Transcript: This is a talk I originally prepared to present as part of the 2206-2007 convocation series at Illinois College. Since then I have given it before several other audiences, and with every presentation Iâ€šÃ„Ã´ve had more people ask, will this be online. Finally, I can saw yes. Hereâ€šÃ„Ã´s the link. Please enjoy.
In todayâ€šÃ„Ã´s crazy world, it is easy to get lost in the details of our overly busy lives. There are projects, deadlines, business meetings and family meetings all demanding our attention. I suspect at least some of your employers have led you to believe their project should be the most important thing in your life right now. And I suspect that at least one person in your family has led you to believe that being at their home on time for some particular family gathering is the most important thing you can do this month. With all these specific day-to-day details demanding attention, it is hard to find a moment to step back and consider the big picture.
Especially when the big picture encompasses the entire universe; past and present, and possibly even parallel.
Right now, I invite you to set aside the details of today, and consider instead the details of the first day, and the implications those details have in creating the universe we live in.
Science in the 20th century has made huge strides in understanding the science of our universe.
We went from not understanding how physical traits like eye color are passed from parent to child, to James Watson and Francis Cricks 1953 discovery of DNA to the 2000 completion of the first draft of the Human Genome project, which is mapping the entire genetic structure of the 25,000 some odd genes that make up each of us.
We went from seeing the entire universe as a continuous distribution of stars and nebulae; to Edwin Hubbleâ€šÃ„Ã´s 1929 discovery that the Andromeda Nebula is actually a separate galaxy apart from our own; to the 1989 realization by Margaret Geller and John Huchra that we live in a universe of structure, with galaxies tracing out voids and filaments and clustering in some cases by the 1000s in giant super clusters.
We went from viewing the universe as a stationary place â€šÃ„Ã¬ where everything was as it always had been and always would be â€šÃ„Ã¬ a Universe that Einstein held in place in 1915 when he published his General Theory of Relativity with a cosmological constant â€šÃ„Ã¬ to seeing Hubbleâ€šÃ„Ã´s late 1929 realization that the universe is expanding, to the 1998 discovery that the universe is not just expanding but accelerating apart.
From the DNA of life to the cosmological expansion of the universe, we have found rules to describe our place in the cosmos. But the rules that describe our place, canâ€šÃ„Ã´t answer the more fundamental questions of why does our universe exist and why is our universe the way that it is.
Today, 21st century science struggles with these more fundamental questions. Physics as we know it does not dictate our universe should be just as it is. Rather, many other possibilities are possible and perhaps even more probable. But we are here, and this has consequences on how we must view our universe, and on what forces might make the improbable possible. It is the improbability of our place in space, and the consequences of our reality that I want to discuss today.
Since this is a discussion of science, we need rules to govern our thinking and our logic. Without rules, it is possible for anyone to say anything and say it is true, just because that anything fits into their own personal set of beliefs. Science, starts with the premise that it is possible to run experiments and make observations that tell us about the universe around us. Any theory I develop to explain the universe must conform to past experimental results and observations, and a good theory can be used to predict the outcome of future experiments and observations.
Put simply, as a scientist, when I observe that a tossed ball goes up and comes back down, I believe that I am observing a real phenomenon. Now, it is possible for me to theorize that any object thrown up into the air will also go up and come back down, and to predict that if any of you toss a ball up into the air, you too will observe the ball go up and come back down.
So far so good, I have a theory, it fits past observations, and it makes concrete predictions. As a scientist however, I also have to be willing to say my theory is wrong if it can be disproved experimentally.
This means, if I observe an object get thrown into the air and not come back down — for instance a space probe getting thrown into space by a giant rocket, that rather than falling back to Earth goes off to explore Mars â€šÃ„Ã¬ then I have to modify my theory to incorporate the new observations. Now, my theory would have to say, any object thrown upward will come back down unless its velocity is greater than the escape velocity needed to get away from Earthâ€šÃ„Ã´s gravity. Such an object will go up, and keep going until it encounters the gravity of something else. Ideas build and grow, and incorporate into themselves the results of each new experiments. I started with my observations of my ball, but then incorporated my observations of a Mars probe.
In the history of science, Newtonâ€šÃ„Ã´s theory of gravity grew into Einsteinâ€šÃ„Ã´s General Theory of Relativity, which someday will probably grow a new name as the theory it self grows to include results pertaining to quantum mechanics and the physics of black holes.
