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SUNDAY, JUL 13, 2014 04:00 PM BST The universe according to Nietzsche: Modern cosmology and the theory of eternal recurrence – PAUL STEINHARDT

Excerpted from “The Universe: Leading Scientists Explore the Origin, Mysteries, and Future of the Cosmos.” It originally appeared as a speech given by Steinhardt at an event in 2002.

If you were to ask most cosmologists to give a summary of where we stand right now in the field, they would tell you that we live in a very special period in human history where, thanks to a whole host of advances in technology, we can suddenly view the very distant and very early universe in ways we haven’t been able to do ever before. For example, we can get a snapshot of what the universe looked like in its infancy, when the first atoms were forming. We can get a snapshot of what the universe looked like in its adolescence, when the first stars and galaxies were forming. And we are now getting a full detail, three-dimensional image of what the local universe looks like today. When you put together this different information, which we’re getting for the first time in human history, you obtain a very tight series of constraints on any model of cosmic evolution.

If you go back to the different theories of cosmic evolution in the early 1990s, the data we’ve gathered in the last decade has eliminated all of them save one, a model that you might think of today as the consensus model. This model involves a combination of the Big Bang model as developed in the 1920s, ’30s, and ’40s; the inflationary theory, which Alan Guth proposed in the 1980s; and a recent amendment that I will discuss shortly. This consensus theory matches the observations we have of the universe today in exquisite detail. For this reason, many cosmologists conclude that we have finally determined the basic cosmic history of the universe.

But I have a rather different point of view, a view that has been stimulated by two events. The first is the recent amendment to which I referred earlier. I want to argue that the recent amendment is not simply an amendment but a real shock to our whole notion of time and cosmic history. And secondly, in the last year I’ve been involved in the development of an alternative theory that turns the cosmic history topsy-turvy: All the events that created the important features of our universe occur in a different order, by different physics, at different times, over different time scales. And yet this model seems capable of reproducing all the successful predictions of the consensus picture with the same exquisite detail.

The key difference between this picture and the consensus picture comes down to the nature of time. The standard model, or consensus model, assumes that time has a beginning that we normally refer to as the Big Bang. According to that model, for reasons we don’t quite understand, the universe sprang from nothingness into somethingness, full of matter and energy, and has been expanding and cooling for the past 15 billion years. In the alternative model, the universe is endless. Time is endless, in the sense that it goes on forever in the past and forever in the future, and in some sense space is endless. Indeed, our three spatial dimensions remain infinite throughout the evolution of the universe.

More specifically, this model proposes a universe in which the evolution of the universe is cyclic. That is to say, the universe goes through periods of evolution from hot to cold, from dense to under-dense, from hot radiation to the structure we see today, and eventually to an empty universe. Then, a sequence of events occurs that cause the cycle to begin again. The empty universe is reinjected with energy, creating a new period of expansion and cooling. This process repeats periodically forever. What we’re witnessing now is simply the latest cycle.

The notion of a cyclic universe is not new. People have considered this idea as far back as recorded history. The ancient Hindus, for example, had a very elaborate and detailed cosmology based on a cyclic universe. They predicted the duration of each cycle to be 8.64 billion years—a prediction with three-digit accuracy. This is very impressive, especially since they had no quantum mechanics and no string theory! It disagrees with the number I’m going suggest, which is trillions of years rather than billions.

The cyclic notion has also been a recurrent theme in Western thought. Edgar Allan Poe and Friedrich Nietzsche, for example, each had cyclic models of the universe, and in the early days of relativistic cosmology Albert Einstein, Alexander Friedmann, Georges Lemaître, and Richard Tolman were interested in the cyclic idea. I think it’s clear why so many have found the cyclic idea to be appealing: If you have a universe with a beginning, you have the challenge of explaining why it began and the conditions under which it began. If you have a universe that’s cyclic, it’s eternal, so you don’t have to explain the beginning.

During the attempts to try to bring cyclic ideas into modern cosmology, it was discovered in the 1920s and ’30s that there are various technical problems. The idea at that time was a cycle in which our three-dimensional universe goes through periods of expansion beginning from the Big Bang and then reversal to contraction and a Big Crunch. The universe bounces, and expansion begins again. One problem is that every time the universe contracts to a crunch, the density and temperature of the universe rises to an infinite value, and it is not clear if the usual laws of physics can be applied.

Second, every cycle of expansion and contraction creates entropy through natural thermodynamic processes, which adds to the entropy from earlier cycles. So at the beginning of a new cycle, there is higher entropy density than the cycle before. It turns out that the duration of a cycle is sensitive to the entropy density. If the entropy increases, the duration of the cycle increases as well. So, going forward in time, each cycle becomes longer than the one before. The problem is that, extrapolating back in time, the cycles become shorter until, after a finite time, they shrink to zero duration. The problem of avoiding a beginning has not been solved; it has simply been pushed back a finite number of cycles. If we’re going to reintroduce the idea of a truly cyclic universe, these two problems must be overcome. The cyclic model I will describe uses new ideas to do just that.

