The observer at the end of time: Of immortal watchers and imaginary data
November 9, 2014 1:01 AM   Subscribe

In a Multiverse, What Are the Odds? "Testing the multiverse hypothesis requires measuring whether our universe is statistically typical among the infinite variety of universes. But infinity does a number on statistics." (previously)
Bousso and his collaborators' causal-diamond measure has now racked up a number of successes. It offers a solution to a mystery of cosmology called the "why now?" problem, which asks why we happen to live at a time when the effects of matter and vacuum energy are comparable, so that the expansion of the universe recently switched from slowing down (signifying a matter-dominated epoch) to speeding up (a vacuum energy-dominated epoch). Bousso's theory suggests it is only natural that we find ourselves at this juncture. The most entropy is produced, and therefore the most observers exist, when universes contain equal parts vacuum energy and matter.

In 2010 Harnik and Bousso used their idea to explain the flatness of the universe and the amount of infrared radiation emitted by cosmic dust. Last year, Bousso and his Berkeley colleague Lawrence Hall reported that observers made of protons and neutrons, like us, will live in universes where the amount of ordinary matter and dark matter are comparable, as is the case here.
When parallel worlds collide, quantum mechanics is born (via)
First, we postulate a fixed, although truly gigantic, number of worlds. All of these exist continuously through time — there is no "branching."

Second, our worlds are not "fuzzy" — they have precisely defined properties. In our approach, a world is specified by the exact position and velocity of every particle in that world — there is no Heisenberg uncertainty principle that applies to a single world. Indeed, if there were only one world in our theory, it would evolve exactly according to Newtonian mechanics, not quantum mechanics.

Third, our worlds do interact and that interaction is the source of all quantum effects. Specifically, there is a repulsive force of a very particular kind, between worlds with nearly the same configuration (that is, having nearly the same position for every single particle). This "interstitial" force prevents nearby worlds from ever coming to have the same configuration, and tends to make nearby worlds diverge.

Fourth, each one of our worlds is equally real. Probability only enters the theory because an observer, made up of particles in a certain world, does not know for sure which world she is in, out of the set of all worlds. Hence she will assign equal probability to every member of that set which is compatible with her experiences (which are very coarse-grained, because she is a macroscopic collection of particles). After performing an experiment she can learn more about which world she is in, and thereby rule out a whole host of worlds that she previously thought she might be in.

Putting all of the above together gives our theory — the Many Interacting Worlds approach to quantum mechanics. There is nothing else in the theory. There is no wavefunction, no special role for observation and no fundamental distinction between macroscopic and microscopic.

Nevertheless, we argue, our approach can reproduce all the standard features of quantum mechanics, including twin-slit interference, zero-point energy, barrier tunneling, unpredictability, and the Bell correlations mentioned above.
An infinite multiverse: A bad idea or inescapable? "Two areas of physics say there may be another you in a different universe." (via)

also btw...
-Viewpoint: Arrow of Time Emerges in a Gravitational System
-How Time Flies: Tracking the Arrow of Time
-Researchers Tackle Complex Question of Time's Arrow
-How Gravity Explains Why Time Never Runs Backward
-How Building a Black Hole for Interstellar Led to an Amazing Scientific Discovery
-Scientists Close In on Creating Black Hole in Lab
posted by kliuless (47 comments total) 37 users marked this as a favorite
 
Paul Steinhardt, a theoretical physicist at Princeton University and one of the early contributors to the theory of eternal inflation, saw the multiverse as a “fatal flaw” in the reasoning he had helped advance, and he remains stridently anti-multiverse today. “Our universe has a simple, natural structure,” he said in September. “The multiverse idea is baroque, unnatural, untestable and, in the end, dangerous to science and society.”