In science, we also have the basic rule that theories are as valid on the other side of the universe as they are here in this room. This means that any theory of tossing balls here on Earth will also be valid on the other side of the cosmos, where some green handed individual might perform the same experiments I perform. Science is one of the few languages that isnâ€šÃ„Ã´t rooted in culture or even planet orgins. The physics here is, simply, the same as the physics everywhere.
Along with the rules being the same everywhere, science also assumes that if you look at a large enough chunk of space, the universe is the same everywhere. Our neighborhood of space, if we define it large enough, is the same as every other neighborhood, with the demographics and the same evolution. No neighborhood is special. Put scientifically, using really big words, this basic tenet, dubbed the Cosmological Principle, states that the universe is homogeneous and isotropic.
We also have one more rule that tries to govern us, and thatâ€šÃ„Ã´s the principle of mediocrity. This is the rule that we donâ€šÃ„Ã´t live in a special place, a special time, or a special anything else. There should never be any result that rests on us being at just the right place and moment in space and time. In considering this rule you again have to think big. The time we live in on the planet Earth, is special. We live during the halceone extinction, and have the privilege of watching global warming. We also live during a special time when our sun isnâ€šÃ„Ã´t too big or too cold or to hot, but is just right for life. When considering the principle of mediocrity you have to look at the entire age of the universe and expance of the cosmos and say, our Sun isnâ€šÃ„Ã´t special, our galaxy isnâ€šÃ„Ã´t special, our lifetime, against all the other 60 to 100 year blocks of time isnâ€šÃ„Ã´t anything great. In the local scheme, we live in far too interesting a time, but cosmically our place is space isnâ€šÃ„Ã´t anything extraordinary.
So there you have it: everything is the same everywhere and none is special. We simple live to observe the same stuff you can observe anywhere, and we use those perfectly boring observations to built theories that, if they are scientific, are able to predict what future observations will see.
With these basic ideas, I have the intellectual tools I need to explore the universe, and what a beautiful universe it is. Todayâ€šÃ„Ã´s modern story of Genesis, starts with a Big Bang that marked the beginning of time and space. From a nothing that some describe as a quantum foam fluctuation, there emerged energy that would condense into the universe we now occupy. For a brief moment, all the atoms that make up you and me and the entire universe were condensed into a single speck of pure energy.
As that early, energy filled universe expanded, it went through a period of exponential growth that is referred to as inflation. During this period, the space itself expanded so rapidly that two points would appear to separate faster than the speed of light. Now, donâ€šÃ„Ã´t misunderstand this. The objects didnâ€šÃ„Ã´t actually move faster than the speed of light, but the actual space grew, as though the entire universe was a piece of graph paper that kept getting run through a Xerox machine set on enlarge.
In this situation, the actual place on the universe that a given point or three might be located, would stay constant with time, but the universe itself expanded, making the space between those spaces bigger, making it appear that the points were moving apart. The apparent velocities, as the grid carried the points with it from a confined space to an enlarged space, could have seemed to be as high as several times the speed of light, but appearances arenâ€šÃ„Ã´t always reflections of reality, and the points in space didnâ€šÃ„Ã´t actually move on the grid of space time. The grid itself simply enlargeded.
Had the inflation gone on longer or pushed things farther apart than it did, the material in the universe would have been spread out too much and become too smooth for stars and galaxies to later condense. Had inflation not spread out matter as much as it did, it might have clumped up so much that everything collapsed back together, producing a big crunch shortly after the big bang. Physics, as we know it, doesnâ€šÃ„Ã´t require inflation to work the way it did, but the universe we live in requires there to have been inflation in order for us to exist.
As the epoch of inflation ended, the universe cooled and matter began to condense. From Einsteinâ€šÃ„Ã´s famous E=mc^2 we know that mass is just another face to energy, and that the two can transform from one to the other. As our universe expanded, it cooled, and matter was able to solidify out of the energy.
The catch is that when energy changes into matter it should also produce anti-matter. For every proton â€šÃ„Ã¬ the key ingredient in atoms â€šÃ„Ã¬ there should also be an anti-proton. For every electron there should be a positron. The reason I say this is a catch is very simple â€šÃ„Ã¬ as you and I look around this room we donâ€šÃ„Ã´t see anyone made of anti-matter. As astronomers look out across the sky, we do not find anti-matter stars or galaxies. In fact, while anti-particles are observed, they are transitory things, which quickly annihilate as they collide with regular matter. If, at the beginning of the universe, matter had condensed into equal parts matter and anti-matter, than no matter should exist today.
