A Universe In Which Time Has No Beginning
December 10, 2013 12:19 PM   Subscribe

"Maybe the Big Bang never happened because the universe never began because it has always existed." Scientific American magazine revisits the decade-old idea that we live in a "Rainbow" universe (where different wavelengths of light experience spacetime differently and where the big bang may never have happened) following the publication of new physics research on the subject.
posted by rcraniac (83 comments total) 27 users marked this as a favorite
 
Arxiv link.
posted by kiltedtaco at 12:24 PM on December 10, 2013 [1 favorite]


So all we need is a Rainbow Connection to put us in tune with the Universe?
posted by blue_beetle at 12:24 PM on December 10, 2013 [1 favorite]


**poof**

That was the sound of my mind being blown
posted by Mister_A at 12:28 PM on December 10, 2013 [1 favorite]


It took scientists that long to ask what existed one second before? They must never have been two year olds...
posted by Alexandra Kitty at 12:31 PM on December 10, 2013 [6 favorites]


Huh... so does that mean the Steady State theory is still a viable idea?

(I always felt a little bad for Fred Hoyle, a Steady State proponent who coined the phrase 'big bang' while trying to convince people of how ridiculous the idea was. The phrase stuck. I'm fairly certain he died still resisting the notion- maybe he'll be vindicated.)
posted by insufficient data at 12:35 PM on December 10, 2013 [3 favorites]


A rainbow universe, where the speed of light is zippy!
posted by popcassady at 12:37 PM on December 10, 2013 [1 favorite]


@ Alexandra Kitty

To be fair, *either* explanation for the universe is a bit mind blowing. Either it started at some point (so what was there before? What 'started' it?) or it's always existed (but... surely there has to be a beginning, right? Everything has a beginning ow my braaaain)

The universe is weird.
posted by insufficient data at 12:39 PM on December 10, 2013 [9 favorites]


Can someone with greater familiarity than I possess with the concept explain what putative property or state of photons leads them to interact differently with the force of gravity, depending on their energy? I would think this would be essential to the credibility of even such a speculative theory as this.
posted by Mister_A at 12:39 PM on December 10, 2013 [1 favorite]


'Beginningless Time' is fundamental to Tibetan Buddhism.
posted by not_that_epiphanius at 12:46 PM on December 10, 2013


I always felt a little bad for Fred Hoyle, a Steady State proponent who coined the phrase 'big bang' while trying to convince people of how ridiculous the idea was.

So, kind of like whoever invented the term 'Obamacare', should it become a huge success.

"Maybe the Big Bang never happened because the universe never began because it has always existed."

I vote we dub this model the Kubrick Shining Universe.
posted by Atom Eyes at 12:52 PM on December 10, 2013 [2 favorites]


Can someone with greater familiarity than I possess with the concept explain what putative property or state of photons leads them to interact differently with the force of gravity, depending on their energy? I would think this would be essential to the credibility of even such a speculative theory as this.

It's not an alleged property of photons, it's an alleged property of spacetime as traced by massless test particles.
posted by kiltedtaco at 12:54 PM on December 10, 2013


A rainbow universe, where the speed of light is zippy!

Didn't Zippy share the same voice actor as the Daleks?
posted by RonButNotStupid at 12:54 PM on December 10, 2013


It took scientists that long to ask what existed one second before? They must never have been two year olds...


Time ('one second before') is tied to the structure of the universe, so it's not really a question that makes sense. Without the universe as we know it there is no time, therefore there cannot be 'one second before'.

Yeah, I know, it gets weird.
posted by unixrat at 12:55 PM on December 10, 2013 [9 favorites]


The Big Bang isn't one precisely defined idea (or maybe the one we agree on as being precisely defined basically has to be wrong).

Every time there's some 'the Big Bang was wrong' idea mentioned in the media it's some new variant on the first instant that leaves the overwhelming majority of the evolution of the universe that is well explained by the Big Bang basically intact.

In other words steady state is not ever coming back.

The above said before I've got on the VPN to work to read the article.
posted by edd at 1:00 PM on December 10, 2013


I dunno kiltedtaco, the ScAm piece makes it sound like this is about the interaction between photons and gravity:

...particles with different energies will actually see different spacetimes, different gravitational fields about...

My limited understanding of this kind of thing is that spacetime is 'shaped' by gravity anyway, so it's kind of a distinction without a difference. I freely admit that I am on that level of understanding that comes before one can claim the title 'novice,' so if you have something useful to add, by all means do so!
posted by Mister_A at 1:02 PM on December 10, 2013


Can someone with greater familiarity than I possess with the concept explain what putative property or state of photons leads them to interact differently with the force of gravity, depending on their energy? I would think this would be essential to the credibility of even such a speculative theory as this.

