Cyclic universe could explain cosmic balancing act

A bouncing universe that expands and then shrinks every trillion years or so could explain one of the most puzzling problems in cosmology: how we can exist at all.

If this explanation, proposed in Science¹ by Paul Steinhardt at Princeton University, New Jersey, and Neil Turok at the University of Cambridge, UK, seems slightly preposterous, that can't really be held against it. Astronomical observations over the past decade have shown that "we live in a preposterous universe", says cosmologist Sean Carroll of the University of Chicago. "It's our job to make sense of it," he says.

In Steinhardt and Turok's cyclic model of the Universe, it expands and contracts repeatedly over timescales that make the 13.7 billion years that have passed since the Big Bang seem a mere blink. This makes the Universe vastly old. And that in turn means that the mysterious 'cosmological constant', which describes how empty space appears to repel itself, has had time to shrink into the strangely small number that we observe today.

In 1996, it was discovered that the universe is not only expanding but is also speeding up. The cosmological constant was used to describe a force of repulsion that might cause this acceleration. But physicists were baffled as to why the cosmological constant was so small.

Quantum theory suggests that 'empty' space is in fact buzzing with subatomic particles that constantly pop in and out of existence. This produces a 'vacuum energy', which makes space repel itself, providing a physical explanation for the cosmological constant.

But the theoretically calculated value of vacuum energy is enormous, making space far too repulsive for particles to come together and form atoms, stars, planets, or life. The observed vacuum energy, in contrast, is smaller by a factor of 10120 - 1 followed by 120 zeros. "It is a huge problem why the vacuum energy is so much smaller than its natural value," says Carroll.

One of the favoured explanations is the 'anthropic principle'. This suggests that in the apparently infinite Universe, the cosmological constant varies from place to place, taking on all possible values. So there's bound to be at least one region where it has the right size for galaxies and life to exist - and that's just where we are, puzzling over why our observable Universe seems so 'special'.

But this runs against the grain for physicists, who prefer to be able to explain our Universe in one shot. "Relying on the anthropic principle is like stepping on quicksand," Steinhardt and Turok write. They think they have a more satisfying explanation.

They have seized on an idea first proposed by physicist Larry Abbott in 1985: that maybe the vacuum energy was once big but has declined to ever smaller values. Abbott showed that this decay of the vacuum energy would proceed through a series of jumps, with each jump taking exponentially longer than the last. Over time, the Universe would spend far longer in states with a vacuum energy close to zero than with a high vacuum energy.

The problem was that Abbott's calculations implied that by the time the vacuum energy decayed to very small values, the expansion of space would have diluted all the matter within it so much that it would effectively be empty.

The cyclic universe gets around this problem, say Steinhardt and Turok. With cycles of growth and collapse taking a trillion years or so, and no limit to how many such cycles have preceded ours, there is plenty of time for the vacuum energy to have decayed almost to zero. And each cycle would concentrate matter during the collapse phase, making sure that the Universe doesn't end up empty.

Steinhardt and Turok say that their idea is testable. The cyclic model predicts that the Big Bang induces gravity waves in space, which physicists are now hunting for. And the decay of the vacuum energy predicts new types of fundamental particles called axions, which may also be detectable.

"It's an interesting idea," says Carroll. He confesses that he has other worries about the cyclic-universe model that temper his enthusiasm. But the wackiness of it doesn't bother him. "Any explanation is quite likely to be extreme," he says, "because all the non-extreme possibilities have already been thoroughly explored."

Maybe not, but I don't think that we can pretend that all possible structures of a quantum field that might accomodate elastic waves have been exhausted

Indeed. It could be turtles all the way down. That's just not very good bet, is all.

The imprecise stochastic nature of the small scale universe isn't a sideshow of quantum physics. It is the reason we see rainbows instead of monotone when light refracts through water. It is the reason the two-slit experiment works the curious way it does. It is the reason there's a Black Body phenomenon that allows us to measure the distance, composition, mass, and temperature of remote stars. It is the reason there is no Law of Identity in quantum physics. You can't throw the baby out without throwing the bathwater out. Stochastic assumptions underlie the math of semi-conductor physics. Throwing out stochastics ends quantum physics. If you manage to do so, it won't be a hiccup, it will a restart, and will have to use some form of deterministic mathematics if things are, as you say, elastic.

