by GENE HOWINGTON
“I am large, I contain multitudes.” – Walt Whitman
Our understanding of the universe changed in a fundamental and exciting way this week when the results of the BICEP2 experiment were revealed. It all revolves around something known as B-mode polarization, a signal in the cosmic microwave background radiation. The CMB is the thermal radiation assumed to be left over from the “Big Bang” of cosmology. These signals are important because they reveal information about the state of the universe before it was directly visually observable. One must keep in mind that astronomy is a kind of time machine and that when we observe the universe we are looking back in time. In “Watchmen”, the character Doctor Manhattan notes that “All we ever see of stars is their old photographs.” The truly staggering physical scale of the universe combined with the speed of light is what makes this so. The universe is so large, it actually takes about eight minutes for the light from the sun to reach Earth. But if optical observations of the oldest stars and galaxies is analogous to “baby pictures” of the universe, then observing the cosmic background radiation is like looking at an ultrasound. However, the results of BICEP2 pull information out of that background radiation that is probably more analogous to a pregnancy test, revealing information about the very first infinitesimally tiny moments of creation when the universe was far less than one-trillionth of a second old.
It tells us, if confirmed, that the inflation model of cosmology proposed in 1980 by physicists Alan Guth and Andrei Linde is right. BICEP2 detected patterns, a gravitational wave, of polarization in the CMB that are a direct result of quantum gravitational fluctuations that occur even in vacuum. This not only illustrates quantum fluctuation and confirms predictions made by the inflation model of the early universe, it also has other implications. Implications that I find truly wondrous and awesome – in the original meaning of that word – and far more substantial than the (at least one) Nobel Prize this fundamental discovery will lead to.
Implications philosophical, sublime and profound.
Why is this important? Aside from the fact that the news of the discovery seems to make Professor Linde and his wife Renata very happy?
For one thing, it explains how we ended up with a universe that is isotropic (it looks the same in every direction, whomever you are, wherever you are) and the relative uniformity of the CMB. The WMAP image of the CMB at the head of the column is colorful, but those colors are falsely highlighted to show what are actually miniscule variations in the temperature of the CMB. The difference between “red” and “blue” is so small, cosmologists consider the WMAP data as showing a “smooth” or homogeneous universe. Although having an isotropic and homogenous universe is the modern terminology embedded in the Cosmological Principle, it is an idea that can be traced all the way back to Newton’s seminal 1687 work the Principia Mathematica. To put it another way, everyone knows that every explosion they’ve ever seen is messy and disordered so that raises the question why isn’t the universe? It is ordered at a sufficiently large scale and physics works the same everywhere. These wave patterns detected in the BICEP2 experiment were not only predicted by the inflation model, but represent evidence of the quantum mechanisms responsible for both isotropy and homogeneity we see in the modern observable universe.
In itself, that is a pretty damn exciting discovery. We know why the Big Bang resulted in order instead of chaos; an oscillation in the quantum fluctuations present at the very start of the Big Bang expansion. But this raises the question of where did the huge amount of energy required to generate this wave pattern come from? Why is that important? We’ll get to that via a brief detour to my 13th summer on this planet.
Like most 13-year old boys, I was curious about girls to be sure. And literally everything else too. I was born curious and inquisitive. It is simply my nature and why I maintain such a broad area of interests to this very day. Some things I’ll even say I’ve figured out. Girls aren’t one of them. But I digress from my digression. When I was 13, I was really interested in quantum mechanics. I had previously found classical physics very interesting and structured. Orderly. F=ma. N=mg. Things I saw could be measured, tested, understood. That led to learning about particle physics. The allure of order at sliding scales was very appealing. E = mc2. Energy and mass the same thing? Wow! Space and time all really part of a connect whole in spacetime but each still a bit of a mystery? Joy! Consequently, that led to the learning about the strange and often counter-intuitive world of quantum mechanics. Why were particles there and not there? Why all the empty space at the atomic level? Why all the randomness? How did such weirdness underpin all of such an orderly reality? So many questions.
It was the intellectual equivalent of sudden onset cocaine addiction, love at first sight, the best meal possible, a Mozart concerto, driving a Ferrari and falling off a cliff all rolled up into one.
I read everything I could lay my hands on and while some of the more esoteric maths were beyond my grasp at that age (some still are), the pictures they painted via the authors explaining them didn’t escape me. At the time, there was one major school of thought on how to interpret the strangeness of quantum mechanics: the Copenhagen interpretation favored by physicist Niels Bohr, Werner Heisenberg and many other physics greats since the 1930’s. It is still widely accepted today.
It has problems though. The Copenhagen interpretation didn’t sit well with me. I soon found out that it didn’t sit well with others including many physics professionals. Even Einstein thought is was wonky and it was his work that led directly to the formulation of quantum mechanics. What kind of problems? These problems are best understood by the famous Schrödinger’s Cat thought experiment and thinking about in the context of a critical feature of the Copenhagen interpretation: the collapse of the wavefunction. The doubts of others about the Copenhagen explanation of this phenomena between observer and observed quantified what didn’t set well with me and we’ll get to that, but first, let’s look at that famous cat, the collapse of the wavefunction and another way to deal with the collapse of the wavefunction that is wildly different than the Copenhagen version.