Yeah, its a consequence of modifications to Special Relativity in order to get at Quantum Gravity by introducing an energy scale as well as a velocity scale.
posted by vacapinta at 1:04 PM on December 10, 2013


This wouldn't be the steady state theory, since it's still saying that the density of the universe increases as you go farther back in time. It's just saying that the universe could have existed in an extremely dense state for an infinite amount of time before expanding to its present position.

Background: Quantum mechanics is our theory for predicting the behavior of very small things, and it's very accurate within that domain. General relativity is our theory for predicting the behavior of very large things, and it's very accurate within its domain too. The problem is that the two models work in very different ways. You can't scale down the rules of relativity and get quantum mechanics, nor can you scale up quantum mechanics and get relativity. A theory that ties the two of them together in some continuous way has been the holy grail for physics for some time.

'Ranbow gravity' (now part of relative locality) is one attempt of many at tying the two together. It's not finished or widely accepted. Awad is exploring some possibilities of what it might mean if rainbow gravity is accurate. This seems a bit premature, since the math hasn't been completely worked out yet, and the originator of rainbow gravity says as much on page 2. So don't take all this stuff about the beginning of the universe too seriously yet. But if someone manages to make testable predictions from it that we can actually test with current technology, maybe it'll let us know if we're on the right path or not.

disclaimer: I am not a physicist, I am not your physicist, and this does not constitute physical advice.
posted by echo target at 1:09 PM on December 10, 2013 [9 favorites]


It's an interesting idea anyway. Also, if you think about it, a stew of near-infinite density existing for a practically infinite or practically zero duration of time, that suddenly starts rapidly becoming a stew of ever-decreasing density is not so different from the big bang.
posted by Mister_A at 1:16 PM on December 10, 2013 [2 favorites]


Never, ever, read the comments.
posted by Joe in Australia at 1:19 PM on December 10, 2013 [5 favorites]


Well of course light exists in different wavelengths at different times and different places.


Sometimes Heimdallr blows the Gjallarhorn and opens the Bifröst to Midgard, sometimes he opens it to Vanaheimr.
posted by TheWhiteSkull at 1:26 PM on December 10, 2013 [22 favorites]


At least for the "does this disprove the Big Bang?" question, one of my previous posts is relevant (spoiler: No, for reasonable definitions of "the Big Bang"). As for the frequency-dependent speed of light thing, I'll have to think a bit before I can discuss it. My suspicion is that this is another case of "not incorrect science coming across as totally crackpot-sounding after passing through the Babelfish translation that is 95% of science reporting."
posted by physicsmatt at 1:29 PM on December 10, 2013 [11 favorites]


My suspicion is that this is another case of "not incorrect science coming across as totally crackpot-sounding after passing through the Babelfish translation that is 95% of science reporting."

Yeah I hope so. My first reaction to this whole thing was to groan "Oh, not again..."
posted by RedOrGreen at 1:47 PM on December 10, 2013


"Oh, not again..."

But why not? Back and forth is how real science works. For the rather open ended questions like "The Infinite Universe(s)" one would expect a rather extended cycle of back and forth (perhaps along many dimensions).

I know there have been more than a few legitimate attempts to model these big topics. I rather like the topological(ish) idea of a connected universe that is something like a really big Klein bottle torus of many dimensions, shoot a fast enough bullet in a straight line and it will eventually (if you wait many billions of years in the same me spot) it'll hit you in the back of the head.

An actual cosmologist at a book reading pointed out that at the moment the big bang handles the current data best right now (or, well, a few years ago... still waiting on that bullet).
posted by sammyo at 2:08 PM on December 10, 2013 [1 favorite]


Never, ever, read the comments

Well, not in this universe.
posted by yoink at 2:09 PM on December 10, 2013


We live at the far end of infinity. Makes me feel old.
posted by night_train at 2:14 PM on December 10, 2013 [1 favorite]


It took scientists that long to ask what existed one second before? They must never have been two year olds...

Then the scientists themselves are analogous to the universe in that they have no beginning either?

How befitting!
posted by fairmettle at 2:24 PM on December 10, 2013


The only result I'm seeing coming from this article is that it will be used to explain UFOs. But then again, that's not really a change at all...
posted by happyroach at 2:27 PM on December 10, 2013


Asking what happened one second before the big bang is like asking what is one mile north of the North Pole.
posted by rocket88 at 2:31 PM on December 10, 2013 [16 favorites]


We have a cold snap here in Los Angeles, and my cat decided to get under the blanket at dawn, leeching off my heat. I was looking at him lying next to me, my eye about 5 inches away from his, and thinking about all the billions and trillions and nthons of features that go into making this cat work. And how this cat - and the human being against whom this cat is resting - were all inherent already in the simple density of the energy at the beginning of the Big Bang in early Planck time. This is what we all came from. How could mere energy result in all this? First the quarks and elementary particles and then more and more and then cat and human. All from this incredibly uniform hot thing, which must have seemed just as uniform as anything ever, and you'd never suspect that there were any two things in it let alone the myriad that followed.