The Bohr picture of the atom wants for an electron to exist as a "cloud of probability" that can occupy two cloud grooves in two or more separate atoms simultaneously. How are you going to cope with explicit violations of a loss of the law of identity like this with some sort of "elastic" construct. The implication of "elastic" is that we aren't going to have to violate the law of identity. If we don't violate the law of identity, how will covalent bonds be explained?

Unless you plan to publish soon, this strikes me as a futile discussion--What you wish to gainsay is vastly underwritten by repeated fruitful investigations and outcomes--however unintuitive it may be, it's got a sterling track record that any "elastic" theory will have to beat to have any serious traction, and I don't think that's happening anytime soon. What we have may not be right, but it works, and, on the whole, we've tended to give scientific priority to what works.

I have to agree that they aren't going to go down this road. I don't really agree, though, that it's impossible to construct a theory that would work along those lines, particularly if that's how reality works. The physicists are content with the model they've got, and it may be another 400 or 500 years before someone decides to try to reinvent the wheel. By then, there will be so many bells and whistles on the old theory that any new idea will be met with an argument like "Well, what about that bell? Where's that bell in your model?" In fact, we are already at that point, as evidenced by your post. Comparing a newborn baby to an adult is a hard comparison.

I have difficulty understanding, though, how a scientist could buy into the notion of stochastic processes like that. What does it imply? It implies that certain physical values are determined randomly--no causal factor, no reason. That seems to undermine the very idea of mechanics. Mechanics implies causation. It also seems contrary to the conservation of energy principle. Something pops out of nowhere, for no reason. It seems supenatural to me. And these random processes don't seem to operate without limit. We don't see them operating on the macro level, for example. If a leaf falls from a tree, we can explain that by supposing that the chemical bonds became weakened. Since it happens primarily in the autumn, that's pretty good evidence that it's not random. And these stochastic processes operate within confined parameters, and only in areas that we can't come up with another theory to explain.

Nothing is, in the strictest sense, impossible. Science can't tell you what's possible or impossible; it can only tell you how the smart money would bet.

The physicists are content with the model they've got, and it may be another 400 or 500 years before someone decides to try to reinvent the wheel.

Highly un-historical baloney.

By then, there will be so many bells and whistles on the old theory that any new idea will be met with an argument like "Well, what about that bell? Where's that bell in your model?" In fact, we are already at that point, as evidenced by your post. Comparing a newborn baby to an adult is a hard comparison.

Yea, well, the fact is, we don't topple major scientific paradigms on the whim of disgruntled cranks who can't put anything any more technical on the table than their dispeptic cynicism.

I have difficulty understanding, though, how a scientist could buy into the notion of stochastic processes like that.

You're not the first, and you won't be the last. Nonetheless, it is a fundamental assumption of quantum physics.

What does it imply? It implies that certain physical values are determined randomly--no causal factor, no reason. That seems to undermine the very idea of mechanics. Mechanics implies causation.

Causation is not a tangible physical reality, it is a human construct of convenience, and even if it were a physical law, it ain't obvious how stochastic events violate it.

It also seems contrary to the conservation of energy principle.

Not particularly.

Something pops out of nowhere, for no reason. It seems supenatural to me.

Maybe it is. Science only digs it's spurs into tangible evidence. An explanation as to why quantum events occur may be permanently outside it's realm of effective concern.

And these random processes don't seem to operate without limit. We don't see them operating on the macro level, for example.

Well, that's a bit of a fine distinction. We've now thrown things as large a buckyballs thru the 2-slit experiment, and still seen them go thru both slits at once. Or are you now claiming that large molecules are just a trick of perspective?

If a leaf falls from a tree, we can explain that by supposing that the chemical bonds became weakened. Since it happens primarily in the autumn, that's pretty good evidence that it's not random. And these stochastic processes operate within confined parameters, and only in areas that we can't come up with another theory to explain.

Yea, we know it's hard to swallow. It countervailed about two centuries of hope that we lived in a clockwork universe that could ultimately be determined by a formal system with just a handful of axioms. Like Euclid's "Geometry", or Newton's "Principia". Sorry about that. There are just too many problems with that model to have any realistic expectation that it will ever be restored to scientific primacy. As comforting as it may seem, it belongs in the museum with Santa Claus and the Easter Bunny. How do you deal with my original objection: that if the universe is completely deterministic, there can't be a smallest irreducible entity?

