We hear about sidechains and "layer 2" solutions a lot with Bitcoin. Usually, this centers around either (a) scaling solutions or (b) alternative use-cases. Normally, these layers involve a separate chain or system which then ultimately reconciles onto Bitcoin. The concept of these layer 2's is that the sidechain uses the security, immutability, and trust of Bitcoin to bolster itself and thereby achieve whatever goal that layer 2 holds.

As an example, the Lightning Network (LN) might be the most oft-used Bitcoin layer 2. The problems it tries to address are scaling, speed of transactions and high fees. The LN system uses Bitcoin to address these problems, does so fairly well, but with its own set of problems.

I've heard chatter of layer 3 solutions, though I'm unsure what distinguishes a layer 2 from a 3. During a podcast recently (I don't recall which podcast), when asked if Cashu was a layer 2 Bitcoin solution, the Cashu dev @calle said something like, "it's a layer 69." (He was implying that it's actually not a separate Bitcoin layer at all (apparently, saying it's a layer 69 is just more fun.) The point here is that there are layers. Or are there?

Bitcoin purists might disagree with the idea of layers altogether. There is only Bitcoin. Bitcoin does what it does and doesn't care about layers or talk of layers or what you think about layers. Bitcoin is.

Whether Bitcoin layers exist or not aside, the idea of a layer 0 has been tossed around a bit. If Bitcoin is layer 1, a layer 0 somehow precedes Bitcoin. I heard a discussion on this, I believe amongst panel members and perhaps at a Nashville conference in 2023. One of the members suggested Bitcoin's layer 0 is the people. (Sorry, again I don't recall whom it was to suggest this so I can't give credit.) The idea was that Bitcoin, at it's basic level, is about people and is the relationships between those people. Money is a representation of work done by people and value and debt owed to people for that work. So, Bitcoin is essentially a technological manifestation of these relationships between people. Bitcoin's blockchain and consensus mechanism records and resolves these relationships. Thus, the people are layer 0 and Bitcoin is layer 1.

Jameson Lopp wrote in 2017 Nobody Understands Bitcoin and That's OK. He suggested that the idea of people interacting was/is a fundamental tenet of Bitcoin. This was evident when he wrote, "bitcoin’s strength comes not from being the embodiment of some dogmatic beliefs of immutability, decentralization or other buzzwords, but from collaboration." That is, people working together.

Nostr might be Bitcoin's layer 0. Nostr is not Bitcoin, however it is connected. It's connected technically in it's decentralized structure and in that sats can be easily zapped. It's connected socially in that many Bitcoiner's are there, connecting, interacting, zapping in a permissionless, decentralized way.

Certainly, Nostr is not the only arena of Bitcoin's layer 0...the interaction of Bitcoiners. Anywhere, in any manner in which Bitcoiners interact, there is the layer 0. Yet, Nostr seems to offer a rather seamless integration of the technical and financial components of Bitcoin with a social component. Nostr gives Bitcoiners a way to connect socially and economically.

Sending sats over the layer 2 Lightning Network, person to person, is so seamlessly integrated into Nostr, the layers 0, 1, and 2 blur. Transferring 10k sats to another Nostrich, or saying "Nice write up" with a 100 sat zap, or simply messaging approval for a dog picture with a 21 sat zap, all integrate layers 0, 1, and 2. What's more, the layers of personal interaction, Bitcoin, and the Lightning Network don't even need to cross anyone's mind...it's just, "Sweet doggo! Here's some sats."

I like Bitcoin and I like dogs.