And then I came across this post on metafilter.
posted by VikingSword at 2:32 PM on December 10, 2013 [16 favorites]


I wonder if any of the following might be possible, and if they have been considered by SCIENCE:

1. Our brains are not flawless reality-perceiving machines.
2. We might someday confront questions that we are incapable of comprehending.
3. This is one of those questions.
4. There is no reality. (There "is" no "reality.")*

*Wait a minute, then how can I be typing this if there is no reality.**

**Uh-oh.***

***

posted by univac at 2:57 PM on December 10, 2013 [1 favorite]


4. There is no reality. (There "is" no "reality.")*

As Nabokov posited, "Reality" is one of the few words which mean nothing without quotes.
posted by Celsius1414 at 3:01 PM on December 10, 2013 [1 favorite]


'Beginningless Time' is fundamental to Tibetan Buddhism.

Not just Tibetan, all buddhism. As a buddhist myself, I reject the Big Bang theory and endorse the Steady State model. This is not just religious dogma, I stuck with Steady State long before I converted to buddhism.
posted by charlie don't surf at 3:05 PM on December 10, 2013 [1 favorite]


Bill Burr has a bit on plancks constant where he claims that it's proof of God because how else would we arrive at the magical number that allowed this to happen? Then he admits he barely understood what he read. I think people who think this is a miracle are like first time gamblers or lotto players that strike it rich, knowing little of the countless millions before who lost. . You don't think the universe has a million bazillion opportunities to get it right? I think there are mechanisms to explain infinite "simulations" in every possible higher outlook. Many worlds, heat death (you mean, the opposite of this where the universe is "nearly infinitely not doing shit" until the last electron strangles the last positron with the entrails of the last nano black hole. You may think it's flat and cold and dead but eventually it dies so much that to die any longer would be to yield into nothingness. That can't happen so let's just bang it up again. Full disclosure, LSD in teen years

I like to say think one was born on third base and thought they hit a triple if you think there's a miracle here. Same story as evolution, same story of success. Try try try. There is no do. Until enough try and die.
posted by lordaych at 3:06 PM on December 10, 2013 [1 favorite]


strikes me as obvious: if there is no god - and I find it hard to believe there is, given the existence of evil yadayadayada - then the universe has always existed. QED.
posted by jpe at 3:09 PM on December 10, 2013


So - if I'm reading the article linked on wiki re: phase space/relative locality...

We have observed higher energy particles arriving later than lower energy particles from gamma-ray bursts:
One idea is to look at light arriving at the Earth from distant gamma-ray bursts. If momentum space is curved in a particular way that mathematicians refer to as "non-metric", then a high-energy photon in the gamma-ray burst should arrive at our telescope a little later than a lower-energy photon from the same burst, despite the two being emitted at the same time.

Just that phenomenon has already been seen, starting with some unusual observations made by a telescope in the Canary Islands in 2005 (New Scientist, 15 August 2009, p 29)Movie Camera. The effect has since been confirmed by NASA's Fermi gamma-ray space telescope, which has been collecting light from cosmic explosions since it launched in 2008. "The Fermi data show that it is an undeniable experimental fact that there is a correlation between arrival time and energy - high-energy photons arrive later than low-energy photons," says Amelino-Camelia. (emphasis mine)
To me, as a non-physicist who likes to dabble in things now and then, it comes as a bit of a shocking thing. I would have thought higher-energy = faster (certainly higher frequency).

Why would the lower energy arrive sooner - is it because the wavelengths are longer and thus one cycle of a low-energy wave would travel farther than a single cycle of a high energy wave?

And what about amplitude? Does that play into it at all?

Hell- what, exactly does it mean to have a higher frequency? Is it, as someone else on a different site said, merely the probability wave of a photon? Are we discussing probabilities as they exist in quantum mechanics (hence energy/momentum -> uncertainty principle)?
posted by symbioid at 3:22 PM on December 10, 2013


I wonder if any of the following might be possible, and if they have been considered by SCIENCE:

1. Our brains are not flawless reality-perceiving machines.
2. We might someday confront questions that we are incapable of comprehending.
I'm pretty sure that no scientist has ever considered those possibilities. And if they did, that they'd just throw their arms in the air and go "well why am I bothering with trying to understand anything then?" and give up on it all.
posted by russm at 3:25 PM on December 10, 2013 [2 favorites]


It's kind of odd to think of the universe existing for an arbitrarily long span of time at nearly infinite density and then suddenly expanding. Why was there a sudden change?

At least the Big Bang seems to make sense on an intuitive level: something "happened" that couldn't remain stable (a singularity), then BOOM and everything that came after.
posted by Kevin Street at 3:47 PM on December 10, 2013


As a buddhist myself, I reject the Big Bang theory and endorse the Steady State model.

strikes me as obvious: if there is no god - and I find it hard to believe there is, given the existence of evil yadayadayada - then the universe has always existed. QED.

