More than likely it didn't. So then what? Is the universe cyclic, with no known beginning? Of course, this is the kind of model Roger Penrose proposed in Cycles of Time: An Extraordinary New View of the Universe (2010). You can read more about Penrose's conformal cyclic cosmology theory at Wikipedia.

What If the Universe Didn’t Start With the Big Bang?

Posted By Nautilus Editors on Oct 01, 2014

Last week, researchers using the Planck spacecraft to study the skies announced that the polarization of light spotted by the BICEP2 experiment could be entirely explained by dust swirling around the Milky Way. This news was a bucket of cold water on the theories of many cosmologists: It meant that BICEP2 might not have been detecting gravitational waves, which were interpreted as being proof of cosmic inflation, the long-held theory that parts of the Universe began growing astonishingly fast very soon after the Big Bang. (Read Maggie McKee’s excellent, more detailed summary of the news.)

But for Paul Steinhardt, the lack of evidence for gravitational waves was good news. Steinhardt advances an alternate theory of cosmology, doing away with inflation in favor of slower expansion of the Universe. This more gentle growth would not produce strong gravitational waves, so the lack of evidence for them means his theory is still a candidate to explain the cosmos.

Steinhardt is also, appropriately, the Nautilus Ingenious for this month. Here is a key part of McKee’s interview with him, where he describes why the Big Bang may have been a transition from a previous phase rather than an absolute beginning. You can see the entire interview and transcript here.


Maggie McKee is a freelance science writer focusing mainly on astronomy and physics. Previously an editor at New Scientist and Astronomy, she lives near Boston with her husband.

* * * * *

Ingenious: Paul J. Steinhardt

The Princeton physicist on what’s wrong with inflation theory and his view of the Big Bang.

By Maggie McKee | Produced by Yvonne Bang September 25, 2014

Paul J. Steinhardt does not look like a firebrand. With his wiry spectacles and buttoned-up bearing, he would not seem out of place in an office of accountants. But the Director of the Princeton Center for Theoretical Science is an academic agitator, vocally criticizing the leading theory of the universe’s infancy, a theory that he himself helped create more than 30 years ago. According to this picture, called inflation, space itself expanded faster than the speed of light just after the universe’s birth in the big bang, doubling in size 100,000 times in less than a billionth of a billionth of a billionth of a second.

But once started, inflation is hard to stop entirely, so pockets of space should constantly be budding off into new universes with different properties. In such a multiverse, anything that can happen will happen somewhere, and that is a fatal flaw for Steinhardt—a theory that cannot rule anything out is not scientific, he argues. He has been pursuing an alternative scenario where our universe cycles between periods of expansion and contraction, so that the big bang was really a big bounce. Most other researchers are skeptical of the approach, but Steinhardt is undeterred.

And his search for alternative schemes is not limited to cosmology. For decades, he has been pondering the different ways atoms might be arranged in crystals, discovering that arrangements previously thought to be impossible were actually allowed. In recent years he even struck out into the wilderness of the Russian Far East to look for the rarest arrangements in nature, an expedition that yielded minerals new to science, including one dubbed “steinhardtite.”

Both Steinhardt’s passion for unsolved puzzles and his critiques of overly accommodating scientific theories are on display in our video interview.

Each video question plays at the top of the screen 
[Go to the Nautilus page to view these video clips - transcripts below].

What does the term “Big Bang” mean?
According to the theory of inflation, what was the early expansion of the universe like?
What caused the expansion of the universe?
You have become a critic of inflation. Why?
Why is it so unsettling to believe we might live in an accidental universe?
What do you think of recent findings supporting the existence of gravitational waves?
You have been working on alternative theories to inflation. What are they?
What is a cyclic universe?
What is the main criticism of the cyclic universe picture?
Can we ever know the full history of the universe?
What does the Higgs boson have to do with cosmology?
How did you get into science?
Can you share some stories about the Nobelist Richard Feynman?
What are quasicrystals?
A quasicrystal is named after you. How did that happen?
How did an inflation researcher like you come to study quasicrystals?
What would you be if you weren’t a scientist?

Interview Transcript

What does the term “Big Bang” mean?

Physicists mean two things when they talk about the Big Bang. What cosmologists usually mean is the idea that the universe was once hot and dense, and has been expanding and cooling. So when people who are non-scientists ask us do we believe in the Big Bang theory, that’s usually what we’re talking about. Is there evidence that the universe was once hot and dense and has been expanding and cooling? And the answer is: There’s overwhelming evidence for that. When the public generally asks us about the Big Bang theory though, they have a different idea in mind. They have the idea of this big bang itself, the big bang beginning, the idea that the universe, you know, at one time didn’t exist and suddenly sprang from nothingness into something-ness and that’s the Big Bang. And if you ask physicists are they confident in that idea, the answer is no. There are different ideas about what might have happened as we go back to that moment in time. People have had ideas over, you know, the last century, of what might have occurred during that time and that’s a subject which is central to a lot of the debates we have in cosmology today.

According to the theory of inflation, what was the early expansion of the universe like?

So if the space between you and me, for example, were stretching at this rate at the present time, you’d be either trying to speak to me by sending a sound wave or we could send light signals, [and] the space between us would be stretching so fast that the light would be having to make up, or the sound would be having to make up the new distance. There would be [space] being created so fast, that [sound waves/light signals] would never get to you, or yours to me. We’d lose sight of one another and lose communication with one another. That’s the kind of expansion we’re talking about when we’re talking about inflation.

And just to put some numbers on it, in typical examples, the inflation begins when the universe is about a billionth, billionth, billionth, billionth of a second old, and it doubles in size roughly every billionth, billionth, billionth, billionth of a second—for maybe a hundred thousand doublings, or a million doublings, or maybe a billion doublings. That means it doubles in size or multiplies by eight in volume, you know, every billionth, billionth, billionth, billionth of a second and after a short time, a region which is smaller than a nucleus blows up to a size which is much larger than the space that we observe today when we look around the universe. We only see a finite patch of the universe. It’d be enormously bigger than that and we’d just be a tiny patch; what we would observe would just be a tiny patch of that piece of space that was once smaller than a nucleus, that blew up and inflated at that time.

What caused the expansion of the universe?  

We do not know what caused the inflation. There are, you know… Over the last 30 years, there are probably hundreds, maybe thousands of papers with people with different proposals for what is the precise field or the precise form of energy which—they all have to have the property they self-repel, they all have to produce this accelerating effect, but as for their precise identity, there are lots and lots and lots and lots of different ideas, some of which involve quantum fields like the original idea; some of which involve the use of extra dimensions; some of which use the idea from string theory, quantum strings, or quantum brains—membranes; many, many different ideas, and whichever one you choose by the time you… What we observe in the universe today doesn’t help us distinguish very keenly which one of these ideas is correct. We can eliminate some possibilities but there’s so many—there are many different options.

They all have to have the property that somehow the inflation ends. And the property… I mean one thing that’s always, that’s bothered me about the story since the very first example, is the property of getting this inflation and having it end has always involved some degree of tuning or fine-tinkering of the model, you know, fine-tuning. Every model has some sort of what we call parameters or coefficients or features in it that have to be finely adjusted in order to get what you want. If you don’t adjust them right you get something entirely different, which you don’t want, which is inconsistent with what we observe. So we don’t have what I would call a pretty theory, a theory that naturally explains this process and that’s, you know, one of the problems at present time—is to find something, a natural explanation, for what we observe. And as we observe more properties of the universe, that becomes more stringent and a more stringent constraint on our models.

You have become a critic of inflation. Why?

What we discovered is that it’s possible, that actually it’s possible, and then eventually realized it’s almost hard to avoid that inflation once it starts is really eternal—that it can end in some patches, but it will always continue yet in other patches of the universe and where it continues, it blows up in volume so much that it occupies the vast majority of the universe. And although it continues to produce patches where it ends, the patches that are inflating are always outrunning the regions where it ends, and so you end up with patch after patch after patch where inflation has ended being tiny little specks in a universe where it’s continuing.