To appreciate why an alternative model is worth pursuing, it’s important to get a more detailed impression of what the consensus picture is like. Certainly some aspects are appealing. But what I want to argue is that, overall, the consensus model is not so simple. In particular, recent observations have forced us to amend the consensus model and make it more complicated. So, let me begin with an overview of the consensus model.

The consensus theory begins with the Big Bang: The universe has a beginning. It’s a standard assumption that people have made over the last fifty years, but it’s not something we can prove at present from any fundamental laws of physics. Furthermore, you have to assume that the universe began with an energy density less than the critical value. Otherwise, the universe would stop expanding and recollapse before the next stage of evolution, the inflationary epoch. In addition, to reach this inflationary stage, there must be some sort of energy to drive the inflation. Typically this is assumed to be due to an inflation field. You have to assume that in those patches of the universe that began at less than the critical density, a significant fraction of the energy is stored in inflation energy so that it can eventually overtake the universe and start the period of accelerated expansion. All of these are reasonable assumption, but assumptions nevertheless. It’s important to take into account these assumptions and ingredients, because they’re helpful in comparing the consensus model to the challenger.

Assuming these conditions are met, the inflation energy overtakes the matter and radiation after a few instants. The inflationary epoch commences, and the expansion of the universe accelerates at a furious pace. The inflation does a number of miraculous things: It makes the universe homogeneous, it makes the universe flat, and it leaves behind certain inhomogeneities, which are supposed to be the seeds for the formation of galaxies. Now the universe is prepared to enter the next stage of evolution with the right conditions. According to the inflationary model, the inflation energy decays into a hot gas of matter and radiation. After a second or so, there form the first light nuclei. After a few tens of thousands of years, the slowly moving matter dominates the universe. It’s during these stages that the first atoms form, the universe becomes transparent, and the structure in the universe begins to form—the first stars and galaxies. Up to this point, the story is relatively simple.

But there is the recent discovery that we’ve entered a new stage in the evolution of the universe. After the stars and galaxies have formed, something strange has happened to cause the expansion of the universe to speed up again. During the 15 billion years when matter and radiation dominated the universe and structure was forming, the expansion of the universe was slowing down, because the matter and radiation within it is gravitationally self-attractive and resists the expansion of the universe. Until very recently, it had been presumed that matter would continue to be the dominant form of energy in the universe and this deceleration would continue forever.

But we’ve discovered instead, due to recent observations, that the expansion of the universe is speeding up. This means that most of the energy of the universe is neither matter nor radiation. Rather, another form of energy has overtaken the matter and radiation. For lack of a better term, this new energy form is called dark energy. Dark energy, unlike the matter and radiation we’re familiar with, is gravitationally self-repulsive. That’s why it causes the expansion to speed up rather than slow down. In Newton’s theory of gravity, all mass is gravitationally attractive, but Einstein’s theory allows the possibility of forms of energy that are gravitationally self-repulsive.

I don’t think either the physics or cosmology communities, or even the general public, have fully absorbed the full implications of this discovery. This is a revolution in the grand historic sense—in the Copernican sense. In fact, if you think about Copernicus—from whom we derive the word “revolution”—his importance was that he changed our notion of space and of our position in the universe. By showing that the Earth revolves around the sun, he triggered a chain of ideas that led us to the notion that we live in no particular place in the universe; there’s nothing special about where we are. Now we’ve discovered something very strange about the nature of time: that we may live in no special place, but we do live at a special time, a time of recent transition from deceleration to acceleration; from one in which matter and radiation dominate the universe to one in which they are rapidly becoming insignificant components; from one in which structure is forming in ever larger scales to one in which now, because of this accelerated expansion, structure formation stops. We are in the midst of the transition between these two stages of evolution. And just as Copernicus’ proposal that the Earth is no longer the center of the universe led to a chain of ideas that changed our whole outlook on the structure of the solar system and eventually to the structure of the universe, it shouldn’t be too surprising that perhaps this new discovery of cosmic acceleration could lead to a whole change in our view of cosmic history. That’s a big part of the motivation for thinking about our alternative proposal.