You guys understand that there's really good evidence for the big bang, right? And that you're both choosing to reject that evidence, not on the basis of its merits as evidence, but because you think it leads to conclusions that contradict your religious beliefs? Is there some reason I should give these declarations more respect than I would to a statement that evolution contradicts creation as described in the Bible?
posted by baf at 3:55 PM on December 10, 2013 [6 favorites]


symbioid: "The Fermi data show that it is an undeniable experimental fact that there is a correlation between arrival time and energy - high-energy photons arrive later than low-energy photons," says Amelino-Camelia.

"Undeniable experimental fact", really? As far as I understand it, the analyses so far show just the opposite:

* Discussion from 2009, early in the Fermi mission.
* Discussion from 2011. Here's an arXiv link to the paper in Physical Review Letters.

I wasn't aware that these papers had been comprehensively refuted. (They may have been - this isn't an area I follow closely, so maybe I'm misunderstanding something here.)
posted by RedOrGreen at 4:07 PM on December 10, 2013


If quantum mechanics allows infinitesimally improbable events to occur, and the universe has existed for an infinite period of time, wouldn't we have already collapsed out of existence, since every possible event that can occur in our universe — however unlikely — would have already occurred?
posted by Blazecock Pileon at 4:29 PM on December 10, 2013


Asking what happened one second before the big bang is like asking what is one mile north of the North Pole..

real north, or magnetic north?
posted by philip-random at 4:30 PM on December 10, 2013


You guys understand that there's really good evidence for the big bang, right? And that you're both choosing to reject that evidence, not on the basis of its merits as evidence, but because you think it leads to conclusions that contradict your religious beliefs?

I said it wasn't a religious sentiment, but it is entirely possible that buddhism fitting well with Steady State was a factor in my interest in buddhism.

I don't disagree with evidence, that is irrational. I disagree with the interpretation. I am not convinced by attempts to debunk QSSC.

In any case, BB vs SS is a red herring here, sorry to have raised it. Whether time has a beginning or not, is a completely separate issue from whether this universe has a beginning or not.
posted by charlie don't surf at 4:31 PM on December 10, 2013 [1 favorite]


If quantum mechanics allows infinitesimally improbable events to occur, and the universe has existed for an infinite period of time, wouldn't we have already collapsed out of existence, since every possible event that can occur in our universe — however unlikely — would have already occurred?

We collapse out of existence every time I close my eyes.
posted by It's Raining Florence Henderson at 4:35 PM on December 10, 2013 [2 favorites]


You know what still blows my mind, even though I kind of get it? The idea that the universe expanded at a rate faster than the speed of light. And the light went right along with it, I suppose, eventually making its way here. But still. Wow. And not for nothing, what did it inflate into? A pasteboard, I guess? Jesus I need some pot.
posted by Mister_A at 4:36 PM on December 10, 2013


The universe isn't quite as big or as old as everyone imagines. It just has a really good agent.
posted by It's Raining Florence Henderson at 4:40 PM on December 10, 2013 [1 favorite]


Blazecock, the Poincare recurrence time for the Universe is somewhere between 10^10^10^10^2.08 and 10^10^10^10^10^1.1 years, and quite possibly much, much, much, much.... much longer than that. The Universe is currently ~10^10 years old. So we haven't quite gotten around to "everything that could possibly happen has happened already and we're into reruns" territory quite yet. Though apparently the recurrence time for physics on metafilter is somewhat less than that, because, as luck would have it, I've talked a little bit about this here.
posted by physicsmatt at 4:45 PM on December 10, 2013 [5 favorites]


You can say that again!
posted by It's Raining Florence Henderson at 4:51 PM on December 10, 2013 [3 favorites]


The Universe is currently ~10^10 years old

I probably misunderstand what "infinite" means in the context presented here. If the universe is posited to have always existed, what does it mean to also say the universe is x years old?
posted by Blazecock Pileon at 4:51 PM on December 10, 2013


The universe is like a vampire. It has always been x years old.
posted by It's Raining Florence Henderson at 4:53 PM on December 10, 2013


There are artifacts like the cosmic microwave background that are just under fourteen billion years old (but not older), so something fundamental happened at that time. Even if you accept the premise of this FPP for argument's sake, that still leaves a division between countless eons of almost infinite compression and the last fourteen billion years of expansion. (IE: the lifetime of our universe.) And that fourteen billion years is way, way under the Poincare recurrence time that physicsmatt mentions.
posted by Kevin Street at 5:10 PM on December 10, 2013


Asking what happened one second before the big bang is like asking what is one mile north of the North Pole.