Now those patches where it’s ended are pretty darn large—they’re large enough to contain us—so maybe you shouldn’t be, you might not be concerned at first. But the problem is, due to the effects of quantum physics these patches are not all the same. The effects of quantum physics, when you include them properly, lead to a situation where some patches are like us, but some patches are not like us; and in fact, every conceivable possible outcome of the universe can occur if you look from patch to patch to patch and there’s no particular reason why ours is more likely than any other. So in a sense we would live in this picture, in an accidental universe. We’re trying to explain the universe in a simple, forcefully deterministic way, and instead in this inflation universe, it looks like it’s an accident that we live in the universe such as we do. It could have many widely different properties.

Why is it so unsettling to believe we might live in an accidental universe?

First of all, the fact that the universe is so simple on large scales. If you observe something which could be complicated, but it turns out to be very simple, it’s screaming at you that there’s some explanation for why it is so. Now the problem with an accidental universe is that it’s not an explanation at all. It’s not even a scientific theory in the form we’re talking about—in the sense that it allows every conceivable possibility. If you allow every conceivable possibility, then there’s no test or combination of tests that can disprove such a concept. You’re allowed to have that idea if you like, but it’s no longer in the realm of science—you’re some kind of metaphysics or philosophy, which is outside the realm of science.

So the problem with inflation is that it began as an idea which seemed to have definite predictions and properties and, and with the discovery of eternal inflation, the multiverse, it moved to this accidental universe picture where it no longer has any particular test or combination of tests that can disprove it. It’s so flexible—and this is just one form of flexibility we’re talking about right now, it has other forms of flexibility—but it’s so flexible just because of this multiverse that there’s nothing… anything you would observe you’d say, “Oh, that could happen in a multiverse. That could happen too,” you know. You could just go on and on. There’d be nothing that would tell you that the theory could possibly be wrong. And such ideas, as I say, lie outside the domain of normal sciences that’s been practiced for the last 400 years. So I think it’s a very… It’s a kind of, I would call it, a failure mode. You know, usually we’re used to theories failing because they make a definite prediction, you go to make the observation, and it disagrees. That’s science as we normally understand it. It makes a prediction, it gets tested, and it fails. This is different.  This is a theory which you thought made definite predictions and now you’ve discovered that it has this sort of infinite way out and so that means it’s just no longer, you know, an ordinary scientific idea, which is a different kind of failure mode than what we’re used to.

What do you think of recent findings supporting the existence of gravitational waves?

You can’t be sure what’s causing that signal. Is it really a signal from the deep part of the sky beyond the galaxies, the thing you’re trying to detect? Is it a signal caused by the dust within our galaxy, twisting the light as it scatters from that dust? Is it a signal that’s caused by the atmosphere, which is constantly fluctuating and distorting the light as it comes to my detector? Is it light that bounces off the ground and comes into my detector and is distorted that way, or is it light that is distorted by the lens in my detector? There are many sources you’d have to look in with just a single frequency. So what they were trying to do was extremely difficult and more than could be done I would say, and so there were reasons to be concerned right off the bat and the biggest concern was, had they taken a proper account of the dust in our own galaxy? And that’s the issue that people have been focusing on most up to this point.

Because we know there is, in our own galaxy, dust, which has the property that light which comes, which scatters off of it, becomes polarized—and that is to say when the light comes, gets scattered off of us, it gets scattered off of the dust. Instead of the light coming toward it with the electric fields oscillating in every possible direction, some directions are preferred over others depending upon the particular dust particle that it scatters off of. Now that is what BICEP2 was trying to measure—was the polarization of light, not by the dust but caused in the early universe by gravitational waves. But they can’t distinguish by themselves which caused it. The dust? Or was it the gravitational waves?
Now, various groups have tried to improve on what they did and conclude that most [likely], that dust is a large contributor and perhaps the entire source of the signal they were seeing. And we’re waiting now for results from the Planck Satellite experiment, which should be presenting us with a detailed map of that particular region of the sky that the BICEP2 team measured and then we’ll be able to say more about the likelihood that they saw these gravitational waves. (See the related blog post, “Excitement About Gravity Waves Comes Crashing Down,” which reports on the Planck team’s finding that the polarization signal could be entirely explained by dust, rather than gravitational waves.)

You have been working on alternative theories to inflation. What are they? 

What if we didn’t start from the Big Bang? Maybe that’s not the beginning of space and time; and maybe what we think of as a bang, is really a bounce: a transition from a preexisting phase—let’s say of contraction—[and then] a bounce into expansion. Now suddenly there’s a whole new domain of time, before the bounce, before the bang, [with] which you can introduce processes that would naturally smooth and flatten the universe.

So the theories I’ve been working on have that property. They transform the bang to a bounce, and they introduce processes that would just naturally occur when, in a contracting universe automatically they would tend to flatten and smooth the universe. And then you add the quantum physics into it—different regions of space contracting at different times due to these random quantum fluctuations. You can’t keep things completely in sync—quantum physics doesn’t allow it—so the slight non-uniformity in the rate of contraction will translate into fluctuations, variations in temperature and density after the bounce, that would produce the fluctuations you see in the microwave background. But because this process of contraction is very gentle and slow compared to the very rapid inflationary expansion, it doesn’t produce the violent effects that produce the big gravitational waves, that high amplitude gravitational wave that inflation does. Instead it produces gravitational waves which are much, much weaker, far too weak to be observed.

We have this more realistic, contemporary version, which produces a multiverse in which anything can happen and is completely unpredictive. And then we have a theory which says in the bouncing theory, we shouldn’t see the gravitational waves in this particular kind of… in this kind of bouncing theory, you shouldn’t see these gravitational waves. And that’s the spectrum of models which we know at present and there may be other models yet to be found.

What is a cyclic universe?  

The bouncing model which I was just describing is one in which I only talked about a single bounce—taking the most recent bang and saying suppose it’s a bounce, and suppose… In that case it allows, opens up the possibility of the smoothing that accounts for the smoothness we see today, [that it] was produced during the period of contraction before that bounce.

Expand the story a bit. Was that the only bounce? Could there have been a sequence of bounces? Could there have been a kind of episodic or cyclic universe? Yes, all those things are natural possibilities. They’re natural possibilities, but I should say that during each period of contraction, and in each preceding… [and] each such bounce, there’s always going to be this smoothing process, this flattening process which has the property that in a sense you’re kind of erasing information, or spreading out information so thinly from what preceded it, [that] there is almost no trace of it in the universe that you can look at today.  You have to look for indirect evidence of this process.

So you don’t see direct evidence of earlier cycles, but you could infer they might exist based on the fact that you see the smoothness and the flatness and the absence of gravitational waves and maybe other properties explained by this sort of episodic or cyclic universe. Now once you have that possibility around theoretically you can also ask the question well, how did it begin? Did it have a beginning? Maybe. It could have had a beginning and then kind of settled into a regular pattern, or as far as we can tell theoretically, it may have continued forever into the past and forever into the future. So there is… the way you get around the problem of beginning is that there is no beginning. It was always there doing this, forever in the past and forever in the future.

What is the main criticism of the cyclic universe picture?

The one remaining issue is the bounce itself. What exactly happens with the bounce, what physics describes that bounce and there, there are several working ideas that people have. Some, in some cases, one [side] thinking about bounces in which the universe contracts to a point and then reverses itself and begins to expand right away before reaching zero size—before having to worry about the effects of quantum gravity. And so we both constructed examples like that. And then there are also examples where [another] says no, let’s go ahead and push on and see if we can explore whether quantum gravity would naturally lead to a bounce. Now both those ideas are under development.
And my view is this, this is the key problem. Whether or not we can have this bounce is the key problem of fundamental physics and cosmology. It relates to fundamental physics of quantum gravity, to the problem of cosmology. Could the smoothing have occurred before? Can we avoid the multiverse problem? They relate. You know, all these things are tied up together and I think it’s the key problem that we should be focusing on, you know, as we enter the 21st century. It’s the key problem we should be focusing on because if we can show it’s impossible, then we have to, definitely have to win, win out over the multiverse. Get control of it. If it’s possible, then I just think it’s a much simpler idea than inflation and the multiverse. Just discard that, and I think this bouncing idea is a much simpler way of explaining the universe in which… the simple universe, which we observe.

