@DannyHamilton, thanks for your quick response.

When you say "everyone else is going to relay the block anyhow" and "the miner doesn't gain anything by refusing to relay the block," what is this assumption based on? I think this is the sticking point I'm having trouble understanding.

From your answer to my second question, my thoughts are that since most of the nodes are not mining nodes on the network and their only job is to validate blocks and transactions, they don't have anything at stake by validating the block and relaying it to other nodes. Therefore, refusing to relay the block becomes pointless. If this is the case, then the comments you made make sense to me. Is this correct?

Thanks @ranochigo and @monsterer2 for the replies to my question. @DannyHamilton, also thank you for offering to talk on the phone. I will try to ask my questions here so that hopefully everyone can benefit.

In regards to the first question I asked, here's a scenario I was thinking of that might better illustrate my question:  

Let's say a miner solves a block and sends it to 5 other nearest nodes (all of which are miners or mining pools) in the network. Those 5 nodes would have to validate the solved block in order for it to propagate through the network. Why would any of those 5 nodes validate another miner's solved block? Wouldn't they want the reward for themselves and choose not to validate the solved block at all? That way, they can solve the block themselves and send their solution to the network instead to get the reward for themselves.


On a related note, @DannyHamilton, I saw a post on the forum you made here: https://bitcointalk.org/index.php?topic=1734235.0

You mentioned that not all nodes are miners or mining pools. Do you have an idea of what percentage of the nodes on the network are non-miners or volunteers whose only job is to validate transactions and blocks and relay the block to other nodes? Also, is there something in the consensus rules that require full nodes (miners and non-miners) to validate solved blocks that they receive?

Hi, I'm new to Bitcoin and had a couple questions that I've tried to research, but haven't been able to find a good answer that I could understand and accept.

1. What's the incentive for peers to validate blocks? I figured miners wouldn't want to validate other miners' blocks in hopes they can get their own block validated instead and collect the reward.

2. I don't understand why you would need 51% or more mining power to alter a transaction? Why is it more secure for more than 50% of the nodes to be independent?

3. Why is the blockchain more secure each time a new block is mined? Why does hacking the blockchain require tremendous speed?

Also, does anyone know a Bitcoin expert who is willing to discuss more about some of these questions in detail over the phone perhaps?

Thanks in advance for any input you can provide.