With these thoughts about the consensus model in mind, let me turn to the cyclic proposal. Since it’s cyclic, I’m allowed to begin the discussion of the cycle at any point I choose. To make the discussion parallel, I’ll begin at a point analogous to the Big Bang; I’ll call it the Bang. This is a point in the cycle where the universe reaches its highest temperature and density. In this scenario, though, unlike the Big Bang model, the temperature and density don’t diverge. There is a maximal, finite temperature. It’s a very high temperature, around 1020 degrees Kelvin—hot enough to evaporate atoms and nuclei into their fundamental constituents—but it’s not infinite. In fact, it’s well below the so-called Planck energy scale, where quantum gravity effects dominate. The theory begins with a bang and then proceeds directly to a phase dominated by radiation. In this scenario you do not have the inflation one has in the standard scenario. You still have to explain why the universe is flat, you still have to explain why the universe is homogeneous, and you still have to explain where the fluctuations came from that led to the formation of galaxies, but that’s not going to be explained by an early stage of inflation. It’s going to be explained by yet a different stage in the cyclic universe, which I’ll get to.

In this new model, you go directly to a radiation-dominated universe and form the usual nuclear abundances; then go directly to a matter-dominated universe in which the atoms and galaxies and larger-scale structure form; and then proceed to a phase of the universe dominated by dark energy. In the standard case, the dark energy comes as a surprise, since it’s something you have to add into the theory to make it consistent with what we observe. In the cyclic model, the dark energy moves to center stage as the key ingredient that is going to drive the universe, and in fact drives the universe, into the cyclic evolution. The first thing the dark energy does when it dominates the universe is what we observe today: It causes the expansion of the universe to begin to accelerate. Why is that important? Although this acceleration rate is 100 orders of magnitude smaller than the acceleration that one gets in inflation, if you give the universe enough time it actually accomplishes the same feat that inflation does. Over time, it thins out the distribution of matter and radiation in the universe, making the universe more and more homogeneous and isotropic—in fact, making it perfectly so—driving it into what is essentially a vacuum state.

Seth Lloyd said there were 1080 or 1090 bits inside the horizon, but if you were to look around the universe in a trillion years, you would find on average no bits inside your horizon, or less than one bit inside your horizon. In fact, when you count these bits, it’s important to realize that now that the universe is accelerating, our computer is actually losing bits from inside our horizon. This is something that we observe.

At the same time that the universe is made homogeneous and isotropic, it is also being made flat. If the universe had any warp or curvature to it, or if you think about the universe stretching over this long period of time, although it’s a slow process it makes the space extremely flat. If it continued forever, of course, that would be the end of the story. But in this scenario, just like inflation, the dark energy survives only for a finite period and triggers a series of events that eventually lead to a transformation of energy from gravity into new energy and radiation that will then start a new period of expansion of the universe. From a local observer’s point of view, it looks like the universe goes through exact cycles; that is to say, it looks like the universe empties out each round and a new matter and radiation is created, leading to a new period of expansion. In this sense it’s a cyclic universe. If you were a global observer and could see the entire universe, you’d discover that our three dimensions are forever infinite in this story. What’s happened is that at each stage when we create matter and radiation, it gets thinned out. It’s out there somewhere, but it’s getting thinned out. Locally, it looks like the universe is cyclic, but globally the universe has a steady evolution, a well-defined era in which, over time and throughout our three dimensions, entropy increases from cycle to cycle.

Exactly how this works in detail can be described in various ways. I will choose to present a very nice geometrical picture that’s motivated by superstring theory. We use only a few basic elements from superstring theory, so you don’t really have to know anything about superstring theory to understand what I’m going to talk about, except to understand that some of the strange things I’m going to introduce I am not introducing for the first time. They’re already sitting there in superstring theory waiting to be put to good purpose.

One of the ideas in superstring theory is that there are extra dimensions; it’s an essential element to that theory, which is necessary to make it mathematically consistent. In one particular formulation of that theory, the universe has a total of eleven dimensions. Six of them are curled up into a little ball so tiny that, for my purposes, I’m just going to pretend they’re not there. However, there are three spatial dimensions, one time dimension, and one additional dimension that I do want to consider. In this picture, our three dimensions with which we’re familiar and through which we move lie along a hypersurface, or membrane. This membrane is a boundary of the extra dimension. There is another boundary, or membrane, on the other side. In between, there’s an extra dimension that, if you like, only exists over a certain interval. It’s like we are one end of a sandwich, in between which there is a so-called bulk volume of space. These surfaces are referred to as orbifolds or branes—the latter referring to the word “membrane.” The branes have physical properties. They have energy and momentum, and when you excite them you can produce things like quarks and electrons. We are composed of the quarks and electrons on one of these branes. And, since quarks and leptons can only move along branes, we are restricted to moving along and seeing only the three dimensions of our brane. We cannot see directly the bulk or any matter on the other brane.

