# Why is multi worlds not a good explanation for abiogenesis

post by solomon alon (solomon-alon) · 2019-04-12T18:53:58.908Z · score: 3 (4 votes) · LW · GW · 25 commentsI'm not a expert in the multi world theory. So this question could very well be extremely stupid. However, given the assumption that there are nearly infinite amount of worlds that are slightly different than each other, nearly every possible event would happen. This includes the formation of life. Now what are the odds that we would be witnessing that world, as far as I can tell 100 percent.

Now I'm not clear exactly how often quantum events lead to a slightly different world but even at the rate of 1 quantum event a year in the entire universe. should lead to a near infinite explosion of completely different universes.

Now I'm not claiming that this is the explanation for abiogenesis or that abiogenesis is proof of multi worlds because that would be multi worlds of the gap fallacy however I'm not clear why I have never even seen this explanation even once for abiogenesis.

I also suspect that mathematically many worlds would usually be the wrong explanation for nearly everything because it runs into serious odds problems and in 99.99999 percent of cases there is a better explanation. however it should at least be considered

COULD SOMEONE EXPLAIN TO ME EXACTLY WHERE I WENT WRONG

## 25 comments

Comments sorted by top scores.

In many worlds, everything happens, but not everything happens with equal "probability". Less miraculous paths towards life are *more likely *than more miraculous paths towards life. Thus, even if the life sees itself with probability 100%, it most likely sees itself evolved *the least miraculous *way.

So, at the end, we are in the same situation as we were before considering many worlds: looking for the most likely way life could have evolved, because that is most likely *our *history.

(In other words, many worlds *do *introduce miracles, but they still favor the solutions that *didn't *use them.)

that's what i thought but I was wondering why this is not used as a counter to theistic proof from abiogenesis

Many worlds is a model that currently has no testable predictions, no micro/macro connection, contradicts general relativity (which assumes there is a single spacetime), and in general proves too much: nearly anything can be a consequence of infinitely many worlds. Additionally, the observable universe has only 10^122 qubits, which limits the number of possible states, including possible worlds.

So, your best bet is to avoid invoking many worlds for explaining anything. You can certainly use possible worlds, as logical counterfactuals based on the lack of knowledge of the "real" world, to consider which decision would be best, for example. But not many worlds. Those currently have zero predictive power and 100% explanatory power, which is equivalent to "God did it".

I know almost no physics so this might be a stupid question, but aren't "makes no testable predictions" and "contradicts general relativity" contradictory? Wouldn't contradicting another theory imply some kind of a prediction?

That's a good point! I was definitely unclear, and even sloppy in my claims.

My first statement, "makes no testable predictions" refers to "pure" quantum physics, specifically quantum mechanics and quantum field theory on a fixed spacetime background, where what the matter is doing does not affect, in the first approximation, what happens to the spacetime itself (which is the subject of general relativity). We know it is not a good assumption in general, because it leads to contradictions like the various black hole evaporation paradoxes. But it works within certain limits. Within those limits, many worlds add absolutely nothing new and predictable.

Sadly, the extrapolation of QM to the realm where gravity is still weak but already matters, is still an uncharted territory, over 90 years later. The generally accepted claim (but only a claim) is that the unitary evolution part of the QM scales up into the macroscopic world in some way, and the measurement postulate emerges from this upscaling eventually. Many worlds make a more specific claim, that we live in many worlds, decohering (splitting) all the time, and that there is nothing new happening beyond the basic decoherence. However, there is still the gravitational footprint of those worlds, unless you figure out how they split the spacetime itself, as well. In that sense, many worlds make a claim in the domain where QM has never been observed that is incompatible with the theory that rules that domain. it is still just an ontological claim though, without any predictive power in it.

