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What's the minimum number of bitcoin nodes needed for it to continue operating and is it reasonable to think that post collapse that many PCs will remain online

What's the minimum number of bitcoin nodes needed for it to continue operating and is it reasonable to think that post collapse that many PCs will remain online? Seems unlikely to me.

monokh 6y ago
2 powered raspberry pis and a moderately functioning internet is the answer. The network adjusts it's requirement for power based on the total power thrown at it. This is called "difficulty adjustment". Beyond total world collapse that would set society back a century, I cannot imagine a scenario where you couldn't continue running Bitcoin as long as a few people had the motivation.
- exdsq 6y ago
  Solar flare?
- Sebb767 6y ago
  If they had the motivation, yes. However, why would the have the motivation instead of simply using well-known limited physical currencies, such as cigarettes, gold etc? Especially since you'd need to make the money using power and if power is sparse, you'd probably need the bit you get for refrigeration or cooking.
friendzis 6y ago
Minimum? 1. That is, however, not the problem. The problem is that in the event of sudden loss of significant fraction of compute power block times skyrocket, because significantly reduced compute power still has to solve problem of previous difficulty. As a consequence block times become so high that transactions are effectively blocked and the only solution to keep the network functional is a fork. Unless you imagine a scenario where everyone goes offline except for a small group and everyone slowly reconnects to the small group, most likely there would be highly partitioned network with its own bitcoin fork with enough of transaction history that a reconnect would mean collapse of local-economy.
- hanniabu 6y ago
  The difficulty will adjust for the reduced compute power
  - ulrikrasmussen 6y ago
    AFAIK it adjusts after a fixed number of blocks have been mined. So if 99.999% of your compute power is gone, you won't be mining enough blocks to adjust the difficulty for a very long time.
  - monokh 6y ago
    The adjustment happens every 2 weeks. It's unlikely that miners would go offline simultaneously across the globe to the extent that it would completely grind the network to a halt.
    - 0x0 6y ago
      No, the adjustment happens every 2016 blocks. If you lose 99.99% of global hash rate, those 2016 blocks will take a million years, instead of two weeks, to compute.
      - hanniabu 6y ago
        Like Unbreakablecoin lmao
      - sv0 6y ago
        It will take about 400 years to adjust difficulty in such case, but not a million years.
      - monokh 6y ago
        Good point, I had taken the mechanism for granted. So the scenario is that miners drop off at a pace where you don't reach the next adjustment? Taking that into account, the "mining death spiral" theory doesn't seem too far fetched? In bad circumstances, if the network drops a substantial amount of hash rate early in the adjustment, and price took a hit, you could see some major disruption from the miners following suit.
drtillberg 6y ago
If the hypothetical crisis divides up the Internet so, for example, U.S. users only can connect to U.S. nodes, and connect to U.S. miners -- and the same is true for Iceland and China and South Africa etc., it would become extremely perilous to trade value for the currency anywhere in the world, right? Because the geographically-separate chains cannot synchronize in any reasonable way. A breakdown of the Internet by geography is definitely a crisis that should be on radar screens, and it wouldn't require anything like a total societal breakdown. Then HAM TOR and whatever else would become essential to keep the network stable.
- alwillis 6y ago
  If the hypothetical crisis divides up the Internet so, for example, U.S. users only can connect to U.S. nodes, and connect to U.S. miners You know that's not how TCP/IP works, right? It originally was a defense department research project that had the requirement of surviving a nuclear attack. Unless every undersea cable is severed and every satellite up-link destroyed, the internet will continue to operate in the event something bad happens. I live in New England; I'm closer to Iceland than I am to California for network purposes. Every full node has copy of the entire blockchain going back to the genesis block created on January 3, 2009. The blockchain may fork, but the longest chain wins and the majority of the mining power will pick that and bitcoin keeps on going. Full nodes will continue to verify those blocks. Nearly all miners are in data centers with redundant power and networking, so many of them will stay online. Many of them are using hydroelectricity, so unless rivers stop flowing, most of them should be good to go. Bitcoin already has a peer-to-peer exchange running on Tor; folks will still be able to exchange Bitcoin for fiat, to the extent that remains useful [1]. I’d imagine the software would be modified to support things other than fiat that would be useful to exchange. With a link-local IPv6 "subnet", you could have thousands of machines on a make-shift mesh network and all you'd need is an uplink to the internet to transact. [1]: https://bisq.network/ https://bisq.network/