And as there are those who claim that god is there in the second before the Big Bang, I suggest that Santa is there, one mile north of the (geological) North Pole.
posted by insert.witticism.here at 5:11 PM on December 10, 2013


The current constituents of the space-time to which we are in causal contact with, which gives every experimental sign of having undergone a period of exponential expansion followed by a reheating to a temperature well above that of the QCD phase transition - though of course the inflationary phase is not as well attested experimentally as the effects of the reheating. This occurred 10^10 years ago (really 13.7 10^9 years ago, but who's counting). Whatever came before that, be it a previous universe, a patch of a much larger universe (call it a multiverse), or whatever, was effectively erased inside the causal patch to which we have access, though there may be some extremely difficult to detect imprints of the inflationary phase of the Universe's life in the CMB B-modes.

Now it is quite possible that the present "Universe" in which we find ourselves is in fact a low-entropy fluctuation of a much larger much older universe - call it a multiverse. However, while this idea has a great deal of appeal, you then have to wrestle with the fact that the low entropy fluctuation that makes up this Universe is far larger than any fluctuation of its sort needs to be. We are exponentially MUCH more likely to have found ourselves in a much smaller low entropy fluctuation; in fact, if this idea is correct, every sentient being is exponentially more likely to be a spontaneous created Boltzmann brain floating in empty space near absolute zero and about to die of complete lack of an environment capable of sustaining them. An exponentially small number of such brains would be poofed into existence with the matter in their brains arranged in such a way that they believe themselves to be evolved beings with memories of a past on a planet like Earth - exactly as you believe yourself to be now. This exponentially small number of Boltzmann brains would still outnumber by exponentially large factors the number of actually evolved sentients who would find themselves in a low-entropy fluctuation as large as the observable Universe.

All this is to say that A) there are serious issues raised by our understanding of statistical mechanics that must be addressed if you wish to postulate an unending (multi-)universe with the current observable Universe being only a low entropy fluctuation there-in, with no other mechanism to generate such a fluctuation (such as some models of eternal inflation). B) Though physics as yet does no have a fully satisfactory answer to these questions, we can now use the tools at our disposal to at least ask pointed questions about the consequences of various possible interpretations of the data. C) the Universe does give every indication that it evolved from a much smaller, denser state, and the colloquial name for that state is "the Big Bang." Steady-state in the sense of the present visible Universe being unchanged over time-scales much beyond a billion years is completely excluded by the evidence. Sorry. D) I have seriously considered the possibility that I am in fact a Boltzmann Brain, as have most serious cosmologists I know, so the argument that physicists are no open-minded about the possibilities holds very little water with me. and E) we don't all necessarily need to be stoned to have these conversations. Though I'm it's had it's place in the annals of scientific thought. So, you know, whatever works for you.
posted by physicsmatt at 5:13 PM on December 10, 2013 [19 favorites]


"...in fact, if this idea is correct, every sentient being is exponentially more likely to be a spontaneous created Boltzmann brain floating in empty space near absolute zero and about to die of complete lack of an environment capable of sustaining them. An exponentially small number of such brains would be poofed into existence with the matter in their brains arranged in such a way that they believe themselves to be evolved beings with memories of a past on a planet like Earth - exactly as you believe yourself to be now. This exponentially small number of Boltzmann brains would still outnumber by exponentially large factors the number of actually evolved sentients who would find themselves in a low-entropy fluctuation as large as the observable Universe."

This is the coolest thing ever!
posted by Kevin Street at 5:24 PM on December 10, 2013 [1 favorite]


I have seriously considered the possibility that I am in fact a Boltzmann Brain

That's an exponentially large coincidence. I have also seriously considered the possibility that you are in fact a Boltzmann Brain.
posted by It's Raining Florence Henderson at 5:25 PM on December 10, 2013 [2 favorites]


it's basically solipsism on the most massive scale imaginable. Which turns out to be what you need for solipsism to be true. I've discarded it mostly because accepting it as true leads to no useful lines of reasoning as far as I can tell. Though if you dislike it enough (as I do), it can lead to possibly fruitful lines of theoretical investigation, trying to figure out how to the Universe (and multiverse) would have to be arranged in order to prevent this being the most likely state of existence. Because it's gotta be wrong, right?
posted by physicsmatt at 5:31 PM on December 10, 2013 [5 favorites]


I guess we'll find out in a second...
posted by Kevin Street at 5:34 PM on December 10, 2013 [3 favorites]


who's this "we" you're talking about, random set of neural connections to which my unlikely set of initial conditions assigned the name "Kevin Street"?
posted by physicsmatt at 5:35 PM on December 10, 2013 [6 favorites]


Well, unless you want to go full college bong hit philosopher and say that the entire universe is God as Boltzmann Brain, I think it's pretty easy for me to dismiss. I'm not smart enough to be a Boltzmann Brain.
posted by It's Raining Florence Henderson at 5:38 PM on December 10, 2013 [1 favorite]


Well, high energy photons are more likely to interact with matter (being absorbed and re-emitted). Even space isn't a perfect vacuum. Seems an obvious source of slowdown.
posted by effugas at 5:41 PM on December 10, 2013


You guys understand that there's really good evidence for the big bang, right?

