3.3 An Inflationary Cosmology

Previous posts in this chapter:

3.1 General and Special Relativity
3.2 Three Cosmologies

3.4 Ex Nihilo Creation
3.5 The Cosmological Argument
3.6 The Fine Tuning Argument 
3.7 The State of the Question
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3.3 In 1981, Alan Guth published a landmark paper hypothesizing that several problems in cosmology might be explained if the early universe underwent a rapid inflation in fractions of a second from a tiny, hot, dense state into a much larger size, from the microscopic to the macroscopic. [1] For one, there was the "horizon problem." This was the fact that the universe appears somewhat uniform in all directions even though it is not old enough for its parts otherwise to have ever been in contact with each other. Similarly, the universe is generally "flat," a condition that would not likely have been the case without some special circumstance such as the expansion Guth proposed.

Finally, "grand unified theories" had proposed that the fundamental forces of nature were all related to each other in the early universe. However, such theories imply the existence of monopoles, lone charges that might exist without their opposing charge. This phenomenon has never been observed. Guth proposed that they might have been so widely distributed by a rapid expansion of the early universe as to be undetected. 

In the decades that have followed, a general consensus has emerged in terms of the timeline and sequence of the universe's early expansion. Later in the chapter, we will explore how the events that unfolded seemed to be "just right" for the universe to form in a way that would eventually allow for stars and planets such as ours. If we did not live in a "Goldilocks universe," none of us would be here today.

As in the image above, the universe is currently thought to have begun in an incredibly hot, dense singularity. Then, something pulls the trigger. It begins to expand rapidly. Three minutes later, we will have atomic nuclei. [2]

The Planck Epoch
In the time from beginning to nuclei, the universe will undergo several rapid "epochs." It starts in the Planck epoch. This is the time immediately after the Big Bang when the laws of physics as we now know them break down. The universe is arguably the smallest possible space, 10^-35 meters, a quantum of space, and the smallest quantum of time passes, around 10^-43 seconds. This is the starting line.

The Grand Unification Epoch
Then gravity distinguishes itself from the other fundamental forces. This is the "Grand Unification Epoch." In the next fraction of a second, from 10^-43 to 10^-36 seconds, the other fundamental forces are still combined. Only gravity has become an independent force.

The Inflationary Epoch
Now comes the inflation. In the period from 10^-36 to 10^-32 seconds, the universe goes from a subatomic size of 10^-26 meters to about the size of a marble of 1cm. This is the period that Guth predicted, explaining the horizon problem, the flatness of the universe, and the lack of detecting monopoles.

The Electroweak Epoch
From 10^-32 to 10^-12 seconds, the strong nuclear force -- which eventually will hold the nuclei of atoms together -- distinguishes itself from the still combined other forces, called the "electroweak" force. The sphere of space that will become the universe is about 300 light seconds in size or a little more than half the distance from the Earth to the Sun.

The Quark Epoch
This epoch begins with the electroweak force dividing into the electromagnetic force and the weak nuclear force. We now have all four of the fundamental forces of nature. In this period from 10^-12 to 10^-6 seconds, we also see quarks and gluons dominate. In the Standard Model of Particle physics, quarks are some of the most fundamental of particles, thought to be the component parts of protons, neutrons, and a host of other subatomic particles. In this period, they are too hot to glue together yet, but make up a quark-gluon plasma. By the end of the epoch, the universe is about the size of our solar system.

The Hadron Epoch
Early in this period from 10^-6 to one second, matter and antimatter annihilate each other following Einstein's famous equation, E = mc². There is slightly more matter than antimatter, allowing the universe as we know it to continue to unfold. Quarks begin to fuse together to form some of the particles we learned about in high school -- protons and neutrons. The universe is now a second old, and it is now several light years across. A light year is the distance light travels in a year, going at a speed of 300,000 kilometers per second.

The Lepton Epoch
The next epoch begins as the universe cools enough for neutrinos to be liberated from matter. From about one to 10 seconds, the universe will expand to be a few million kilometers across. Particles like electrons and neutrinos dominate.  

The Nucleosynthesis Epoch
From 10 seconds to about 3 minutes, the universe has cooled enough for protons and neutrons to fuse together to form nuclei. It is still too hot for electrons to orbit, but the nuclei of hydrogen, helium, as well as some deuterium and lithium to form. [4] The universe is now several light minutes across.

The Photon Epoch
Up to this point, it seems like there is little that might conflict between science and faith. In the standard timeline, the universe is only 3 minutes old. However, the current model now supposes a period of some 380,000 years in which the universe exists in a plasma of photons (light particles), electrons, and nuclei. The soup is initially too hot to form atoms, but it is cooling. By the end of this period, the universe is thought to be about 84 millions light years in diameter.

From about 280,000 years on, the universe is getting cool enough for atoms to begin to "recombine." This will gradually happen all over the universe, reaching the peak of recombination at the end of this epoch.