But, we do have matter. We exist. Observationally, we know that somehow, for every 10 billion anti-matter particles that formed, there must have been 10 billion and 1 particles of regular matter. When the 10 billion matter and anti-matter particles combined they left behind 1 particle of matter and a lot of light. This fine tuning created a universe that was just right for us to be able to be in this room, but that is mathematically ugly, requiring asymmetries in the matter and anti-matter. These are asymmetries that theorists canâ€šÃ„Ã´t make fall naturally out of any equations. It seems the universe simple was made just so.
And it made it just so in the flash of an eye. Within a second, all this was over. Inflation was over. The self-annihilation of matter on anti-matter was over. And then, from about 100 seconds after the big bang until 3 minutes after the Big Bang, the entire universe did its best imitation of the inside of a star. Protonâ€šÃ„Ã´s collided together with such high velocities that nuclear reactions built hydrogen into helium, and a little bit of lithium and beryllium. The results of this early, Big Bang Nucleosynthesis is still visible in the ingredient lists of the oldest stars. After the Big Bang the universe was 25 percent He, and little bit of deuterium, a heavy form of Hydrogen, and it contained trace amounts of Lithium.
After those first three minutes, it was too cool for nuclear reactions to continue, but too hot for much of anything else to occur. For nearly 400,000 years electrons, atomic nuclei, and radiation formed a thermally interacting soup that simple expanded and cooled, but didnâ€šÃ„Ã´t do much else. Finally, around year 380,000 the universe cooled to a point where normal atoms could form, and the electrons bonded with the nuclei, and the radiation was free to fly away.
That radiation, the radiation created when the matter and the antimatter collided, was set free when electrons bonded with nuclei, and it continues to permeate all of space today and we observe it in the form of the cosmic microwave background. Slight temperature differences in the universe at the moment of recombination, reflect slight changes in density from one part to another. And when I say slight I mean slight â€šÃ„Ã¬ the variations seen in this temperature map represent differences of just one part in 100,000.
Today, the Cosmic Microwave Background has a temperature of 2.725 degrees above absolute zero with fluctuations of just 0.000018 degrees.
These small variations would eventually collapse into the large-scale structures â€šÃ„Ã¬ the galaxies, and galaxy clusters â€šÃ„Ã¬ of todayâ€šÃ„Ã´s universe, but that would take time. The largest structures formed first, creating the scaffolding into which all the matter would flow. Within these structures the first generation of stars formed as material streamed into forming galaxies. And at the junctions of these structures super clusters formed at the location of the largest temperature fluctuations. Today we can see the distribution of temperature fluctuations reflected in the distribution of matter in space.
Initially, the neutral universe was a dark place. It stayed dark for almost 400 million years while the material slowly collapsed. For almost 400 million years the universe consisted entirely of neutral gas that didnâ€šÃ„Ã´t create light and in fact would have been opaque to any light that might have existed. Than finally, one day the first stars were born and their light cleared the opaque gas, making the universe transparent. At that moment the just forming galaxies lit up the early universe. In the billions of years since then, stars have continued to be born, and galaxies have continued to grow, and today we can trace out the evolution of these objects using telescopes as time machines.
Because light travels at a finite speed, it takes time for information to travel from one object to another. Over small distances, such as the distance from me to any of you, this time is unnoticable. I speak, and faster than I can blink, you see my lips move if we were in the same room. Still, in all truth, you can never see me in the moment, and I can never see you as you appear at the exact now that I say now. The light always must take some time to travel, even if it is sometimes an unimaginably short time.
As distances grow, however, the time it takes light to travel becomes meaningful. When reporters try and report live from overseas locations, we can see the lag introduced as a question travels from the american studios, up to a satellite, across to a different satellite and then back down to the reporter, only to have to return again. As we move farther and farther and farther away, this time grows. When we look at the Sun, we see it as it appeared 8 minutes ago. Jupiter is seen as it was 40 minutes ago. Scientists sending probes to distant planets must program the robotic explorers to act autonomously because it isnâ€šÃ„Ã´t possible, with even a few minutes of lag, to drive a space ship like a remote control car.