You guys understand that anyone who's ever followed this field of science closely at some point in their life knows that BBT is not a final solution to everything forever as it's sometimes mischaracterized, but only a damn good explanation of certain pieces of evidence as observed to-date, but with more than a few open questions and gaps that most cosmologists acknowledge will likely ultimately be explained by a larger theoretical framework (like for example certain string theory variants and other models like the Big Bounce model that are also compatible with the evidence). There's a reason people are still entering the field of cosmology and publishing new theoretical papers--Big Bang is almost certainly correct as far as it goes, but there are still many open questions that the scientific community acknowledges make viewing BBT as a complete theory problematic. It doesn't do the subject or the science any favors to be haughtily self-confident and certain about issues that aren't nearly as settled as you might think.
posted by saulgoodman at 6:28 PM on December 10, 2013


Everybody shush! We don't want physicsmatt waking up us out of existence.
posted by zengargoyle at 6:29 PM on December 10, 2013 [3 favorites]


What's the relative probability of a fluctuation giving rise to me as a Boltzmann brain vs a fluctuation that gives rise to another planet indistinguishable (though not identical) to Earth that undergoes the same pattern of evolution and gives rise to a person and environment indistinguishable from me?

Serious question. The latter may seem more unlikely, but I wouldn't be so sure. A local universe that's indistinguishable to me from the current one requires a merely astronomical coincidence, and a rerun of evolution (up to being indistinguishable to me), while fantastically unlikely, is I suspect much more likely than an equal number of atoms spontaneously assembling into the Earth, or even into one single brain-state. If the former is indeed more likely then I am almost surely really me (or at least some actual person indistinguishable from "me") and not a Boltzmann brain. But this requires calculation -- envelope-backs are needed!
posted by chortly at 6:37 PM on December 10, 2013


I am having trouble understanding the Poincaré recurrence theorem. I can easily see how a dynamical system with a finite configuration space would have to return to some state it passed through in the past, but I don't see why it would have to return to its initial state. A state machine can have the map 0 → 1 ↔ 2, so that if the initial state is 0, it is never returned to, but states 1 and 2 will be. What aspect of the Poincaré recurrence theorem is it that eliminates this sort of possibility?
posted by jepler at 6:54 PM on December 10, 2013


I guess that you can time-evolve an ODE in either direction, but my FSM can't be time-evolved in reverse from state 0. I'm not sure if this is stating the same principle (it's sure doing it sloppily), but once you argue that going forward you must self-intersect at some point, and that going backward you must self-intersect at some point, then you must have something shaped like a 0, not like a ρ.
posted by jepler at 6:59 PM on December 10, 2013


If I had to make an estimate, I'd say the recurrence time for an object should be roughly given by the number of states of a black hole of equivalent mass. This gives an upper bound, at least for an envelope calculation, due to the Bekenstein limit, which tells us that the entropy of a region is always less than that of an black hole (though now I'm questioning whether I want equivalent mass or equivalent volume).

A black hole of lets say 70 kg has a Schwarzschild radius of 8e-28 m, that of the Earth (6e24 kg) is 9e-3m. The entropy of the black hole is proportional to the surface area in Planck units (1.6e-35m). Thus, the 70kg black hole has an entropy of something like 9.5e15 in natural units, and the Earth-size one has 1.3e66. However, the relative probabilities should go like the ratios of the exponentials of these numbers, as it's the ratio of available microstates (and you only want one particular microstate). Thus, the Earth-like fluctuation is some e^(1.3e66-9.5e15)~e^(1.3e66) times less likely. And that's ignoring whether you want the Sun around or not. For reference, there are some 10^80 atoms in the observable Universe.

Of course, that doesn't tell you how long you have to wait, but that's the hard bit and I'm not doing that. Normalize to the recurrence time of the Universe.

jepler. It's a statistical statement saying the average time you'd have to wait to see a system repeat itself, not a guarantee that the system will return to a particular configuration. You might get lucky and have it reoccur earlier, or unlucky and have to wait longer. The assumption going in is that every possible configuration will be populated eventually, which in a quantum system is true, though any particular state is suppressed.
posted by physicsmatt at 7:10 PM on December 10, 2013 [4 favorites]


(I always felt a little bad for Fred Hoyle, a Steady State proponent who coined the phrase 'big bang' while trying to convince people of how ridiculous the idea was. The phrase stuck. I'm fairly certain he died still resisting the notion- maybe he'll be vindicated.)

Yup.

Did you ever read Hoyle's SF novel, The Black Cloud?

