Do computers defy the law of conservation of mass? Because, if a computer can copy a program there is twice the amount of space taken up. But how can you just duplicate an amount of space (MB, KB, GB,etc.) if you add nothing to it?
The only mass involved in computer memory is the mass of the electronic components that make up the memory, and this mass is unchanged when information is stored in memory. If your computer has, say, 256 MB of memory, then it has memory chips inside it that are capable of holding 256 MB of information. When information is stored in memory, the physical state of those memory chips is changed, but no new mass is added. Perhaps an analogy will help. Imagine a row of ten coins sitting on a table. By letting tails represent 0 and heads represent 1, you could think of this row of coins as a primitive kind of memory, capable of storing a sequence of ten 0's and 1's. You would store such a sequence of 0's and 1's by flipping over some of the coins in order to get the appropriate sequence of heads and tails. Flipping the coins changes their physical arrangement, but not their mass. So mass is conserved during this operation.