Can we ever know the full history of the universe?

I’m optimistic about our being able to figure out the history of the universe at this point because what we’ve observed about it on a large scale is this extraordinary simplicity. If it were complicated, if it looked like it came out of some complicated sausage-making machine, then you’d say, well the fact that I can only observe one part of it and I’m only seeing a little piece of the sausage, it makes it pretty hard for me to figure out the machine that produced it. But that’s not what we’re observing. We’re not observing some complicated sausage—we’re observing an extraordinary symbol of uniformed, featureless—very few degrees of freedom here to describe the universe on large scales. 
It’s also true that our fundamental physics if you, you know… recent discoveries about the Higgs in fundamental physics have just shown that to be simpler than many theorists thought it should be. So what… at the present time, I’m saying there’s fascinating simplicity observed on large scales. There’s fascinating simplicity observed on small scales. That makes me optimistic that it should be, that we should be looking for a very simple solution with so little, so few degrees of freedom that you would be in, you’d immediately be able to recognize that that’s a very sensible compelling model to explain what we observe.

What does the Higgs boson have to do with cosmology?

If we assume for the moment that the Large Hadron Collider has seen all the particles to be seen up to high, you know, reasonably high energies, there’s a surprising result that emerges from this analysis. And that is that our present universe is in a metastable state. Instead of being at the lowest energy state in the universe, it’s actually at a state of relatively high energy compared to what would be the minimum. It’s separated from that minimum by a large energy barrier, which is why we are in the state we are in and aren’t immediately jumping to a state of low energy. But ultimately if this picture is correct, we can’t be in a stable state. Eventually, some sort of quantum fluctuation or a thermal fluctuation could, is going to kick us out and we’re no longer going to be in the present vacuum state.

So that means in our present vacuum state, instead of being in a universe in which the vacuum, energy in the vacuum is relatively small and positive—which is the way it is today—and instead of being in a universe which is accelerating its expansion, it’s going to jump at some point into a state in which… that the universe is going to be begin to contract.

This kind of idea is interesting because in the kind of cyclic universe as I was describing, this is exactly what has to be the case. If the universe is going to cycle, it can’t remain in the present accelerating universe, it has to eventually end its acceleration and enter a phase of contraction and here’s the Higgs, maybe providing us with that hint that that will be, that that could occur. Then if it turns out that when you contract you bounce, that would lead to the Higgs coming back to the current vacuum, but now in a universe which is hot and expanding again and the process of expanding and cooling and forming galaxies and stars could begin again.   

So this work on microphysics which we, in the Large Hadron Collider, which we don’t normally think about as cosmology—it was really just designed to see if we could see if there was a Higgs at all—has turned out to be potentially very interesting for cosmology, much more interesting maybe even then you’d say for particle physics because it may be pointing us to new possibilities for the past and future of our universe that, that we didn’t dream were possible, and that the Higgs is pointing us to.

How did you get into science?

I think ever since I was a toddler I always wanted to be a scientist. My father used to tell me—he was not a scientist, he was a lawyer—for some reason, he used to tell me stories about scientists and discovering things in science and that just sounded to me so exciting to discover something new that no one had ever known before. I just found that extremely thrilling and so I always wanted to be a scientist of some sort. And so you know from the first books I remember you know, all my experiences were… science was always a big part of my life. And so you know, as a kid growing up I had a chemistry lab between a biology laboratory, between a telescope, and doing that kind of thing, doing lots of research that I could. You know getting, kind of getting involved in research as young as I could.

The one area which I had very little exposure to up to that point was physics and it wasn’t until I was an undergraduate at Caltech that I… I mean I took physics in high school but they were pretty prosaic courses but when I first, you know, realized that physics was really interesting was when I was an undergraduate at Caltech and I, the first year forced to take physics, for the first two years and that professor… you know, within weeks I’d met you know, very exciting people including Richard Feynman and I was completely sold: That’s, that was the science I wanted to do. And then I began to explore different areas of physics because I didn’t know much about physics when I started in it and the very last one I came to was cosmology. As I mentioned earlier, it really was as a post-doc, and I happened to walk into a lecture by Alan Guth—really never having taken a course in cosmology—that’s when I was first exposed to it and it has occupied a big part of my research life ever since.

Can you share some stories about the Nobelist Richard Feynman?  

I had several interactions with Feynman. I started a course with him called “Physics X.” My roommate and I asked him if he’d be willing to teach a “pseudo-course”—a false course—called “Physics X” in which he would come every week and he would answer any questions that you might throw at him. And that was a real thrill because literally the discussion, you know, ranged all over the map. It wasn’t just about things you know, the obvious things about particle physics you could ask about. He didn’t even particularly like that kind of question. He wanted you to bring in some phenomenon, some mysterious phenomenon and we would be discussing about you know, what might explain that phenomena. And so it’s a, it was a really important influential experience for me. 
And then I also did my senior thesis project with him, so that was another set of experiences so it left there a real mark on my thinking, including my thinking about science which has been coming back to me since the BICEP2. A lot of… BICEP2 has brought in a lot of interesting debate about… that you wouldn’t think scientists would have to debate about—about what is the nature of science, this issue of whether it’s important that science be testable or not testable, falsifiable or not falsifiable. These were issues which I think in Feynman’s mind were extremely clear and I think conventional—I would have said conventional—and certainly in my own mind, conventional and very clear, but, you know, I’ve been hearing some very interesting views that, you know, having a theory which is not falsifiable may be okay in science—and I find that very strange and actually I find it rather dangerous—but it sort of brought me back to rethinking some of my experience with Feynman from those days.

What are quasicrystals?  

Back in the 1980s, my student and I had been hypothesizing that there could exist forms of matter in which the atoms and molecules could organize themselves into patterns that were impossible for crystals, but they weren’t random either. In fact they would have symmetries which crystals, patterns do—but symmetries which crystals aren’t allowed to have.
So it’s been known for 200 years that atoms could organize themselves like building blocks into certain patterns where the atoms or clusters of atoms regularly repeat. That’s what makes a crystal a crystal. And if I make things out of building blocks that way, it’s been known for nearly 200 years, there are only certain symmetries which are possible. So all the crystals that you observe in nature up until recently, only conform to one of 32 symmetry possibilities established, you know, in the 19th century. Everything we’ve known up to that point lived that way.

But what we showed, my student, Dov Levine and I showed is that if you get away from the idea of just a single repeating unit, if you allow yourself let’s say two repeating units, so two repeating atoms, which repeat at different frequencies, suddenly symmetries which were impossible become possible. So for example, crystals can never organize themselves into any kind of structure which has five-fold symmetry. It’s forbidden for crystals—mathematically, it’s impossible. But the quasi-, the systems we were thinking about which we call quasicrystals could. In fact, they could arrange themselves and to form a solid with the symmetry of a soccer ball—which has you know many pentagons on it, many, many different axes of five-fold symmetry—we could even get that kind of structure. And while we were working on the this idea, there was a group at the National Bureau of Standards led by Dan Shechtman, which was looking at various aluminum alloys and they stumbled across one which produced a pattern of diffraction which had five-fold symmetry, which was inconsistent with the laws of crystallography. They had no explanation for it but they, you know, said, “Here it is! We don’t understand it, but you know, here’s a possibility.” And it turned out the patterns they were getting conformed precisely with the kinds of patterns we had predicted hypothetically. And so that’s how the idea of, that’s how the discovery of quasicrystals was made—the realization that the hypothetical idea and the experimental idea actually related, came through that and in 2011, Dan Shechtman won the Nobel Prize in Chemistry for his discovery of the… we now call the first quasicrystal.

A quasicrystal is named after you. How did that happen?

