I got this letter in the mail the other day:
I Don’t know if you Exist But I Do! I bo not Agree with your Articl and I Do not Beleave that “MOMBO-JOMBO” if you do … Well! it’s Disturbing thought But I know How to Deal with it! I will Not let the Wolb Disiper under My Nose But if you Do I cant say I’m sorry!
Sincerely
a ten year old who knows a little more than some Pepeol!
George Wing
ps. some peopl Have a little to Much time.
In response, of course, to the NYT story about Boltzmann’s Brain. George’s father Michael, a high-school science teacher, was moved to send it along (and gave me permission to post it), suggesting that “maybe it is really a Boltzmann brain speaking.”
To which I can only respond: awesome. A fourth-grader reads an article in the Science Times, and is so moved by outrage that he pens a stern missive to the scientists quoted? It’s not very often that you have a chance to inspire a young mind like that, even if you do inspire him to berate you.
Of course, George did fall into a slight trap with respect to the logic underlying the article. But that’s okay — he’s only ten years old, and there are plenty of grownups with Ph.D.’s in physics who fell into the same trap! The trap is to imagine, despite explicit disclaimers to the contrary, that the Boltzmann’s Brain argument goes something like this:
Certain cosmological scenarios predict that it’s more likely for a brain like yours or mine to arise as a random fluctuation, rather than through orderly evolution.
Isn’t that cool????
That’s really not the argument that anyone is trying to make. Rather, it goes like this:
Certain cosmological scenarios predict that it’s more likely for a brain like yours or mine to arise as a random fluctuation, rather than through orderly evolution.
Our brains aren’t like that.
Therefore, those scenarios are not correct.
It’s kind of an old-fashioned argument. Take a theory, use it to make a prediction, the prediction isn’t correct, and therefore the theory has been falsified! Rubs a lot of people the wrong way, but it works for me.
Other critics are uncharitable for different reasons. For example Don Walton, founder and president of Time For Truth Ministeries:
I believe the accusation leveled against the Apostle Paul by Festus in Acts 26:24 — “much learning is making you mad” — is most apropos for today’s cosmologists.
Hey, question my existence and suggest that I have too much time on my hands, fine — I can deal with that. But comparing me to Saint Paul? That is a low blow, sir. And somewhat unprecedented.
When you’re ten years old, you don’t have to be right — you should be curious and passionate, and George definitely is on the right track. I look forward to recruiting him to grad school some day. For the grownups I have less hope.
Yahoo, I have no idea how to communicate with anonymi, I don’t know your level of expertise or background, so we are likely to talk past each other. In any event, I don’t think I said anything controversial in that comment, comparing probabilities in the multiverse is very ill-understood subject at present, which makes it an interesting topic for research. As I understand the state of the art is trying to understand precisely what :more likely: means, nobody is going around falsifying theories as of yet. The only thing in the original piece that struck a false note was the characterization of statistical arguments as business as usual. I am over it by now.
As for your more technical point, using the entropy as measure of likelihood as you suggest, even if you define that concept precisely, is exactly the original argument which produces the Boltzmann brain paradox, I think…so you would have to use another measure. I am not sure how nature, as opposed to us, is supposed to pick that measure.
Hi B–
Just run the movie backwards; the evolution law is pretty much time-reversal invariant. Take whatever macrocondition you want to fluctuate to — our current universe, a brain surrounded by chaos, whatever. Then evolve backward in time, you’ll find some initial conditions that would create it. Of course, because it’s a “macrocondition,” it corresponds to many specific states, each of which will have a distinct trajectory. By the same reasoning that we teach undergraduates about stat mech, the vast majority of such trajectories will have come from a higher-entropy boundary condition.
Talking about multiverses blah blah blah is a bit of a red herring here. The reasoning that says that — in the absence of some low-entropy past boundary condition — our current state is likely to have come from a higher-entropy past is exactly the same reasoning that we use to conclude that ice cubes generally melt. Namely, the overwhelming majority (in the canonical Liouville measure on phase space) of microstates compatible with the current macrostate have that property.