Schrödinger’s Cat is a thought experiment created by Erwin Schrödinger as a way to think about quantum entanglement. Using an example in reductio ad absurdum, Schrödinger concocted an experiment to illustrate how the Copenhagen interpretation deals with paradoxes created by the probabilities inherent when pairs or groups of particles are generated or interact in ways such that the quantum state of each particle cannot be described independently. Instead a quantum state may be given for the system as a whole. He did this by describing a cat in a box whose life or death was dependent upon the decay of a radioactive isotope. As described by the man himself:
One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following device (which must be secured against direct interference by the cat): in a Geiger counter, there is a tiny bit of radioactive substance, so small, that perhaps in the course of the hour one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges and through a relay releases a hammer that shatters a small flask of hydrocyanic acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The psi-function of the entire system would express this by having in it the living and dead cat (pardon the expression) mixed or smeared out in equal parts.
It is typical of these cases that an indeterminacy originally restricted to the atomic domain becomes transformed into macroscopic indeterminacy, which can then be resolved by direct observation. That prevents us from so naively accepting as valid a “blurred model” for representing reality. In itself, it would not embody anything unclear or contradictory. There is a difference between a shaky or out-of-focus photograph and a snapshot of clouds and fog banks.” — Erwin Schrödinger, Die gegenwärtige Situation in der Quantenmechanik
So the indeterminacy of the system (all its possible outcomes) are resolved when the event is observed and the wavefunction collapses to a single “point of reality”. The cat is both alive and dead – a paradox – until it is observed. It is a way to deal with the uncertainty in the system, but it nagged at me when I read about it. So I read some more. I found out that physicists had some issues with that result as well. When I read their chief criticism, I had one of those moments where one has been pummeled by the obvious missed. I believe at the time I may have even said words to the effect of “Well . . . duh.” The problem with this is that this explanation isn’t treating the observer as part of the greater set of quantum probabilities that is the entire universe. They are rooted in the classical world. But still the question remains: how to reconcile the paradox of the probable and the observed?
That is when I found out about Hugh Everett. He had a totally different idea on how to explain the collapse of the wavefunction. He called it the Theory of Universal Wavefunction. It later came to be known as the Many-worlds interpretation of quantum mechanics. As described by Everett’s introduction to his 1956 thesis paper The Theory of the Universal Wave Function, “Since the universal validity of the state function description is asserted, one can regard the state functions themselves as the fundamental entities, and one can even consider the state function of the entire universe. In this sense this theory can be called the theory of the ‘universal wave function,’ since all of physics is presumed to follow from this function alone.” In other words, all of objective reality is a single wavefunction and all other observable wavefunctions and their subsequent outcomes are a subset of this universal wavefunction. This not only addressed the flaw in the Copenhagen interpretation as illustrated by Schrödinger’s Cat, it has a really interesting consequence for understanding the apparent collapse of wavefunctions. The observation is a subjective event. In Many-worlds, this subjective appearance of collapse of the wavefunction is explained by quantum decoherence. I was thinking of a tidy way to summarize quantum decoherence, but the summary at Wikipedia is really quite good:
Decoherence does not generate actual wave function collapse. It only provides an explanation for the observance of wave function collapse, as the quantum nature of the system ‘leaks’ into the environment. That is, components of the wavefunction are decoupled from a coherent system, and acquire phases from their immediate surroundings. A total superposition of the global or universal wavefunction still exists (and remains coherent at the global level), but its ultimate fate remains an interpretational issue. Specifically, decoherence does not attempt to explain the measurement problem. Rather, decoherence provides an explanation for the transition of the system to a mixture of states that seem to correspond to those states observers perceive. Moreover, our observation tells us that this mixture looks like a proper quantum ensemble in a measurement situation, as we observe that measurements lead to the ‘realization’ of precisely one state in the ‘ensemble’.”
Paradox resolved, wavefunctions don’t really collapse and observation becomes a moot point. Everything that can happen, does happen. Just not in the same universe.
What an intriguing idea. At a philosophical level, I also find that proposition strangely comforting. It is no secret I am not a religious person, but when I first read about Everett’s work, I was still exploring the idea of God quite actively. To me, the notion of an all powerful being was limited by a single universe with one set of outcomes. Wouldn’t an omnipotent and omnipresent being unfettered by the rules of any physics be interested in everything possible? I know if I were a god, I’d want a multiverse instead of a universe to play with.
That is what I find so interesting about the BICEP2 discovery. It is not only the first evidence of Hawking radiation (the gravitational wave proper are a result of the same kind of quantum fluctuation Hawking previously described happening around the event horizons of black holes), the first experimental evidence of quantum gravity, and confirmation of the inflation theory, but almost all versions of inflation theory require the Many-worlds interpretation. As Andrei Linde himself notes “In most of the models of inflation, if inflation is there, then the multiverse is there. It’s possible to invent models of inflation that do not allow [a] multiverse, but it’s difficult. Every experiment that brings better credence to inflationary theory brings us much closer to hints that the multiverse is real.” This is also good for another physics theory for which I am a proponent: M-theory. Where did the huge amount of energy required to generate this wave pattern come from? The high energies required to generate this gravitational wave at the start of the Big Bang are best explained by the M-theory version of the Big Bang where a universe is “kicked off” by the collision of “dimensional membranes” that not only result in multiverses, but cyclical multiverses.
Not only does everything that can happen, happen, everything has happened before and will happen again.
If I were a god and I wanted a cosmic playset? A cyclical infinite multiverse would make me think of the title of a great short story by Brian Aldiss: “Supertoys Last All Summer Long”.
Somewhere, you are everything you ever and never wanted to be.
How exciting is that?
And last, but certainly not least, congratulations Professors Guth and Linde. This not only goes a long way to confirming your theory, but I am confident that it will be remembered by the history of science (at least in this universe) as one of the greatest discoveries in the history of humanity. Good show, gents.
Creation just got a little more wondrous.
What do you think?