In the cyclic universe, at regular intervals of trillions of years, these two branes smash together. This creates all kinds of excitations—particles and radiation. The collision thereby heats up the branes, and then they bounce apart again. The branes are attracted to each other through a force that acts just like a spring, causing the branes to come together at regular intervals. To describe it more completely, what’s happening is that the universe goes through two kinds of stages of motion. When the universe has matter and radiation in it, or when the branes are far enough apart, the main motion is the branes stretching, or, equivalently, our three dimensions expanding. During this period, the branes more or less remain a fixed distance apart. That’s what’s been happening, for example, in the last 15 billion years. During these stages, our three dimensions are stretching just as they normally would. At a microscopic distance away, there is another brane sitting and expanding, but since we can’t touch, feel, or see across the bulk, we can’t sense it directly. If there is a clump of matter over there, we can feel the gravitational effect, but we can’t see any light or anything else it emits, because anything it emits is going to move along that brane. We only see things that move along our own brane.

Next, the energy associated with the force between these branes takes over the universe. From our vantage point on one of the branes, this acts just like the dark energy we observe today. It causes the branes to accelerate in their stretching, to the point where all the matter and radiation produced since the last collision is spread out and the branes become essentially smooth, flat, empty surfaces. If you like, you can think of them as being wrinkled and full of matter up to this point, and then stretching by a fantastic amount over the next trillion years. The stretching causes the mass and energy on the brane to thin out and the wrinkles to be smoothed out. After trillions of years, the branes are, for all intents and purposes, smooth, flat, parallel, and empty.

Then the force between these two branes slowly brings the branes together. As it brings them together, the force grows stronger and the branes speed toward one another. When they collide, there’s a walloping impact—enough to create a high density of matter and radiation with a very high, albeit finite, temperature. The two branes go flying apart, more or less back to where they are, and then the new matter and radiation, through the action of gravity, causes the branes to begin a new period of stretching.

In this picture, it’s clear that the universe is going through periods of expansion and a funny kind of contraction. Where the two branes come together, it’s not a contraction of our dimensions but a contraction of the extra dimension. Before the contraction, all matter and radiation has been spread out, but, unlike the old cyclic models of the 1920s and ’30s, it doesn’t come back together again during the contraction, because our three dimensions—that is, the branes—remain stretched out. Only the extra dimension contracts. This process repeats itself cycle after cycle.

If you compare the cyclic model to the consensus picture, two of the functions of inflation—namely, flattening and homogenizing the universe—are accomplished by the period of accelerated expansion that we’ve now just begun. Of course, I really mean the analogous expansion that occurred one cycle ago, before the most recent Bang. The third function of inflation—producing fluctuations in the density—occurs as these two branes come together. As they approach, quantum fluctuations cause the branes to begin to wrinkle. And because they’re wrinkled, they don’t collide everywhere at the same time. Rather, some regions collide a bit earlier than others. This means that some regions reheat to a finite temperature and begin to cool a little bit before other regions. When the branes come apart again, the temperature of the universe is not perfectly homogeneous but has spatial variations left over from the quantum wrinkles.

Remarkably, although the physical processes are completely different and the time scale is completely different—this is taking billions of years, instead of 10-30 seconds—it turns out that the spectrum of fluctuations you get in the distribution of energy and temperature is essentially the same as what you get in inflation. Hence, the cyclic model is also in exquisite agreement with all of the measurements of the temperature and mass distribution of the universe that we have today.

Because the physics in these two models is quite different, there is an important distinction in what we would observe if one or the other were actually true—although this effect has not been detected yet. In inflation when you create fluctuations, you don’t just create fluctuations in energy and temperature but you also create fluctuations in spacetime itself, so-called gravitational waves. That’s a feature we hope to look for in experiments in the coming decades as a verification of the consensus model. In our model, you don’t get those gravitational waves. The essential difference is that inflationary fluctuations are created in a hyperrapid, violent process that is strong enough to create gravitational waves, whereas cyclic fluctuations are created in an ultraslow, gentle process that is too weak to produce gravitational waves. That’s an example where the two models give an observational prediction that is dramatically different. It’s just difficult to observe at the present time.

What’s fascinating at the moment is that we have two paradigms now available to us. On the one hand, they are poles apart in terms of what they tell us about the nature of time, about our cosmic history, about the order in which events occur, and about the time scale on which they occur. On the other hand, they are remarkably similar in terms of what they predict about the universe today. Ultimately what will decide between the two is a combination of observations—for example, the search for cosmic gravitational waves—and theory, because a key aspect to this scenario entails assumptions about what happens at the collision between branes that might be checked or refuted in superstring theory. In the meantime, for the next few years, we can all have great fun speculating about the implications of each of these ideas and how we can best distinguish between them.