How do you deal with my original objection: that if the universe is completely deterministic, there can't be a smallest irreducible entity?

I'm not sure how you reach that conclusion, so it's kind of hard to respond. When you think about graininess, though, the fact that the universe is grainy at some level doesn't in any event necessarily mean that there is nothing smaller than that grain. There might be something smaller, but you can't discern it because of the graininess at the larger level.

I don't see why anything I've said is inconsistent with the two slit results. In fact, the two slit experiments are perfectly consistent with the notion that particles are waves in an elastic field. Waves would be spread out, and of course, would go thru both slits. It's the idea that particles are not waves that runs into problems with the two slit experiments.

What you can or cannot detect is irrelevant. If the universe isn't stochastic, than it's deterministic. If it's deterministic, stuff is made out of stuff. If it were truly the case that you are somehow limited by nature from seeing any smaller than some given limit, than you have just hit the heisenburg uncertainty limit, whether you are willing to name it or not. If it looks like a horse, and smells like a horse, and sounds like a horse, it's a horse.

I don't see why anything I've said is inconsistent with the two slit results. In fact, the two slit experiments are perfectly consistent with the notion that particles are waves in an elastic field.

Waves would be spread out, and of course, would go thru both slits. It's the idea that particles are not waves that runs into problems with the two slit experiments.

I don't understand what the argument is here. Are you going to describe 60-atom bucky balls as purely a wave phenomenon so you can avoid acknowledging the quantum nature of light?

I don't deny the Heisenburg uncertainty principle. But it's a matter of not having the tools to measure. Even Einstein had no problem with that. That's not the same thing as saying that the parameter is simply not defined.

Let me qualify the last remark... I can envision a situation where a parameter is not defined, without resorting to randomness as an explanation. When you are dealing with waves, it really is misleading to say the wave is here or the wave is there. The truth is that the wave is everywhere. It's just a question of what the displacement is at that particular point. You might be able to detect a certain displacement, but not a smaller one. But that doesn't mean that the wave is where you can detect it, and not where you can't.

Are you going to describe 60-atom bucky balls as purely a wave phenomenon so you can avoid acknowledging the quantum nature of light?

If a particle is a wave, then an atom is simply a group of waves stuck together. It really doesn't matter whether it's 60, or a mass the size of the earth. I don't know why you think that denies the quantum nature of light, though.

In my view, a particle is a buckling of the field, while light is simply a displacement not rising to the level of a buckling. Since a particle involves a buckling, it is more like a standing wave that fills all space, than it is like a moving wave. Clearly a particle can move, but motion is not essential to its existence.

Whether it's light or a particle you're talking about though, it makes sense that there would be points at which the displacement was much greater than at other points, particularly if you are talking about a field that is partially discontinuous at the finest level, like a three-dimensional matrix of force lines, which are connected only at their points of intersection. Obviously, the place where the displacement is greatest is most likely to be at the interval between those intersections, and so the waves are going to appear to be very focused on that interval, and thus the particle nature.

The Heisenburg uncertainty principle is a matter of not having the tools to measure? If that's what you intended to say, I think you don't understand the issues in question... What does some parameters being defined or not have to do with any of this this argument?

Let me qualify the last remark... I can envision a situation where a parameter is not defined, without resorting to randomness as an explanation.

OK, now I really don't understand. How does this address the question: "If the universe is utterly deterministic, why isn't anything that's made of stuff composed of even smaller stuff, infinitely?" What difference does it make if said stuff has, or doesn't, "defined" parameters.

When you are dealing with waves, it really is misleading to say the wave is here or the wave is there. The truth is that the wave is everywhere. It's just a question of what the displacement is at that particular point. You might be able to detect a certain displacement, but not a smaller one. But that doesn't mean that the wave is where you can detect it, and not where you can't.

As a zen-like philosophical conjecture which, in fact, agrees with some interpretations of quantum physics, I can go along with the notion that waves are just a little bit everywhere. As a useful assumption of physics, I have to pretty much go along with the notion that, for all practical purposes, photons, like bucky balls are pretty much where I detect them to be.