All the quasicrystals that have been discovered since 1984, up until recently, were discovered in the laboratory synthetically—and people even argued that they required that; they were such delicate forms of matter that they could only form that way whereas, my own thinking based on, you know, theoretical reasoning was there was no reason why that had to be so. Some quasicrystals might be energetically stable and if so, maybe they’d be found in nature. So I launched a search, a worldwide search to look for natural quasicrystals around 1998 and there’s a long story that goes with it, but about 10 years later we actually found a sample in a museum in Florence thanks to a mineralogist there, Luca Bindi, who helped us search. We found a sample of quasicrystal in a very complicated rock and there’s no question it was a quasicrystal so that could have been the end of the story, but what happened was that when we began to show this rock to geologists, or our results to geologists, they became very skeptical that it could possibly be natural. Not because it was a quasicrystal, but because it… of the particular chemistry of our quasicrystal. It had metallic aluminum in it and aluminum has a strong affinity for oxygen—so in nature, there’s lots of aluminum but there’s no metallic aluminum unless you go to as aluminum foundry. So they said this must come from an aluminum foundry, not from nature.

So that then launched a quest to try to figure out where this guy came from—where the sample from Florence came from—and over the next two years we eventually were able to show that it came from a very obscure region of far Eastern Russia, was found in the ground, was not formed in a foundry, and was actually part of a meteorite that fell there—probably about 10,000 years ago—and a meteorite that comes from the very beginning of the solar system, about 4 and a half billion years ago, so our quasicrystal’s about 4 and a half billion years old. And then I put together a geological expedition… I put together a geological expedition to go there to look for more samples, which we found, because we only had the one in the museum to begin with, and we found more and it not only had the quasicrystal but it had other new minerals that had never been seen before. And one of them is a mixture of aluminum, iron, and nickel and the team decided… so when you find a new mineral you have to write a paper explaining its properties and then you have to post a name for it and they did me the honor of calling it Steinhardtite. So that’s the Steinhardtite mineral. It’s one of the minerals found this meteorite that’s 4 and a half billion years old and that includes the first known natural quasicrystal.

How did an inflation researcher like you come to study quasicrystals?

I came to physics rather late, so when I decided I was interested in physics, I had to find out what area of physics I wanted to investigate. So what I decided to do was spend, you know, each of my undergraduate years exploring some area of science, physics rather, to decide which one I would want to choose, figuring at the end I would choose one. But what actually… I didn’t choose. Every one of those experiences led to some, you know, by some trajectory or another, to other projects that continued, almost all of them up to the present day, including spending a summer at Yale University studying, what was originally their structure of amorphous silicon—so silicon when you cool it rapidly will form a random network, and its properties have never been… were at that time and even today aren’t really fully understood, so I started on that project. That got me interested into thinking about what kind of structures, atoms, and molecules can form. Do they have to really conform to the rules of crystallography? And then again like most of you know these stories, there’s a long circuitous story—trying different things, failing, eventually led to the idea of quasicrystals.

I’m always looking around for good problems to work on so I don’t have any rules about what problems I work on, I have to… but I need an idea. So I’m always listening, to lots of different areas of science in hopes that I’ll find a good puzzle.

What would you be if you weren’t a scientist?

Hmm. That’s tough because really, that’s the only thing I’ve been thinking about. What would I be doing if I were not a scientist? Well I’d probably be teaching something about science. Yeah, I wouldn’t be a scientist but I’d probably be a teacher of some sort. At least I could… you know, I enjoy learning about it as well as doing research in it. But it’s hard for me to believe that I wouldn’t be doing research in it—at least tinkering on my own.

Maggie McKee is a freelance science writer focusing mainly on astronomy and physics. Previously an editor at New Scientist and Astronomy, she lives near Boston with her husband.

Amanda Gefter - How Is it Possible to Get Something from Nothing?

Cool article, as is often the case, from Nautilus. This piece contains one of the best lines, ever: "Heisenberg’s Uncertainty Principle is a natural source of quantum maggots." There is some context to this statement, going back to Aristotle and the thought that the arrival of maggots on rotting meat somehow happened like magic, a kind of "spontaneous generation."

The Bridge From Nowhere

How is it possible to get something from nothing?

By Amanda Gefter | August 7, 2014

THE QUESTION of being is the darkest in all philosophy.” So concluded William James in thinking about that most basic of riddles: how did something come from nothing? The question infuriates, James realized, because it demands an explanation while denying the very possibility of explanation. “From nothing to being there is no logical bridge,” he wrote.

In science, explanations are built of cause and effect. But if nothing is truly nothing, it lacks the power to cause. It’s not simply that we can’t find the right explanation—it’s that explanation itself fails in the face of nothing.

This failure hits us where it hurts. We are a narrative species. Our most basic understanding comes through stories, and how something came from nothing is the ultimate story, the primordial narrative, more fundamental than the hero’s journey or boy meets girl. Yet it is a story that undermines the notion of story. It is a narrative woven of self-destruction and paradox. 

How could it not be? It stars Nothing—a word that is a paradox by its mere existence as a word. It’s a noun, a thing, and yet it is no thing. The minute we imagine it or speak its name, we spoil its emptiness with the stain of meaning. One has to wonder, then, is the problem with nothingness or is the problem with us? Is it cosmic or linguistic? Existential or psychological? Is this a paradox of physics or a paradox of thought?

Either way, here’s the thing to remember: The solution to a paradox lies in the question, never in the answer. Somewhere there must be a glitch, a flawed assumption, a mistaken identity. In so succinct a question as “how did something come from nothing?” there aren’t many places to hide. Perhaps that is why we return again and again to the same old ideas in new and improved guises, playing the trajectory of science like a fugue, or variations on a theme. With each pass, we try to lay another stepping stone in James’s elusive bridge.

THE OLDEST STONE is this: If you can’t get something from nothing, try making nothing less like nothing. The ancient Greeks suggested that empty space is filled with substance—a plenum, an ether. Aristotle conceived of the ether as an unchanging fifth element, more perfect and heavenly in its invariance than earth, air, fire, or water. True nothingness was at odds with Aristotle’s physics, which said that bodies rise up or fall down as dictated by their rightful place in the natural order of things. Nothingness, however, would be perfectly symmetric—it would look the same from every angle—rendering absolute spatial directions like “up” and “down” utterly meaningless. An ether, Aristotle figured, could serve as a kind of cosmic compass, an ultimate reference frame against which all motion could be measured. For those who abhorred a vacuum, the ether banished every last trace of it. 

The ancient ether stuck around for millennia until it was re-imagined in the late 19th century by physicists like James Clerk Maxwell, who discovered that light behaves as a wave that always travels at a particular speed. What was waving, and speed relative to what? The ether was a handy answer, providing both a medium for light waves to travel through, and, as Aristotle originally imagined, a reference frame against which all change in the universe would unfold. But when Albert Michelson and Edward Morley set out to measure the motion of the Earth through the “ether wind” in 1887, they couldn’t find it. With his special theory of relativity, Einstein put the final nail in the coffin of the ether soon after.

For decades, we have looked at the ether as a historical oddity, a throwback. But it is harder to kill than we imagined. Today, it can be glimpsed in a new form: the Higgs field, which permeates the vacuum of empty space and whose excitation is the now-famous Higgs boson. The Higgs is what’s known as a scalar field, the only experimentally verified specimen of its kind. That means it has only a single value at every point in space (unlike the field that describes light, which at every point has both a size and direction). That’s important, because it means the field will look the same to any observer regardless of whether they are standing still or accelerating. 

What’s more, its quantum spin is zero, ensuring that it looks the same from every angle. Spin is a measure of how much you have to rotate a particle before it looks the same as when it started. Force-carrying particles (photons, gluons) have integer spin—rotations by 360 degrees will leave them unchanged. Matter particles (electrons, quarks) have half-integer spin, which means you’d have to rotate them twice, 720 degrees, before they’re back to where they started. But the Higgs has zero spin. No matter how you rotate it, it always looks the same. Just like empty space. Symmetry equals invisibility.

Following Aristotle’s intuition, physicists today conceive of nothing as the ultimate state of symmetry—a relentless sameness that precludes the differentiation one would need to define any “thing.” Indeed, as physicists run the cosmic film in reverse, tracing deep history back in time, they see the disparate shards of reality reunite and coalesce into an ever-growing symmetry, a symmetry that signifies an origin—and a nothing. 