Paul Steinhardt is a theoretical physicist, an Albert Einstein Professor of Science at Princeton University and coauthor (with Neil Turok) of “Endless Universe: Beyond the Big Bang.” This piece originally appeared as a speech by Steinhardt at an event in 2002. It has been excerpted here as it appears in “The Universe: Leading Scientists Explore the Origin, Mysteries, and Future of the Cosmos.” Copyright © 2014 by Edge Foundation Inc. Published by Harper Perennial

What Happened Before The Big Bang? July 3, 2007 Penn State

Summary

New discoveries have been made about another universe whose collapse appears to have given birth to the one we have today. The research introduces a new mathematical model that gives new details about the beginning of our universe, which now appears to have been a Big Bounce, according to a new theory of quantum gravity, and not a Big Bang, as described by Einstein’s Theory of General Relativity.

New discoveries have been made about another universe whose collapse appears to have given birth to the one we live in today. They will be announced in the early on-line edition of the journal Nature Physics on 1 July 2007 and will be published in the August 2007 issue of the journal’s print edition. “My paper introduces a new mathematical model that we can use to derive new details about the properties of a quantum state as it travels through the Big Bounce, which replaces the classical idea of a Big Bang as the beginning of our universe,” said Martin Bojowald, assistant professor of physics at Penn State. Bojowald’s research also suggests that, although it is possible to learn about many properties of the earlier universe, we always will be uncertain about some of these properties because his calculations reveal a “cosmic forgetfulness” that results from the extreme quantum forces during the Big Bounce.

The idea that the universe erupted with a Big Bang explosion has been a big barrier in scientific attempts to understand the origin of our expanding universe, although the Big Bang long has been considered by physicists to be the best model. As described by Einstein’s Theory of General Relativity, the origin of the Big Bang is a mathematically nonsensical state — a “singularity” of zero volume that nevertheless contained infinite density and infinitely large energy.

Now, however, Bojowald and other physicists at Penn State are exploring territory unknown even to Einstein — the time before the Big Bang — using a mathematical time machine called Loop Quantum Gravity. This theory, which combines Einstein’s Theory of General Relativity with equations of quantum physics that did not exist in Einstein’s day, is the first mathematical description to systematically establish the existence of the Big Bounce and to deduce properties of the earlier universe from which our own may have sprung. For scientists, the Big Bounce opens a crack in the barrier that was the Big Bang.

“Einstein’s Theory of General Relativity does not include the quantum physics that you must have in order to describe the extremely high energies that dominated our universe during its very early evolution,” Bojowald explained, “but we now have Loop Quantum Gravity, a theory that does include the necessary quantum physics.” Loop Quantum Gravity was pioneered and is being developed in the Penn State Institute for Gravitational Physics and Geometry, and is now a leading approach to the goal of unifying general relativity with quantum physics. Scientists using this theory to trace our universe backward in time have found that its beginning point had a minimum volume that is not zero and a maximum energy that is not infinite. As a result of these limits, the theory’s equations continue to produce valid mathematical results past the point of the classical Big Bang, giving scientists a window into the time before the Big Bounce.

Quantum-gravity theory indicates that the fabric of space-time has an “atomic” geometry that is woven with one-dimensional quantum threads. This fabric tears violently under the extreme conditions dominated by quantum physics near the Big Bounce, causing gravity to become strongly repulsive so that, instead of vanishing into infinity as predicted by Einstein’s Theory of General Relativity, the universe rebounded in the Big Bounce that gave birth to our expanding universe. The theory reveals a contracting universe before the Big Bounce, with space-time geometry that otherwise was similar to that of our universe today.

Bojowald found he had to create a new mathematical model to use with the theory of Loop Quantum Gravity in order to explore the universe before the Big Bounce with more precision. “A more precise model was needed within Loop Quantum Gravity than the existing numerical methods, which require successive approximations of the solutions and yield results that are not as general and complete as one would like,” Bojowald explained. He developed a mathematical model that produces precise analytical solutions by solving of a set of mathematical equations.

In addition to being more precise, Bojowald’s new model also is much shorter. He reformulated the quantum-gravity models using a different mathematical description, which he says made it possible to solve the equations explicitly and also turned out to be a strong simplification. “The earlier numerical model looked much more complicated, but its solutions looked very clean, which was a clue that such a mathematical simplification might exist,” he said. Bojowald reformulated quantum gravity’s differential equations — which require many calculations of numerous consecutive small changes in time — into an integrable system — in which a cumulative length of time can be specified for adding up all the small incremental changes.

The model’s equations require parameters that describe the state of our current universe accurately so that scientists then can use the model to travel backward in time, mathematically “un-evolving” the universe to reveal its state at earlier times. The model’s equations also contain some “free” parameters that are not yet known precisely but are nevertheless necessary to describe certain properties. Bojowald discovered that two of these free parameters are complementary: one is relevant almost exclusively after the Big Bounce and the other is relevant almost exclusively before the Big Bounce. Because one of these free parameters has essentially no influence on calculations of our current universe, Bojowald colludes that it cannot be used as a tool for back-calculating its value in the earlier universe before the Big Bounce.