At the end of ths period, the universe cools enough for photons to be released. This is thought to be the basis for the cosmic microwave background that was discovered in 1965 by Penzias and Wilson. If one is sympathetic to the idea that the days of Genesis 1 could have been epochs, then it is fascinating that the event of Day 1 is the creation of light (Gen. 1:3). According to the current inflationary model, in the 380,000th year, the universe said, "Let there be light."

The Dark Ages
The universe grows dark. The frequency of the light from the cosmic photon release gets stretched as the universe expands and red-shifts everywhere. It goes into the infrared part of the spectrum, the stuff of night goggles. According to the prevailing model, the next 150 million years are a time when gravity slowly pulls hydrogen and helium together into clumps. The expansion was uneven, so there are concentrations of matter where galaxies can form. The dark ages end as the first stars ignite, and there is a cosmic dawn.

If you would like to take Genesis metaphorically, you might see this slow separation and gathering of hydrogen across the universe as analogous to the separation of the waters in Genesis 1:6-8. Now the sky appears.

Galaxy Formation
In the prevailing model, the next 300 million years or so see the formation of huge stars that burn out quickly. The first galaxies begin to form. In the current theory, the oldest observable galaxy is MoM-z14, thought to date to about 300 million years after the Big Bang. 

Reionization Period
In the current model, at the same time galaxies are forming until about a billion years after the Big Bang, the newly formed stars and quasars begin to detach hydrogen nuclei from their electrons. It is called re-ionization because you'll remember that they had been separated in the early universe. Bubbles of ionized hydrogen gas merged with each other, leaving the transparent universe we see today when we look up to the skies.

Generations of Stars
For the next 8 billion years or so -- at least in the current model -- the first generation of stars burn out and go supernova. Some become black holes. Others crunch helium together to begin to form heavier elements like carbon and oxygen. According to the prevailing theory, the elements that will soon become the fundamental elements of life are being created in the burning out, collapsing, and re-formation of stars.

Our Solar System
Again, in the current model, our solar system forms about 4.5 billion years ago, about 9 billion years into the existence of the universe. Our Sun is thought to be a third generation star, meaning that a first star burned out and exploded. Then a second star formed with heavier elements in the mix. It burned out and exploded, creating all the elements we now know. Then that material coalesed around our Sun, Sol, with at least eight planets in tow.

The main feature of this model that could present a potential conflict with faith is the timeline. Those who take Genesis 1 to teach a full creation in six 24 hour days will object to a universe that is 13.5 billion years old. However, there are also interpretations of Genesis 1 that see no conflict here.

We will discuss various interpretations and science strategies in the next chapter. Apart from the timeline, nothing in this sequence seems intrinsically unbiblical or contrary to faith. Indeed, one could suppose that God himself was orchestrating these developments, as we will argue in the later section in this chapter on the Fine-Tuning argument.

[1] Alan H. Guth, “Inflationary universe: A possible solution to the horizon and flatness problems,” Physical Review D 23, no. 2 (1981): 347–356. He published a more popular version of his argument that same year as The Inflationary Universe: The Quest for a New Theory of Cosmic Origins (Basic, 1981).

[2] See Stephen Weinberg, The First Three Minutes: A Modern View of the Origin of the Universe (Basic, 1993).

[3] Deuterium is hydrogen with a neutron in the nucleus. Normally hydrogen has no neutrons. Lithium has three protons and four neutrons in its nucleus.

Friday Science: Cosmic Inflation

Another chapter of Brian Greene's, The Fabric of the Cosmos. I'm now within 200 pages of the end. My first nine summaries are at the bottom.

I thought I would quote his summary of this chapter from p. 301 and then add some "expansionary" comments:

1. "Early on, the energy of the universe was carried by the inflaton field, which was perched away from its minimum energy state."

The current majority opinion is that the "bang" of the big bang did not happen immediately but a small fraction of a fraction of a fraction of a second after zero (let's call it creation). Measurements indicate that the universe is expanding. And yet the temperature of the universe as a whole is more or less the same.

Alan Guth and Henry Tye realized in 1979 that if the Higgs field paused for the briefest of fractions at a not quite minimum value ("supercooled"), a special situation would be set up where gravity didn't attract but actually would repel at a tremendous value. This could explain how the universe could go from a speck to its massive size in a fraction of a fraction of a second.

2. "Because of its negative pressure, the inflaton field drove an enormous burst of inflationary expansion. Then, some 10^-35 seconds later, as the inflaton field slid down its potential energy bowl, the burst of expansion drew to a close and the inflaton released its pent-up energy to the production of ordinary matter and radiation."

So this would explain the "horizon problem," the fact that microwave background radiation is basically the same wherever you look in the universe. All the parts of space we see were once touching each other. Another problem it eventually helped solve is the "flatness problem."

The density of the universe would seem to be just right for a flat universe--at least as far as we can see. Nebraska seems flat when you're standing in it. But in the light of the earth, it isn't. But the matter/energy density of the universe seems just right, a "critical density." This is quite astounding at first glance. If it were a little more or a little less, we would think we would observe a vast difference today from what we do.