Not sure if this makes sense.

while i can't actually understand what your saying because I don't understand physics well enough. As far as I know its not controversial to use the multi world model in the less wrong forums and that most people I respect use it fully. Is what your writing relevant to my question or to the entire lesswrong that believe that the many worlds explanation is correct

its not controversial to use the multi world model in the less wrong forums and that most people I respect use it fully

the key word is "in the lesswrong forums". This is because Eliezer Yudkowsky, the founder and the main contributor for a long time, promoted both MWI and Bayesianism as cornerstones of rationality. Neither is necessary for either epistemic or instrumental rationality, but they are useful reasoning devices. No one really "uses" those directly to make decisions in life, even though most people pretend to. In actuality, they use those to justify the decisions already made, consciously or subconsciously. The reason is that the Bayes theorem relies on evaluation of probabilities, something humans are not very good at. At least not until you spend as much time as Eliezer, Scott and some others on self-calibration [LW · GW]. And MWI is generally used as a fancy name for "imagine possible outcomes and assign probabilities to them", which has nothing to do with physics whatsoever, when it is not misused for discussing quantum suicide/immortality, or, well, to justify anthropics.

nearly anything can be a consequence of infinitely many worlds

This feels like complaining that if you flip a coin million times, all outcomes are possible.

Why do you call it complaining?

I stipulate that nearly anything can be a consequence of MWI, but not with equal probability. If I see a thousand quantum coinflips in a row all come up heads, I don't think "well, under MWI anything is possible, so I haven't learned anything". So I'm not sure in what sense you think it proves too much.

(I think this is roughly what Villiam was getting at, though I can't speak for him.)

I stipulate that nearly anything can be a consequence of MWI, but not with equal probability.

Note that MWI postulates unitary evolution of the wave function, and in unitary evolution there are no probabilities, everything is completely deterministic, no exceptions. None. Let it sink in:

*NO PROBABILITIES. PURE DETERMINISM OF THE WAVE FUNCTION EVOLUTION*

There have been numerous attempts to saddle this unitary evolution with something extra that would give us the empirically observed probabilities. Everett suggested some in his PhD, many others did, with marginal success. The only statement nearly everyone is on board with is that, if we were to look for a way to assign probabilities, the Born rule is the only sensible one. In that sense, the Born rule is not an arbitrary one, but a unique way to map wave function to probability. The need to get probabilities from the unitary evolution of the wave function is not built into the MWI, but is grafted on it by the need to connect this theory with observations, exactly like the Born rule in the Copenhagen interpretation was.

That said, we might be on the cusp of something super mega extra interesting observed in the next few years, much more so than the recent black hole doughnut seen by the EHT: Measuring gravitational field from Schrodinger cat-like objects. There are no definite predictions on what we will see in this case, because QM and general relativity currently do not mix, and this is what makes it so exciting. I have mentioned it in a blog post discussing how MWI emerges from unitary evolution:

https://edgeofgravity.wordpress.com/2019/01/19/entanglement-many-worlds-and-general-relativity/

There is some discussion of this issue online, and I have mused about it on my blog some time ago:

https://edgeofgravity.wordpress.com/2019/02/25/schrodingers-cattraction/

I'm still not entirely clear what you mean by "MWI proves too much".

If I try to translate this into simpler terms, I get something like: MWI only matches our observations if we apply the Born rule, but it doesn't motivate the Born rule. So there are many sets of observations that would be compatible with MWI, which means P(data | MWI) is low and that in turn means we can't update very much on P(MWI | data).

Is that approximately what you're getting at?

(That would be a nonstandard usage of the phrase, especially given that you linked to the wikipedia article when using it. But it kind of fits the name, and I can't think of a way for the standard usage to fit.)

It seems like we are talking about something similar. If you interpret MWI as "anything can happen with some probability, and, given that we are here observing it, the posterior probability is obviously high enough", then you can use it to explain anything. I agree that my usage was not quite standard, but it fits somewhat, because you can use MWI to justify any conclusion, including an absurd one.

The nub of the argument is that every time we look in our sock drawer, we see all our socks to be black.

Many worlds says that our socks are always black.

The Copenhagen interpretation says that us observing the socks causes them to be black. The rest of the time the socks are pink with green spots.

Both theories make identical predictions. Many worlds is much simpler to fully specify with equations, and has elegant mathematical properties. The Copenhagen interpretation has special case rules that only kick in when observing something. According to this theory, there is a fundamental physical difference between a complex collection of atoms, and an "observer" and somewhere in the development of life, creatures flipped from one to the other.