The two free parameters, which Bojowald found were complementary, represent the quantum uncertainty in the total volume of the universe before and after the Big Bang. “These uncertainties are additional parameters that apply when you put a system into a quantum context such as a theory of quantum gravity,” Bojowald said. “It is similar to the uncertainty relations in quantum physics, where there is complimentarity between the position of an object and its velocity — if you measure one you cannot simultaneously measure the other.”

Similarly, Bojowald’s study indicates that there is complementarity between the uncertainty factors for the volume of the universe before the Big Bounce and the universe after the Big Bounce. “For all practical purposes, the precise uncertainty factor for the volume of the previous universe never will be determined by a procedure of calculating backwards from conditions in our present universe, even with most accurate measurements we ever will be able to make,” Bojowald explained. This discovery implies further limitations for discovering whether the matter in the universe before the Big Bang was dominated more strongly by quantum or classical properties.

“A problem with the earlier numerical model is you don’t see so clearly what the free parameters really are and what their influence is,” Bojowald said. “This mathematical model gives you an improved expression that contains all the free parameters and you can immediately see the influence of each one,” he explained. “After the equations were solved, it was rather immediate to reach conclusions from the results.”

Bojowald reached an additional conclusion after finding that at least one of the parameters of the previous universe did not survive its trip through the Big Bounce — that successive universes likely will not be perfect replicas of each other. He said, “the eternal recurrence of absolutely identical universes would seem to be prevented by the apparent existence of an intrinsic cosmic forgetfulness.”

The research was sponsored, in part, by the National Science Foundation.

The above post is reprinted from materials provided by Penn State.

What if the Big Bang was really the “Big Bounce”? – Primordial inflation data may provide a clue to a unified quantum gravity. – by Chris Lee – Jul 9, 2014 5:30pm BST

Not so long ago, our very own Matthew Francis attended the press conference in which results were announced from Antarctic observatory BICEP 2. Researchers claimed that the instruments there had located the unmistakable signature of gravitational waves during primordial inflation—a period of time during which the Universe expanded at a furious rate.

But our initial article also hinted at trouble to come.

The BICEP 2 experiment measures the ratio between light scattered by gravitational waves and light scattered by everything else, which shows up in the polarization of the cosmic microwave background (CMB) radiation. BICEP 2, however, is not the only instrument that can measure the properties of the CMB. Scientists have used the Planck satellite to measure the same ratio of light scatters—and guess what? The value obtained from BICEP 2 data doesn’t agree with the value obtained from the Planck data.

Under these circumstances, we’re faced with two possibilities: either one set of experimental data has not been interpreted properly or the Universe plays by unexpected rules. These possibilities are not mutually exclusive, providing lots of room for an interesting range of explanations. Under these circumstances, theoretical physicists tend to get a bit wild around the eyes and start stocking up on food, water, paper, and pencils. Once they are in their safe place, they let their imaginations run wild…

Bounce house

A group of Chinese and Canadian physicists asked themselves if a bouncing Universe might explain both the BICEP 2 and Planck results. A bouncing Universe is a consequence of loop quantum gravity, an attempt to unify quantum mechanics and relativity. One neat feature of loop quantum gravity is that, when the Universe is dense, gravity becomes repulsive. This means that inflation occurs naturally and doesn’t require additional physics.

A secondary consequence of gravity becoming repulsive is that the Universe can’t collapse to a singularity. This implies that the Universe may not have started at the Big Bang, which (under this model) just represents the point at which the Universe was at its minimum size. At times before the Big Bang, the Universe was still collapsing from a previous expansion. In this view, the Universe is a bit like a jackalope: bounding and rebounding.

Could a bouncy Universe explain the discrepancy between BICEP 2 and Planck? As with all theoretical physics papers, the details are rather murky, but the core of the argument has to do with the fact that the Universe’s singularity is no longer a singularity.

If the Big Bang was truly a singularity, any trace of the Universe that existed before the Big Bang would have been erased in it; the singularity destroys all. However, in loop quantum gravity, the beginning of the Universe is not a singularity, and so some of the CMB has its origin in the contracting Universe that existed prior to the Big Bang.

Even this, by itself, cannot explain the discrepancy between BICEP 2 and Planck. But, according to this paper, the contraction of the Universe just before the Big Bang was slower than its expansion after the Big Bang. The contraction and expansion of the Universe modifies the spectrum of the CMB. As a result, the contribution to the CMB from before the Big Bang is different from the CMB generated by the Big Bang. Meaning that, to understand what we’re seeing, we need to separate these two contributions.

The researchers showed that the contribution from before the Big Bang suppresses the amount of power pushed into some features of the CMB (the lowest order multipoles) and, simultaneously, increases the degree to which these same modes are polarized by gravitational interactions.

