Why do miners help transfer bitcoins if they do not charge a fee for their services?
Do not worry, miners get money for contributing to the work of the blockchain. We can say they are paid by the creators of bitcoin. True, not personally – the reward for the preservation of information is provided for in the blockchain code. Saving information about the latest, not yet hashed bitcoin transactions is called block creation. For this, the miner receives bitcoins. Initially, the reward was 50 BTC, but every 210,000 blocks it is halved. Now for the creation of the block, miners receive 12.50 BTC. In addition, sometimes a transfer fee will have to be paid – if the message containing information about your transaction weighs more than 1000 bytes. Then the system will request a commission of 0.0001 BTC (15 rubles 3 kopecks at the exchange rate on 07/10/2017) for every 1000 bytes. But such heavy messages by the standards of the blockchain are very rare (one last week – check for yourself ). Also, the sender can appoint a reward to the miner himself, so that his transaction is processed in the first place.
Why do miners need video cards?
To earn more. Although there are some nuances tied to the nature of bitcoin. Bitcoins are finite. They can be created no more than 21,000,000. When this amount is reached, miners will no longer be given a reward for creating blocks. So that this does not happen too quickly, and Bitcoin inflation does not begin, new blocks can only be created once every 10 minutes. To create a block, the computer needs to solve the problem of selecting a number. Hundreds of computers all over the world are engaged in the solution at the same time, but the block will create only one – the one that first picked the right number. In this, mining is like a lottery. And the more the miner has the capacity to solve the problem (= lottery tickets), the more likely it is he who will create the block and receive a reward. Since the selection of numbers is a monotonous task, video cards do a good job of it. Therefore, they are bought in batches. True, now this is done rather by slow-blowers than seasoned miners. Because creating a farm for mining from video cards is already unprofitable – too much energy is consumed, too little profit. Bitcoin is not a fool either. In order for the blocks to be created stably every 10 minutes, approximately once every 2 weeks it adapts to new capacities. And if in the previous period, miners bought a bunch of equipment and created more blocks than was intended by the creators of the cryptocurrency, the tasks will become more complicated. And their solution will require even more resources.