Understanding Orphan and Stale Blocks in Blockchain

I was reading this paper on Bitcoin and got confused by the part about orphan blocks. The paper said they just kind of happen along with everything else, but that doesn’t make sense to me. How can a block be discarded after it's already mined?

You might wanna check out this link instead. Way simpler than that paper! They didn’t mention this, but orphan blocks get created when two blocks are mined at the same height.

Yeah, orphan blocks can pop up at any height. If two miners hit the same block, both are legit at first but then chain reorganization happens. Only one stays valid based on which chain is the longest.

It's much clearer when you read that guide. They say it’s rare but possible for both blocks having the same transactions to be mined simultaneously. Then the next block decides which one is the longest and the other gets discarded.

In some places, they call them "stale" blocks instead of "orphan." Orphan blocks have no parents, which is just the Genesis block. You should try mining on easy difficulty to see it yourself. Sometimes two valid blocks show up!

That’s not right, you’re mixing things up. An orphan block has no valid parent according to the node, so it’s cut off from the main chain. Stats show no orphan blocks found since a while ago.

For real, that site's been broken. It’s only about stale blocks, and those still happen nowadays.

There’s a real difference between stale and orphan blocks. Orphan blocks are on hold because their parent ain't been mined yet, and they can be swapped out later.

I remember asking this about a couple years ago. Some old threads explain it better than I can.

It’s a common confusion, honestly. Orphan blocks never make it to the longest chain, which is kinda unavoidable unless mining becomes centralized.

Got it, that makes sense. So now it seems like orphan and stale blocks can kinda overlap in meaning.

Yeah, they do overlap sometimes. I got a good visual understanding from that diagram shared earlier in this thread. It's helpful to clarify the differences.