
Can the multiverse explain human history? - jonbaer
http://www.aeonmagazine.com/world-views/can-the-multiverse-explain-the-course-of-history/
======
pstuart
I prefer this version, if only for the spiritual component:

[http://www.galactanet.com/oneoff/theegg.html](http://www.galactanet.com/oneoff/theegg.html)

~~~
Namrog84
Always one of my favorite storied to share with people. It always helps people
open their mind and perspective on things.

------
eli_gottlieb
No. The anthropic principle/branching universes theory _explains_ nothing, and
in fact is so utterly unfalsifiable it's kind of surprising intelligent people
take it seriously.

~~~
gjm11
I wonder exactly what "it" is here.

Quantum mechanics with the "many worlds" interpretation explains lots of
things: it explains all the same things as quantum mechanics with some other
interpretation. But QM (many worlds) has all the same observable consequences
as, say, QM (Copenhagen), so "many worlds" _as opposed to_ Copenhagen doesn't
explain anything[1].

But how does that mean that intelligent people shouldn't take the "many
worlds" interpretation seriously?

Consider two "interpretations" of Newtonian mechanics. One says that the world
mechanically obeys Newton's laws. Another says that the world is controlled by
incorporeal angels who are very fond of Newton's laws and always freely choose
to push the universe around in such a way that those laws are obeyed. These
two interpretations have the same observable consequences (namely, a universe
in which Newton's laws always hold), but that doesn't make it surprising if
intelligent people take the "mechanical" version of it seriously.

Nor, actually, does it make it surprising if intelligent people take the
"angels" version seriously. What (at least for me) makes that option hard to
take seriously is its gratuitous complexity: it has the same observable
consequences as the "mechanical" system but, at least in my view, is vastly
more complicated -- if you wanted to describe such a universe completely you'd
need to do all the same work as for the "mechanical" version and then go on to
set down everything about the angels' nature, personalities, etc.

In much the same way, you might choose to prefer "many worlds" or Copenhagen
or some other specific interpretation of QM on the grounds of simplicity.
"Many worlds is simplest because it avoids notions of 'measurement' and
'collapse' that do no real work, and just says that everything obeys
Schroedinger's equation all the time." Or: "Many worlds is horribly complex
because it involves all those extra worlds we never observe."

So if you mean: "The many-worlds interpretation of QM explains nothing more
than any other interpretation of QM does, and therefore it's surprising that
intelligent people take the many-worlds interpretation seriously", I think
that's wrong. But perhaps what you're surprised that people take seriously is
some other thing like, e.g., some particular application of the anthropic
principle that appeals to "many worlds"?

[1] Actually, that's maybe slightly debatable; it depends on fine details of
what you understand by "explain". For instance: any theorem in pure
mathematics is logically necessary[2] and therefore has _no_ observable
consequences that you couldn't derive without it -- but it still seems
reasonable to say, e.g., that a proof that even-length palindromes have to be
multiples of 11 "explains" why I've never seen a palindromic prime number with
4, 6, 8, ... digits. So the fact that QM (many worlds) has no extra observable
consequences beyond "uninterpreted" QM might not be enough to guarantee that
it doesn't explain anything.

[2] Given whatever axioms you start with.

~~~
chrislipa
While there are Occam's razor and complexity arguments concerning the relative
merits of the Many Worlds Interpretation and the Copenhagen Interpretation, I
think this is at best a weak argument. Because, who knows? We could actually
be living in a world with very complicated physics.

However, there's a different flaw that I believe completely torpedoes the
Copenhagen Interpretation: the Copenhagen Interpretation is not a fully
specified theory because it never actually gets around to defining when a
measurement is performed. What algorithm can an experimenter run to tell when
a measurement takes place? There is none. When a system is considered to be
"measured" is always determined with the help of human judgement ex post
facto, and alway in such a way as to fit the experimental outcome. If
proponents of the Copenhagen Interpretation ever proffered such algorithm to
determine when a measurement takes place, then at least we'd have something
testable, even if the test were outlandish. But as it is now, the lack of such
concrete specification makes the Copenhagen Interpretation unfalsifiable with
respect to the Many Worlds interpretation.

Besides that, there are a couple other weaker reasons to be very suspicious of
the Copenhagen Interpretation. It doesn't seem to address in any way the fact
that experimenters and detectors are a part of physics themselves. If you
believe that consciousness arises from physical processes happening inside of
the universe, it's very hard to imagine how the Copenhagen Interpretation
would compute and explain (even in theory) the physics of what's happening
inside of the brain. [1] And if waveform collapse _actually_ occurred, it
would be the only known law of physics that's non-local, inherently random,
has a preferred reference frame (breaking relativity), destroys information,
and violates CPT symmetry. This rule is not like the other rules.

[1] - There actually is a serious school of thought that conscious beings
brings the universe into existence, rather than the other way around. I don't
know of any experimental evidence for or against this theory, but I'm
personally not a big fan of it because the Kolmogorov complexity required to
fully specify the theory is fantastically large, because it would need to
fully specify how consciousness operates. Without a corresponding amount of
evidence in its favor, there's no reason to elevate this hypothesis among all
the others with the same or less complexity.

