Blockchains are considered to be introduced to the public by the BitCoin technology. There is one big, fundamental problem with them.
A blockchain is, as its name suggets, a chain of blocks. After a block is constructed, it is appended to the chain, to the list of blocks. BitCoin uses a mechanism based on cryptographic hash functions which tells nodes which block to accept as the next one.
There is nothing wrong with this mechanism in theory. There is, in practice, one fundamental problem.
The blockchain grows. And grows. And grows. It only grows. It never shrinks.
Looking at statistics available at Blockchain, the BitCoin blockchain has currently () around 99495 MiB in size. The chart shows a more or less exponential increase in time. In , the size of the blockchain was at around 14 GiB. In 2, 3 years, the size increased almost tenfold.
From what _ know, full nodes are supposed to store the blockchain in whole. If the current growth rate is maintained, in the size of the blockchain may be counted in TiB. Then in PiB. Then in EiB.
Who is it that would store so much historic data? Who is it that needs to know about a transaction made 10 years ago?
Does a full node really needs access to the whole chain in order to verify new blocks? If it does, then _ say with confidence – BitCoin has no future. The cost of running a full node will only increase. You will spend more than you earn. You will need to constantly maintain your full node, buying it more and more storage space. You will waste your time on something which brings you nothing in return. Might as well kill yourself.
There needs to be some kind of method of compression and archival. _ hope there is.