You might be asking what a multipole is. If I understand it correctly, this is a way of describing the spatial distribution of the CMB. Basically, the CMB is very slightly irregular in space. Any irregular shape can be described by a series of wave-like shapes with different amplitudes and a regular frequency spacing. These amplitudes tell us how much power was radiated into a particular shape early in the Universe, which tells us a lot about what was happening at the earliest moments of the Big Bang.

The BICEP 2 experiment obtained data for the very high-order multipoles, but no data at all for the low-order multipoles. Planck, on the other hand, has great data for the high-order multipoles and very noisy data for the low-order multipoles.

The researchers claim that their model fits the two datasets better than some common standard models (known as lambda-cold dark matter models). But the lambda-CDM models are constrained by lots of data from other sources, and they simply cannot be twisted to fit the new information. This means that, if both the BICEP 2 and Planck results hold up, some of the lambda-CDM models are in trouble. Loop quantum gravity, by contrast, isn’t as well developed and has two completely unknown parameters. This gives the model the freedom to be tweaked to fit both data sets.

Unfortunately, this also means that loop quantum gravity requires some other source of data to constrain these two free parameters. At the moment, the researchers are in the position of stating that loop quantum gravity fits the existing data better and of simultaneously using that same data to determine the values of their free parameters. Once data from other sources comes in, the true test for loop quantum gravity will begin. In the meantime, I still love the idea of a bouncy cosmos.

Since its announcement, the BICEP 2 analysis has been called into question, leading Physical Review Letters to publish a warning alongside the letter reporting the BICEP 2 results. Why publish those initial results if they might be wrong? Because the work is a great first attempt, and everybody’s future results will only build on this. Science is mostly about putting down layers of bricks and mortar, rather than dropping pre-constructed buildings. The next set of results from BICEP 2, along with improved analysis of Planck data, should clarify things substantially.

Physical Review Letters, 2014, DOI: 10.1103/PhysRevLett.112.251301

Chris Lee / Chris writes for Ars Technica’s science section. A physicist by day and science writer by night, he specializes in quantum physics and optics. He lives and works in Eindhoven, the Netherlands.

Dr Param Singh – Quantum Mechanics – Bouncing Universe – Perimeter Institute

Dr Param Singh Quantum Mechanics

Dr Param Singh is working on a theory that he hopes will shorten the odds. He’s trying to overcome the same problem as everyone else, namely the rather inconvenient idea of everything emerging from nothing, one Thursday afternoon 13.7 billion years ago. But Dr Param Singh’s ideas strike at the fundamental principles that caused all the problems in the first place.

Dr Param Singh “So, if you believe the universe is expanding and if you look at its history then the universe must have expanded from something. And if you look backward and backward, what big bang theory tells you is that the universe starts expanding from nothing.”

Retracing Hubble is impossible – mathematically

The principal mathematical objection is that, as the clock is wound back, and Hubble’s zero hour is approached, all the stuff of the universe is crammed into a smaller and smaller space. Eventually, that space will become infinitely small. And in mathematics, invoking Infinity is the same as giving up. Or cheating.

Dr Param Singh “Even if the mathematical laws would not have broken down at this point, even then its philosophically very incomplete, like, how can something just originate from nothing? And that is what the theory has to explain.”

It’s Param’s job to understand how the unimaginably large emerged from the infinitesimally small.

But it’s not just philosophy and Infinity that stand in his way.

Param Singh “If you look at our universe which is at large scales, the mathematics that we know from Einstein’s theory very well describes most of the phenomena – like all phenomena. Like this ball which I throw up – it comes back.”

Quantum Mechanics

Dr Dr Param Singh “But if I want to describe what is inside this ball, the atomic structure of the ball, or how the molecules are made and how atoms are made, what are their fundamental constituents, then I don’t use classical gravity, I use a completely different physics called quantum mechanics. If I look at the universe, and I ask the question, I want to describe how it came from nothing, what was its nature when it was very small, then I have to use both the classical gravity and quantum mechanics and they don’t talk to each other. What they need is a new theory, and new mathematics. And that is the biggest problem to find.”

Dr Param Singh has been working on a new way to combine the two systems. A scheme that works in the very big AND the very small. What he’s found is that the maths predicts a very peculiar phenomenon.

Dr Param Singh “What we find is, that gravitational force, which is attractive, becomes repulsive when the universe is very small. That is predicted by the mathematics, the new mathematics which we obtain by the marriage of quantum mechanics and Einstein’s gravity. It is a completely different paradigm now.”

The problem of the Big Bang. infinities are swept away by the new “repulsive” gravity. The point of “everything is nothing” is never reached.

