user-1: I am interested in experimenting with layer 2 solutions like Lightning, Liquid, Rootstock etc. Is "spacechain" a new concept and how does it improve Bitcoin ecosystem?
What are space chains? How is it different from sidechain? What are its use cases? Where can I read more about it?

user-1: Spacechains are a combination of two ideas, blind merge mining and perpetual one-way peg. The combined concept is called space chains.
Mentioned few points from the transcript of Youtube Video by Ruben Somsen: https://www.youtube.com/watch?v=N2ow4Q34Jeg

So the key points are we're going to create some kind of blockchain but we're going to do it by outsourcing mining to the bitcoin blockchain with only a single transaction per block so there's not going to be a lot of overhead on the bitcoin blockchain.
It's going to be a trustless chain. Multiple trustless chains as many chains as you like that can be created in a permissionless way and they essentially serve the bitcoin ecosystem there's not going to be any altcoin trying to be bitcoin.
No speculative asset involved. This is hopefully going to open a door to more permissionless innovation where essentially anyone can create blockchains that serve the bitcoin ecosystem.
One caveat that needs to be said is its not a two-way peg so this is not going to be a system where you take your bitcoin you move to a space chain and then you do your thing there and you move back.
Comparison with "sidechains" concept : The one it doesn't hit on is there's no trustless two way back. However it allows permissionless chain creation without another speculative asset and it serves the bitcoin ecosystem. I think that is one of the dream of what sidechain idea was all about.
What is a Blockchain? It's an open database essentially but it's an open database that is rate limited by sacrifice and in the case of bitcoin obviously the sacrifice is proof of work. Essentially anyone can create a block, if too many blocks come in at the same time or within a certain time frame the difficulty goes up so this naturally rate limits how many blocks can be created. This ensures that even though it's an open database that anybody can add data to there's never going to be too much data there's only going to be roughly two megabytes every every 10 minutes right now. So the interesting thing is that the resulting scarcity at least in the way bitcoin did it can be tokenized because there can only be one block every 10 minutes on an average.
One interesting thing quite underappreciated is that Satoshi came up with a way to do mining or leave it to other people to do mining. The importance of it cannot be understated as you don't have to take your transaction and put it into block yourself, mine it but what you can do is just add a fee and anyone can take it you after you send it over through the p2p network. Anyone can take those transactions put them into a block and claim the fee for themselves if they're successful and that's a non-interactive process. It is really one of the key things that makes bitcoin work and maybe it looks obvious in hindsight.
So roughly what we're trying to do here is create yet another blockchain or multiple blockchains but we want to skip the tokenization step as we don't want to create yet another another altcoin.
Everything else we kind of need for "spacechain". We need an open database that's rate limited by sacrifice and we need some kind of way to outsource the mining where we just send our transaction and somebody else puts into a block for us so these two features are basically what we're going to try and recreate.
The mechanism I am using here to create a blockchain is called blind merge mining. Essentially you use the bitcoin blockchain or use bitcoin to simulate or emulate mining. Maybe I burn a bitcoin or maybe I lock up my bitcoin or maybe I waste a bunch of block space in the background blockchain which is a
terrible idea don't do that but it works. Fee bidding is in my opinion the better of these options although they all can work to some extent and the reason for that is very space efficient and it's fully incentive compatible where if somebody tries to censor you it essentially works the same way bitcoin works where it's costly to censor somebody. In terms of space efficiency as I already told you what we're going to get it down to one transaction per block. So there's also regular merge mining and I have to specify that it is better than regular merge mining because with regular merge mining you need bitcoin miners to essentially participate, run the software and create blocks for you and here in this system anybody can create a block, anybody can propose it to the miners and the miners just take whoever pays them the most in bitcoin fees.



All the slides related to "Spacechains": https://docs.google.com/presentation/d/1QbLS6-OLhkNlZVrHme843NM0AyPWz-qU3OYLEsOzByA/edit
Usecases:

Create tokens
Decentralized DNS without an altcoin
Trust minimized stablecoin
DEX, DAO and other Decentralized Finance applications you can think of

Reddit post: https://www.reddit.com/r/Bitcoin/comments/kbwzxg/spacechains_permissionless_blockchains_for_bitcoin/