Even here, he couldn't resist having a cosmic omniscience reveal to Earthly scientists the TRVTH of the Steady State Universe (and of panspermia, another hobby-horse of his).
 
posted by Herodios at 7:23 PM on December 10, 2013 [1 favorite]


But as I understand you, e^(1.3e66) is the chance of getting a spontaneous identical earth vs a spontaneous identical human body. But that's not the core philosophical issue. The Bolzmann Brain (BB) logic is that, given the phenomenological indistinguishability of being a BB or being the original chortly, I am vastly more likely to be a BB in a very long-lived universe, since there is only one original chortly, and many BBs given enough time. But given enough time, there won't just be spontaneous BB-chortlys and spontaneous identical Earths (which of course are even less likely), but there will also be things vastly different from Earth (on the atomic level) but which evolve towards having someone phenomenologically indistinguishable from chortly on them. The trick is that the evolutionary process moves us into extremely unlikely phase space just by merit of what evolution does. So for instance, if we think that an Earth-like planet is reasonably likely to evolve not just life, but things like homo sapiens, then we need vastly fewer coincidences to get someone just like me at the right time. I don't know how many billions of years it would take to spontaneously form a BB-me (I presume a very large number), but it seems plausible that there are quite a few very Earth-like planets with very human-like creatures in just this one 10-billion-year run (so far); with a cyclic universe or multiple universes or budding universes or whatever, it might not take very many (on the scale we're talking about here) to evolve a world pretty darn similar to ours, and not that many more to produce one indistinguishable (to me) from this one. Whereas the spontaneous-BB route seems even compared to all that, vastly more unlikely. But I grant that's pretty hard to calculate, envelopes or no.
posted by chortly at 7:40 PM on December 10, 2013 [2 favorites]


This is now my favorite thread ever.
posted by It's Raining Florence Henderson at 7:44 PM on December 10, 2013 [1 favorite]


Maybe the Big Bang never happened because the universe never began because it has always existed.

This seems like a non-sequitur to me.

If you accept that all of spacetime was a singularity at the point of the big bang, then zero and infinite time [and spatial dimensions] have the same meaning with respect to the singularity.

The Big Bang implies a universe that has existed for all time.

People often trip themselves up when talking about this subject because they use language that implies passage of time to discuss a situation where time did not exist.

Instead of asking "what caused the Big Bang" maybe we should be thinking about that singularity and asking how change is possible in the absence of time?
posted by HiroProtagonist at 7:51 PM on December 10, 2013 [1 favorite]


Just to remind people, when we talk about the Big Bang, we can be talking about one of two things. The first is the reasonable extrapolation of current observations, which strongly implies that the Universe started in a dense hot thermal bath and expanded from there. This evidence only takes us to a temperature of 1 GeV. We do not at this point have unassailable evidence of the previous state of that thermal system, but I think it's not a terrible use of terminology to dub "the hot thermal system of the early observable Universe" "the Big Bang."

It is reasonable and tempting to continue to extrapolate backwards, though we must recall we do so in the absence of direct data, only hints. If we do so, barring new physics we hit a singularity above a temperature of 10^19 GeV (the Planck scale). We do not know if that singularity (and the breakdown of space-time) ever existed, maybe the new physics we expect to exist at the unification of quantum field theory and relativity will prevent one from having formed. However, under this extrapolation, it is also not unreasonable to define the expansion of that singularity as "the Big Bang."

But remember these two definitions are not exactly equivalent. One (the first) is confirmed by experiment to the degree that anything in science is confirmed. The other is a theoretical extrapolation that may or may not be true. And personally, I suspect that there was no singularity (or, not only a singularity), and the present Universe is some inflated part of a larger multiverse, though that's just my opinion and I don't have dog in this race. These days I am but a mere particle phenomenologist. I live at the TeV-scale, none of this super-Planckian inflaton stuff for me at the moment. I'll be happy to be swayed by later evidence or more compelling arguments from the cosmologists that do this for a living, or if I get really bored with the LHC or dark matter experiments, I'll dive back into this stuff in my research.

Chortly, trust me, I think the Boltzmann Brain argument is completely ridiculous. I'm just showing why, given an infinite amount of time, the numeric arguments get us into this situation it the first place.
posted by physicsmatt at 8:05 PM on December 10, 2013 [5 favorites]


I have always been suspicious of probabilistic cosmological arguments. It seems easy to have some sleight-of-hand regarding what the appropriate set of interesting events is and what the universe of possibilities is. Am I considering the probability that any Boltzman brain exists, that one identical to me exists, or one of the many points in between?
posted by PMdixon at 8:11 PM on December 10, 2013 [1 favorite]


I have seriously considered the possibility that I am in fact a Boltzmann Brain, as have most serious cosmologists I know, so the argument that physicists are no[t] open-minded about the possibilities [. . .]
I see what you did there.
posted by mistersquid at 8:26 PM on December 10, 2013




I am Brian Boltzman and I approve this thread.
posted by Napoleonic Terrier at 9:12 PM on December 10, 2013 [1 favorite]


It seems easy to have some sleight-of-hand regarding what the appropriate set of interesting events is and what the universe of possibilities is.