The Higgs has become famous for giving elementary particles their mass, but this obscures its true meaning. After all, giving particles mass is easy—slow them down below the speed of light and, voilà, mass. The hard part is to give particles mass without breaking the primordial symmetry in the process. The Higgs field achieves this remarkable feat by taking on a nonzero value even in its lowest energy state. Crouching in every corner of empty space sit 246 gigaelectronvolts of Higgs—only we’ll never notice, because it’s the same at every point. Only a scalar field could hide in plain sight and get away with it. But elementary particles notice. Every time a particle’s mass breaks the symmetry of the universe, the Higgs is there, posing as empty space, repairing the damage. Constantly laboring in the shadows, the Higgs keeps the universe’s original symmetry intact. One can understand (if not forgive) the journalist’s inclination to wax religious about “the God particle”—even if Leon Lederman, who coined the reviled term, originally called it “the Goddamn particle” though his publisher wouldn’t let it fly. 

All this means that the Higgs field is closer to nothing than, say, Maxwell’s notion of the ether. It is our latest paintbrush for coloring in the void. With its unusual symmetry, the Higgs functions as nothing’s covert disguise—but it is not in itself nothing. It has structure; it interacts. The physical origin of its 246 gigaelectronvolts remains unknown. With the Higgs, we can approach the boundary with nothingness, but we cannot cross it.

IF MAKING NOTHING less like nothing doesn’t answer the question “how did something come from nothing,” perhaps we ought to make cause less like a cause. This, too, has a history. The sudden appearance of maggots in the presence of rotting meat led to a widespread belief in spontaneous generation in the time of Aristotle; the breath of life could materialize from thin air. The boundary between nothing and something was shared with the one between life and death, spirit and matter, God and earth. This in turn brought to bear the whole complex of religion and faith, making for a rather comprehensive answer to our paradox. We accepted this theory for some 2,000 years, until it was dispelled by the microbiologist Louis Pasteur in 1864. Omne vivum ex vivo—all life from life. In the decades that followed, we saw spontaneous generation as yet another historical oddity. But, like the ether, today it is back again, wearing the sheep’s clothing of quantum fluctuations.

Wrought by uncertainty, quantum fluctuations are effects without causes, the noise beneath the signal, a primeval static, random to the bone. The rules of quantum mechanics allow—actually, require—energy (and, by E=mc², mass) to appear “out of nowhere,” from nothing. Creation ex nihilo—or so it seems.

Heisenberg’s Uncertainty Principle is a natural source of quantum maggots. It says that certain pairs of physical features—position and momentum, energy and time—are bound together by a fundamental indeterminacy, so that the more accurately we specify one, the more ambiguous becomes the other. Together they form what’s known as a conjugate pair, and together they preclude the existence of nothingness. Home in on a spatial position and momentum will fluctuate wildly to compensate; specify smaller, more precise quantities of time and energy will vacillate across a wider swath of improbable values. In the shortest eye blinks, across the smallest distances, whole universes can boil up into existence, then disappear. Zoom in closely enough on the world and our calm, structured reality gives way to chaos and randomness.

Only these conjugate pairs are not in themselves random: They are the pairs of properties that would be impossible for an observer to measure simultaneously. In spite of the way quantum fluctuations are typically described, what sits “out there” in the world is not some preexisting reality wiggling around. Experiment has consistently proven that what sits “out there” isn’t sitting at all, but waiting. Unborn. Quantum fluctuations are not existential descriptions but conditional ones—they are not a reflection of what is, but of what could be, should an observer choose to make a particular measurement. It’s as if the observer’s ability to measure determines what exists. Ontology recapitulates epistemology. The uncertainty of nature is an uncertainty of observation.

The fundamental inability to assign determinate values to all the features of a physical system means that when an observer does make a measurement, the outcome will be truly random. At the tiny scales where quantum effects reign, the causal chain suffers a fatal kink. Quantum mechanics, said its founding father Niels Bohr, “is irreconcilable with the very idea of causality.” Einstein famously balked. “God doesn’t play dice,” he said, to which Bohr replied, “Einstein, stop telling God what to do.”

But perhaps it is we who are to blame for expecting causality to hold up in the first place. Evolution has trained us to find causal patterns at any cost. As our ancestors wandered the African savanna, the ability to suss out effects from their causes marked a line between life and death. She ate that speckled mushroom and then fell ill. The tiger crouched before it pounced. Narrative equals survival. Natural selection had no use for quantum physics—how were we to see it coming? Nonetheless, here it is. Causality is an approximation. Our minds, hungry for story, reel. 

Is that it, then? The answer to the question of “why being” is simply that there is no “why,” that existence is a random quantum fluctuation? Then we can forget explanation altogether and simply quantum leap across James’s bridge. How did something come from nothing? No reason. Unfortunately, the trick only takes us so far. While cosmologists do believe that the laws of quantum mechanics can spontaneously generate a universe, this story just passes the buck. For where did the laws come from? Remember, we wanted to explain how something came from nothing—not how something came from the preexisting laws of physics. Removing causality from the equation is not enough. The paradox stands.

THERE WAS NOTHING. Then, there was something. 

The lead character in this story is Time, Bearer of Change. Could the key to solving our paradox be the denial of time itself? If time, as Einstein said, is but a stubbornly persistent illusion, then we can dispense at once, not just with causality issuing from natural laws, but also with the question of where those laws came from. They didn’t come from anywhere, because nothing evolves. The narrative dissolves. There is no story. There is no bridge.

The notion of an eternal universe—or a cyclic one, fueled by eternal return—makes appearances in our earliest myths and stories, from Bantu mythology to the Australian Aboriginal “Dreamtime” to Anaximander’s cosmology to the Hindu Puranas texts. One can see the appeal. Eternity evades nothingness. 

In the modern era, this ancient idea returned as the steady-state theory, formulated by Sir James Jeans in the 1920s and refined and popularized by Fred Hoyle and others in the late 1940s. The universe expands, they said, but new matter is constantly popping into existence to fill in the gaps, so that, on net, the universe never changes at all. That theory turned out to be wrong. It was supplanted by the Big Bang theory and eternity was reduced to a mere 13.8 billion years. 

But in the 1960s, the eternal universe reappeared in a strange new form—specifically, in an equation that looked something like this: H(x)|Ψ> = 0. The physicists John Archibald Wheeler and Bryce DeWitt wrote the equation—which is now known as the Wheeler-DeWitt equation, though DeWitt prefers to call it “that damned equation” (no relation to that goddamned particle)—in their attempt to apply the strange laws of quantum mechanics to the universe as a whole, as described by Einstein’s theory of general relativity. It’s the right-hand side of the thing that’s worth noting: zero. The total energy of the system is zilch. There is no time evolution. Nothing can happen. The problem, ultimately, is that Einstein’s universe is a four-dimensional spacetime, a combination of space and time. Quantum mechanics, meanwhile, requires the wavefunction of a physical system to evolve in time. But how can spacetime evolve in time when it is time? It’s an infuriating dilemma—a universe described by quantum mechanics is inevitably frozen. The Wheeler-DeWitt equation is steady-state cosmology inverted. Rather than a universe that always was, we find ourselves with a universe that never will be.

In and of itself, the Wheeler-DeWitt equation elegantly solves our problem. How did something come from nothing? It didn’t. Of course, it’s a perplexing solution given that, well, we’re here.
And that’s precisely the point. In quantum mechanics, nothing happens until an observer (be it a human or any other configuration of particles) makes a measurement. But when it comes to the universe as a whole, there is no observer. No one can stand outside the universe. The universe as a whole is stuck in an eternal instant. But things look different here on the inside.

On the inside, an observer can’t measure the whole universe, and by necessity splits reality in two—observer and observed—by the simple yet profound fact that the observer cannot measure himself. As the physicist Raphael Bousso wrote, “Obviously the apparatus must have at least as many degrees of freedom as the system whose quantum state it attempts to establish.” The philosopher of science Thomas Breuer used a Gödelian argument to emphasize the same point: “No observer can obtain or store information sufficient to distinguish all states of a system in which he is contained.”
As observers, we are forever doomed to see only a piece of the larger puzzle of which we are a part. And that, it turns out, could be our saving grace. When the universe splits in two, the zero on the right-hand side of the equation takes on a new value. Things change. Physics happens. Time begins to flow. You might even say the universe is born.

