ok.. back to basics
I know it isn't all that fun for pros to explain it that basic, so THANK YOU for taking your time! It is highly appreciated, and I want you to know that!
imagine i have a chequebook..
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so a cheque is not cleared until the bank makes the transfer where only one recipients cheque is going to clear. (as it should be)
But with a bank, they would simply confirm the first cheque cashed (Dave), when there was money enough, and deny the second (Betty), when the account was too low. Right? There is no real evaluation of either cheque's validity, just first come first served, and maybe some consequence for the writer of the cheques. Or so I think, never wrote or cashed a cheque in my life...
so.. the mining is replacing the bank clearing house.
.. this answers your first question in first post about why users cant just collect transactions and deem them as valid independently
Sorry for being dense (it is an old crse of mine...), but I still fail to see how the mining truly adds to the validity/trust in the included transactions. I think I am missing some clever detail. To me, speedy confirmation and thus spreading information on a transaction makes the difference, just as it would with the two cheques example.
.....
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now to stop other bank clearing houses making multiple batches in milliseconds declaring them the sole central bank
the batch ID have to go through a lengthy process of of calculations. to get a special batch id with several leading zeros.
the first bank clearing house to get this result. and check that the data and ID correspond. wins
and that batch(block)) is declared the confirmed block. and all the transactions listed within it are declared as confirmed(cleared)
inshort dont accept a payment as final/cleared until its confirmed and in a block
This actually puts a bit more of a point on it, but still leaves some.... confusion. Demanding PoW means a 'bank' cannot simply pack doubles by the thousands. Which ever 'cheque' gets cashed into a block supported by PoW gets confirmed. And if later blocks have the other cheque, they get discarded as doubles. I kiiinda get that. But how is this an improvement over the initial spread of the transaction through the network? First come is still first served, it seems. The blocks just cements one batch of transactions over another. The network should have already weeded out doubles by discarding the later transaction.
Those nodes cummulatively contribute to the decentralization and alos the digitization of the ledger system. Normally, these things were been done by one person or institution in the regular regional way of finance but looking at it from a decentralised system, it eliminates the need for trust and also the possibility of an easy hack. it is necessary to have all those nodes as they all help to make the network safer.
I know the basics, the problem is that I am not quite getting how this exact method adds significantly to the validity. The overall theory makes perfect sense and is, in a way, beautiful, but there are just some aspects that I feel a need to really pick apart to get a firm grasp on. This is one such aspect.