“Talking about multiverses blah blah blah is a bit of a red herring here.”
Absolutely. And the fact, mentioned by Moshe, that there are problems with measures on multiverses seems to have absolutely nothing to do with Sean’s refutation of Boltzmann!
Let me see if I am missing something. The original argument of Boltzmann is that we are a large fluctuation away from equilibrium state, whose likelihood is therefore weighted by the entropy. This idea was safely falsified long before any of us was born, because of the Boltzmann brain paradox- those are much more likely in this scenario than ordinary evolution leading to the current situation. The recent interest in the subject is in the context of the multiverse blah, blah, blah, where the conjecture is that our universe is selected as the most probable one (compatible with life) according to some unknown measure. The Boltzmann brains are then used to constraint that measure. Is that about right?
What I am confused about is where this measure is supposed to come from. The choice of entropy as measure is not arbitrary, it corresponds to preparing the system according to a known recipe, called thermal equilibrium, and one can argue that if the universe had long evolution before the random fluctuation it was at equilibrium. I fail to see such rationale for any measure in multiverse scenario, and that is not to say there is none.
That’s a good question, and I don’t know what the measure is supposed to be, and that’s why I am not especially convinced by the argument in the multiverse context. But some people, including Hartle and Srednicki, are questioning the argument in the original context — whether or not our universe can be fruitfully explained as a thermal fluctuation in an equilibrium background. Which is why, in my post about the NYT article, I wrote “it’s important to recognize that there is a much stronger argument against the idea that Boltzmann’s Brains were originally invented to counter — that our universe is just a statistical fluctuation around an equilibrium background.”
Thanks Sean, that makes sense, I missed that context.
Is it “fluctuation,” or “fluctuations?” It seems the brain/thinking is a function of interactions, so it would seem the initial condition might be a background against which a range of fluctuations might occur, as opposed to the possibility that a singular fluctuation away from equilibrium created the undoubtfully complex reality in which we exist, in its fall back to equilibrium.
Infinite micro fluctuations would create expanding space, just as one macro fluctuation would cause an expanding universe.
Hi Sean,
Thanks for your reply. You say
“Just run the movie backwards; the evolution law is pretty much time-reversal invariant. Take whatever macrocondition you want to fluctuate to — our current universe, a brain surrounded by chaos, whatever. Then evolve backward in time, you’ll find some initial conditions that would create it.”
That I understand. But it seems to me if one does that, specifying the condition (e.g. all the atoms of my brain in the appropriate places with their momenta), then one is not free to further specify anything about the evolution that brought the atoms there, precisely because you say you can evolve backwards in time. So how do I know there is an allowed solution in which the condition ‘all the atoms of my brain in the appropriate places with their momenta’ appear and dissolve like a ‘fluctuation’ as you previously wrote:
Out of the background thermal equilibrium, a fluctuation randomly appears that collects some degrees of freedom into the form of a conscious brain, with just enough sensory apparatus to look around and say “Hey! I exist!”, before dissolving back into the equilibrated ooze.
Maybe my problem is just that I understand in this scenario ‘everything that can happen, does happen’ (if you wait long enough) but not how helpful this is without knowing what ‘can happen’ to begin with (since ‘can’ stretches out over time as in ‘appearing’ and ‘dissolving’ or as I wrote above ‘wasn’t there’ – ‘is there’ – ‘won’t be there’)? Not sure though if that explanation of my confusion makes it better or worse.
@ Yahoo #25, you write addressed to me
Emotions like “are these guys serious?” are not helpful at all, particularly when they lead to excessive hobby-horse-riding, an exercise likely to lead to further abrasive injuries to delicate body parts.
Are you sure you are replying to my comment? I neither said anything about Vilenkin, nor did I ask who is or isn’t serious with what. What I find bizarre and what not is my brain’s business.
