Electromagnetic waves take between ~4 and ~24 minutes (mean: ~14 minutes) to travel a one-way trip between Earth and Mars. Suppose I set up a Bitcoin network on Mars. Is it guaranteed to eventually fork from the Bitcoin network on Earth?
I would expect the Bitcoin network on Mars to fork from the one on Earth, because Bitcoin's target inter-block time is 10 minutes, which is less than average time it takes for electromagnetic waves to travel between Earth and Mars. Am I correct?
No, not necessarily, but mining in both locations is infeasible.
As Pieter explained in Is it possible to use bitcoin as interplanetary money/store of value?, exorbitant latency between miners would cause perpetual forks especially when the latency exceeds the targeted block interval. Only one of the two latency-separated mining clusters can be profitable: the stronger mining cluster will over-proportionally win cases of competing chain-tips, curbing the revenue of the weaker mining cluster due to mostly losing rewards to extinction of their blocks.
While mining is impractical, it would be possible to send and receive Bitcoin payments. Since communication between the planets could potentially be censored, a user located on Mars (i.e. the weaker mining cluster) must wait for an ample number of confirmations before relying on the payment's finality.
Yes, I'd say it's guaranteed to fork because a longer block time wouldn't mean higher latency is tolerated; it's assumed that all miners have infinitesimal-latency access to new blocks.
However, lots of blocks being orphaned doesn't mean a fork has to happen. I'm telling you a fork is guaranteed because of economical reasons: It's much healthier for every miner if there are two different networks but each having zero latency in itself. They can trade their coins when they need, which is much less destructive and variable than orphaning.