The Copenhagen interpretation doesn't make it clear if a cat is a very complex arrangement of molecules, that could in theory be understood as a quantum process that doesn't involve the collapse of wave functions, or if cats are observers and so collapses wave functions.

Many worlds says that our socks are always black.

Nope. What distinguishes worlds, if their contents are the same?

The Copenhagen interpretation says that us observing the socks causes them to be black.

Nope. That would be consciousness-causes-collapse. Which is a different theory.

According to this theory, there is a fundamental physical difference between a complex collection of atoms, and an "observer" and somewhere in the development of life, creatures flipped from one to the other.

You seem to refer to some strawman version of the Copenhagen interpretation that no physicist subscribes to. Being brainwashed by Eliezer's writings can do that. He is very eloquent and persuasive. Consider reading other sources. Scott Aaronson's blog is a good start. Wikipedia has a bunch of useful links, too.

Consider a theory to be a collection of formal mathematical statements about how idealized objects behave. For example, Conways game of life is a theory in the sense of a completely self contained set of rules.

If you have multiple theories that produce similar results, its helpful to have a bridging law. If your theories were Newtonian mechanics, and general relativity, a bridging law would say which numbers in relativity matched up with which numbers in Newtonian mechanics. This allows you to translate a relativistic problem into a Newtonian one, solve that, and translate the answer back into the relativistic framework. This produces some errors, but often makes the maths easier.

Quantum many worlds is a simple theory. It could be simulated on a hypercomputer with less than a page of code. There is also a theory where you take the code for quantum many worlds, and add "observers" and "wavefunction collapse" with extra functions within your code. This can be done, but it is many pages of arbitrary hacks. Call this theory B. If you think this is a strawman of many worlds, describe how you could get a hypercomputer outside the universe to simulate many worlds with a short computer program.

The bridging between Quantum many worlds and human classical intuitions is quite difficult and subtle. Faced with a simulation of quantum many worlds, it would take a lot of understanding of quantum physics to make everyday changes, like creating or moving macroscopic objects.

Theory B however is substantially easier to bridge to our classical intuitions. Theory B looks like a chunk of quantum many worlds, plus a chunk of classical intuition, plus a bridging rule between the two.

The any description of the Copenhagen interpretation of quantum mechanics seems to involve references to the classical results of a measurement, or a classical observer. Most versions would allow a superposition of an atom being in two different places, but not a superposition of two different presidents winning an election.

If you don't believe atoms can be in superposition, you are ignoring lots of experiments, if you do believe that you can get a superposition of two different people being president, that you yourself could be in a superposition of doing two different things right now, then you believe many worlds by another name. Otherwise, you need to draw some sort of arbitrary cutoff. Its almost like you are bridging between a theory that allows superpositions, and an intuition that doesn't.

"Now I'm not clear exactly how often quantum events lead to a slightly different world"

The answer is Very Very often. If you have a piece of glass and shine a photon at it, such that it has an equal chance of bouncing and going through, the two possibilities become separate worlds. Shine a million photons at it and you split into worlds, one for each combination of photons going through and bouncing. Note that in most of the worlds, the pattern of bounces looks random, so this is a good source of random numbers. Photons bouncing of glass are just an easy example, almost any physical process splits the universe very fast.

The problem is that, at some level, pure Boltzmann brains become more probable than quantum abiogenesis. That is, if abiogenesis is very improbable, than appearing of the whole conscious mind from the ocean full of amino acids become more probable, and such mind unlikely will observe the whole evolutionary history.

However, as we observe abiogenesis, it means that this event is more probable than Boltzmann brain formation, and such probabilities could be calculated. Some cosmologists did it.

It seems weird that given our laws of nature it would be more probable that boltzmann brains would form because boltzmann brains are more complicated than rna as far as I could tell

I thought the whole problem with boltzmann brains was in the fine tuning argument and the multiverse

Could you also link me to a good explanation of the odds of boltzmann brains

Thank you

thanks for the reply

Can you please link me to these cosmologists

Start here reading articles by Page, Carroll, Smolin, Linde, Bostrom.

while i have not read the link you sent and I plan on

They all seem to be referring to the fine tuning argument vs abiogenesis

thanks