Wow! I'd like to hear more about how it undermines society. It just promotes nihilism, or something, to think that we aren't living in the One True Universe? Anything goes, man - it'll all be made good in some other universe?
posted by thelonius at 1:34 AM on November 9, 2014


Dancers, not just observers.
posted by mwhybark at 1:39 AM on November 9, 2014 [1 favorite]


Reminds me of one of my earliest (and funnest) AskMe questions: Oh, boy, parallel universe #57339! That's where I'm a Viking. Lots of interesting answers.
posted by Rhaomi at 2:02 AM on November 9, 2014 [2 favorites]


Probability only enters the theory because an observer, made up of particles in a certain world, does not know for sure which world she is in, out of the set of all worlds.
It looks like the plot of Coherence.
posted by elgilito at 2:17 AM on November 9, 2014


Proponents of the multiverse idea must show that, among the rare universes that support life, ours is statistically typical. The exact dose of vacuum energy, the precise mass of our underweight Higgs boson, and other anomalies must have high odds within the subset of habitable universes. If the properties of this universe still seem atypical even in the habitable subset, then the multiverse explanation fails.
Correct me if I'm wrong, but I thought the mass of the Higgs boson is what indicated a multiverse in the first place. That a higher or lower mass indicates how distributed the variety of life-supporting universes are within the multiverse (with the lowest reasonable mass indicating a unique, supersymmetric universe). But I also don't have a clear understanding of the difference between our definitional universe and "a region where cosmic inflation has stabilized." Is inflation supposed to be interchangeable with space-time?

Such abstract theorizing... I'm inclined to Bousso et alia's approach to take things one step at a time. Why does the Big Bang and inflation within our universe suggest the entire multiverse to be "eternally inflating" and infinite? And why attempt to comprehend a cross-section of the entire thing at once? How does one even comprehend the space or interaction (if any exists) between the "bubbles" of universes?
posted by Johann Georg Faust at 3:00 AM on November 9, 2014 [1 favorite]


"Nevertheless, we argue, our approach can reproduce all the standard features of quantum mechanics, including twin-slit interference, zero-point energy, barrier tunneling, unpredictability, and the Bell correlations mentioned above."

This is fun.
posted by vapidave at 3:50 AM on November 9, 2014


" The basic premise of sorcery for a sorcerer is that the world of everyday life is not real, or out there, as we believe it is. For a sorcerer, reality, or the world we all know, is only a description."
So Don Juan (Carlos Casteneda) was right.
posted by JohnR at 5:06 AM on November 9, 2014


This is fun.

Yep, it's all fun and games... until one unknown genius in a basement invents a way to slide between and lets the Kromaggs enter our small quiet universe.
posted by sammyo at 5:16 AM on November 9, 2014 [2 favorites]


Wow! I'd like to hear more about how it undermines society.

There's a Larry Niven story for that!
posted by moonmilk at 5:16 AM on November 9, 2014 [4 favorites]


"The multiverse idea is baroque, unnatural, untestable and, in the end, dangerous to science and society.”

I never understand why the first idea gets a pass just because it was a first. The single universe idea is no more natural or testable. And "baroque" is only a matter of perspective. If you have a mechanism for creating universes (which both the single and mult-universe ideas must), then doesn't the single universe theory need an *extra* mechanism for *stopping*?
posted by DU at 5:21 AM on November 9, 2014 [4 favorites]


The most entropy is produced, and therefore the most observers exist, when universes contain equal parts vacuum energy and matter.

Doesn't the expansion of the universe itself produce entropy, insofar as it increases the volume of space and therefore the number of possible microstates? If so, doesn't that make expansion inevitable, so long as it remains possible?

The single universe idea is no more natural or testable.

We can prove that at least one universe exists. We can't yet prove that multiple universes exist (or don't exist). Therefore, I think the conservative position would be to assume just the one for now.
posted by dephlogisticated at 5:27 AM on November 9, 2014 [3 favorites]


In 2010 Harnik and Bousso used their idea to explain the flatness of the universe and the amount of infrared radiation emitted by cosmic dust. Last year, Bousso and his Berkeley colleague Lawrence Hall reported that observers made of protons and neutrons, like us, will live in universes where the amount of ordinary matter and dark matter are comparable, as is the case here.

Nevertheless, we argue, our approach can reproduce all the standard features of quantum mechanics, including twin-slit interference, zero-point energy, barrier tunneling, unpredictability, and the Bell correlations mentioned above.

