What we care about is getting all the nodes to agree on what order the transactions occurred (aka "Proof of History"). And Solana's goal is to reach that agreement quickly, that's why they call themselves the most performant blockchain.
So how does Solana introduce a concept of "time" without relying on a central authority?
Solana uses a "hash that runs over itself continuously with the previous output used as the next input". Performing a hash over and over again takes some time. Then, someone can quickly verify that this "time" has occurred. The verification of the hashes can be parallelized on a GPU, which makes the verification extremely quick.
Do you mean Proof of History? The concept is made concrete in Solana, but actually any blockchain that hashes a set of transactions in each of its successive slots/blocks can be used to prove that time has passed.
You can verifiably be assured of a temporal ordering between transactions that were hashed in different slots because the output of a slot/block is hashed and used as an input for the next block/slot.
Solana claims to prove that a certain duration of time has passed, which is a different and much stronger claim than just temporal ordering. The details of their claims, last I heard (which was some talks in Berlin years ago) were extremely hand-wavy and apparently not well understood even by some people working on the project.
So how does Solana introduce a concept of "time" without relying on a central authority?
Solana uses a "hash that runs over itself continuously with the previous output used as the next input". Performing a hash over and over again takes some time. Then, someone can quickly verify that this "time" has occurred. The verification of the hashes can be parallelized on a GPU, which makes the verification extremely quick.
https://medium.com/solana-labs/proof-of-history-a-clock-for-...