What's the minimum number of bitcoin nodes needed for it to continue operating and is it reasonable to think that post collapse that many PCs will remain online? Seems unlikely to me.

monokh 6y ago

2 powered raspberry pis and a moderately functioning internet is the answer. The network adjusts it's requirement for power based on the total power thrown at it. This is called "difficulty adjustment". Beyond total world collapse that would set society back a century, I cannot imagine a scenario where you couldn't continue running Bitcoin as long as a few people had the motivation.

exdsq 6y ago
Solar flare?
Sebb767 6y ago
If they had the motivation, yes. However, why would the have the motivation instead of simply using well-known limited physical currencies, such as cigarettes, gold etc? Especially since you'd need to make the money using power and if power is sparse, you'd probably need the bit you get for refrigeration or cooking.

friendzis 6y ago

Minimum? 1. That is, however, not the problem. The problem is that in the event of sudden loss of significant fraction of compute power block times skyrocket, because significantly reduced compute power still has to solve problem of previous difficulty. As a consequence block times become so high that transactions are effectively blocked and the only solution to keep the network functional is a fork. Unless you imagine a scenario where everyone goes offline except for a small group and everyone slowly reconnects to the small group, most likely there would be highly partitioned network with its own bitcoin fork with enough of transaction history that a reconnect would mean collapse of local-economy.

hanniabu 6y ago
The difficulty will adjust for the reduced compute power
- ulrikrasmussen 6y ago
  AFAIK it adjusts after a fixed number of blocks have been mined. So if 99.999% of your compute power is gone, you won't be mining enough blocks to adjust the difficulty for a very long time.
- monokh 6y ago
  The adjustment happens every 2 weeks. It's unlikely that miners would go offline simultaneously across the globe to the extent that it would completely grind the network to a halt.
  - 0x0 6y ago
    No, the adjustment happens every 2016 blocks. If you lose 99.99% of global hash rate, those 2016 blocks will take a million years, instead of two weeks, to compute.
    - hanniabu 6y ago
      Like Unbreakablecoin lmao
    - sv0 6y ago
      It will take about 400 years to adjust difficulty in such case, but not a million years.
    - monokh 6y ago
      Good point, I had taken the mechanism for granted. So the scenario is that miners drop off at a pace where you don't reach the next adjustment? Taking that into account, the "mining death spiral" theory doesn't seem too far fetched? In bad circumstances, if the network drops a substantial amount of hash rate early in the adjustment, and price took a hit, you could see some major disruption from the miners following suit.

drtillberg 6y ago

If the hypothetical crisis divides up the Internet so, for example, U.S. users only can connect to U.S. nodes, and connect to U.S. miners -- and the same is true for Iceland and China and South Africa etc., it would become extremely perilous to trade value for the currency anywhere in the world, right? Because the geographically-separate chains cannot synchronize in any reasonable way. A breakdown of the Internet by geography is definitely a crisis that should be on radar screens, and it wouldn't require anything like a total societal breakdown. Then HAM TOR and whatever else would become essential to keep the network stable.

alwillis 6y ago
If the hypothetical crisis divides up the Internet so, for example, U.S. users only can connect to U.S. nodes, and connect to U.S. miners You know that's not how TCP/IP works, right? It originally was a defense department research project that had the requirement of surviving a nuclear attack. Unless every undersea cable is severed and every satellite up-link destroyed, the internet will continue to operate in the event something bad happens. I live in New England; I'm closer to Iceland than I am to California for network purposes. Every full node has copy of the entire blockchain going back to the genesis block created on January 3, 2009. The blockchain may fork, but the longest chain wins and the majority of the mining power will pick that and bitcoin keeps on going. Full nodes will continue to verify those blocks. Nearly all miners are in data centers with redundant power and networking, so many of them will stay online. Many of them are using hydroelectricity, so unless rivers stop flowing, most of them should be good to go. Bitcoin already has a peer-to-peer exchange running on Tor; folks will still be able to exchange Bitcoin for fiat, to the extent that remains useful [1]. I’d imagine the software would be modified to support things other than fiat that would be useful to exchange. With a link-local IPv6 "subnet", you could have thousands of machines on a make-shift mesh network and all you'd need is an uplink to the internet to transact. [1]: https://bisq.network/ https://bisq.network/