I sure am glad this isn't a humanities paper, or people would be pointing out how much of this is counterintuitive, poorly-explained jargon and then dismissing it as the kind of stuff you'd expect from book three of Gulliver's Travels.
posted by kewb at 5:50 AM on November 9, 2014 [1 favorite]


If Humanities papers had testable predictions you'd certainly have a point.
posted by Sportswriters at 5:58 AM on November 9, 2014


If Humanities papers had testable predictions you'd certainly have a point.

From the second link:
In our theory, the interaction between nearby worlds is the source of all of the bizarre features of quantum mechanics that are revealed by experiment.

[...]

We call our theory an “approach” rather than an “interpretation” because for any finite number of worlds, our theory is only an approximation to quantum mechanics. This gives the exciting possibility that it might be possible to test for the existence of these other worlds.
Most of this stuff does not appear directly testable in any meaningful way at present. It's mostly mathematical inference and projection based upon a comparatively less distinct number of tested or observed results. And then there's dark matter and dark energy, placeholder concepts for the stuff the calculations to date can't make work. In other word, it's much more like an extended narrative or theoretical extrapolation from reality than like an experimental report.
posted by kewb at 6:08 AM on November 9, 2014


kewb- the article you are quoting from is not the journal paper, although it is linked there. It's available at arxiv here. Before insulting something it might behoove you to see what it is you are insulting.
posted by nat at 6:13 AM on November 9, 2014 [1 favorite]


One problem I have with multiverse theory is the loose way they use the word "exist". For something to exist, it has to exist at a point in space and time. If this other universe is theoretically outside of space and time then it doesn't exist even on a theoretical level.
posted by bhnyc at 6:15 AM on November 9, 2014


Previously
posted by Potomac Avenue at 6:23 AM on November 9, 2014


One great reason not to commit suicide: your consciousness might fork infinitely into more and more improbable scenarios where the gun jams or an eagle swoops down and takes the bullet for you and that would be even more depressing.
posted by Potomac Avenue at 6:25 AM on November 9, 2014 [2 favorites]


What I'm worried about is that this model kind of vindicates the Epicurian "swerve," one of the most "pulled out of thin air" bits in Classical Western philosophy....
posted by GenjiandProust at 6:26 AM on November 9, 2014 [3 favorites]


The cool theory in Anathem that I still think about (which is probably not Neil's but he presents it well) is that it's not that there are many worlds, but that probability itself is a function of the quantum nature of our consciousness. There is one Us, existing as multiple likelihoods at all times. Or something. Anyway, stay positive!
posted by Potomac Avenue at 6:30 AM on November 9, 2014


Getcha swerve on
posted by Potomac Avenue at 6:31 AM on November 9, 2014 [1 favorite]


If Humanities papers had testable predictions you'd certainly have a point.

Yeah, it's a derail, but: humanities papers often have testable predictions. They aren't testable by experiment but observation (much like a lot of, say, geosciences or botony). If I assert that Writer X uses Theme Y in a certain way, others are able to look at X's work and see if my assertion stands up. If I interpret historical evidence to construct a narrative of past events, that narrative can be tested against other (especially newer) evidence to see if the narrative holds water, and so on. It's not like sciences are "true" and humanities are "made up."
posted by GenjiandProust at 6:32 AM on November 9, 2014 [6 favorites]


kewb, I don't understand your objection here. The bits you quote simply seem to be stating "Theoretical model 𝕨 reproduces observed phenomena 𝕩, 𝕪, and 𝕫." How is that counterintuitive? Where does intuition even come into it at that point? And as far as jargon, are you saying that you don't like the way the referenced phenomena are named in those sentences, or that they're somehow artefacts of language rather than coherent observed phenomena?
posted by XMLicious at 6:46 AM on November 9, 2014


Before insulting something it might behoove you to see what it is you are insulting.

What I see is a paper that takes some observations and uses very complex mathematical models to extrapolate tremendously from them to support an extended narrative about how things "might" work. The base observations are testable, but huge chunks of the proposed explanation are basically efforts to talk the observations back into a narratable model.