~~~
chrischen
> While there are Occam's razor and complexity arguments concerning the
> relative merits of the Many Worlds Interpretation and the Copenhagen
> Interpretation.

Exactly, we don't know anything, but Occam's razor is all we have, and I
believe many smart people take many-worlds seriously because it is simpler.

~~~
chrislipa
I hope someone will correct me if I'm wrong, but I _think_ Many Worlds is the
simplest known hypothesis that explains the available evidence.

~~~
VladRussian2
the simplest is statistical aggregate interpretation.

An interpretation of QM experiments depends on your interpretation of QM :)
When one sees the world through Copenhagen interpretation (i.e. superposition
of states, simultaneously dead/alive cat) one sees miracles like entanglement,
and starts wondering about many worlds, etc... On the other side one can look
at Hitachi's electron double-slit experiment :

[http://www.youtube.com/watch?v=ZJ-0PBRuthc](http://www.youtube.com/watch?v=ZJ-0PBRuthc)

It doesn't refute superposition, it just allows to interpret/explain things
without it. Of course with superposition gone, quantum computers are gone, and
no miracles like entanglement, and many worlds while still may exist lose a
potent argument in their favor :)

(note: the experiment clearly shows 2 separate things:

1\. the main point of QM that, for example, position of a particle is
described by wave-function/quantized

2\. superposition of many positions is visible as a characteristic of the
whole set of particles

Bringing in additional superposition at the level of one particle doesn't add
anything for explanation, it only brings "miracles" that Copenhagen
interpretation is filled with )

~~~
chrislipa
While, you're right, it is minimalistic, Einstein's Statistical Ensemble
Interpretation is an incomplete theory. It doesn't tell you which possible
future you'll end up in. And if you try to patch the theory by saying there's
some deeper element of reality that we just haven't found yet that's deciding
the outcome of experiments, then the violation of the Bell Inequalities
renders that whole line of thinking moot. If, instead, you try to patch it the
other way and say that everything in the ensemble _is_ real, then you've just
reinvented Many Worlds by a different name.

I'm unclear why you're bringing up Hitach's experiment and what you think it
shows. Maybe you could elaborate? My understanding is that the raison d'être
of the experiment is to show that multiple particles are not necessary for
quantum interference to occur, and that a single particle is perfectly capable
of destructively interfering with itself. This is pretty direct evidence for
superposition, because you're getting measurable effects from the
superposition. And if anything, it's evidence against the Ensemble
Interpretation.

Also, quantum computers are real and here today. Any successful theory of
physics must explain how 15 was factored using Shor's Algorithm.
([http://arxiv.org/abs/quant-ph/0112176](http://arxiv.org/abs/quant-
ph/0112176))

~~~
VladRussian2
>Einstein's Statistical Ensemble Interpretation is an incomplete theory. It
doesn't tell you which possible future you'll end up in.

not sure that we're talking about the same. My understanding here is that one
calculates probabilities the same way. It is the interpretation different. In
Copenhagen the particle is supposed to carry all probabilities which magically
"collapse" on the measurement, while in statistical a given particle is in
"collapsed" state to start with (there is a distribution of the states over
the ensemble), and the probabilistic model describes the evolution of these
states and distribution of final states - there is no collapse on measurement,
we just measure specific state.

>I'm unclear why you're bringing up Hitach's experiment and what you think it
shows. Maybe you could elaborate? My understanding is that the raison d'être
of the experiment is to show that multiple particles are not necessary for
quantum interference to occur, and that a single particle is perfectly capable
of destructively interfering with itself.

in Hitachi experiment it is shown explicitly clear that quantum interference
is emerging only for multiple particles. It is basically a visualization of
underlying probability distribution, like it happens in any statistical
experiment when enough samples are taken. During the Hitachi experiment
nothing happened that looks like or requires an explanation by a single
particle supposedly interferencing with itself.

