Basic Mining Question

[GeminiSimba]

Hey so I'm sitting here at work (supposed to be doing tech support) but actually have that new Draper university online course playing in the background and going through it since why not properly learn the basics (in a structured way) even though I've been playing around in the space for about a year.

Anyways the question, so I've gotten a bit more understanding of the point of miners, we make a transaction and a node sends it to the miners and a transaction is "not" confirmed until at least 51% of the miners in the network make it official with the action of their problem solving... If this is the case, that me sending bitcoin to someone else or any transaction is ultimately only set in stone due to Miners, what exactly happens once all 21 million bitcoins are distributed? What will miners do? What will be the incentive to mine when they are all out? And, how will transactions be "confirmed" without miners when/if the mining is over?

Maybe I interpreted things wrong but...

[deepceleron]

A quote from my signature site: "Transactions fees may supplement, and must eventually replace, the diminishing block reward paid to miners."

It is economically uncertain if purely profit-motivated mining would maintain a sufficient difficulty against attack, however there will be holders of 20+M BTC at that time that will have an economic interest in the operation and stability of the network and may mine as part of their business interests.

[GeminiSimba]

A quote from my signature site: "Transactions fees may supplement, and must eventually replace, the diminishing block reward paid to miners."

It is economically uncertain if purely profit-motivated mining would maintain a sufficient difficulty against attack, however there will be holders of 20+M BTC at that time that will have an economic interest in the operation and stability of the network and may mine as part of their business interests.

Oh ok, transaction fees will supplement, that makes a lot of sense since in the hypothetical scenario we'd assume bitcoin (or whatever digital currency is the subject of interest) is a widely adopted coin on a global scale so the worth of 1 full bitcoin would probably be so immense that a miner just being paid on transactional fees will find that it's still worth it to mine. Gotcha.

[work2heat]

Right. It's also not the case that "51% of miners must confirm the transaction". Only one miner has to include your transaction in a block and "solve" that block (ie find a nonce such that the hash of the block header (which includes the nonce and a fingerprint of the transactions in the block) is less than some number), to have it officially added to the blockchain. Of course, most people wait for a few blocks before accepting the transaction as truly confirmed to protect against the possibility of some other blocks being released that replace the one with your transaction. It takes 51% to be able to guarantee control of what new blocks are added to the blockchain.