For example:
Such an interaction is quite unlike anything in classical physics, and it is clear that our hypothetical A-composed observer would have no ex- perience of the B world in its everyday observations, but by careful experiment might detect a subtle and nonlo- cal action on the A molecules of its world. Such action, though involving very many, rather than just two, worlds, is what we propose could lie behind the subtle and non- local character of quantum mechanics.
In other words, you cannot ever really observe an "A" molecule directly if you are in the "B" world, but you can notice some sort of behavior of "B" molecules inconsistent with your models to date and from there work up some mathematical projections and turn those into a story about how some universe "A" (or, as the observations tend here, multiple universes "A" and perhaps "C" through "Z") are causing the aforesaid effect. And if you work really hard, you can avoid throwing out most of the other, admittedly linked mathematical modeling that accounts for prior observations. Then you cross your fingers and hope that no one makes an observation tomorrow that is inconsistent with some fragment of your very sophisticated math, because then you have to rewrite a substantial chunk of your narrative.

The non-scientist's question will be, "what did you test or observe yourself, and how" and there really isn't a simple, easy response to it that wouldn't require teaching a multi-year course in physics. The paper is full of moments where a mathematical term is replaced by an "approximation" designed to fit the theory, which turns out to fit the existing observations.

But you will look in vain through most of this paper for anything like a clearly observed phenomenon. Where they occur, they are less like data and more like cases of observation employed by the various models being compared.

But complex mathematical modeling of relatively marginal phenomena is how physics works past a certain point. And in the very long term, it may be possible to test more of the architecture here. But that is not where we are now, and the claim that most of this is "testable" is vulnerable to even a minor conflicting result down the line. And there are many, many things of great concern to us that simply elude even this highly attenuated notion of strict empiricism.

There's a reason, after all, that it's called "theoretical" physics. The paper is about modeling around a set of existing observations in order to fit a projected model to them, and in that sense it is scientific...but the relationship between the work here and the work of testing and observation is mediated by complex abstractions which are not in and of themselves observable physical realities.

And as to incomprehensible jargon, well...
The same toy model also captures the nonclassical phenomenon that a barrier can reflect a portion of a quantum wavepacket, even when the incident wavepacket has a large average kinetic energy.


and when they define terms, it's even worse:
In its simplest form, the ‘double-slit’ scenario comprises the free evolution of a 1-dimensional wave function Ψt for an initial value Ψ0 given by a symmetric superpo- sition of two identical separated wavepackets.
I'd hate to see the "complex" form!

I don't deny that this is probably very interesting, exciting, and meaningful stuff. Nor do I deny that considerable training and expertise are likely required to really appreciate it. You'll notice that the linked articles really don't bother to translate some of this terminology, which is what I was making fun of in the first place. Popular science reporting can't do much with material at this level of complexity other than pass it by quickly or mount a reductive metaphor for, well, a complex mathematical metaphor.

However, most of the architecture they propose is definitionally *impossible to observe or directly test* in the commonly understood sense. You may object to the notion that this sense should prevail, and I'd object along with you; but then we might have to give a lot of allowances to a lot of specialist work across the disciplines, or even modify our notion of what constitutes "observation" or "testing." And some people whose idea of being pro-science often boils down to defining an "other team" and rooting against it would be very disappointed in the both of us for spoiling their childish fun.

So I hope you'll forgive me when I say that it's intensely irritating, even proudly ignorant, of people to claim that papers in one discipline are pointless nonsense and papers in another are the perfectly lucid keys to understanding all reality. And I think it's especially absurd that some people demand tolerance for the sort of writing I've excerpted here when it's a theoretical physics paper, but not when it's a humanities paper, and then defend their prejudices with a hazily recollected third-hand version of Karl Popper.
posted by kewb at 6:59 AM on November 9, 2014 [5 favorites]


I'd like to hear more about how it undermines society.

Steinhardt feels the variables in quantum computing are more dependent upon variable states of matter, similar to positive and negative polarity or the transitions of water from a vapor to ice. He'd argue that putting stock in multiple realities would be equivalent to pseudoscience at best; any investment in Many Worlds research could run the risk of diverting funds from other scientific studies and possibly discredit the reputation of federally-funded programs in general.
posted by Smart Dalek at 7:01 AM on November 9, 2014


I remember reading a short story about our universe becoming increasingly outlandish and super-improbable things happening because another universe nearby was somehow stealing our quantum... things... anyway, I think it may have been by Peter Watts and I'd love to read it again.
posted by infinitewindow at 7:55 AM on November 9, 2014 [1 favorite]


Proponents of the multiverse idea must show that, among the rare universes that support life, ours is statistically typical.