If you don't see this in Hitachi experiment, lets run the following
experiment. Imagine 2 doors in a wall, and imagine another, parallel, wall at
several meters distance from the doors. Imagine that frogs jump out, one at a
time, from either door pretty randomly. The frogs jump in general direction of
the wall opposite the doors. The precise direction of each frog is varying a
bit. It takes a frog several jumps to reach the wall. The probability density
of the places where the frog's legs touch the ground is square of cos(pi*x/A)
(correctly scaled to be a probability density) where x is the distance from
the door the frog jumped out, and A is the avg. frog jump length. A frog only
exist (i.e. can interact with anything else) when it touches the ground, and
doesn't exist when it is flying during the jump. Whenever a frog lands near
the wall, say not farther than a body distance from the wall, it touches the
wall and leaves a wet spot.

It is easy to see that after a big enough bunch of frogs, there would be an
"interference pattern" of dry and really wet areas on the wall - i.e. some
places have low probability of a frog landing near it while some have high,
and that probability distribution looks like an "interference pattern". No
superposition, no destructive interference of a frog with itself is necessary
to observe the effect. This is what Hitachi experiment shows.

>This is pretty direct evidence for superposition,

yes, an interference of a particle with itself would be such evidence. I'm yet
to learn about an experiment which can only be explained by such interference.

> Any successful theory of physics must explain how 15 was factored using
> Shor's Algorithm.

agree. While 15 seems too small a number to exclusively lock a superposition
explanation, i don't have another ready. I'd like to have quantum computers
and other quantum miracles too :) I just want them to be a bona fide miracles,
not figments of our interpretation :)

~~~
chrislipa
The way you're describing the theory sure seems like the Ensemble
Interpretation to me, but to be honest, I have never heard of the "Statistical
Aggregate Interpretation". Just to be sure I know what we're discussing, could
you provide a reference to the Statistical Aggregate Interpretation? What
you're suggesting -- that the information is there, but we just don't know
which one -- sounds a lot like a hidden variables theory. Unfortunately, all
theories with local realism (which includes hidden variables theories) are
ruled out experimentally by Bell's theorem. [1]

I like your classical frog example because it's a thought experiment that
illustrates how classical particles behave, and we can compare the
distribution of the classical frogs to the distribution of whatever we're
measuring (like electrons), and if the distributions we get are different,
then we'll learn that whatever we're measuring is behaving non-classically.
However, the probability density you gave for the frogs in the classical case,
cos^2(pi*X/A), is incorrect. The probability distribution for the classical
case the way you set it up will, in fact, be almost Gaussian (but not
precisely for reasons that aren't relevant or worth discussing here)[2]. The
combined probability distributions for frogs coming from the two doors will be
the sum of two individual Gaussians, so it will be a "two-humped"
distribution. As a point of fact, if you run your frog experiment, there will
be two wet spots. It will not look like an interference pattern precisely
because there is no superposition and no destructive interference. The fact
that electrons in Hitachi's experiment display a "many-humped" distribution is
good evidence that the electrons are not following the same rules as the
frogs, and hence that the electrons are behaving non-classically.

> in Hitachi experiment it is shown explicitly clear that quantum interference
> is emerging only for multiple particles.

This is the exact opposite of what the Hitachi experiment shows. The
experiment is interesting and surprising precisely because particles are sent
one at a time but still show an interference pattern. The experiment shows a
single particle interfering with itself.

[1]
[http://en.wikipedia.org/wiki/Bell%27s_theorem](http://en.wikipedia.org/wiki/Bell%27s_theorem)

[2] It's easy enough to show the general idea with a Monte-Carlo simulation.

~~~
VladRussian2
>The way you're describing the theory sure seems like the Ensemble
Interpretation to me, but to be honest, I have never heard of the "Statistical
Aggregate Interpretation".

yes, my mistype, it is basically Ensemble Interpretation.

> However, the probability density you gave for the frogs in the classical
> case, cos^2(pi*X/A), is incorrect.

it isn't resulting probability distribution on the wall. It is probability
distribution of the frog legs touching the ground on a radial line from door
to the wall, i.e. peaks at 0, A, 2A, 3A,.... It is about the same as position
operator for electron would produce on a radial line from slit to the screen.
Also note that the frog doesn't interact with the wall if the frog is
"airborne" (i.e. one can imagine that it just goes through the wall without
leaving a wet spot or even better - the wall is too low, say 0.1m , so
airborne, mid-flight, frogs would fly over it).