You will see this pretty much everywhere in metaphysical or theological speculation. For example, people will come to blows arguing over something like if "reality" exists, but they never consider ideas like whether things might be real only partially. Perhaps God exists, but there are no souls. How would we know? I say, if you hang your hat in the metaphysical whorehouse, you should have to come all the way in.
posted by thelonius at 12:18 AM on December 11, 2013


It's an interesting idea anyway. Also, if you think about it, a stew of near-infinite density existing for a practically infinite or practically zero duration of time, that suddenly starts rapidly becoming a stew of ever-decreasing density is not so different from the big bang.
It's worth pointing out that exponentially increasing but never zero models have been around as part of fairly standard cosmology for a long time. With the right ratios of components in the usual cosmological model you get exactly that. However, those are ruled out by data - see the top left of this plot for example. To make something like them fit what we see you have to do something funny (like this rainbow gravity thing).


Well, high energy photons are more likely to interact with matter (being absorbed and re-emitted). Even space isn't a perfect vacuum. Seems an obvious source of slowdown.
You have to be a bit careful with such things. Most of the stuff in space doesn't slow down light like that - it'll simply scatter it instead. And you will probably also run into problems with the amount of this slowdown if it happened being different in different directions, having funny wavelength dependences and so on, and also the Fermi results are really quite tight limits on what can happen so you have to put a lot of work into contriving something that produces an effect but only a really really tiny one.
posted by edd at 4:12 AM on December 11, 2013


Needing, wanting a beginning and an end is how humans anthropomorphize existence.
posted by judson at 7:53 AM on December 11, 2013


(but... surely there has to be a beginning, right?

No, not everything needs a beginning -- or an end. There can be a series of transmutations that we interpret as beginnings and ends -- but boundaries are a hypothetical constructs forever being challenged and dismantled...
posted by Alexandra Kitty at 10:15 AM on December 11, 2013


Chortly, trust me, I think the Boltzmann Brain argument is completely ridiculous. I'm just showing why, given an infinite amount of time, the numeric arguments get us into this situation it the first place.

That's how I used to think about these things too, but over the years -- and particularly after seeing the progress philosophers like Nick Bostrom have made -- it's become more interesting to actually take these things a bit more seriously, or at least, to see what happens if we push them a bit farther with a few rough calculations. Infinite time, at least, is not a major problem if the philosophical question turns on the ratio of BB-chortlys to re-evolved chortlys. And we can at least try to answer the question conditional upon various possible cosmological models. The hard part really is the evolution side of things, since we wander into imponderables like the Drake equation, etc. But Fermi paradox aside, it's hard to believe that even in our own single universe there are fewer than trillions of earth-like planets with homo-sapiens-like organisms, many of which may even have had continents, constellations, and histories much like ours. It seems like it would take far fewer than a few googol more rolls of the universe-replay dice to get something very like me again, which is still much more likely than a BB. But certainly the error bars have at this point gotten very wide indeed...
posted by chortly at 12:38 PM on December 11, 2013


Does the behavior of a rational actor change when the best estimate is P(BB) ≥ .999 instead of P(BB) ≤ .001? As I understand it, the outcome if BB is basically suffocating in empty space warmed only by a remnant of the CMB (if indeed you had even that much embodiment, which you probably didn't), so unless an available choice is to climb into a space suit or not you might as well act as though ¬BB.

If BB, then any estimate you have for P(BB) is suspect, being based not on observation and knowledge but on random circumstance (why wouldn't BBs have uniformly-distributed estimates of P(BB)? That seems more likely than having an accurate estimate). So any high estimate of P(BB) itself throws doubt on P(BB) being high.

Well this is a fun game.
posted by jepler at 5:56 PM on December 11, 2013


If BB, then any estimate you have for P(BB) is suspect, being based not on observation and knowledge but on random circumstance (why wouldn't BBs have uniformly-distributed estimates of P(BB)? That seems more likely than having an accurate estimate). So any high estimate of P(BB) itself throws doubt on P(BB) being high.

I believe this is the standard argument as to why we (who have the concept of Boltzman brains) are not in fact Boltzman brains.
posted by PMdixon at 8:52 PM on December 11, 2013


strikes me as obvious: if there is no god - and I find it hard to believe there is, given the existence of evil yadayadayada - then the universe has always existed. QED.

If God does exist, she must be laughing her ass off reading this thread.
posted by Golden Eternity at 9:23 PM on December 11, 2013


I just read last night that Socrates said time has no beginning and no end and neither does a person's soul.

399 BC or thereabouts.

Now we agree with the first half, right?
posted by aryma at 12:28 AM on December 12, 2013


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