And also that among the rare multiverses that support rare universes that support life and in which our universe is statistically typical, our multiverse is statistically typical. And of all the rare meta-multiverses that support...
posted by shivohum at 8:14 AM on November 9, 2014 [1 favorite]


I remember reading a short story about our universe becoming increasingly outlandish and super-improbable things happening because another universe nearby was somehow stealing our quantum... things...

Rudy Rucker has a few pieces like that.
posted by Smart Dalek at 8:31 AM on November 9, 2014


I think it's kind of putting the cart before the horse to raise objections about directly testing the model with novel experimentation. What is testable is whether the model really can reproduce all of those existing, documented phenomena.

If it can reproduce all of those phenomena, that's what would be the actual achievement here in the domain of theoretical physics. The model in that case will at least in part be mathematically isomorphic to any more workable, more "accurate" as it were, model that we might eventually come up with, the way that Newtonian mechanics is mathematically isomorphic to specific cases of General Relativity.

I sympathize with your frustration over people who employ crude reductive populist understandings of what science is, kewb, but I think you're actually undermining the point you want to make by highlighting intolerance surrounding wording and presentation, regardless of substance, in the humanities. It looks like the mathematician author of the paper, Deckert, may not even be a native English speaker.

And actually, upon re-reading, I still don't understand the objection you're making about jargon. In particular the first paragraph you quote about the "toy model" actually seems pretty intelligible in terms of the claim it's attempting to make, without even reading the rest of the paper or trying to follow the math, though I have to admit a good part of my undergraduate degree involved mathematics. I can't think of how you'd convey the same thing in simpler words without losing expressiveness and specificity, nor am I really sure there would be any point in trying to do so in an eighteen page paper written with academic physicists as its audience.
posted by XMLicious at 8:45 AM on November 9, 2014


There seem to be unresolvable problems over identity with a multiverse theory. It's supposed to resolve the fact that certain constants seem arbitrary. But they remain arbitrary for any given universe even in a multiverse. The fact that other universes have different constants fails to explain why this particular one has these particular values. The initial problem is untouched.

Also, please note that the existence of an infinite number of universes would not mean that all logical possibilities were necessarily realised in some universe. I'm sick of that one.
posted by Segundus at 8:57 AM on November 9, 2014 [2 favorites]


One problem I have with multiverse theory is the loose way they use the word "exist". For something to exist, it has to exist at a point in space and time. If this other universe is theoretically outside of space and time then it doesn't exist even on a theoretical level.

This isn't what's being proposed. These things have spacetime, just regions of spacetime that can't be accessed from our region of spacetime. The exact relationship between two different regions of spacetime and reason for why one can't be accessed from the other vary from model to model, but that doesn't mean that it's somehow outside of space and time.

Even without a multiverse, we still have regions of spacetime which are unaccessible to us because they're permanently outside of our light horizon. You could assume that nothing meaningfully exists outside of that, I guess, but that requires that the extent of what exists is a big sphere, exactly centered on humans. I don't think many people will go with that.

This is barring particularly inclusive multiverse models like Max Tegmark's Ultimate Ensemble, which would probably include structures without any kind of spacetime or spacetime analogue. But that's not what we're talking about here.
posted by vibratory manner of working at 9:32 AM on November 9, 2014


I sympathize with your frustration over people who employ crude reductive populist understandings of what science is, kewb, but I think you're actually undermining the point you want to make by highlighting intolerance surrounding wording and presentation, regardless of substance, in the humanities. It looks like the mathematician author of the paper, Deckert, may not even be a native English speaker.

Part of my point is that non-specialists and crude reductivists are rightly, if sometimes unhelpfully criticized when they misinterpret or offhandedly dismiss scientific work because of its difficulty and style, but are given a pass when they do the same to papers in the humanities and social sciences. (Some of those, of course, use work from other languages as well.)