If you look at this image

[http://micro.magnet.fsu.edu/primer/java/interference/doubles...](http://micro.magnet.fsu.edu/primer/java/interference/doubleslit/doubleslitjavafigure1.jpg)

the red concentric lines is where a frog most probably touches the ground and
the greenish-yellow - where a frog is most probably mid-jump airborne (flying
at the height enough to fly over the wall). Where 2 yellow-greenish lines
intersect right near the wall - it is the place with minimal probability of a
frog landing near the wall, ie. dry place. While intersection of 2 reds -
correspondingly a very wet place.

>The fact that electrons in Hitachi's experiment display a "many-humped"
distribution is good evidence that the electrons are not following the same
rules as the frogs, and hence that the electrons are behaving non-classically.

this non-classical behavior is the quantization of position, ie. position
probability density looks like concentric waves starting at a slit. I.e. cut
along the radial line, the profile of that density is a correctly scaled
cos(x), with x - distance from the slit. The superposition isn't necessary for
the observed effect.

>> in Hitachi experiment it is shown explicitly clear that quantum
interference is emerging only for multiple particles.

>This is the exact opposite of what the Hitachi experiment shows. The
experiment is interesting and surprising precisely because particles are sent
one at a time but still show an interference pattern. The experiment shows a
single particle interfering with itself.

i'm trying to understand where do you see the interference of a particle with
itself. Lets say the experiment was run only until there is only 1 (i.e. 2 sec
into the clip), or say 3 particles hit the screen (4 seconds into the clip).
What would be an indication of the interference in such a case?

~~~
chrislipa
Ah, I see. Yes, I did misunderstand the mechanics of your frog thought
experiment. However the math for the classical case still doesn't work out the
way you need it to. Setting up the mechanics the way you did, you will not get
the probability distribution you mentioned on the frog's radial distance from
the wall. Nor will you get many alternating wet and dry spots on the wall,
even allowing for frogs to jump through the wall. I encourage you to try the
math yourself or to set up a Monte-Carlo simulation to estimate the classical
consequences of your jumping rules.

If you're not convinced yet, consider the following:

What happens if Hitachi's experimental setup had only one path for the
electron to follow rather than two? You're claiming that the frogs are a good
model for Hitachi's setup, so it should be the same result that you claim for
the frog model with one door. You're claiming that the frog model with one
door produces a pattern of alternating wet and dry. What happens in the lab
when you try it with electrons? Electrons following a single path _don 't_
produce an alternating pattern; they produce a pattern very close to a
Gaussian.

Moreover, here's the really wild part of the experiment. If you let electrons
go through either just one path or just the other path, you'll get nice smooth
Gaussians from both (translated a bit from each other). But open both paths
up, you'll see the distribution dim at places. That's very unexpected! Somehow
letting more electrons through has decreased the electrons hitting certain
parts of the screen. And if you carefully observe your experiment, you'll see
that some other areas of the wall _more_ than double in intensity when you
open up both paths. It's pretty clear that you'll never be able to invent
mechanical rules for classical frogs that can mirror these experimental
results.

> i'm trying to understand where do you see the interference of a particle
> with itself.

This is a slightly subtly distinction, and it's easy to miss what's going on.
You "see" the effect of a particle destructively interfering with itself when
there's only a single electron on the screen. You "see" the effect in the
probability distribution for where that electron appears, but you can't say
with high confidence that this is a real effect until you've seen a
statistically significant number of particles. But the effect had to have been
there the whole time because destructive interference happens independently
and individually on each electron. If you still think there's some effect
being transmitted between different electrons, then realize that the fact that
all the electrons are showing up on the same screen is just a convenience for
the experimenter. You would get exactly the same effects by setting up a
statistically significant number of screens all spatially separated from each
other and running the experiments without signals being able to be
communicated between screens and then overlaying the resultant observed
positions.

However, the Mach–Zehnder Interferometer is, I believe, an better physical
model to witness a single photon interfering with itself. Young's double-slit
experiment was invented first, so for really that reason alone, it's taught
first, but because of its continuous nature, it's easier to get bogged down in
certain irrelevancies. The Mach–Zehnder Interferometer is really much more
plainly impossible in a classical universe, or an ensemble interpretation
universe for that matter.

~~~
VladRussian2
> Nor will you get many alternating wet and dry spots on the wall, even
> allowing for frogs to jump through the wall.

...

>What happens if Hitachi's experimental setup had only one path for the
electron to follow rather than two? You're claiming that the frogs are a good
model for Hitachi's setup, so it should be the same result that you claim for
the frog model with one door. You're claiming that the frog model with one
door produces a pattern of alternating wet and dry. What happens in the lab
when you try it with electrons? Electrons following a single path don't
produce an alternating pattern; they produce a pattern very close to a
Gaussian.