Equation Detail
Dr Param Singh “The maths is here, so this is one of the equations which took a couple of years to derive and the part in orange is the one that is predicted by Einstein’s theory and the part in the white is the corrections which come from quantum gravity. So if you look at this orange part, this orange part tells you that if you look at the universe, which is becoming smaller and smaller as you approach a big bang, the left-hand side and the right-hand side, they both become Infinity. And we know that whenever we encountered Infinity in mathematics, something has gone terribly wrong. So what quantum gravity gives us is this expression, which ensures that as we approach the big bang, when universe is becoming smaller and smaller, both sides become zero, and after that, the universe starts expanding again on the other direction and the same laws remain valid.”

Bouncing Universe

In Param Singh’s scheme, instead of emerging from nothing, our universe owes its existence to a previous one that had the misfortune to collapse in on itself, then, thanks to some clever maths, rebounded to become what we see today. So the big bang was not a bang at all. It was, rather, a bouncing universe, big bounce.

Dr Param Singh “It’s a surprising thing, a bouncing universe, but in nature, if you look around us, there are lots of cycles, always happening, like we have seasons, we have even the motion of planets around the sun. In fact, nature tries to prefer things were just cyclic and a way. But if we look at the whole lifespan of the age of the universe, which is billions of years, then maybe these cycles or the bounces, may not at all be surprising, and these are just the cycles of weather, in a way, for the universe, of going through contraction and expansion and contraction and expansion and so on.”

Of course, it might all be nothing more than a fantasy world of mathematics and little else. And there’s always the nagging question of what started the infinite bouncing in the first place.

Dr Param Singh “Well, that’s the most important question and I don’t know the answer to that. Maybe very soon will find an answer to how it all started.”

Scientists find first evidence that many universes exist December 17, 2010 by Lisa Zyga

(PhysOrg.com) — By looking far out into space and observing what’s going on there, scientists have been led to theorize that it all started with a Big Bang, immediately followed by a brief period of super-accelerated expansion called inflation. Perhaps this was the beginning of everything, but lately a few scientists have been wondering if something could have come before that, setting up the initial conditions for the birth of our universe.

In the most recent study on pre-Big Bang science posted at arXiv.org, a team of researchers from the UK, Canada, and the US, Stephen M. Feeney, et al, have revealed that they have discovered four statistically unlikely circular patterns in the cosmic microwave background (CMB). The researchers think that these marks could be “bruises” that our universe has incurred from being bumped four times by other universes. If they turn out to be correct, it would be the first evidence that universes other than ours do exist.

The idea that there are many other universes out there is not new, as scientists have previously suggested that we live in a “multiverse” consisting of an infinite number of universes. The multiverse concept stems from the idea of eternal inflation, in which the inflationary period that our universe went through right after the Big Bang was just one of many inflationary periods that different parts of space were and are still undergoing. When one part of space undergoes one of these dramatic growth spurts, it balloons into its own universe with its own physical properties. As its name suggests, eternal inflation occurs an infinite number of times, creating an infinite number of universes, resulting in the multiverse.

These infinite universes are sometimes called bubble universes even though they are irregular-shaped, not round. The bubble universes can move around and occasionally collide with other bubble universes. As Feeney, et al., explain in their paper, these collisions produce inhomogeneities in the inner-bubble cosmology, which could appear in the CMB. The scientists developed an algorithm to search for bubble collisions in the CMB with specific properties, which led them to find the four circular patterns.

Still, the scientists acknowledge that it is rather easy to find a variety of statistically unlikely properties in a large dataset like the CMB. The researchers emphasize that more work is needed to confirm this claim, which could come in short time from the Planck satellite, which has a resolution three times better than that of WMAP (where the current data comes from), as well as an order of magnitude greater sensitivity. Nevertheless, they hope that the search for bubble collisions could provide some insight into the history of our universe, whether or not the collisions turn out to be real.

“The conclusive non-detection of a bubble collision can be used to place stringent limits on theories giving rise to eternal inflation; however, if a bubble collision is verified by future data, then we will gain an insight not only into our own universe but a multiverse beyond,” the researchers write in their study.

This is the second study in the past month that has used CMB data to search for what could have occurred before the Big Bang. In the first study, Roger Penrose and Vahe Gurzadyan found concentric circles with lower-than-average temperature variation in the CMB, which could be evidence for a cyclic cosmology in which Big Bangs occur over and over.

© 2010 PhysOrg.com

The Augustinian Era

Big History begins at 0.0000000000000000000000000000000000000000001 seconds after The Big Bang, or the first Planck Unit, when Eienstein’s Theory of Relativy breaks down.

Saint Augustine believed that before the birth of the universe there was no time. Eienstein’s Theory of Relativity backs this up. This period has become known as the Augustinian Era since it was named in 1952 by George Gamow.