Best,
B.
Two things. First, the relevant feature of your brain is its macrocondition, not its exact quantum state. You don’t know, or need to have specified, the precise position and momentum of every atom in your brain — more than a few momenta could be changed and you would never know. So there are many microstates that correspond to the relevant macrostate of your brain, not just the small number that came from a low-entropy past.
Second, even if we specify precisely the microstate of your brain, that says exactly nothing about the rest of the universe. I could start with an arbitrary state of your brain plus a chaotic outside world, and wind it backward to find a high-entropy condition that would evolve into your brain.
Hi Sean:
Yes. In my first comment I wrote let’s forget QM for a moment as I don’t see how it is relevant to my question. Again, I do not question you can always ‘wind an arbitrary state backward’ to get an initial condition that would seen the other way round appropriately evolve into that state. My question is how do you know this ‘evolution’ does indeed ‘evolve’ my brain according to the picture you suggest which I quote in #33. If you ‘wind the state backward’ you can’t also specify the way it evolves, I mean, that’s what the evolution law is good for. So how do we know the picture of spontaneous assembly out of chaos and subsequent disappearance with the intermediate state you wish to have (my brain, your brain, Boltzmann’s brain) is actually a scenario that ‘can’ happen? Best,
B.
Okay, now my turn to be confused. Nothing that I said was dependent on QM, you can speak classically just as well. The Hamiltonian equations of motion are first-order differential equations in phase space, with a solution that is uniquely defined once you give a single boundary condition. So, take that boundary condition to be any one of the many many microstates that could possibly correspond to “your brain”. Almost all of them will evolve to the past to a state which (after suitable coarse-graining) is very high entropy. The proof is just the conventional proof of the H-theorem, just run backward in time.
I’m not sure this will help, as I think I’m just repeating.
Okay thanks, will think about it. Best – B.
BTW, if anyone is trying to explain our current universe (or it’s properties at least) in terms of a ‘”fluctuation”, remember that the mass-energy in the space in which the fluctuation occurs is subject to gravitational compression (REM why a stable universe can’t exist: even if there’s a lambda that happens to cancel out gravity in a given configuration, the slightest change will likely tip the whole thing to collapse or eternal expansion (or a mix of lumpy contractions with overall expansion.) That’s because lambda is a property of space, but lumping of matter changes the local gravity.
So, “fluctuation” in what? It can’t be like an ordinary space filled with matter. How could something our universe came out of, avoid either having to be big-banged in turn, or not have already expanded into rarefaction?
Neil,
What if there is some sort of convective cycle at work here, so that if gravitaational compression were to increase, it would simply speed the rest of the cycle up. Whether it’s normal radiation from gravitational wells, or that fluctuation across space is in some way sourced to what falls into black holes. Physics has no poroblem proposing any number of extra dimensions, alternate universes, entangled properties, etc. This way, there is some relationship between expanding space and collapsing space, That they should be two distinct phenomena seems the more far fetched proposal.
One must be careful with the term fluctuation. Quantum wave equations are completely deterministic. There are really no stochastic processes in quantum mechanics. This sounds odd, for we are so inculcated with the idea that QM is a statistical theory. It is true that the amplitudes in QM corresponding to certain eigenvalues determine probabilities under a modulus squared, but how these probabilities obtain is because we observe quantum systems under incomplete circumstances. Our measurement apparatus is made of many quantum states which we have not characterized. Remember a quantum experiment involves the preparation of a quantum state. Yet we don’t do the same for the apparatus states, which couple to the quantum system to measure an observable. This is by some definition a fluctuation, or how a quantum system can appear to pop into some configuration spontaneously. Yet this is because we are working with knowledge of some aspect of the system, say some sub-matrix of the density operator, and we have summed over a whole lot of states we have not characterized or perpared.