I'm not sure you can separate "crude reductive populist understandings of science" from the devaluation of disciplines other than sciences, that is, from the broader trend of "crude reductive populist understandings" of specialist work and disciplinary labels in general. In recent years, of course, that sort of pro-"science" attitude has been increasingly replaced by general anti-intellectualism of the "why do we waste tax money on studies of banana slugs and dormant volcanoes?" sort.

If I wanted to be especially reductivist and snarky, I'd also point out that very few people here have made a good case for the importance of this work to nonspecialists. The prevailing sentiment seems to be, "Hey, this makes a science fiction novel I read sound broadly more plausible/predictive!" Way down the line this may be extremely important in application terms, but that's going to take a lot of further, probably incremental and more directly experimental work. ("Spooky interaction" is a good example here; it's very easy to suggest what that might lead to in terms of information transfer speeds and communications technology, but it's unlikely that the technology itself will be widely used or available in the near future.)

Even without a multiverse, we still have regions of spacetime which are unaccessible to us because they're permanently outside of our light horizon. You could assume that nothing meaningfully exists outside of that, I guess, but that requires that the extent of what exists is a big sphere, exactly centered on humans. I don't think many people will go with that.

I suspect that the great majority of people will go on with exactly that assumption whether they have read of this discovery or not.
posted by kewb at 10:03 AM on November 9, 2014


If I wanted to be especially reductivist and snarky, I'd also point out that very few people here have made a good case for the importance of this work to nonspecialists.

Well, since you're asking, on that specific point my off-the-top-of-the-head answer would be that our civilization is already dependent on a variety of processes and technologies that rely on quantum effects, such as synthesis of chemicals and nanometer-scale electronics, so a greater understanding of quantum physics (particularly a model that can explain quantum phenomena deterministically, I should think, which is what I believe we're talking about here?) would seem to be of great value, both material and scientific, and not too far down the line.

But if you want to build a Large Hemingway Collider, I'm in favor of that too!

Good name for a library.
posted by XMLicious at 10:45 AM on November 9, 2014 [1 favorite]


Well, since you're asking, on that specific point my off-the-top-of-the-head answer would be that our civilization is already dependent on a variety of processes and technologies that rely on quantum effects, such as synthesis of chemicals and nanometer-scale electronics, so a greater understanding of quantum physics (particularly a model that can explain quantum phenomena deterministically, I should think, which is what I believe we're talking about here?) would seem to be of great value, both material and scientific, and not too far down the line.

I'm not so sure about this argument. To use a simple analogy, many people in the United States use smartphones and much of our society and infrastructure are built around them, but comparatively few people could explain the physics research and concepts that went into their smartphone. Almost none of them could explain how quantum phenomena helped produce the electronics revolution, or would know that quantum mechanics were instrumental in the development of semiconductor technology. Nor would knowing those things enable such people to, say, repair or alter their smartphones themselves.

And let's not forget that the relative infrequency of short-term gains from "pure" theoretical work or "pure" research is a large part of the reason such endeavors are shamefully underfunded and misrepresented.

But if you want to build a Large Hemingway Collider, I'm in favor of that too!

Reminds me of an old issue of The Tick where a community of farmers becomes a community of mad scientists thanks to a 2001-esque monolith turning up in a field.

"That's our homemade particle accelerator."
"Neat!"
"Next year, we're hopin' to build one that accelerates grapefruit."
posted by kewb at 11:15 AM on November 9, 2014 [1 favorite]


Most people can't do surgery, either, but that doesn't mean we shouldn't bother with medical research.
posted by empath at 11:27 AM on November 9, 2014


Most people can't do surgery, either, but that doesn't mean we shouldn't bother with medical research.

And I'm not arguing against doing research; as I implied, I think we need much more funding for pure research in all fields. However, this does not mean that specialist research in any given subject is easily understandable or that it will be popularly received with anything like accuracy.
posted by kewb at 12:22 PM on November 9, 2014 [1 favorite]


For something to exist, it has to exist at a point in space and time.