And consider this fact: Light from our neighboring galaxy, Andromeda, takes more than 2.36 million years to reach us. This means that we see Andromeda as it was when early humans were just starting to walk the Earth.
As we look at the most distant objects, we are able to look back at our universeâ€šÃ„Ã´s infancy. What we find is a fascinating story of gravity and some mysterious expansion causing force playing a game of tug-a-war with our expansion rate. In the early days of the universe, matter dominated everything, and the gravitational force of everything on everything else worked to slow the expansion left over from the original Big Bang. Until recently, it was believed that our universe might someday reverse directions, and collapse in on itself, or that perhaps it would slowly coast outward at ever slowing rates that might or might not eventually hit zero.
But, all because you think something is true doesnâ€šÃ„Ã´t make it true. In 1998, the entire astronomical community had to rethink how we view the universe when it was discovered that the rate of the universeâ€šÃ„Ã´s expansion began to accelerate 5-6 billion years ago.
Using type 1a supernova, a type of exploding stars that give off set amounts of light, astronomers can measure distances out to the far corners of the universe the same way that you estimate the distance to an oncoming car at night. The light from any standard light source appears more or less bright depending on the distance to the light. If you are standing in the middle of the road and see really bright headlights you might correctly realize youâ€šÃ„Ã´re about to get hurt, while if you see really faint headlights, you might decide you can pause to pick up a penny in the road. Your brain is automatically doing math, and astronomers do that same math to figure out where supernovae of different brightnesses are located.
Once we know where and when a supernova is located, we can get at the expansion rate in their corners of time using the same technique that policemen use to measure the speed of your car. When a light is either moving or reflecting off a moving object, it gets shifted in color.
The color shift we observe is related to the direction of motion. As an object moves toward an observer, the light waves get squished together, appearing more blue. Conversely, light waves get spread apart, appearing more red, when an object moves away from an observer. Today, astronomers have distance and velocity information for dozens of supernovae spread all over the cosmos, and from this information we can plot the changing expansion rate of the universe.
From our plots, we know that roughly 5-6 billion years ago, the universeâ€šÃ„Ã´s expansion began to accelerate. The culprit, the repulsive force, behind this acceleration is called Dark Energy. Itâ€šÃ„Ã´s always been there, affecting each cubic meter of space, and trying to push things apart, but itâ€šÃ„Ã´s only in the modern universe, where the space between objects is vast, and the total volume of space is something much greater than vast, that Dark Energy has been able to become a major effect.
Each cubic meter of space has the same repulsive quality. As the universe continues to expand, each new square meter of space has the same repulsive quality, and the total amount of repulsion grows with the universe. As the universe expands, it will accelerate itself apart as an ever-growing proportion is made up of dark energy.
Think of it this way, when you first mix the ingredients for bread dough, the dough is dense, and every square centimeter is primarily made of flour. As the dough rises and is eventually baked into bread, each square centimeter consists more and more of air. Now imagine the dough could expand forever until each square centimeter consists of only 1 grain of flour, and all the rest of the space is air. In our own universe, the mass is getting spread out more and more each moment and dark energy fills in all the intervening spaces.
As best as anyone knows, dark energy arises from the vacuum of space. In this vast, seeming nothing, there is energy, and this energy constantly boils with particles that are forming and annihilating one another. Some of these particles, those that fall into the category of bosons, such as protons and neutrons, have a positive energy, and those that fall under the label fermions, like electrons, contribute a negative energy. Observationally, the total amount of dark energy seems to work out to an energy equivalent to roughly 3 protons per cubic meter.
This is a very small value â€šÃ„Ã¬ which is good, because if it were any larger the universe would have been shredded apart. Just an increase of a factor of 10 would have prevented our universe from forming stars, galaxies, planets, and life. This is called the big shred, and some strange coincidence of space and time saved us from that fate. The physics, as far as we know, doesnâ€šÃ„Ã´t require dark energy to be so small, in fact, most theories predict that it should be 10 to the power of 120 times larger! Theory doesnâ€šÃ„Ã´t even require dark energy to be positive. Because the universe happened to be set up with a positive dark energy of this roughly 3 protons per cubic meter and no larger we are able to exist.
And it is because of another magically just so number that we are able to understand dark energy and also be able to exist.
That other magic number is the the fine structure constant.