The electrons, photons, and frogs (jumping over the wall when probability
below some threshold) would produce an alternating pattern like this one:

[http://www.a-levelphysicstutor.com/images/waves/ys-1s-2s-gra...](http://www.a-levelphysicstutor.com/images/waves/ys-1s-2s-graphs.jpg)

Because it is result of the same geometry as on the image that i posted before
: where 2 greens touch the wall simultaneously - deep trough, zero intensity,
and where 2 reds - peak. The meaning of the green/red isn't important - be it
probability of a frog's legs touching ground or the probability density of
position of electron - the resulting pattern is the same. The image can be
interpreted as either while it is just an image of concentric circles
originating from 2 points. Gaussian outline comes to play only because it
describes the normal deviation of a frog/electron from the preferred direction
they jump/fired along.

> If you let electrons go through either just one path or just the other path,
> you'll get nice smooth Gaussians from both (translated a bit from each
> other).

this is true only in classical mechanics where position of electron or a
bullet isn't quantized - you'll get a smooth Gaussian. In QM, i.e. real
electrons, photons (or jumping frogs having the property of going through/over
the wall where ground touch probability is close to 0) single slit produces
dim/light pattern like on the image above. Like the double-slit pattern, this
single-slit pattern is also result of position quantization.

> But open both paths up, you'll see the distribution dim at places. That's
> very unexpected! Somehow letting more electrons through has decreased the
> electrons hitting certain parts of the screen.

This - double slit is more frequent than single-slit or dimming at some places
- happens only for stream of photons as photons interfere with one another and
the photon's wavelength is the same as its position quantization period (note
- for electron DeBroglie and positional quantization are different
wavelengths), so the photon_A-photon_B interference is visible on the scale of
the pattern produced as a result of positional quantization. In case of
Hitachi, we have single electrons, so no electron_A-to-electron_B
interference, so the double-slit pattern is less frequent than single-slit,
ie. where was light on single slit - there will continue to be the same or
brighter light on double-slit, it is just some (not all) troughs/dims will
disappear.

> You "see" the effect in the probability distribution for where that electron
> appears

The quantized position probability distribution already explains the pattern.
I don't see how adding the interference or superposition changes it.

>If you still think there's some effect being transmitted between different
electrons

no, the many particles, i.e. many samples is just results in better
visualization of underlying probability distribution. I think here we agree.

> You would get exactly the same effects by setting up a statistically
> significant number of screens all spatially separated from each other and
> running the experiments without signals being able to be communicated
> between screens and then overlaying the resultant observed positions.

the same here. We agree about independent events and their cumulative
statistics. Let frogs jump in separate setups, and mark their results on a
separate screen - the pattern will emerge as if they all jumped in the same
yard.

>However, the Mach–Zehnder Interferometer is, I believe, an better physical
model to witness a single photon interfering with itself.

Will definitely spend a time on it.

> Young's double-slit experiment was invented first, so for really that reason
> alone, it's taught first, but because of its continuous nature, it's easier
> to get bogged down in certain irrelevancies.

it only looks somewhat "continuous" with light. That is the beauty of the
Hitachi experiment as it took away a lot of "continuity" effect as well as
"photon A interfering with photon B" effect.

------
guard-of-terra
Even if multiverse exists, I doubt it would ever influence your day-to-day
life, much less history.

It's too low level. It's all about quantum states, and we're like ten levels
above them.

Low level processes tend to either go unnoticed by high level ones (think
radio waves) or be harmful to them (think radiation) by messing with their
high-level organization.

So please forget about hiding a knife in a parallel universe.

~~~
TelmoMenezes
You do realise that this high-level / low-level distinction is all in our
minds, right? It's just an intellectual tool we use to understand nature. If
Quantum Mechanics is correct, _everything_ is made of quantum states, not just
radio waves and radiation. Also, Chaos Theory.

~~~
gizmo686
True, but under our current understanding of QM, it is literally impossible
for you to interact with parallel worlds. Someone 'outside' the universe may
observe[0] that we are in a superposition, but it is theoraticly impossible
for our state to be influenced by any of the other states.

[0] Under a loose definition of observe.

------
spindritf
I still don't really know how it would explain human history but I enjoyed the
scroll through ideas.

------
stared
As a side comment, a story inspired by many-words:
[http://physicsnapkins.wordpress.com/2013/05/20/all-paths-
to-...](http://physicsnapkins.wordpress.com/2013/05/20/all-paths-to-
happiness/)