In statistical mechanics a similar situation applies, though over a real valued sample space of states. The atoms or molecules in a gas or thermal system obey individually Newtonian mechanics, or QM where that applies, and their collisions with other molecules are determined as such. Of course characterizing this is impossible. Indeed we can’t solve a three body problem exactly since the polynomials over the first integrals of motion are not Galois factorizable, as found by Poincare and for which he won the Sweden prize. So we use statistical methods for a large number of molecules. What is a fluctuation is then something which occurs because we are necessarily ignorant of a fine grained description of the system. So the phase space is partitioned off into macrostates, we apply the H-theorem to define these macrostates with an energy surface and we work forwards. What we call fluctuations are then deviations, the first of which are standard deviations. IN Poisson statistics [itex]1/sqrt{n}[/itex] define fluctuations for n trials or a system with n particles. Shot noise in electronics originates from this.
Lawrence B. Crowell
Spot the differance :-
http://www.mpa-garching.mpg.de/galform/millennium/seqF_037a_half.jpg
http://www.mpa-garching.mpg.de/HIGHLIGHT/2002/fig0206_1.jpg
One is brain neurons the other is galactic clusters.
LC said,
“One must be careful with the term fluctuation. Quantum wave equations are completely deterministic. There are really no stochastic processes in quantum mechanics. This sounds odd, for we are so inculcated with the idea that QM is a statistical theory.”
“What is a fluctuation is then something which occurs because we are necessarily ignorant of a fine grained description of the system.”
VERY appropriate comments…profound too. This principle conceptually, is at the heart of entanglement, and implies how and why information and complexity develop and can be conserved within an appropriate space-time geometry (lattice) in a quantum universe.
Another very powerful and impressive thread which started with a perceptive (but not completely informed) kids’ “the king is naked” comment.
Sam,
I still find it intriguing that this lattice should be both collapsing down into points of infinite density and expanding across the unimaginable distances in between, with no theoretical connection. Even if I don’t have sufficient resources to tie what is falling in to what is spreading out, the other side would seem to be out in the open. What is spreading out is presumably the same space that is falling in, or is there some barrier preventing expanding space from falling into gravity wells? I realize that with gravity, it’s collapsing material defining space and with expansion, it’s increasing space dissipating material, if space is defined by the material defining it, as is the case with gravity, then wouldn’t the addition of material, such as radiation, or dark energy cause it to expand? And wouldn’t this matter also be susceptible to falling into gravitational wells?
Lawrence,
I’m as willing to be careful with the term “fluctuation” as anybody, but how do you explain “dark energy?”
Hi John,
Conceptually I think it is well to remember that the SR/GR/QM universe is always everywhere…there is nothing outside it at all- at any “time”. This is true in spite of the fact that as we observe the universe from our 4D frame, we measure the universe as having a finite mass and being spatially unbounded…marginally closed space. We observe time to proceed in as “flat” a manner as we observe the shape of space. From our frame, we look outward astronomically to a “bang” and inward microscopically to gravitational collapse. From our frame also, this astronomical “bang” occurred 13.7 BY ago and the overall collapse of the universe seems billions of years in the future.
The reason why we observe this way relates to our space time coordinates. At the origin of of the universe (the “bang”) , the other side of the universe was still the other side of the universe…it was “here” because neither space nor time existed. Yet each event which happens in the universe has its own invariant frame of reference and what really “happens” reflects NOT the 4D processes of inorganic and organic evolution as we so logically observe them, but rather, information and complexity develop (as is the topic of this thread) from ” a kind of quantum “fluctuation” at each of an almost infinite set of energy density, invariant frames…which are all tied together and related by entanglement.
In fact, the geometry of the system…invariance and entanglement, plus energy density relationships form a set of basic cosmological contraints within which infomation and complexity can form, develop, relate and be conserved…not immediately lost.
