On Tuesday at 11:34 AM UTC, the long-awaited Bellatrix upgrade was finally implemented. The hard fork upgrade introduced an "execution payload" parameter needed for validators to start creating mainnet blocks, which had until now been missing from the Beacon Chain.
It appears to have gone off without a hitch, and validators even included a bit of graffiti on the blockchain: "Welcome to the New Beginning."
Now all eyes are on the next step: The Merge.
The Ethereum Foundation likens The Merge to “changing an engine on a rocket ship mid-flight." As such, it is “designed to be performed without needing to pause anything during the switch." But changing that engine is a two-step process, and Bellatrix is just the first part, gearing up for the main change. The second and final step is Paris.
Think of the Bellatrix upgrade as preparing the Beacon Chain — the consensus layer — to be merged with the Ethereum mainnet, and the Paris upgrade as when this happens. When Paris takes place, the execution layer will transition from proof of work to proof of stake.
When will The Merge happen?
The Paris upgrade is expected at some point between September 10 and September 20. This will be triggered by reaching the specific Total Difficulty threshold, also called Terminal Total Difficulty (TTD).
As per the Ethereum Foundation, TTD “is a cumulative measure of the total mining power that has gone into building the chain,” and Paris will trigger when it hits 58,750,000,000,000,000,000,000.
Put more simply, once the difficulty of mining a block meets or exceeds this level, the next block will be produced using proof of stake. It's expected that the first block produced under the proof-of-stake mechanism will complete approximately 13 minutes after the Paris upgrade.
“When the time comes, and this criterion is met, blocks will go from being built using proof-of-work in one block to being built by proof-of-stake in the next,” the Ethereum Foundation said.
The actual time at which the TTD is reached is dependent on Ethereum hash power after Bellatrix, which is why it’s difficult to put an exact date on The Merge. But Ethereum developers chose the TTD in order to target September 15, knowing that the actual date might fluctuate by a few days either side.
From a technical standpoint, a successful Paris upgrade marks the completion of The Merge.
Going beyond The Merge
Once The Merge is complete, there are still some more things to be done in relation to the move to proof of stake
That includes investors being able to unstake their staked ether. For that, they will have to wait until the Shanghai upgrade, the “next major upgrade” post-Merge. This means newly issued ETH accumulating on the Beacon Chain will remain locked and illiquid for another six to 12 months.
Beyond this, Ethereum co-founder Vitalik Buterin has also outlined a longer-term vision for the future of the chain.
There’s still a lot of speculation as to what future upgrades will involve, but he’s already given them catchy names. Once The Merge is finally complete, we could see the Surge, Verge, Purge and Splurge.
“The Merge is proof of stake. The Surge is sharding, and The Verge is Verkle Trees, The Purge is things like state expiry and deleting old history, and The Splurge is basically just all of the other fun stuff,” Buterin said at the Ethereum Community Conference in France in July.
These future upgrades will focus on addressing some of the key issues that have been plaguing Ethereum for years such as scalability. But these updates could be a long time coming. It’s estimated that truly “completing” Ethereum could take as long as six years.
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