When we observe supernovae, we study the way they give off light in some colors and not in others. Every atom gives off itâ€šÃ„Ã´s own specific set of colors. When you see a neon â€šÃ„ÃºOpenâ€šÃ„Ã¹ sign, you are seeing red light given off by excited neon gas. Blues come from argon, and purple from Xeon. These colors come from the energy transitions of electrons orbiting the proton neutron core within an atom.
Letâ€šÃ„Ã´s consider for a moment the atom most required for human life – carbon. This atom consists of 6 protons, 6 neutrons, and 6 electrons. It is formed in stars like our own Sun, and can be found throughout the galaxy.
When we observe supernovae, we study the way they give off light in some colors and not in others. Every atom has its on characteristic energy levels that orbiting electrons are allowed to occupy. Light carries energy that corresponds to its color. When light of the wrong color collides with an atom, nothing happens, but when light of the right color comes in, for instance when light from the center of a supernova collides with matter surrounding the supernova, the light gets absorbed.
Atoms can also give off light. That red neon â€šÃ„ÃºOpenâ€šÃ„Ã¹ sign you see documents the energy drop of electrons within the gas.
Sometimes light is absorbed by atoms, and sometimes atoms give off light.
These absorptions and emissions lead to bright and dark bands in the spectra of the objects we observe, whether they be stars, nebulae, supernovae or galaxies. The exact fingerprint of these atoms is governed by quantum mechanics, and in the midst of a lot of elegant equations sits an experimentally determined fine structure constant.
The value of the fine structure constant isnâ€šÃ„Ã´t defined by the physics. It just is. Along with determining fine divisions within the colors we see in neon signs, and in supernovae, the fine structure constant also defines how well the cathode tubes in old TVâ€šÃ„Ã´s were able to form a picture, and it plays a role in the electromagnetic force between all charged particles. If its value changed, the properties of all atoms would change, and we probably would not exist to view supernovae and the expansion of the universe.
The list of things that appear to just be the way they are â€šÃ„Ãºjust becauseâ€šÃ„Ã¹ is an ever-growing list. One of the holy grails of science is that one underlying elegant equation that will explain everything; the fine structure constant, the amount of dark energy, the length of the inflation epoch, the proportion of matter to anti-matterâ€šÃ„Â¶ all these things and more we keep hoping will fall out of some magic perfect equation that elegantly sums up everything.
But we canâ€šÃ„Ã´t find that theory.
Einstein spent his life searching for it. Hawking has looked. Every great cosmologist has asked, â€šÃ„ÃºHmmm, what ifâ€šÃ„Â¶,â€šÃ„Ã¹ and theyâ€šÃ„Ã´ve come back with nothing certain. There is string theory â€šÃ„Ã¬ a mathematical model that attempts to unify all of the forces by assuming particles are multi-dimensional strings rather than point sources, butâ€šÃ„Â¶ There are perhaps 4 people in the world fully understand string theory, and there no one who has been able to come up with a way that we can either verify or falsify string theory. Without experimental testing, string theory canâ€šÃ„Ã´t be considered science. It is just a pretty mathematical art form that might some day grow into making testable predictions. But, itâ€šÃ„Ã´s just not there yet.
So for now, as I scientist, I find myself in a universe that has a lot of things that seem to be just so, just because. I also have this rule that states that I can not live in a special time, place, or special anything else. These two things seem to be contradiction. I could brush it off and say itâ€šÃ„Ã´s a coincidence, donâ€šÃ„Ã´t sweat it, butâ€šÃ„Â¶ But at a certain point, if the same person, or in this case the same universe, wins the lotto day after day after day, you have to wonder if something funny is going on.
And right now a lot of scientists are wondering how it is that so many things are so improbably just so.
It seems that there are three possibilities.
1) We could of course not really understand the universe. It could be there is some yet undiscovered underlying rule, some beautiful set of equations, that will dictate all the impossible coincidences must exist. This is the hole grail so many cosmologists seek.
2) Another possibility is there is force outside our universe, outside our space and time, that is dictating the constants of our cosmos. Perhaps there is a God, a watchmaker, a greater power tweaking our forces to make life possible. But, this possibility is beyond the testing of science. We donâ€šÃ„Ã´t know how to verify or falsify it and, as scientists, we must set it aside as something beyond science.
3) The third possibility is to some the ugliest and to others the most elegant. This third theory says that our universe is just one of many and that our improbable reality is able to occur because every possible combination of constants exists somewhere in the multiverse of universes.