How do you know that?
posted by thelonius at 4:32 PM on November 9, 2014 [1 favorite]


Wow! I'd like to hear more about how it undermines society.

There's a Larry Niven story for that!


Niven's story is psychologically incomprehensible to me. Why would the existence of other mes in other universes undermine my own desire to make decisions? If in one universe I eat a sandwich for lunch and in another I eat pizza, that doesn't make my decision meaningless. I'm choosing whether I want to live in the sandwich universe or the pizza universe.

If the point is that I don't actually choose, that I just eat the sandwich because I happen to live in the sandwich universe, well those kinds of deterministic arguments that free will doesn't exist are the same whether many worlds is true or not.
posted by straight at 4:58 PM on November 9, 2014


and when they define terms, it's even worse:
In its simplest form, the ‘double-slit’ scenario comprises the free evolution of a 1-dimensional wave function Ψt for an initial value Ψ0 given by a symmetric superpo- sition of two identical separated wavepackets.
I'd hate to see the "complex" form!
kewb, Leonard Susskind has a large number of lectures up on Youtube, on quantum mechanics, particle physics, relativity, entanglement, cosmology.... I heartily recommend them - they're generally aimed at a continuing education public and are quite accessible... so long as you don't mind a few complex numbers (like Ψ0) here and there.
posted by Fruny at 5:09 PM on November 9, 2014 [2 favorites]


*Spoilers for a Larry Niven story ahead. Also, discussion of suicide*

Niven's story is psychologically incomprehensible to me. Why would the existence of other mes in other universes undermine my own desire to make decisions? If in one universe I eat a sandwich for lunch and in another I eat pizza, that doesn't make my decision meaningless. I'm choosing whether I want to live in the sandwich universe or the pizza universe.

I read it as: there is no "choice." Life is totally deterministic, and you inhabit whatever universe you inhabit, which determines the choices you make (so the Epicurean "swerve" happens only between universes, not for individuals). The universe of our protagonist is the one where people who realize this realize that a) they might as well commit suicide, since somewhere they will, b) make the attempt, and c) the attempt is successful. It's not a very deep story, but it plays with the idea of determinism and physics.
posted by GenjiandProust at 7:21 AM on November 10, 2014


They tried to make me go to rehab but I said, 'OK, let me approach this with an open mind.'

Lyrics from a hit song from a portion of the multiverse where Amy Winehouse survives and thrives.
posted by Renoroc at 8:18 AM on November 10, 2014 [1 favorite]


and when they define terms, it's even worse:
In its simplest form, the ‘double-slit’ scenario comprises the free evolution of a 1-dimensional wave function Ψt for an initial value Ψ0 given by a symmetric superpo- sition of two identical separated wavepackets.
I'd hate to see the "complex" form!


When they say 'simple' here, they mean the simplest form of the experiment, not the simplest explanation for what it is, of which there are many.
posted by empath at 9:28 AM on November 10, 2014


'chapter 2' is up! Multiverse Collisions May Dot the Sky - "Early in cosmic history, our universe may have bumped into another — a primordial clash that could have left traces in the Big Bang’s afterglow."

also btw: If You Can Explain What Happens When Smoke Comes Off A Cigarette, You'll Get A $1 Million Prize :P
posted by kliuless at 10:04 AM on November 10, 2014


Life is totally deterministic, and you inhabit whatever universe you inhabit, which determines the choices you make

But whether this is true or not has nothing to do with the existence or non-existence of other universes.
posted by straight at 10:28 AM on November 10, 2014


For something to exist, it has to exist at a point in space and time.

How do you know that?


So this thing exists, but not anywhere, and not at any time, and has no causal relationship with our universe. That is a very abstract form of existence that reminds me of religious faith in an afterworld.
posted by bhnyc at 12:16 PM on November 14, 2014


So this thing exists, but not anywhere, and not at any time, and has no causal relationship with our universe. That is a very abstract form of existence that reminds me of religious faith in an afterworld.

Or platonism -- where and when is pi or truth?
posted by empath at 12:53 PM on November 14, 2014


Paging Alexius Meinong...
posted by Segundus at 5:28 AM on November 15, 2014


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