Are you going to describe 60-atom bucky balls as purely a wave phenomenon so you can avoid acknowledging the quantum nature of light?

Because the bucky balls, like the photons, don't go thru both slits, they go thru one slit or the other.

Well, I'm not quite sure where you think you are in disagreement with quantum physicists, but here's your problem, in my opinion: the two slit experiment cannot be dragged back into sensible shape with "elastic" determinism. The light, or the buckyballs go thru one slit or the other, but definitely not both. If your theory held water, the itty bitty bit of wave that went thru the other slit would cause an itty bitty bit of diffraction. That ain't the case. The two slit experiment produces symmetric diffraction--as if two stones of the same size had been dropped in a pond. It's a genuine amazing paradox, not a trick with mirrors you can lawyer into deterministic phenomenon by shear force of confidence. That's why it violates Identity: one particle is, in a very substantial sense, availing itself of distinctly, visibly separated slits, at the same time. And that's why it needs a better explanation than the deterministic one you are touting.

The Heisenberg uncertainty principle was originally very much like not having the tools to measure. If you measured with the tools you have, it changes, and you can't get an accurate measurement. I say you don't have the tools to measure because there are no tools you can measure with that won't in some way affect the outcome of the measurement, and that was the whole point of the Heisenberg uncertainty principle. Of course, quantum physics took it one step further, and said that it's not merely that you can't measure accurately, it's actually that the parameter you are trying to measure is not defined until you measure it. That's the part Einstein had a problem with, and it's the part I have a problem with.

I'll grant you that a buckyball is different from a single particle, and might be expected to behave differently in a two slit experiment. A single particle has a field that possesses a given flux. The particles stick together because the flux of their fields is complementary. In other words, their fields become more neutral when you put them together. With a larger group of particles, you are dealing with a more neutral field, and a larger mass. At some degree of greater size, the field that you are dealing with is only a gravitaional field, and that of course is very neutral and very weak. So if it goes thru a two slit apparatus, the surrounding field (which I regard as part of the wave) is not going to have much impact on the diffraction of the particles. In the case of a single particle, there is more flux per unit of mass, so you can expect different behavior.

I don't know that you can say that a photon goes only thru one slit or the other. You might be able to say that the detectible part of the photon goes thru one slit or the other. But that does not necessarily mean that there is not a part of the wave front that also goes thru the other slit and alters the path of the photon.

Well, it's been an interesting discussion. I don't think you're going to persuade me, nor am I going to persuade you. Just out of curiosity, are you a physicist, or perhaps an engineer?

No matter how peachy the tools you have, you can still only determine precisely either the frequency or location of a particle, but not both. Tools are irrelevant.

I'll grant you that a buckyball is different from a single particle, and might be expected to behave differently in a two slit experiment.

And yet does not, respecting the behaviors in question.

A single particle has a field that possesses a given flux. The particles stick together because the flux of their fields is complementary. In other words, their fields become more neutral when you put them together. With a larger group of particles, you are dealing with a more neutral field, and a larger mass. At some degree of greater size, the field that you are dealing with is only a gravitaional field, and that of course is very neutral and very weak. So if it goes thru a two slit apparatus, the surrounding field (which I regard as part of the wave) is not going to have much impact on the diffraction of the particles. In the case of a single particle, there is more flux per unit of mass, so you can expect different behavior.

But my point was that you don't get different behavior, relevant to the discussion. Photons and buckyballs both create the same sort of equilateral diffraction patterns.

I don't know that you can say that a photon goes only thru one slit or the other. You might be able to say that the detectible part of the photon goes thru one slit or the other. But that does not necessarily mean that there is not a part of the wave front that also goes thru the other slit and alters the path of the photon.

Well, than you must say the same thing about a 60 atom buckyball. Some part of it, which you can't detect, of so much invisible presence that it has a gravitas equal to or greater than the part you can see. Since the diffraction effects are symmetric. This sounds to me very much like one of the original 8 common attempts to try to understand quantum physics in more intuitive terms. Regardless, I don't see how your invisible elephants are any better than anyone else's invisible elephants.

Well, it's been an interesting discussion. I don't think you're going to persuade me, nor am I going to persuade you. Just out of curiosity, are you a physicist, or perhaps an engineer?

Engineer, if I have to choose.

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