it took to mine block 759,054 is not a problem at all, just a statistical anomaly.

There is no way to calculate with absolute accuracy how long it takes to mine a block, because actually the miners proceed randomly, and sometimes the randomness causes it to take much longer to extract the correct hash.

The important thing is not that all blocks are mined 10 minutes after the previous one, but that on average a block is mined every 10 minutes or so. Today’s average is only slightly above this threshold, while for example Saturday the 15th was 9 minutes 40 seconds.

For example, at the end of September several days ended with an average of more than 11 minutes, so everything is completely normal. Such statistical anomalies are actually quite normal.

Hashrate and Bitcoin network issues

The really strange thing is that this morning, around 07:00 (UTC), there was a small increase in the hashrate, which rose to 264.5 Eh/s from 248.8 at 23:00 (UTC) yesterday. So the decline in mining of block 759,054 was not due to a drop in hashrate, although as of this morning at 08:00 (UTC) it had dropped to 256.3 Eh/s. For the rest of the morning, however, it dropped as low as 240 Eh/s, and no other blocks as slow.

This is still a slightly lower hash rate than previous days, although for example the average daily hash rate on Thursday the 13th was only 234 Eh/s.

Recently have difficulty has grown a lot, with an increase that has been one of the largest ever, bringing it to all-time highs. Then again, the hashrate is also near all-time highs, recorded last week.

The increase in difficulty was precisely to extend the block time since due to the very high hashrate, the average daily block time in early October had dropped below 8 minutes. It stayed well under 10 minutes for a good 12 days, due to the very high hashrate, before the sharp increase in difficulty brought it back to around the desired 10 minutes again.

Therefore, it is more than obvious that as of October 10, the times to mine Bitcoin blocks have increased slightly, and with a hash rate that is no longer close to 300 Eh/san occasional decline is to be expected.

This is well within the norm to such an extent that it does not allow any really interesting information to be extracted except about the technical functioning of Bitcoin. The fact that in the face of all this, the profitability of mining still falling, suggests that many miners are mining by accepting little or very little profit in order to accumulate BTC which they hope will be worth more in the future.