But repulsive gravity apparently pushes the value of the matter/energy density toward its critical value, so that space in our neck of the woods at least looks flat. Also, repulsive gravity seems to have gone "slower" at the beginning of the fraction of a fraction of a fraction of a second so that the temperature could even out (cf. Andrei Linde, Paul Steinhardt, and Andreas Albrecht).

3. "For many billions of years, these familiar constituents of the universe exerted an ordinary attractive gravitational pull that slowed the spatial expansion."

There is a bit of a puzzle in that, while the universe seems to fit with the critical density being the case, we can only observe 5% of matter and energy toward what that amount should be. Starting in the 1930s, there was a suggestion that some sort of matter we cannot see must be out there, keeping the stars of the galaxies we see from flinging out of them.

Thus the idea that there is some sort of "dark matter" out there has been around a long time. And it seems to account for another 25% of the matter/energy we would need for the critical density number that fits with observation to be realized.

4. "But as the universe grew and thinned out, the gravitational pull diminished. About 7 billion years ago, ordinary gravitational attraction became weak enough for the gravitational repulsion of the universe's cosmological constant to become dominant, and since then the rate of spatial expansion has been continually increasing."

By "cosmological constant," Greene refers to a debate that goes back to Einstein. Einstein didn't like the idea of an expanding universe, so he suggested a constant in his equations that held the universe static. When Hubble observed in 1929 that the universe was expanding, Einstein was embarrassed for letting his sense of how the universe should be interfere with his equations.

Years later, though, something like Einstein's constant seems to be in play. In particular, careful measurements in the 1990s suggest that the universe suddenly began to speed up big time at some point. If something else was functioning something like the constant Einstein had speculated about, it would explain it. In fact, if the remaining missing 70% of the matter/energy density were some kind of "dark energy" we can't see, that would do it.

And so there is the current suggestion. The observable universe is only 5% of the matter/energy that exists. Another 25% is a kind of matter we cannot observe ("dark matter") that holds galaxies together. The remaining 70% is a kind of energy we cannot observe ("dark energy") which is responsible for the massive acceleration that started about half-way through time. It will eventually result in a cosmic rip where the universe looks very dark and empty indeed.

Reality's Arena
1. Overview
2. Spinning Space Buckets
3. Relativity and the Absolute
4. Particles Separated at Birth

Time and Experience
5. Does time flow?
6. Does time have an arrow?
7. Quantum crazy

Spacetime and Cosmology
8. Universal symmetry
9. The Higgs Ocean

Friday Science: Fabric of Cosmos 1

1. I had been reading a book called, Our Mathematical Universe. I got through the part of the book that is generally accepted by physicists of the universe. But I came to realize that most view the rest of the book not only speculative, but perhaps bordering on the irresponsibly speculative.

So I've switched to another book on the current state of physics: Brian Greene's The Fabric of the Cosmos. Now he is also speculative. He obviously likes string theory and the idea of multiple universes. I'm not real fond of either but at least these are well-trodden paths.

So I thought I'd dawdle through this book for a few Fridays. Chapter one is called "Roads to Reality: Space, Time, and Why Things Are as They Are."

2. The progression of the chapter is roughly:

• Classical Reality
• Relativistic Reality
• Quantum Reality
• Cosmological Reality
• Past and Future Reality

The first half of this material will be familiar to the science enthusiast. He starts with Newton's sense that space and time are fixed entities in which we move. Einstein transformed our understanding here, for space and time become adjustable.

Entering the quantum reality apparently requires us to throw all our intuitions out the window. Here we encounter an idea I believe I first saw in Richard Feynman. Human intuitions were formed to help us survive and thrive in the macro-world. (I think you might say so whether you are speaking of how God made us or of how evolution developed us). The implication is that our "common sense" and our intuitions have no point of reference for the quantum world.

So the math seems to work, but no one really knows what it means. There are aspects of math itself that are are like this. Take Euler's famous equation from the 1700s: e^iπ - 1 = 0. What does it mean to raise something to the power of the square root of negative 1? I don't have a clue, but it works.

In the quantum world, at least so far, you cannot predict things. Rather, each event has a probability of happening. The universe is not determined. It is a game of chance.

3. When Greene gets to his section on cosmological reality, he covers some of the bases that I had been reading in Tegmark. One cosmological reality is the fact that the arrow of time only points in one direction. In theory, it would not have to be so. But the current sense of things is that something that happened very early in the history of the universe flipped the switch that makes time unidirectional.

Then he covers the big bang, the idea that the universe expanded rapidly into something like its current form from a much smaller version. He also mentions ideas new to me from Tegmark, which apparently have been around since the 70s and 80s--inflationary cosmology. This is a supposed period before the big bang when space itself expanded a million trillion trillion times in less than a millionth of a trillionth of a trillionth of a second.

4. What's missing is a grand unified theory that can reconcile both quantum mechanics and relativity. He seems to like Superstring theory and M theory. I sense increasing disgruntlement with these theories because there is no experimental data to suggest them whatsoever. They are completely hypothetical. Even Sheldon has given up on string theory. :-)