If that sounds like retrocausation (the future causing events in the past)—well, it is. Quantum theory requires this strange reversal of time’s arrow. Wheeler emphasized this fact with his famous delayed choice experiment, which he first posed as a thought experiment but that was later demonstrated successfully in the lab. In the delayed choice, an observer’s measurement in the present determines the behavior of a particle in the past—a past that can stretch back for millions, even 13.8 billions, of years. The causal chain turns in on itself, its end links back to its beginning: James’s bridge is a loop.
Could it be that something is just what nothing looks like from the inside? If so, our discomfort with nothingness may have been hinting at something profound: It is our human nature that recoils at the notion of nothing, and yet it may also be our limited, human perspective that ultimately solves the paradox.

~ Amanda Gefter is a physics writer and author of Trespassing on Einstein’s Lawn: A father, a daughter, the meaning of nothing and the beginning of everything. She lives in Cambridge, Massachusetts.

Photo by Ben A. Pruchnie/Getty Images for Pace London

Big Bang Discovery Opens Doors to the "Multiverse" (National Geographic)

This short article (considering the subject matter) from National Geographic Daily News is a good explainer about Monday's announcement of gravitational waves and how that discovery opens the door even wider for multiverse theories (that our universe is only one of MANY universes separated by vast distances of space).

Big Bang Discovery Opens Doors to the "Multiverse"

Gravitational waves detected in the aftermath of the Big Bang suggest one universe just might not be enough.

This illustration depicts a main membrane out of which individual universes arise; they then expand in size through time. 

Written by Dan Vergano

National Geographic
Published March 18, 2014

Bored with your old dimensions—up and down, right and left, and back and forth? So tiresome. Take heart, folks. The latest news from Big Bang cosmologists offers us some relief from our humdrum four-dimensional universe.

Gravitational waves rippling through the aftermath of the cosmic fireball, physicists suggest, point to us inhabiting a multiverse, a universe filled with many universes. (See: "Big Bang's 'Smoking Gun' Confirms Early Universe's Exponential Growth.")

That's because those gravitational wave results point to a particularly prolific and potent kind of "inflation" of the early universe, an exponential expansion of the dimensions of space to many times the size of our own cosmos in the first fraction of a second of the Big Bang, some 13.82 billion years ago.

"In most models, if you have inflation, then you have a multiverse," said Stanford physicist Andrei Linde. Linde, one of cosmological inflation's inventors, spoke on Monday at the Harvard-Smithsonian Center for Astrophysics event where the BICEP2 astrophysics team unveiled the gravitational wave results.

Essentially, in the models favored by the BICEP2 team's observations, the process that inflates a universe looks just too potent to happen only once; rather, once a Big Bang starts, the process would happen repeatedly and in multiple ways. (Learn more about how universes form in "Cosmic Dawn" on the National Geographic website.)

"A multiverse offers one good possible explanation for a lot of the unique observations we have made about our universe," says MIT physicist Alan Guth, who first wrote about inflation theory in 1980. "Life being here, for example."

Lunchtime

The Big Bang and inflation make the universe look like the ultimate free lunch, Guth has suggested, where we have received something for nothing.

But Linde takes this even further, suggesting the universe is a smorgasbord stuffed with every possible free lunch imaginable.

That means every kind of cosmos is out there in the aftermath of the Big Bang, from our familiar universe chock full of stars and planets to extravaganzas that encompass many more dimensions, but are devoid of such mundane things as atoms or photons of light.

In this multiverse spawned by "chaotic" inflation, the Big Bang is just a starting point, giving rise to multiple universes (including ours) separated by unimaginable gulfs of distance. How far does the multiverse stretch? Perhaps to infinity, suggests MIT physicist Max Tegmark, writing for Scientific American.

That means that spread across space at distances far larger than the roughly 92 billion light-year width of the universe that we can observe, other universes reside, some with many more dimensions and different physical properties and trajectories. (While the light from the most distant stuff we can see started out around 14 billion light-years away, the universe is expanding at an accelerating rate, stretching the boundaries of the observable universe since then.)

Comic Mismatches

"I'm a fan of the multiverse, but I wouldn't claim it is true," says Guth. Nevertheless, he adds, a multiverse explains a lot of things that now confuse cosmologists about our universe.

For example, there is the 1998 discovery that galaxies in our universe seem to be spreading apart at an accelerating rate, when their mutual gravitational attraction should be slowing them down. This discovery, which garnered the 2011 Nobel Prize in physics, is generally thought to imply the existence of a "dark energy" that counteracts gravity on cosmic scales. Its nature is a profound mystery. About the only thing we understand about dark energy, physicists such as Michael Turner of the University of Chicago have long said, is its name.

"There is a tremendous mismatch between what we calculate [dark energy] ought to be and what we observe," Guth says. According to quantum theory, subatomic particles are constantly popping into existence and vanishing again in the vacuum of space, which should endow it with energy—but that vacuum energy, according to theoretical calculations, would be 120 orders of magnitude (a 1 followed by 120 zeroes) too large to explain the galaxy observations. The discrepancy has been a great source of embarrassment to physicists.

A multiverse could wipe the cosmic egg off their faces. On the bell curve of all possible universes spawned by inflation, our universe might just happen to be one of the few universes in which the dark energy is relatively lame. In others, the antigravity force might conform to physicists' expectations and be strong enough to rip all matter apart.

A multiverse might also explain away another embarrassment: the number of dimensions predicted by modern "superstring" theory. String theory describes subatomic particles as being composed of tiny strings of energy, but it requires there to be 11 dimensions instead of the four we actually observe. Maybe it's just describing all possible universes instead of our own. (It suggests there could be a staggeringly large number of possibilities—a 1 with 500 zeroes after it.)

Join the "multiverse club," Linde wrote in a March 9 review of inflationary cosmology, and what looks like a series of mathematical embarrassments disappears in a cloud of explanation. In a multiverse, there can be more things dreamt of in physicists' philosophy than happen to be found in our sad little heaven and earth.

Life, the Universe, and Everything

The multiverse may even help explain one of the more vexing paradoxes about our world, sometimes called the "anthropic" principle: the fact that we are here to observe it.

To cosmologists, our universe looks disturbingly fine-tuned for life. Without its Goldilocks-perfect alignment of the physical constants—everything from the strength of the force attaching electrons to atoms to the relative weakness of gravity—planets and suns, biochemistry, and life itself would be impossible. Atoms wouldn't stick together in a universe with more than four dimensions, Guth notes.

If ours was the only cosmos spawned by a Big Bang, these life-friendly properties would seem impossibly unlikely. But in a multiverse containing zillions of universes, a small number of life-friendly ones would arise by chance—and we could just happen to reside in one of them.

"Life may have formed in the small number of vacua where it was possible, in a multiverse," says Guth. "That's why we are seeing what we are seeing. Not because we are special, but because we can."


Learn more about the birth of our universe in our April issue.

Follow Dan Vergano on Twitter. 
ART BY MOONRUNNER DESIGN 

Daniel Wolf Savin - Before There Were Stars (via Nautilus)

This article from Nautilus Magazine offers some insight into the two unlikely heroes of the formation of the stars and planets that made our universe the way it is - dark matter and molecular hydrogen.

Before There Were Stars

The unlikely heroes that made starlight possible.

By Daniel Wolf Savin | Illustration by Jon Han | February 27, 2014


THE UNIVERSE is the grandest merger story that there is. Complete with mysterious origins, forces of light and darkness, and chemistry complex enough to make the chemical conglomerate BASF blush, the trip from the first moments after the Big Bang to the formation of the first stars is a story of coming together at length scales spanning many orders of magnitude. To piece together this story, scientists have turned to the skies, but also to the laboratory to simulate some of the most extreme environments in the history our universe. The resulting narrative is full of surprises. Not least among these, is how nearly it didn’t happen—and wouldn’t have, without the roles played by some unlikely heroes. Two of the most important, at least when it comes to the formation of stars, which produced the heavier elements necessary for life to emerge, are a bit surprising: dark matter and molecular hydrogen. Details aside, here is their story.

