In Segwit, people agreed to put signatures in a separate space called "witness". Why do you think they won't agree to put the whole chain in a separate space (called "archive"?).
Witness is not separate at all. It is an inseparable part of the transaction like any other parts (version, locktime, input count,etc.). Any full node sees this part and fully verifies it (any node that doesn't see or verify it is no longer a full node).
What you are suggesting is eliminating the history meaning the full nodes can no longer verify "everything".
Thanks (and I
can’t believe can totally believe that we are still correcting these misconceptions five years later).
However, a node that doesn’t see these data is still a full node. It won’t be able to validate Segwit rules; and as a practical matter, it has quite limited functionality as most people move to Segwit. The concept of a softfork is to make consensus validation rules
more restrictive; the outdated node will apply laxer rules which are a strict subset of the current rules.
Nonetheless, the old node still has the same security
for its own non-Segwit funds as it always did. Consensus validation of pre-Segwit transactions works just the same as before; and a pre-Segwit full node can still follow the correct chaintip, without the SPV/light-wallet vulnerability of being misled onto a malicious minority fork.
The import of this backwards compatibility is driven home by experience with blockchains where a centralized dev team can effectually force upgrades; there are even some chains where you can lose your money if you fail to upgrade timely. In Bitcoin, your money is safe even if you don’t upgrade to the latest Core; and the Bitcoin Core developers deliberately make sure that they do
not have the power to coerce nodes to upgrade.
There are not a few technical howlers in this thread. Another one, just for instance:
to build centralized systems upon a decentralized system, but not the other way around
It depends what do you mean by "centralized" and "decentralized". I can imagine a scenario, where all coins would flow inside the Lightning Network, then all on-chain transaction fees could be gone, and then guess, what will happen next: you will have a system that will run out of coins. Miners will mine all 21 million coins in circulation, and what then? No new coins, so the basic block reward would be zero. And then imagine that all coins could be locked in some LN channels, and stay there. If so, then miners will stop mining (because of no incentive), and then the whole chain will stop, because the whole life will be present entirely in some lower layers.
Lightning Network is entirely dependent on the blockchain. If miners stop mining, then Lightning loses its security. The whole concept of Lighting is to maintain, in effect, private local ledgers that can be enforced by recourse to the global ledger (blockchain) in case of attempted theft.
By dead simple logic, it is also obvious that if Lighting or a Lightning-style network
could function without the blockchain, then we would shut down the blockchain right now. Why would anyone pay the costs of mining, if a Lightning-style network could function without it? Although I myself have some criticisms of Lightning, the benefit of running L2 without L1 would so drastically outweigh the downsides that it’s a clear win—unless it wouldn’t work it all, which it wouldn’t.
(Nit, but a telling one: The blockchain
is the lower layer; Lightning is the upper layer.)
On these and other points: Please stop speculating wildly on Bitcoin’s future without adequate technical knowledge. Regardless of your intentions, all it achieves is to sow misinformation, rumours, and FUD.
With my apologies, I am still behind on replies to some others who addressed me above. I’ll be back...