Understanding blockchain ‘behind the scene’ how a block is created

Bitcoin newbie here: I’m trying to understand the concept of the blockchain but what I don’t get is what’s going on behind the scenes?

So let’s say that there are only 10 miners in the universe and Alice sends 15 BTC to Bob, what happens now?

I understand that a verification needs to happen (to ensure that Alice has 15 BTC to transfer)

  1. Assume miner_1 gets this ‘request’ and verifies the request as valid. Does he build a block?
  2. How a block is created? Is it created for every request?
  3. How all nodes on the network are being updated that there s a request/new block?
  4. When SHA256(SHA256(transaction?) occurs? On verification or when adding a block? Is there a good example that shows how this works?
  5. How the miner who managed to find the hash get’s a reward?

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Understanding a Bitcoin Double Spending Transaction by Performing one on yourself

Everyone talks about preventing a double spend transaction, but how does one do one to yourself in order to better understand the steps involved by the attacker?

  • What is required to do a double spend? Two phones running the same btc wallet?
  • Do you send at the same exact time?
  • Is it random a double spend happens when sending to multiple addresses?
  • How do certain online services that don’t wait for the 1st confirmation stay in business? Wouldn’t every attacker want to scam that no-confirmation service?
  • What are some preventive measures a business can use to prevent a double spend aside from waiting for 1-confirmation.

Recent Questions – Bitcoin Stack Exchange