Dark Matter

The Big Bang created matter through processes we still do not fully understand. Most of it—around 84 percent by mass—was a form of matter that does not interact with or emit light. Called dark matter, it appears to interact only gravitationally. The remaining 16 percent, dubbed baryonic or ordinary matter, makes up the everyday universe that we call home. Ordinary matter interacts not only gravitationally but also electromagnetically, by emitting and absorbing photons (sometimes called radiation by the cognoscenti and known as light in the vernacular).

As the universe expanded and cooled, some of the energy from the Big Bang converted into ordinary matter: electrons, neutrons, and protons (the latter are equivalent to ionized hydrogen atoms). Today, protons and neutrons comfortably rest together in the nuclei of atoms. But in the seconds after the Big Bang, any protons and neutrons that fused to form heavier atomic nuclei were rapidly blown apart by high-energy photons called gamma rays. The residual thermal radiation field of the Big Bang provided plenty of those. It was too hot to cook. But things got better a few seconds later, when the radiation temperature dropped to about a trillion degrees Kelvin—still quite a bit hotter than the 300 Kelvin room temperature to which we are accustomed, but a world of difference for matter in the early universe.

Heavier nuclei could now survive the gamma-ray bombardment. Primordial nucleosynthesis kicked in, enabling nuclear forces to bind protons and neutrons together, until the expansion of the universe made it too cold for these fusion reactions to continue. In these 20 minutes, the universe was populated with atoms. The resulting elemental composition of the universe weighed in at roughly 76 percent hydrogen, 24 percent helium, and trace amounts of lithium—all ionized, since it was too hot for electrons to stably orbit these nuclei. And that was it, until the first stars formed and began to forge all the other elements of the periodic table.

Before these stars could form, however, newly-formed hydrogen and helium atoms needed to gather together to make dense clouds. These clouds would have been produced when slightly denser regions of the universe gravitationally attracted matter from their surroundings. The question is, was the early universe clumpy enough for this to have happened?

To answer the question, we can look to the modern-day night sky. In it, we see a faint glow of microwave radiation that has an even fainter pattern in it. This so-called cosmic microwave background structure dates back to 377,000 years after the Big Bang, a mere fraction of the universe’s current age of 13.8 billion years, and analogous to less than a day in the 81-year life expectancy for a woman living today in the United States.

At that time, the universe had just cooled to about 3,000 Kelvin. Free electrons started to be captured into orbit around protons, forming neutral hydrogen atoms. Photons from the flash of the Big Bang, whose progress had been impeded by their scattering off of unbound electrons, could now finally stream throughout the cosmos, essentially free. These photons continue to permeate the universe today, at a frigid temperature of only 2.7 Kelvin, and constitute the cosmic microwave background that we have measured using an array of ground-based, balloon-born, and satellite telescopes.

These sky maps suggested something surprising: The intensity of the residual heat from the Big Bang made the early universe too smooth for gas clouds to form.

Enter dark matter. Because it does not interact directly with light, it was unaffected by the same radiation that smoothed out ordinary matter. Therefore it was left with a relatively high degree of clumpiness. It, rather than regular matter, initiated the formation of the stars and galaxies that make up the modern structure of the universe. Regions of space with an above-average density of dark matter gravitationally attracted matter from regions with lower densities. Halos of dark matter formed and merged with other halos, bringing ordinary matter along for the ride.

Molecular Hydrogen

Once the universe went neutral, gas began to form into clouds. As ordinary matter accelerated into the gravitational wells of dark matter, gravitational potential energy converted into kinetic energy, creating a hot gas of fast-moving particles with high kinetic energies embedded within halos of dark matter. Starting from temperatures around 1,000 Kelvin, these gas clouds eventually gave birth to the first stars when the universe was roughly half a billion years old (about four years into the lifespan of the typical U.S. woman).

For a star to form, a gas cloud needs to reach a certain density; but if its constituent molecules are too hot, zipping around in every direction, this density may be unreachable. The first step toward making star-forming clouds was for gas atoms to slow down by radiating their kinetic energy out of the cloud and into the larger universe, which by this time had cooled to below 100 Kelvin.

But they can’t cool themselves: As atoms collide like billiard balls, they exchange kinetic energy. But the total kinetic energy of the gas remains unchanged. They needed a catalyst to cool off.

This catalyst was molecular hydrogen (two hydrogen atoms bound together by sharing their electrons). Hot particles colliding with this dumbbell-shaped molecule transferred some of their own energy to the molecule, causing it to rotate. Eventually these excited hydrogen molecules would relax back to their lowest-energy (or ground) state by emitting a photon that escaped from the cloud, carrying the energy out into the universe.

To make molecular hydrogen, the atomic gas clouds needed to do some chemistry. It might be surprising to hear that any chemistry was going on at all, given that the entire universe had just three elements. The most sophisticated chemical models of early gas clouds, however, include nearly 500 possible reactions. Fortunately, to understand molecular hydrogen formation, we need concern ourselves with only two key processes.

Chemists have named the first reaction associative detachment, a name fit for a psychiatric condition out of the DSM-V for which a clinician might prescribe some primordial lithium. Initially, most of the hydrogen in a gas cloud was in neutral atomic form, with the positive charge of a single proton cancelled out by the negative charge of a single orbiting electron. However, a small fraction of its atoms captured two electrons, creating a negatively charged hydrogen ion. These neutral hydrogen atoms and charged hydrogen ions “associated” with each other, causing the extra electron to detach and leaving behind neutral molecular hydrogen. In chemical notation, this can be represented as H + H- → H2 + e-. Associative detachment converted only about 0.01 percent of atomic hydrogen to molecules, but that small fraction allowed the clouds to begin to cool and become denser.

When the cloud had become sufficiently cool and dense, a second chemical reaction began. It is called three-body association, and written as H + H + H → H2 + H. This ménage-à-trois begins with three separate hydrogen atoms, and ends with two of them coupled and the third one left out in the cold. Three-body association converted essentially all of the cloud’s remaining atomic hydrogen into molecular hydrogen. Once all of the hydrogen was fully molecular, the cloud cooled to the point where its gas could condense enough to form a star.

Stars

From the formation of a dense cloud to the ignition of fusion at the heart of a star is a process whose complexity far exceeds what came before it. In fact, even the most sophisticated computer simulations available have yet to reach the point where the object becomes stellar in size, and fusion begins. Simulating most of the 200-million-year process is relatively easy, requiring only about 12 hours using high speed, parallel processing computer power. The problem lies in the final 10,000 years. As the density of the gas goes up, the structure of the cloud changes more and more rapidly. So, whereas for early times one needs only to calculate how the cloud changes every 100,000 years or so, for the final 10,000 years one must calculate the change every few days. This dramatic increase in the required number of calculation translates into more than a year of non-stop computer time on today’s fastest machines. Running simulations for the full range of possible starting conditions in these primordial clouds exceeds what can be achieved in a human lifetime. As a result, we still do not know the mass distribution for the first generation of stars. Since the mass of a star determines what elements it forges in its core, this hinders our ability to follow the pathway by which the universe began to synthesize the elements needed for life. Those of us who cannot wait to know the answer are counting on yet another hero: Moore’s Law.


~ Daniel Wolf Savin is a contrabass-playing astrophysicist at Columbia University

Do We Live in a Fluid Universe?

If we conceive of the universe as a kind of fluid, the physics of the cosmos makes a lot more sense (at least in my limited understanding). This cool article from Quanta Magazine offers a fluid model of the cosmos.

Big Bang Secrets Swirling in a Fluid Universe

By: Natalie Wolchover
February 12, 2014


A new model that treats the matter in the universe as a fluid could enable researchers to retrace the flow of the cosmos back to the Big Bang. In this image, fluidlike wisps are created as ejected gas from a supernova collides with gas and dust in the surrounding interstellar medium. Canada-France-Hawaii Telescope/Coelum
To a sound wave, the cosmos has the consistency of chocolate syrup.

That’s one discovery that scientists investigating the Big Bang have made using a new approach that treats the matter in the universe as a peculiar kind of fluid. They have calculated properties that characterize the universe’s behavior and evolution, including its viscosity, or resistance to deformation by sound waves and other disturbances.

