Payment channels are on-chain, just not necessarily in the most immediate block. The transactions are verified by checking their hash has the correct value in reference to the original mining rewards that it's inputs came from, just as they are now. The only difference is delaying the stage where the blockchain itself records where the money moved to. The delay provides an opportunity for patterns in the transaction flows to be aggregated together, meaning that when they are finally written to the blockchain, the space they use is far more efficient.
I like to think of this as "pre-chain", as all the same checks and balances are applied right up to the point where a normal transaction would just get processed in the next available block. And all the verification that happens pre-chain carries more than sufficient security and veracity to maintain Bitcoin's monetary properties.
wrong on so many levels
payment channels (lightening network) are multisigs.
say you want to spend funds regularly with a merchant.
you set up a multisig with the merchant, by both sides giving a public key to create a multisig address. they doublecheck the multisig is correct and matches to the same 3Bl4ahBlahBlahBlahBlah address before funding it.
both sides put funds in and lock them for X blocks (onchain)
onchain shows 2 deposits
eg person 1btc, merchant 1btc making so both sides have collateral and incentive to not mess around, because they both have something to lose
now without broadcasting to the network(offchain) person and merchant agree on who owes what amount of the funds in the multisig to each other and both sign the transaction (but dont transmit it onchain). it just sits in each others individual mempool, not random nodes.
making it a private transaction at this point
day 0 both parties agree merchant gets 0.1btc person gets 0.1btc, both sign
EG
the first day (offchain) both parties agree that when person buys a coffee merchant gets 0.11 person gets 0.09, both sign
the next day (offchain) both parties agree that when person buys another coffee merchant 0.12 person gets 0.08, both sign
the next day (offchain) both parties agree that when person buys another coffee merchant 0.13 person gets 0.07, both sign
and so on and so on.. untill the locktime has expired and both sides decide its time to settle the transaction by closing the channel and broadcast the most upto date transaction ONCHAIN.
carlton. please research harder
payment channels can be useful. but we should not rely on them for every transaction. just the ones where you would regularly spend and happy to and X funds over upfront so you dont have 10mins+ at the cashiers aisle.
signing the transaction of who owes what is a split second activity. thus allowing fast "spending"
the reasons we should not rely on merchants holding all the coin is that places like walmart and starbucks could become the new banks, by being the middleman required to authorise payments with people begging those middle men permission(to close channel) to pull out money to spend elsewhere..
we still need onchain scaling too, otherwise bitcoin becomes middlemen controlled by hub hoarding all the coins and we needing their signature to move our money