This third theory may or may not be testable. And this possibility, falls out of many different ideas.
There is the probability argument: In theory, if enough monkeys pound on typewriters for enough years, Hamlet will emerge, and it makes sense to say that if enough universes are allowed to exist, eventually life will emerge. But saying that something makes sense just isnâ€šÃ„Ã´t enough.
Luckily, many scientists find more compelling ways to get at multiple universes.
According to Quantum Mechanics, the outcome of a quantum event doesnâ€šÃ„Ã´t exist until itâ€šÃ„Ã´s observed. This is the premise behind the Schodingerâ€šÃ„Ã´s Cat thought experiment. The experiment goes something like this: You lock a cat in a sealed container. In the container with the cat is a Geiger Counter and a small bit of radioactive material. At any given moment each atom in the radioactive material has a certain probability of decaying. If, for instance, itâ€šÃ„Ã´s a bit of 210Polonium, the half life is 138 days. This means that statistically, if you have a bunch of atoms of Polonium, half of them will decay within 138 days. The thing is, statistics doesnâ€šÃ„Ã´t require half the atoms must decay. It could be that more decay or that less decay. Itâ€šÃ„Ã´s just a probability.
If I flip a coin a bunch of times, I should get heads half the time, but it doesnâ€šÃ„Ã´t mean I will.
Now if my bunch of Polonium happens to add up to 138 atoms, statistics say that on any given day, I have a 50/50 probability of one atom decaying. So, imagine I have a cat in a box with 138 atoms of Polonium, and I have a Geiger counter to detect if any atoms actually decay. Just to make things interesting, I attach a vial of poison to the Geiger counter, such that if some atom decays, the Geiger counter will trigger and burst the poison, killing the cat.
According to Quantum Mechanics, the atoms each exist at every moment in both a decayed and a not decayed state. Only at that philosophically painful moment when the atoms are observered do the wave function collapse, and the atoms become absolutely decayed or absolutely not decayed. This means, until observed those atoms hover in the decayed/not decayed state and the cat hovers in both a state of alive and dead.
In all reality, the cat is a perfectly good observer of its own death. But still, the atom could be decayed and not decayed the Geiger counter or something else cames along to interact with its wave function and observe the outcome.
Radioactive decay isnâ€šÃ„Ã´t the only weirdly probabilistic thing we observe. For instance, if I have the worldâ€šÃ„Ã´s most pathetic laser and it gives off just 1 photon at a time, and I point my pathetic laser at a series of slits, the photons will go through and scatter out onto a screen on the far side of the slit. If I keep watching where the photons have landed for a period of time, they will build up a pattern that just happens to be identical to the interference pattern that you get if a bunch of photons from a very bright source all going through the slits at once. Thus, for several odd quantum mechanics reason, photons have some weird probabilistic way going through slits as waves and interacting in probabilistic ways. While no one can predict where any one photon will land, using quantum mechanics we can predict the pattern lots of photons will build up.
But why should any one photon do one thing, when in the exact same situation another photon does something totally different?
But why should any one photon do one thing, when in the exact same situation another photon does something totally different? According to what is called the Oxford Interpretation or the Many Worldâ€šÃ„Ã´s Interpretation, each photon actually takes every single different option, but each option occurs in a different, parallel, branching universe. Every time a choice is made, the universe branches. In this way, every possibility that could happen, does happen, just not necessarily in the universe we know as the one we live in. It also means that if I make it through this talk in this universe, in some other universe my computer self destructs, and in some other universe my car broke down on the way here. Everything that could happen, does happen, somewhere.
In this way, every possible value for every possible factor in our universe is played on in some parallel universe.
The question is, how do you test this Quantum-based multi-universe theory?
Unfortunately, the only way that has been defined really only tests the theory for the poor person running the test. Imagine the poor person who places a radioactive decay triggered gun at their head and steps into a box and waits to see if the world ends. With each moment the gun doesnâ€šÃ„Ã´t fire, the world splits into a world in which the scientist dies, and a world in which she lives. If she continues to live beyond what statistics say is reasonable, than probability weakly claims that there should be other universeâ€šÃ„Ã´s where the scientist has died. Itâ€šÃ„Ã´s a weak argument. Itâ€šÃ„Ã´s an a moral experiment, butâ€šÃ„Â¶ Itâ€šÃ„Ã´s at least one test we have the technology to do, even if no one will, I hope, ever do it.