Those on this thread who understand energy density and scale relationships know that at small scales (as observed from our frame), tiny energy densities are more than enough to take the characteristics of the singular. As tiny energy densities enter this region, tiny event horizon surfaces…particles form. Because of the constriants of the geometry, the “particles” which form, form groups which have distinct characterisitics…”classical sets of particles”.
Atomic particles and structures are stable because of the way we observe them- in extreme, remotely observed, gravitational time dilation. From our frame, space and time appear…a vast universe filled with a great variety of stable energy density configurations. Actually, indications are that at the quark level, the entire baryonic universe everywhere and simultaneously collapses and
“bangs” as much as 2.8 trillion times per Earth second- obviously eternally preserving information and complexity.
“Dark Energy” is the stuff of which the entire universe is made…the substance of reality itself. Since the Planck Realm is everywhere singular from our frame, most of the mass of the universe is found within the Planck Realm. From our frame, areas of greater energy density than the Planck Realm are observed as “particles”, “atoms”, “stars”, “planets”, and of course, “black holes”, where the Planck Realm, rather than existing at 10 to the minus 33rd CM, has NO depth at all.
If the standard model is correct, and I believe it is, singularity is the common denominator of the universe. Time and space result from our observing energy density in certain ways. The “Big Bang” (Schwarzschild white hole) and the “big crunch” are happening eternally under our feet as we discuss this matter. There is a “place” in the universe where the Earth is “banging”…it is nothing but a singular object with an event horizon surface the size of a golfball…and exists simultaneously with everything else in the universe (at its own invariant frame) as a low entropy singular object- it literally contains and is physically linked with all of the information regarding its own history and the causes and effects of everything else in the universe.
We measure the universe we see using a very “cool” set of mathematical relationships which describe the proportions in which matter and energy relate, and the manifold or lattice which results when baryonic information and complexity observes reality in a certain way…SR/GR/QM.
LC’s comments on QM are very important and he has a PROFOUND understanding of the nature of these mathematical relationships. I feel like I am in his classroom, in fact. To study this stuff and begin- just begin, mind you- to understand how structured (deterministic) the univsese really is; to understand HOW information need not be actually stored in a black hole in a QM/GR/SR universe is very exciting. As I once again read LC’s comments it made the hair stand up on the back of my head. The universe is truly awesome!
I think that what everyone is forgetting is that QM is a deterministic MODEL. Radioactive decay is our best example of the underlying random nature of the universe.
That things become correlated is interesting, but can be explained with our knowledge that bound states have less energy than unbound ones. Quantum entaglement is a phenomenon that occurs when interaction leaves two particles in a bound state. This causes a correlation between the two particles. There is nothing particularly mysterious about it.
There is no need to resort to faster than light travel or other hocus pocus.
Sam,
I can understand reality as a singularity, in that there is a oneness to everything, but I just don’t translate it into the singular. Oneness isn’t one. Unity isn’t a unit. Monotheism makes the same mistake; The absolute isn’t one, it’s zero.
So trying to formulate the universe as a singular entity, with a narrative structure of time, results in a mashup of deep insights and prejudicial assumptions.
I do see it as a singular process that is both “crunching”/gravitationally collapsing and “banging”/energetically expanding simultaneously. Not only that, but that time is going both directions as well, as events/order falls away into the past, as energy proceeds into the future. “Energy is that which is conserved.” To me, these two examples of collapsing order and expanding energy are aspects of the same essential reality.
M-Physics said,
“I think that what everyone is forgetting is that QM is a deterministic MODEL.”
I would hope that no one is forgetting that QM is a model!…or that SR/GR are models of reality as well. If these models failed to precisely describe the behavior of the universe, neither we nor anyone else would be discussing them here. However, since these models work, and since we know that any future concept will have to be inclusive of their general parameters, I’m not sure that making the point that QM is a model is of much significance as an argument that just maybe QM may not be correct. The field work says QM IS an accurate description of the universe. My opinion is my opinion, but SR/GR/QM are the best we have. I know they work. I have seen them work. I know how accurate they are in describing reality…so accurate, in fact, that technologies can be formulated around them. The rest, as Einstein said about SR/GR are “the details”.