-1: <p>I am interested in experimenting with layer 2 solutions like Lightning, Liquid, Rootstock etc. Is &quot;spacechain&quot; a new concept and how does it improve Bitcoin ecosystem?</p>
<p>What are space chains? How is it different from sidechain? What are its use cases? Where can I read more about it?</p>
 -1: <p><strong>Spacechains</strong> are a combination of two ideas, <a href="https://gist.github.com/RubenSomsen/5e4be6d18e5fa526b17d8b34906b16a5" rel="noreferrer">blind merge mining</a> and <a href="https://medium.com/@RubenSomsen/21-million-bitcoins-to-rule-all-sidechains-the-perpetual-one-way-peg-96cb2f8ac302" rel="noreferrer">perpetual one-way peg</a>. The combined concept is called <em>space chains</em>.</p>
<p>Mentioned few points from the transcript of Youtube Video by <a href="https://twitter.com/SomsenRuben" rel="noreferrer">Ruben Somsen</a>: <a href="https://www.youtube.com/watch?v=N2ow4Q34Jeg" rel="noreferrer">https://www.youtube.com/watch?v=N2ow4Q34Jeg</a></p>
<ol>
<li>So the key points are we're going to create some kind of blockchain but we're going to do it by <em>outsourcing mining</em> to the bitcoin blockchain with only a single transaction per block so there's not going to be a lot of overhead on the bitcoin blockchain.</li>
<li>It's going to be a <em>trustless chain</em>. Multiple trustless chains as many chains as you like that can be created in a permissionless way and they essentially serve the bitcoin ecosystem there's not going to be any altcoin trying to be bitcoin.</li>
<li><em>No speculative asset involved</em>. This is hopefully going to open a door to more permissionless innovation where essentially anyone can create blockchains that serve the bitcoin ecosystem.</li>
<li>One caveat that needs to be said is its not a two-way peg so this is not going to be a system where you take your bitcoin you move to a space chain and then you do your thing there and you move back.</li>
<li>Comparison with &quot;<em>sidechains</em>&quot; concept : The one it doesn't hit on is there's no trustless two way back. However it allows permissionless chain creation without another speculative asset and it serves the bitcoin ecosystem. I think that is one of the dream of what <em>sidechain</em> idea was all about.</li>
<li>What is a <em>Blockchain</em>? It's an open database essentially but it's an open database that is rate limited by sacrifice and in the case of bitcoin obviously the sacrifice is proof of work. Essentially anyone can create a block, if too many blocks come in at the same time or within a certain time frame the difficulty goes up so this naturally rate limits how many blocks can be created. This ensures that even though it's an open database that anybody can add data to there's never going to be too much data there's only going to be roughly two megabytes every every 10 minutes right now. So the interesting thing is that the resulting scarcity at least in the way bitcoin did it can be tokenized because there can only be one block every 10 minutes on an average.</li>
<li>One interesting thing quite underappreciated is that Satoshi came up with a way to do mining or leave it to other people to do mining. The importance of it cannot be understated as you don't have to take your transaction and put it into block yourself, mine it but what you can do is just add a fee and anyone can take it you after you send it over through the p2p network. Anyone can take those transactions put them into a block and claim the fee for themselves if they're successful and that's a non-interactive process. It is really one of the key things that makes bitcoin work and maybe it looks obvious in hindsight.</li>
<li>So roughly what we're trying to do here is create yet another blockchain or multiple blockchains but we want to skip the tokenization step as we don't want to create yet another another altcoin.</li>
<li>Everything else we kind of need for &quot;spacechain&quot;. We need an open database that's rate limited by sacrifice and we need some kind of way to outsource the mining where we just send our transaction and somebody else puts into a block for us so these two features are basically what we're going to try and recreate.</li>
<li>The mechanism I am using here to create a blockchain is called <em>blind merge mining</em>. Essentially you use the bitcoin blockchain or use bitcoin to simulate or emulate mining. Maybe I burn a bitcoin or maybe I lock up my bitcoin or maybe I waste a bunch of block space in the background blockchain which is a
terrible idea don't do that but it works. Fee bidding is in my opinion the better of these options although they all can work to some extent and the reason for that is very space efficient and it's fully incentive compatible where if somebody tries to censor you it essentially works the same way bitcoin works where it's costly to censor somebody. In terms of space efficiency as I already told you what we're going to get it down to one transaction per block. So there's also regular merge mining and I have to specify that it is better than regular merge mining because with regular merge mining you need bitcoin miners to essentially participate, run the software and create blocks for you and here in this system anybody can create a block, anybody can propose it to the miners and the miners just take whoever pays them the most in bitcoin fees.</li>
</ol>
<p><a href="https://i.stack.imgur.com/Pt18B.png" rel="noreferrer"><img src="https://i.stack.imgur.com/Pt18B.png" alt="Fee Bidding- BMM" /></a></p>
<p><a href="https://i.stack.imgur.com/nXH7V.png" rel="noreferrer"><img src="https://i.stack.imgur.com/nXH7V.png" alt="P1WP" /></a></p>
<p>All the slides related to &quot;Spacechains&quot;: <a href="https://docs.google.com/presentation/d/1QbLS6-OLhkNlZVrHme843NM0AyPWz-qU3OYLEsOzByA/edit" rel="noreferrer">https://docs.google.com/presentation/d/1QbLS6-OLhkNlZVrHme843NM0AyPWz-qU3OYLEsOzByA/edit</a></p>
<p><strong>Usecases</strong>:</p>
<ul>
<li>Create tokens</li>
<li>Decentralized DNS without an altcoin</li>
<li>Trust minimized stablecoin</li>
<li>DEX, DAO and other Decentralized Finance applications you can think of</li>
</ul>
<p>Reddit post: <a href="https://www.reddit.com/r/Bitcoin/comments/kbwzxg/spacechains_permissionless_blockchains_for_bitcoin/" rel="noreferrer">https://www.reddit.com/r/Bitcoin/comments/kbwzxg/spacechains_permissionless_blockchains_for_bitcoin/</a></p>