Other methods are also being proposed, but weâ€šÃ„Ã´re not in a position to run those experiments – the technology isnâ€šÃ„Ã´t there. Perhaps in time, but not today.
So, while this theory is built on experimental results, and conforms to past experiments, it doesnâ€šÃ„Ã´t make any useful predictions. In many ways, this theory, like string theory, is a nice bit of pretty mathematical art that might be true, but we really have no way of proving.
But quantum mechanics isnâ€šÃ„Ã´t the only way to get at multiverses. According to Andrei Linde (of Standford University) and many others, it is possible that the field that drove the early period of inflation didnâ€šÃ„Ã´t act the same way in all places. What if in some some places expansion continued, with fluctuations in the inflation leading to bubble universes expanding one from another extending on forever?
This â€šÃ„Ãºwhat if â€šÃ„Ãº is layered on top of detailed theories that match our observed universe, and elegantly explain how inflation could have occurred. The multiverse falls naturally out of theories that drive the period of inflation with a (scalar) field that reacts to itâ€šÃ„Ã´s environment. The early universe was filled with bubbling quantum fluctuations that acted like waves. As the universe expanded, the waves froze. The largest fluctuations froze first, and as the universe expanded, stretching the small waves with itâ€šÃ„Ã´s growth, they eventually reached sizes where they also froze. Now, when waves interact, they can enhance one another or cancel one another. Depending on where you are sitting in this room, you hear my voice as louder or softer, depending on how the sound waves interact. In places, the interacting waves enhance my voice, and in the early universe, the waves in some places interacted to enhance the expansion.
In these spikes of chaotic inflation, new bubble universes could form, each growing out of a bit of the universe before it, each branching growing bubbling with itâ€šÃ„Ã´s own physical characteristics. These universes can sprout out of one another nearly forever, and some theories suggest there could be 10^10^12 universes sitting along side one another, and in some cases branching off of our own universe. Thatâ€šÃ„Ã´s a 1 followed by a trillion zeros of branching universes.
But, while this theory conforms to observations and explains what we experience, we currently have no way of knowing if it is true. Again, we have left the realm of testable science.
It seems, that with todayâ€šÃ„Ã´s technology and physics knowledge we must at a certain level label the first moments of the universe with the warning â€šÃ„ÃºHere be dragons.â€šÃ„Ã¹ We donâ€šÃ„Ã´t know what set our universe in place, we donâ€šÃ„Ã´t know why we are in a universe so precisely tuned to allowing life to exist. We have ideas, butâ€šÃ„Â¶ But ideas arenâ€šÃ„Ã´t answers.
So this leaves us in a queasy place. In talking about the subject of this talk with my peers at SIUE, several put forward emotional opinions on what they want to be the truth. We all have our emotional feelings. But as a scientist, I look at untestable theories and have to say they really canâ€šÃ„Ã´t be proven to be any more valid than Stephen Kingâ€šÃ„Ã´s parallel universe series, the Dark Tower, in which there is one true universe and infinite child universes, with alternate, not real pasts and futures.
In this book, one of the characters, at the moment of his death, says â€šÃ„ÃºGo, then. There are other worlds than theseâ€šÃ„Â¶â€šÃ„Ã¹ In these words he propels the main character, the gun slinger to other truths, other possibilities, and other places in time and space. I donâ€šÃ„Ã´t know if there are other multi-verses, parallel to this one, but I know our reality is not uniquely dictated by physics as we know it today. Our life in our universe is frighteningly improbable, and yet none the less real. Science doesnâ€šÃ„Ã´t offer all the answers, but it does offer questions and a set of rules by which we can seek the answers.
For now, we are faced with three possibilities: Perhaps there is underlying physics that dictates our universe be one that allows us to be here. If that physics exists, I hope someone finds it quickly. Perhaps we live in some sort of a multiverse. If that is the case, I hope some experiments to test that possibility are defined soon. And, if it was a higher power that tweaked the parameters, I really hope he created some underlying physics that we can study and use to end at least this one line of questions while we open up many more. Science doesnâ€šÃ„Ã´t answer the more fundamental questions of why does our universe exist and why is our universe the way that it is. All we can say is at the moment of the Big Bang, there be dragons.
<small>Images for this education presentation are from Getty’s Royalty Free Image collection (all photos), NASA, WMAP, jivaro, Corey Ford, and my own artwork. </small>