JM,
Your comments are interesting and I can see from your last comment that you get the idea of a permanent, everything and everywhere universe which, when observed from different frames and in different ways, is measured to be expanding and contracting at the same time. I think that is the substance of your original question to me and the reason why I answered it as I did. As baryonic infomational complexity, we electromagnetically “cross-read” the progression of events in the expansion and gravitational collapse of the universe remotely.
To use a simplified but obvious illustration of the permanence of embedded information in the universal manifold, people on Earth, now dead, could be observed, with proper equpment as living their lives at their own “place” in space and time anywhere in the universe. Every event since the big bang, and presumably into the future as well is permanently embedded in the energy density matrix and preserved at invariant frames. One would need only to tamper slightly with the past, to change everything…and possibly even destroy all life on Earth- and everywhere else.
A great thread! I’ll continue to read along!
Sam,
Actually I am arguing with the description of time as a form of metadimension, where all events exist, much as different points in space can co-exist. Given that it’s the energy that’s conserved, it is the same energy that manifests as successive points in time, so it requires the dissolution of past events for future events to take their place.
The story is that it was Edgar Allen Poe who first proposed that space and “duration” are the same. E. A. Poe was a master of narrative and that’s what time as a dimension is. That selective linear description of cause and effect that describes our thought processes. Time as dimension is the intuitive understanding of time, not necessarily the logical description. The point I keep making is that time is a consequence of motion, not its basis.
If time is a fundamental dimension, then physical reality proceeds along it, from past events to future ones. On the other hand, if time is a consequence of motion, then physical reality is simply energy in space and as the events are formed, they go from being in the future to being in the past. Time as consequence of motion means it has more in common with temperature, then space, since they are both descriptions of and methods for measuring motion, rather then dimensional basis for it. This relationship between the matter/energy moving forward in time, as the events created move back in time applies to all scales, whether the earth rotating and creating days, or a cesium atom going through transitions, or strings and their vibrations.
Consider a thermal medium, say a pot of hot water, with lots of water molecules moving about. To construct a time keeping device we would take the motion of one of these points of reference and measure it against the medium it is moving through. The point is the hand and the medium is the face of the clock. Obviously all the other points are hands of their own clocks, but are medium/face for all other clocks. The motion of any point/hand is balanced by the reaction of the medium/face of the clock. To the hand of the clock, the face goes counterclockwise. At any one moment, the positions of all these points constitute an event, so while any and all of them go from past events to future ones, the medium against which any point is being judged is the overall context, which once created, is displaced by the next, as all these individual points move around, so the events go from future potential to past circumstance. The illusion of direction is created because the physical reality of the points moves one way through the series of circumstances, though these events go the other way. There are innumerable points of reference describing their own narrative and all this activity exists in an equilibrium, so every potential clock constitutes its own measure of time.
This isn’t presentism, since time isn’t fundamental, either as point or line. The only absolute time would be like absolute temperature, the complete absence of it. Zero. No singular point of reference, because that would imply some way to measure it and that would require motion.
J.M. , I think your view is better represented by Julian Barbour’s ideas. Look him up.
A quantum entanglement does not involve any force between particles. It means that the wave amplitudes of two particles exist in a product form in a density matrix. An entanglement can in principle exist across any distance. For instance light from a distant galaxy that is Einstein lensed around an intervening galaxy can define EPR entanglement pairs. In fact it is in principle possible to do a Wheeler Delayed Choice experiment with these photons to determine which of the arms the photon traveled. A photon amplitudes for going around the intervening galaxy to the left or right can be made nonlocally to choose a path here on Earth.
Entanglements define a certain relationship structure which is different from the standard coordinate or space-spacetime understanding of things. They also do not involve gauge forces or the binding of two particles by an energy potential.
Lawrence B. Crowell