Ethereum: What happens if two miners mine another block at the same time?

In the world of cryptocurrency mining, the process is as complicated and complex as it sounds. As we described in our previous answers, multiple miners work together to solve a mathematical puzzle known as a “proof-of-work” (PoW) algorithm. Solving this puzzle requires significant computing power and energy. A key aspect of the PoW algorithm is that each miner has to solve it individually. But what if two miners are trying to solve the same puzzle at the same time?

The answer lies in the concept of time synchronization, which ensures that all miners finish their work at roughly the same time.

How ​​time synchronization works

In the case of Ethereum and other cryptocurrencies that use a proof-of-work algorithm, miners use specialized hardware called ASICs (Application-Specific Integrated Circuits) or GPUs (Graphics Processing Units). These tools are used to quickly solve complex mathematical equations. To achieve synchronization, many miners typically use a process called “timestamping” or “time synchronization.”

When a miner solves a puzzle, they immediately calculate the block number using the current timestamp and the previous block’s hash value. If two miners attempt to solve the same puzzle at roughly the same time, their calculated block numbers will be close to each other.

What happens if two miners find the next block at the same time?

In a hypothetical scenario where two miners simultaneously find the next block, a few things can happen:

• Block duplication: If two miners run PoW algorithms at the same time, they can generate blocks containing identical code or data. In this case, one of the miners must discard the duplicate block and send it back to the network, ensuring that only one valid block is added to the blockchain.

• Transaction duplication

  : A duplicate block can also contain conflicting transactions that can be automatically resolved by a validator (a node on the Ethereum network). Alternatively, nodes can manually unblock them.

• Block overwriting

  : In some cases, if two miners find the same block at the same time, they will have to overwrite each other’s blocks with their own code or data.

Key Considerations

It is important to note that several factors affect whether a recurring block occurs and how it should be treated:

• Network latency: The time it takes miners to solve the puzzle affects the probability of finding a duplicate.

• PoW difficulty: As the PoW difficulty increases, the chance that two simultaneous attempts will be duplicates decreases.

• Hash Collision: If two miners try to solve the same puzzle at roughly the same time, this can lead to a condition called a “hash collision,” where their code or data becomes identical.

In summary, while it is theoretically possible for two miners to find the next block at the same time, the probability of this happening in practice is extremely low. The network’s robust timestamping mechanism and PoW difficulty work together to prevent duplicate blocks from being added to the blockchain.