Timing of the Merge
Rather than a specific time, Ethereum’s Merge is scheduled around something called its Terminal Total Difficulty number – a value representing the cumulative difficulty of all blocks that have ever been mined under the network’s proof-of-work system.
The TTD number has been set at 587506-00000000000000000, but you don’t need to do the math yourself in order to figure out what this means in human time.
To keep tabs on the Merge, one can bookmark websites like bordel.wtf and wenmerge.com, which both feature live estimates for when the upgrade will happen. Even easier, you can look up “When is the Ethereum Merge?” on Google, and you’ll be greeted with a big, fat countdown timer.
At press time, most estimates are placing the Merge around 4:23 UTC on Thursday – late into the evening (around midnight Thursday morning) if you are on the east coast of North America. (We only have an estimate because Ethereum proof-of-work blocks fluctuate in difficulty, and they aren’t issued at a set interval).
Block proposals
Ben Edgington, a product lead at the Ethereum research and development firm ConsenSys, told CoinDesk that the first thing he’ll be paying attention to when the Merge happens is whether or not blocks of transactions are being proposed to Ethereum’s proof-of-stake chain.
Recall that Ethereum is a decentralized ledger – a balance sheet that gets updated by a disintermediated community of volunteers, called “validators.” Every 12 seconds under Ethereum's new system, a validator will be randomly selected to propose a “block” to the chain – a list of transactions that it wants to write into the ledger.
“We expect a block like clockwork every 12 seconds on the proof-of-stake chain. Every ‘slot,’ which is a 12-second interval, a validator is chosen by the protocol to propose a block for that slot. If that validator is offline, is on a different fork, or is otherwise not participating correctly, then that block goes missing,” Edgington explained.
One can view this data on chain explorers like beaconcha.in or beaconscan.com. Both sites list every new slot as it happens, along with whether or not a block has been proposed for it.
“Immediately, we will ‘see empty slot, empty slot empty slot,’ and that would be the first sign of trouble. If we see ‘block, block, block, block, block,’ then we know we're good,” Edgington explained.
A few missed slots, according to Edgington, are “not immediately calls for desperate concern.”
Over the past few months, several Ethereum test networks (testnets) have undergone their own transitions from proof-of-work to proof-of-stake – each serving as a kind of dress rehearsal for the real thing.
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