The author's opinion:

Miners have high capital investment in the form of ASIC mining machines. These machines rely on SHA-256 being the mining hash algorithm in order to be able to create new Bitcoin blocks.

I believe that in the case of a 51% attack, the greatest threat the Bitcoin community has against miners is switching the mining hash algorithm. This would make all SHA-256 ASICs completely useless, therefore highly disincentivizing a 51% attack in the first place.

The new hash algorithm used could be provably randomly picked to ensure no advantage is given to any entity. The new algorithm should be easy to ASIC so that the same properties are kept for a possible future 51% attack.

We should keep in mind, In case of a 51% attack there is always the remaining 49% who will keep mining regular blocks. That would give time for bitcoiners to launch a counter attack (bitcoiners get into mining who were previously not, switch mining pools etc).

Also it is immensely non profitable for an entity launching the 51% attack whose revenue depends on the protocol they are attacking. So, any rational being driven by motive of profit will not support it. So, the attack can come only from the government.

In a multipolar world getting governments to agree on a single goal is not possible. Also for any country that goes against such a coalition the reward will be hard to resist. (more mining, bitcoin capital moving to the country) along with increased transaction fees due to reduced number of real blocks.

so what should we do? - we should just let the free market economics to play out and thank the attacker for speeding up hyperbitcoinization!

Dance off.

It's a psyop

If a 51% majority of the hashrate started to flat out ignore blocks, then the rest of the miners can exercise a couple different options (the options below are non-exhaustive):

If 1 were to happen we would see a lot of reorgs and lose confidence in transaction finality by transactions mined by honest (solely profit-driven) miners. For the majority malicious miners, they'd be able to create some concept of finality but would have to deal with the ongoing noise from honest miners.

If 2 were to happen then you'd occasionally have the honest chain overtake the malicious parts of the chain in the beginning, but would approach a point where the malicious miners would overtake the honest chain by a significant amount.

With 3 it would be a war of attrition on who would run out of money first. If I was an honest miner I'd probably stop broadcasting blocks and selfish mine on the tip when the malicious hashrate lowers. This is on the assumption that malicious miners would run out of money eventually. Changing the permissionless mechanics are sure to cause impacts to the price of Bitcoin and if the dishonest miners are choosing selectively off a whitelist from a pool of transactions, they'd definitely be missing out on profits.

What selfish mining would allow me to do is hide my hashrate from the malicious miners and coax them into spending as much money as they can maintaining the existing hashrate for a short period of time, or stretch out their operation by lowering their hashrate. Both would be favorable to me in the context of a counterattack.

As I write this, I acknowledge there are many other scenarios, and decisions that can be made in those scenarios, but I'd need to write a much longer post to expand on them. My personal beliefs are that with the way things are structured, Bitcoin will always win out in the end as long as there's a population that acknowledges its usefulness.

I don't think this scenario is discussed, so here:

The aftermath would be disasterous, since all transactions which occured during the time would be invalidated. Altough it's probably impossible to do, this would, in fact, harm bitcoin. This why, imo, it's important to have a steady hashrate growth, without massive drops.

What should happen?! It shouldn't happen! 😂

My plan is to just freeze to death if the sun disappears tonight.

The worry about a 51% attack, I have never really understood it. Can someone explain why they actually think it is an important threat? The only thing one can do with a 51 attack is double spend one's own coins. You can not steel anyone else's coins, you can not change the consensus rules. OK so you want to to double spend your own coins. I mean how much are we talking about here? you want to spend 500 mio 1 shot? and if so the person on the other of the transaction is not going to be suspicious? they will not say for that I want 10 blocks for the transaction to be confirmed? or someone wants to spend billions to "de-stabilize" the network to prove a point. I mean what is the big threat really? I don't get it

My guess: There will be a hard fork. Some nodes stick to the longest chain, others will consider that chain invalid. Market will determine which chain has more value. The more malicious the 51% attacker behaves, the more likely nodes will consider that chain invalid and switch to the fork