I think what OP means is to separate from the network, and mine with a really low hashrate. Then, because of the lack of blocks found, the difficulty in OP's network would drop by a lot, and he/she would use a large amount of hashing power to catch up and overtake the main network's blocks.
cutepuppy is even more correct than i am
as cutepuppy says
if you separated yourself from the main network at block 2015 exactly... the difficulty adjusts to the timing of that hashrate (which ofcourse is still MANY petahashs,
THEN
its your turn, at still 35,000,000,000 difficulty(because average still based on the many petahash of that last cycle). now YOU have to get 2016 blocks to get your network to adjust down, because now its based on your hashrate. so yea it wont be 2 weeks as thats based on the main networks rate and they have the power to solve blocks every 10 minutes. so you will be sat there for months/years trying to get 2016 blocks to force the difficulty to adjust down.
so by the time it has adjusted down. the main network will be many many cycles of 2016 blocks ahead of you, that catching up wont help. and as i said initially by the time you try to rejoin the network, you are still going to be behind the main network. meaning your chain will be ignored.
but lets get imaginative. lets say you did catch up. infact lets say you found a way to overtake.. usually you would find that your dozen connections to proper international peers of the main net will see your chain. and compare it to the chain they have and see that your transactions do not correspond with theirs. so even if not "orphaned" it will simply not get accepted