“Twenty pascal-seconds is the viscosity of the universe,” said Leonardo Senatore, an assistant professor of physics at Stanford University — just as it is for the ice cream topping.

Leonardo Senatore, an assistant professor at Stanford University, is leading an effort to develop a new computational approach to cosmology that could reveal details about how the universe began.

The viscosity calculation could help cosmologists sleuth out the details of the Big Bang, and possibly someday identify its trigger, by enabling them to track the fluidlike flow of the cosmos back 13.8 billion years to its initial state.

As other techniques for probing the Big Bang reach their limits of sensitivity, cosmologists are co-opting the fluid approach, called “effective field theory,” from particle physics and condensed matter physics, fields in which it has been used for decades. By modeling the matter swirling throughout space as a viscous fluid, the cosmologists say they can precisely calculate how the fluid has evolved under the force of gravity — and then rewind this cosmic evolution back to the beginning. “With this approach, you can really zoom in on the initial conditions of the universe and start asking more and more precise questions,” said Enrico Pajer, a postdoctoral research fellow at Princeton University with a recent paper on the technique that has been accepted by the Journal of Cosmology and Astroparticle Physics.

The more information that astronomers gather about the distribution of galaxies throughout space — known as the “large-scale structure” of the universe — the more accurate the fluid model becomes. And the data are pouring in. The sketchy scatter plot of several thousand nearby galaxies that existed in the 1980s has given way to a far richer map of millions of galaxies, and planned telescopes will soon push the count into the billions. Proponents believe that tuned with these data points, the fluid model may grow precise enough within 10 or 15 years to prove or refute a promising Big Bang theory called “slow-roll inflation” that says the universe ballooned into existence when an entity called an inflation field slowly slid from one state to another. “There has been a big community trying to do this type of calculation for a long time,” said Matias Zaldarriaga, a professor of cosmology at the Institute for Advanced Study in Princeton, N.J. Further in the future, the researchers say, applying effective field theory to even bigger datasets could reveal properties of the inflation field, which would help physicists build a theory to explain it.

M. Blanton and Sloan Digital Sky Survey. Cosmologists hope to extract information about the Big Bang from the the next generation of large-scale structure surveys like this one from the Sloan Digital Sky Survey, which shows the distribution of galaxies from the Earth at the center to a distance of two billion light-years at the outer circle.

“It’s obviously the right tool to be using,” said John Joseph Carrasco, a theoretical physicist at Stanford. “And it’s the right time.”

Senatore, Carrasco and their Stanford collaborator Mark Hertzberg first proposed the fluid approach to modeling the universe’s large-scale structure in a 2012 paper in the Journal of High Energy Physics, motivated by the Big Bang details it could help them glean from the increasingly enormous data sets. Other researchers have since jumped on board, helping to hone the method in a slew of papers, talks and an upcoming workshop. “We’re a small, plucky band of people who are convinced this is the way forward,” said Sean Carroll, a theoretical cosmologist at the California Institute of Technology.

A Fluid Cosmos

In water, chocolate syrup and other fluids, matter is smoothly distributed on large scales and partitioned into chunks, such as atoms or molecules, on small scales. To calculate the behavior of water on the human scale, where it is a fluid, it isn’t necessary to take into account every collision between H₂O molecules on the atomic scale. In fact, having to do so would render the calculation impossible. Instead, the collective effects of all the molecular interactions at the atomic scale can be averaged and represented in the fluid equations as “bulk” properties. (Viscosity, for example, is a measure of the friction between particles and depends on their size and shape as well as the forces between them.)

Enrico Pajer, a postdoctoral fellow at Princeton University, says the matter in the universe behaves “in a very similar way as water or air.”

A similar trick works for modeling the evolution of the universe’s large-scale structure.

Just like water, the universe is smooth on large scales: The same amount of matter exists in one billion-light-year-wide region as the next. Slight variations in the matter distribution, such as more- and less-dense patches of galaxies, appear when you zoom in. At short distances, the variation becomes extreme: Individual galaxies are surrounded by voids, and within the galaxies, stars pinprick empty space. The matter distribution is constantly changing at every scale as gravity causes stars, galaxies and galaxy clusters alike to clump together and dark energy stretches the space between them. By modeling these changes, cosmologists can use the output — galaxy distribution data — to deduce the input — the initial conditions of the universe.

To a first approximation, the matter distribution at each distance scale (from large to small) can be treated as if it evolves independently. However, just as small ripples in the surface of water can affect the evolution of bigger waves, smaller clumps of matter in the universe (such as galaxy clusters) gravitationally influence the larger clumps that encompass them (such as superclusters). Accounting for this interplay in models of cosmic evolution is problematic because the gravitational effects at the shortest distance scales — at which the universe is not smooth like a fluid but rather condensed into isolated, particlelike objects — sabotage the calculation.

Effective field theory fixes the problem by accounting for the interplay between scales only down to a few times the distance between galaxies. “Everything smaller than that length scale, we treat as complicated and hard to understand, and whatever goes on at those small scales can be bundled up into one big effect,” Carroll explained. The average gravitational effect of matter on small scales is represented as a fluid’s viscosity; hence, the connection between the cosmos and chocolate syrup.

Although the former is sparse and cold while the latter is thick and usually served warm, their viscosities are calculated from data and simulations to be almost exactly equal. The number means both fluids immediately damp out an incident sound wave. “It just goes ‘dum,’ and then it disappears,” Pajer said.

The Ultimate Probe

“It’s still early days for the effective field theory of large-scale structure,” said Marc Kamionkowski, a professor of physics and astronomy at Johns Hopkins University who is not involved in developing the approach. While “it certainly does present some advantages,” he said, much work is needed before the tool can be used to extract new discoveries from astronomical data.

For example, so far, cosmologists have only developed an effective field theory model of the evolution of dark matter, an invisible substance that makes up roughly six-sevenths of the matter in the universe. Visible matter is slightly more complicated, and researchers say its behavior on short distance scales might be more difficult to represent as bulk properties of a fluid. “That is the next challenge,” said Zaldarriaga, who co-authored a November 2013 paper on the effective field theory approach. “We are doing one thing at a time.”

The researchers’ ultimate goal is to measure so-called “non-Gaussianities” in the initial conditions of the universe. If inflation theory is correct and an inflation field briefly transitioned to an unstable state, causing space to balloon 1078 times in volume, random ripples of energy called quantum fluctuations would have surfaced in the field and later grown into the large-scale structure that exists today. These ripples would be expected to follow a “Gaussian” distribution, in which energy is evenly distributed on both sides of a bell curve. Cosmologists look for non-Gaussianities, or subtle biases in the energy distribution, as signs of other, more meaningful events during inflation, such as interactions between multiple inflation fields. The recently released Planck satellite image of the cosmic microwave background indicated that energy fluctuations in the primordial universe followed a Gaussian curve to at least one part in 100,000, compatible with the slow-roll model in which the universe arose from a single inflation field. But alternative models that would have produced even smaller amounts of non-Gaussianity have not yet been ruled out.

By tuning the effective field theory model with galaxy distribution data from imminent sky surveys such as the Large Synoptic Survey Telescope project and Euclid mission, cosmologists estimate that it may be possible to improve detection of non-Gaussianities by a factor of 10 or 20. If none is detected at that sensitivity level, “we can be sure it is standard slow-roll inflation,” Senatore said. “This is extremely exciting.”

If it can be proved that the Big Bang began with slow-roll inflation, the next task would be to probe the properties of the “inflaton” — the particle associated with the inflation field, and a component of an all-encompassing theory of nature. During inflation, the inflaton must at least have interacted with itself and gravity, and both interactions would nudge the inflation field’s energy distribution ever so slightly to one side or another. Planned sky surveys will not be sensitive enough to detect such subtle non-Gaussianities, but researchers expect them to be imprinted on a signal emitted by hydrogen gas in the early universe. “This is the ultimate probe,” Pajer said.

Telescopes should detect this hydrogen signal, called the 21-centimeter line, in approximately 30 or 40 years, and effective field theory will be used to try to tease out the non-Gaussianities. “While we’re old,” said Senatore, who is 35, “we will for sure detect something.”

This article was reprinted on ScientificAmerican.com.